Patent Application
20240316836
Embodiments of the present invention relate to a system and method for manufacturing parts using continuous roll molding.
Parts, such as plastic or metal consumer products, may be made using various manufacturing methods. Injection molding is one method that produces parts by heating material to beyond its melting point and adding molten material into a mold shaped to form the particular part. The material is then cooled to allow for part removal from the mold.
Examples of parts that may be formed by manipulating plastic or metal include fasteners for securing materials to a work surface, such as staples having legs. The fasteners may beneficially protect the surface from damage while allowing the nail to secure the material to the surface. Such fasteners may be generally circular caps made from metal or plastic. Each cap may receive the legs of the nail and surround the legs as the nail is engaged with a surface. Cap feeders are powered tools that drive nails through caps to secure a material to a surface.
Embodiments provide an apparatus to form a frangible cap strip. The apparatus may include a sheet die configured to form thermoplastic material into thermoplastic sheet material, the thermoplastic sheet material including an upper surface, a lower surface, and an intermediate portion disposed between the upper surface and the lower surface. The apparatus may also include a continuous roll molder having an upper mold and a lower mold, the upper mold including a first shape and the lower mold including a second shape, the first shape and the second shape configured to form the thermoplastic sheet material into the frangible cap strip. The apparatus may also include a calendering system disposed between the sheet die and the continuous roll molder such that the calendering system may be downstream of the sheet die and upstream of the continuous roll molder, the calendering system configured to convey the thermoplastic sheet material from the sheet die to the continuous roll molder, the upper surface and the lower surface of the thermoplastic sheet material being at a first temperature after exiting the sheet die and at a second temperature lower than the first temperature when entering the continuous roll molder. The apparatus may also include a collection system configured to collect the frangible cap strip from the continuous roll molder, the collection system being downstream of the continuous roll molder, and the continuous roll molder configured to convey the thermoplastic sheet material to the collection system.
In some embodiments, the first temperature may be between about 100 degrees and about 300 degrees Celsius.
In some embodiments, the first temperature may be between about 150 degrees and about 250 degrees Celsius.
In some embodiments, the first temperature may be about 190 degrees Celsius.
In some embodiments, the second temperature may be between about 50 degrees and about 100 degrees Celsius.
In some embodiments, the second temperature is about 71 degrees Celsius.
In some embodiments, the intermediate portion of the thermoplastic sheet material may be at a third temperature after exiting the sheet die that may be approximately the first temperature.
In some embodiments, the intermediate portion of the thermoplastic sheet material may be at a fourth temperature greater than the second temperature when entering the continuous roll molder. In some embodiments, the fourth temperature may be greater than the first temperature by at least about five degrees Celsius. In some embodiments, the fourth temperature may be greater than the second temperature by at least about five degrees Celsius.
In some embodiments, the continuous roll molder includes a surface at a fifth temperature lower than the second temperature of the upper surface and the lower surface of the thermoplastic sheet material. In some embodiments, the fifth temperature may be greater than an ambient temperature. In some embodiments, the fifth temperature may be between about 45 degrees Celsius and about 55 degrees Celsius. In some embodiments, the fifth temperature may be about 50 degrees Celsius.
In some embodiments, the frangible cap strip includes a plurality of fastening caps such that the collection system may be configured to collect a continuous stream of the plurality of fastening caps from the continuous roll molder.
In some embodiments, the calendering system may be configured to reduce the temperature of the first surface and the second surface when conveying the thermoplastic sheet material from the sheet die to the continuous roll molder.
In some embodiments, the thermoplastic sheet material includes a first density when exiting the sheet die and a second density greater than the first density when entering the continuous roll molder.
In some embodiments, a thickness of the thermoplastic sheet material may be between about 0.04 inches and about 0.05 inches when entering the continuous roll molder.
In some embodiments, a thickness of the thermoplastic sheet material may be about 0.045 inches when entering the continuous roll molder.
In some embodiments, a thickness of the thermoplastic sheet material may be about 0.045 inches after exiting the sheet die.
In some embodiments, a thickness of the thermoplastic sheet material may be about 0.045 inches in the calendering system.
In some embodiments, the calendering system may be configured to reduce a thickness of the thermoplastic sheet material.
In some embodiments, the calendering system includes a plurality of temperature controlled nip roller pairs arranged in a series, the nip roller pairs configured to convey the thermoplastic sheet material between adjacent nip rollers in each nip roller pair. Each successive temperature controlled nip roller pair in a flow direction of the thermoplastic sheet material includes one of a decreasing temperature and an increasing surface roughness. The plurality of temperature controlled nip roller pairs may be configured to reduce the thickness of the thermoplastic sheet material from when the thermoplastic sheet material exits the sheet die to when the thermoplastic sheet material exits the calendering system.
In some embodiments, the apparatus may further include a thermoplastic extruder disposed upstream of the sheet die and configured to extrude the thermoplastic material by an extruder screw to the sheet die.
In some embodiments, the apparatus may further include a secondary temperature control station disposed between the calendering system and the continuous roll molder such that the secondary temperature control station may be downstream of the calendering system and upstream of the continuous roll molder, the secondary temperature control station configured to modify the temperature of the thermoplastic sheet material by one of raising or lowering a temperature of the thermoplastic sheet material.
In some embodiments, the first shape and the second shape are the same.
In some embodiments, the upper mold may be configured to form a top surface of the frangible cap strip. The lower mold may be configured to form a bottom side of the frangible cap strip.
In some embodiments, the first shape includes knives configured to cut the thermoplastic sheet material.
In some embodiments, the knives run perpendicularly to a flow direction of the thermoplastic sheet material.
In some embodiments, the second shape includes a depression.
In some embodiments, the lower mold is an anvil against which the knives cut.
In some embodiments, the knives kiss cut the frangible cap strip by landing on substantially the same plane as the surfaces of the second shape while limiting contact between the knives and the surfaces of the second shape.
In some embodiments, the lower mold includes a metal of a lower hardness than a metal of the upper mold such that the knives of the upper mold kiss cut across a shear zone of the frangible cap strip.
In some embodiments, the apparatus may further include a nip gap disposed between the upper roller and the lower roller, the thermoplastic sheet material configured to enter the continuous roll molder through the nip gap.
In some embodiments, the apparatus further includes a temperature control system configured to maintain a gap between the first shape and the second shape. In some embodiments, the gap is approximately five microns. In some embodiments, the temperature control system may include a temperature-controlled mixture, the upper mold configured to receive the temperature-controlled mixture. In some embodiments, the lower mold configured to receive the temperature-controlled mixture. In some embodiments, the temperature control system is configured to circulate the temperature-controlled mixture to each of the first shape and the second shape.
In some embodiments, the first shape of the upper mold may be one of a plurality of first shapes of the upper mold. The plurality of first shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the first shape pairs of the first series are offset from the second shape pairs of the second series.
In some embodiments, the second shape of the lower mold may be one of a plurality of second shapes of the lower mold. The plurality of second shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the second shape pairs of the first series are offset from the second shape pairs of the second series.
In some embodiments, the upper surface of the thermoplastic sheet material includes a matte finish. The lower surface of the thermoplastic sheet material includes a gloss finish.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the lower mold may include an insert configured to act as a negative for the upper mold. In some embodiments, the insert may include aluminum. In some embodiments, the upper mold and the lower mold may include steel. In some embodiments, the second shape may include a transverse length and a lateral length and the insert extends to substantially the lateral length of the second shape. In some embodiments, the insert extends beyond the transverse length of the second shape such that the insert is configured to be a bumper between the upper mold and the lower mold to maintain a gap therebetween. In some embodiments, the insert is fixed to the lower mold.
Embodiments provide a method of forming a frangible cap strip. The method may include conveying a thermoplastic material through a sheet die to form a thermoplastic sheet material, the thermoplastic sheet material including an upper surface, a lower surface, and an intermediate portion disposed between the upper surface and the lower surface. The method may also include conveying the thermoplastic sheet material through a calendering system configured to reduce the temperature of the upper surface and the lower surface when conveying the thermoplastic sheet material through the calendering system. The method may also include conveying the thermoplastic sheet material through a continuous roll molder including an upper mold and a lower mold, the upper mold including a first shape and the lower mold including a second shape, the first shape and the second shape configured to form the thermoplastic sheet material into the frangible cap strip.
In some embodiments, the method may further include collecting the frangible cap strip from the continuous roll molder in a collection system.
In some embodiments, the method may further include before conveying the thermoplastic material through the sheet die, inserting raw thermoplastic material into a hopper configured to mix and dose the raw thermoplastic material into the thermoplastic material.
In some embodiments, the method may further include between conveying the thermoplastic sheet material through the calendering system and conveying the thermoplastic sheet material through the continuous roll molder, conveying the thermoplastic sheet material through a secondary temperature control station configured to raise or lower the temperature of the thermoplastic sheet material.
In some embodiments, conveying the thermoplastic sheet material through the calendering system includes conveying the thermoplastic sheet material through a series of temperature controlled rollers which conveys the thermoplastic sheet material between adjacent temperature controlled rollers. Each successive temperature controlled roller in a flow direction of the thermoplastic sheet material includes a decreasing temperature and an increasing surface roughness.
Embodiments provide a frangible cap strip made from the method.
In some embodiments, the method may further include before conveying the thermoplastic material through the sheet die, inserting recycled material into a hopper configured to mix and dose the recycled material into a thermoplastic material.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
Embodiments provide a frangible cap strip. The frangible cap strip may include a plurality of continuous roll-molded fastening caps arranged consecutively along the frangible cap strip, the fastening caps being spaced from one another. The frangible cap strip may also include a plurality of frangible tabs, each of the frangible tabs configured to join adjacent fastening caps and to extend along a first axis extending through a center of each of the fastening caps along the frangible cap strip. Each of the frangible tabs may include a frangible zone including a depression; a shear line; and a divot disposed at the shear line, the divot being closer along the first axis to a first one of a pair of adjacent fastening caps than to a second one of the pair of adjacent fastening caps. Each of the frangible tabs may also include a first tab portion formed between the divot and the first one of the pair of adjacent fastening caps. Each of the frangible tabs may also include a second tab portion formed between the divot and the second one of the pair of adjacent fastening caps, the depression being disposed in the second tab portion.
In some embodiments, a transition from the divot to the second tab portion includes a slope.
In some embodiments, the depression of each of the frangible tabs extends below a medial plane defined by a bottom side of each of the fastening caps.
In some embodiments, the depression of each of the frangible tabs may be substantially T-shaped. In some embodiments, the T-shaped depression includes an outer edge configured to engage a center feed finger of a CH38A cap feeder.
In some embodiments, the depression of each of the frangible tabs includes a first portion having a first length and a second portion having a second length smaller than the first length. In some embodiments, a transition between the first portion and the second portion includes a curve. In some embodiments, the first length may be about 0.29 inches. The second length may be about 0.15 inches. In some embodiments, the first portion includes a first width and the second portion includes a second width equal to the first width. In some embodiments, the divot may be positioned along an outer edge of the first portion.
In some embodiments, the second tab portion of each of the frangible tabs includes a raised surface disposed between the depression and the second one of the pair of adjacent fastening caps.
In some embodiments, a depth of the raised surface of each of the frangible tabs may be about 0.555 inches.
In some embodiments, a depth of the depression of each of the frangible tabs may be about 0.02 inches.
In some embodiments, the depression of each of the frangible tabs includes a shape configured to facilitate engagement of the respective frangible tab with a cap feeder.
In some embodiments, the second tab portion may be configured to form a hinge configured to increase compression, and prevent inversion of the fastening cap from overshooting or overpressing the fastening cap down onto a working surface.
In some embodiments, the frangible zone includes a thermoplastic material having a molecular alignment integrated into the material through calendering with continuous roll molds. The molecular alignment may be in the general direction of the first axis.
In some embodiments, the molecular alignment may be more linear than the molecular alignment of frangible cap strips that are injection molded. In some embodiments, the thermoplastic material may be high density polyethylene. In some embodiments, the high density polyethylene has a tensile strength of between 32000 psi and 6600 psi. In some embodiments, the high density polyethylene has a shear strength of between 4600 psi and 4800 psi. In some embodiments, the high density polyethylene has a tensile strength of between 0.93 g/cm3 and 0.97 g/cm3.
In some embodiments, the divot may be perforated.
In some embodiments, each of the frangible tabs further includes solid attachment leg portions at a first end and a second end of the respective divot.
In some embodiments, each of the frangible tabs may be devoid of through openings.
In some embodiments, the frangible cap strip may be not injection molded.
In some embodiments, the frangible cap strip may also include molecularly aligned, sheet extruded thermoplastic material. In some embodiments, the molecularly aligned, sheet extruded thermoplastic material has a crystallinity of between about 60-85%. In some embodiments, the molecularly aligned, sheet extruded thermoplastic material includes a density between about 0.93 g/cm3 and about 0.97 g/cm3. In some embodiments, each of the fastening caps includes a top side and a bottom side opposing the top side, each of the bottom sides including at least one depression. In some embodiments, the at least one depression includes at least one of a kidney shape and a circular shape. In some embodiments, the bottom side includes a circumferential bevel.
In some embodiments, each of the fastening caps includes a top side and a bottom side, each of the bottom sides including a plurality of first depressions and a plurality of second depressions. In some embodiments, the first depressions are positioned along the first axis. In some embodiments, the second depressions are positioned along a second axis perpendicular to the first axis. In some embodiments, each of the first depressions includes a first surface area. Each of the second depressions includes a second surface area larger than the first surface area. In some embodiments, the first depressions and the second depressions are alternately positioned along an inner radius of each of the bottom sides.
In some embodiments, a width of each of the frangible tabs may be about 0.1 inches.
In some embodiments, a length of each of the frangible tabs may be about 0.3 inches.
In some embodiments, a density of the frangible cap strip may be between about 0.955 g/cm3 and about 0.970 g/cm3.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
Embodiments provide a continuous roll molding apparatus to form a part. The apparatus may include a sheet die configured to form thermoplastic material into thermoplastic sheet material. The apparatus may also include a continuous roll molder configured to form the thermoplastic sheet material into the part. The apparatus may also include a calendering system disposed between the sheet die and the continuous roll molder such that the calendering system may be downstream of the sheet die and upstream of the continuous roll molder. The calendering system may be configured to convey the thermoplastic sheet material from the sheet die to the continuous roll molder.
In some embodiments, the thermoplastic sheet material includes an upper surface, a lower surface, and an intermediate portion disposed between the upper surface and the lower surface. In some embodiments, the upper surface and the lower surface of the thermoplastic sheet material are at a first temperature after exiting the sheet die and at a second temperature lower than the first temperature when entering the continuous roll molder. In some embodiments, the intermediate portion of the thermoplastic sheet material may be at a third temperature after exiting the sheet die that may be approximately the first temperature. In some embodiments, the intermediate portion of the thermoplastic sheet material may be at a fourth temperature greater than the second temperature when entering the continuous roll molder. In some embodiments, the calendering system may be configured to reduce the temperature of the first surface and the second surface when conveying the thermoplastic sheet material from the sheet die to the continuous roll molder.
In some embodiments, the thermoplastic sheet material includes a first density when exiting the sheet die and a second density greater than the first density when entering the continuous roll molder.
In some embodiments, the thermoplastic material may be selected from the group consisting of polyethylenes, high density polyethylene, polypropylene, low density polyethylene, acrylonitrile butadiene styrene, polystyrene, high impact polystyrene, polyvinylchloride, polyethylene terephthalate, aliphatic polyamides, polylactic acid, and high-impact polystyrene. In some embodiments, the thermoplastic material may additionally or alternatively be selected from the group consisting of polyamides, polyethylene terephthalate, polyimide, polyolefin, perfluoroalkoxy alkane, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, fluorinated ethylene propylene, and polyphenylene sulfide.
In some embodiments, the continuous roll molding apparatus may also include a thermoplastic extruder disposed upstream of the sheet die and configured to extrude the thermoplastic material by an extruder screw to the sheet die.
In some embodiments, the continuous roll molding apparatus may also include a secondary temperature control station disposed between the calendering system and the continuous roll molder such that the secondary temperature control station may be downstream of the calendering system and upstream of the continuous roll molder. The secondary temperature control station may be configured to modify the temperature of the thermoplastic sheet material by one of raising or lowering a temperature of the thermoplastic sheet material.
In some embodiments, the continuous roll molder includes a first mold and a second mold, the first mold including a first shape and the second mold including a second shape. In some embodiments, the first shape of the first mold may be one of a plurality of first shapes of the first mold. The plurality of first shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the first shape pairs of the first series are offset from the second shape pairs of the second series.
In some embodiments, the second shape of the second mold may be one of a plurality of second shapes of the second mold. The plurality of second shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the second shape pairs of the first series are offset from the second shape pairs of the second series. In some embodiments, the first mold may be configured to form a top surface of the part. The second mold may be configured to form a bottom side of the part. In some embodiments, the first shape includes knives configured to cut the thermoplastic sheet material.
In some embodiments, the calendering system may be configured to reduce a thickness of the thermoplastic sheet material.
In some embodiments, the calendering system includes a plurality of temperature controlled nip roller pairs arranged in a series, the nip roller pairs configured to convey the thermoplastic sheet material between adjacent nip rollers in each nip roller pair. Each successive temperature controlled nip roller pair in a flow direction of the thermoplastic sheet material includes one of a decreasing temperature and an increasing surface roughness. The plurality of temperature controlled nip roller pairs may be configured to reduce the thickness of the thermoplastic sheet material from when the thermoplastic sheet material exits the sheet die to when the thermoplastic sheet material exits the calendering system.
In some embodiments, the continuous roll molding apparatus may also include a collection system configured to collect the part from the continuous roll molder, the collection system being downstream of the continuous roll molder, and the continuous roll molder configured to convey the thermoplastic sheet material to the collection system.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
Embodiments provide a method of roll molding a part. The method may include extruding a thermoplastic sheet material. The method may also include calendering the thermoplastic sheet material through a calendering system. The method may also include roll molding the thermoplastic sheet material through a continuous roll molder to form the part.
In some embodiments, the thermoplastic material may be extruded through a sheet die configured to heat the thermoplastic material to above a melt temperature TM of the thermoplastic sheet material.
In some embodiments, the calendering system may be configured to reduce the temperature of the thermoplastic sheet material from above a melt temperature TM of the thermoplastic sheet material to below the melt temperature TM but above the glass transition temperature TG.
In some embodiments, the calendering system includes a first nip roller pair and a second nip roller pair. The thermoplastic sheet material may be conveyed through the first nip roller pair before the second nip roller pair. The second nip roller pair may be cooler than the first nip roller pair.
In some embodiments, the thermoplastic sheet material includes an upper surface, a lower surface, and an intermediate portion between the upper surface and the upper surface. The intermediate portion may be hotter than the upper surface and the lower surface after the thermoplastic sheet material may be conveyed through the second nip roller pair.
In some embodiments, the thermoplastic sheet material includes an upper surface, a lower surface, and an intermediate portion between the upper surface and the upper surface. The intermediate portion may be at a first temperature different from a second temperature of the upper surface and the lower surface. In some embodiments, the first temperature may be below a glass transition temperature TG of the thermoplastic sheet material. In some embodiments, the first temperature may be above a glass transition temperature TG of the thermoplastic sheet material and below a melt temperature TM of the thermoplastic sheet material. In some embodiments, the first temperature may be above a melt temperature TM of the thermoplastic sheet material.
In some embodiments, the calendering includes imparting a surface finish onto the thermoplastic sheet material.
In some embodiments, the roll molding includes kiss cutting the thermoplastic sheet material to impart a shape onto the thermoplastic sheet material.
In some embodiments, the roll molding includes crush cutting the thermoplastic sheet material to form the part.
In some embodiments, the method may also include conveying the thermoplastic sheet material through a nip roller guide between the calendering and the roll molding. In some embodiments, the nip roller guide may be faster than the continuous roll molder to thin at least a portion of the thermoplastic sheet material. In some embodiments, the nip roller guide may be slower than the continuous roll molder to thicken at least a portion of the thermoplastic sheet material.
In some embodiments, the method may also include slowing the thermoplastic sheet material as it may be conveyed between the calendering system and the continuous roll molder to thin at least a portion of the thermoplastic sheet material. In some embodiments, at least the portion of the thermoplastic sheet material may be reduced in thickness between about 20% and about 300%.
In some embodiments, at least a portion of the thermoplastic sheet material may be above a melt temperature TM of the thermoplastic sheet material when entering the continuous roll molder.
In some embodiments, at least a portion of the thermoplastic sheet material may be above a glass transition temperature TG of the thermoplastic sheet material when entering the continuous roll molder.
In some embodiments, a surface temperature of the continuous roll molder may be greater than an ambient temperature.
In some embodiments, a first temperature of the continuous roll molder may be lower than a second temperature of the thermoplastic sheet material.
In some embodiments, the method may also include conveying the part from the continuous roll molder as a continuous strip of parts. In some embodiments, the continuous strip of parts are attached at frangible zones between parts of the continuous strip.
In some embodiments, the method may also include conveying the part from the continuous roll molder as a discrete part.
In some embodiments, the continuous roll molder includes an upper mold and a lower mold, the upper mold including a first shape and the lower mold including a second shape. In some embodiments, the upper mold and the lower mold form an open mold. In some embodiments, the upper mold and the lower mold each include an open mold cavity.
In some embodiments, the upper mold may be configured to form a top surface of the part. The lower mold may be configured to form a bottom side of the part. In some embodiments, the first shape includes knives configured to cut the thermoplastic sheet material. In some embodiments, the knives run perpendicularly to a flow direction of the thermoplastic sheet material. In some embodiments, the second shape may include a depression. In some embodiments, the first shape of the upper mold may be one of a plurality of first shapes of the upper mold. The plurality of first shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the first shape pairs of the first series are offset from the second shape pairs of the second series. In some embodiments, the second shape of the lower mold may be one of a plurality of second shapes of the lower mold. The plurality of second shapes may be arranged in pairs, the pairs being arranged in a first series and a second series. The first series and the second series are adjacent and offset such that the second shape pairs of the first series are offset from the second shape pairs of the second series. In some embodiments, the first shape may be a depression configured to reduce sliding of the thermoplastic sheet material. In some embodiments, at least one of the first shape and the second shape may be a depression configured to reduce sliding of the thermoplastic sheet material. In some embodiments, at least one of the first shape and the second shape includes a ramped edge configured to facilitate flow of the thermoplastic sheet material. In some embodiments, the continuous roll molder includes an open mold. In some embodiments, the continuous roll molder may be configured to form the part with a tolerance of within about 0.0762 millimeter. In some embodiments, the continuous roll molder includes an open mold. In some embodiments, the continuous roll molder does not include an ejector pin to release the part. In some embodiments, the continuous roll molder does not include air pressure to release the part. In some embodiments, the continuous roll molder does not include a draft angle.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
A continuous roll molding system is provided. The system may include a continuous roll molder including an upper mold including a first shape and a lower mold including a second shape, the first shape and the second shape configured to form a thermoplastic sheet material into a product; and a temperature control system configured to maintain a gap between the first shape and the second shape.
In some embodiments, the lower mold may include an insert configured to act as a negative for the upper mold. In some embodiments, the insert may include aluminum, and the upper mold and the lower mold may include steel. In some embodiments, the second shape may include a transverse length and a lateral length, and the insert extends to substantially the lateral length of the second shape. In some embodiments, the insert extends beyond the transverse length of the second shape such that the insert is configured to be a bumper between the upper mold and the lower mold to maintain a gap therebetween. In some embodiments, the insert is fixed to the lower mold.
In some embodiments, the upper mold may include a first steel, and the lower mold may include a second steel, the second steel having a lower hardness than the first steel.
In some embodiments, the gap is approximately five microns.
In some embodiments, the upper mold is configured to receive a temperature-controlled mixture of the temperature control system. In some embodiments, the temperature control system is configured to circulate the temperature-controlled mixture to each of the first shape and the second shape.
In some embodiments, the continuous roll molder further may include a frame surrounding the upper mold and the lower mold, and the frame is configured to receive a temperature-controlled mixture of the temperature control system. In some embodiments, the temperature control system is configured to maintain the temperature of the upper mold and the lower mold at a temperature between about 5 degrees Fahrenheit and about 15 degrees Fahrenheit above the temperature of the frame. In some embodiments, the chiller is set to about 50 degrees Fahrenheit. In some embodiments, the temperature control unit is set to between about 5 and about 15 degrees Fahrenheit above a temperature of a frame of the continuous roll molder. In some embodiments, the frame may include a sensor configured to adjust the flow of the temperature-controlled mixture.
In some embodiments, the temperature control system may include a chiller, a temperature control unit, the continuous roll molder, and a temperature-controlled mixture.
In some embodiments, the continuous roll molder may include a bar and a nip roller, the bar configured to receive the product, and the nip roller configured to receive waste from the thermoplastic sheet material. In some embodiments, an angle between the bar and the nip roller is about 150 degrees.
In some embodiments, the system further includes an environment configured to comprise the continuous roll molder, the environment being temperature controlled to maintain a temperature of the continuous roll molder. In some embodiments, the environment is temperature controlled to about 62 degrees Fahrenheit.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
Embodiments provide a method of forming a part. The method may include conveying a thermoplastic material through a sheet die to form a thermoplastic sheet material, the thermoplastic sheet material including an upper surface, a lower surface, and an intermediate portion disposed between the upper surface and the lower surface; conveying the thermoplastic sheet material through a calendering system configured to reduce the temperature of the upper surface and the lower surface when conveying the thermoplastic sheet material through the calendering system; and conveying the thermoplastic sheet material through a continuous roll molder including an upper mold and a lower mold, the upper mold including a first shape and the lower mold including a second shape, the first shape and the second shape configured to cut the thermoplastic sheet material into the part and separate the part from waste thermoplastic sheet material such that the part and the waste thermoplastic sheet material continue along separate streams after release from the continuous roll molder.
In some embodiments, the method may further include between conveying the thermoplastic sheet material through the calendering system and conveying the thermoplastic sheet material through the continuous roll molder: conveying the thermoplastic sheet material through a secondary temperature control station configured to raise or lower the temperature of the thermoplastic sheet material.
In some embodiments, the continuous roll molder may include a bar and a nip roller, the bar configured to receive the part being conveyed along a first stream released from the first shape, and the nip roller configured to receive the waste thermoplastic sheet material being conveyed along a second stream released from the second shape. In some embodiments, the first stream and the second stream are angled away from one another, an angle between the first stream and the second stream being an obtuse angle.
In some embodiments, the part is a frangible cap strip.
In some embodiments, the first shape may include knives configured to cut the thermoplastic sheet material. In some embodiments, the lower mold is an anvil against which the knives cut, and the knives kiss cut the parts by landing on substantially the same plane as the surfaces of the second shape while limiting contact between the knives and the surfaces of the second shape.
In some embodiments, the second shape may include an insert configured to act as a negative for the upper mold. In some embodiments, the insert may include aluminum, and the upper mold and the lower mold comprise steel.
In some embodiments, the method may further include adjusting a temperature control system to maintain a gap between the first shape and the second shape, the continuous roll molder including one or more channels configured to receive a temperature-controlled mixture of the temperature control system. In some embodiments, the gap is approximately five microns.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
Embodiments provide a method of forming a frangible cap strip. The method may include providing a thermoplastic sheet material; and conveying the thermoplastic sheet material through a continuous roll molder including an upper mold and a lower mold, the upper mold including a first shape and the lower mold including a second shape, the first shape and the second shape configured to cut the thermoplastic sheet material into the frangible cap strip and separate the frangible cap strip from waste thermoplastic sheet material such that the frangible cap strip and the waste thermoplastic sheet material continue along separate streams after release from the continuous roll molder, the first shape including knives configured to cut the thermoplastic sheet material. The frangible cap strip may include a plurality of continuous roll-molded fastening caps arranged consecutively along the frangible cap strip, the fastening caps being spaced from one another; and a plurality of frangible tabs, each of the frangible tabs configured to join adjacent fastening caps and to extend along a first axis extending through a center of each of the fastening caps along the frangible cap strip. Each of the frangible tables may include a frangible zone including a divot, the divot being closer along the first axis to a first one of a pair of adjacent fastening caps than to a second one of the pair of adjacent fastening caps; a first tab portion formed between the divot and the first one of the pair of adjacent fastening caps; and a second tab portion formed between the divot and the second one of the pair of adjacent fastening caps.
In some embodiments, the method may further include conveying the thermoplastic material through a sheet die to form a thermoplastic sheet material, the thermoplastic sheet material including an upper surface, a lower surface, and an intermediate portion disposed between the upper surface and the lower surface; and conveying the thermoplastic sheet material through a calendering system configured to reduce the temperature of the upper surface and the lower surface when conveying the thermoplastic sheet material through the calendering system. In some embodiments, the method may further include between conveying the thermoplastic sheet material through the calendering system and conveying the thermoplastic sheet material through the continuous roll molder: conveying the thermoplastic sheet material through a secondary temperature control station configured to raise or lower the temperature of the thermoplastic sheet material.
In some embodiments, the continuous roll molder may include a bar and a nip roller, the bar configured to receive the frangible cap strip being conveyed along a first stream released from the first shape, and the nip roller configured to receive the waste thermoplastic sheet material being conveyed along a second stream released from the second shape. In some embodiments, the first stream and the second stream are angled away from one another, an angle between the first stream and the second stream being an obtuse angle.
In some embodiments, the frangible cap strip is provided made from the method.
In some embodiments, the lower mold is an anvil against which the knives cut, and the knives kiss cut the frangible cap strip by landing on substantially the same plane as the surfaces of the second shape while limiting contact between the knives and the surfaces of the second shape.
In some embodiments, the knives run perpendicularly to a flow direction of the thermoplastic sheet material.
In some embodiments, the second shape may include an insert configured to act as a negative for the upper mold.
In some embodiments, the method may further include adjusting a temperature control system to maintain a gap between the first shape and the second shape. In some embodiments, the gap is approximately five microns.
In some embodiments, the frangible zone further may include a depression and a shear line, the divot is disposed at the shear line, and the depression is disposed in the second tab portion.
In some embodiments, the depression of each of the frangible tabs extends below a medial plane defined by a bottom side of each of the fastening caps.
In some embodiments, the depression of each of the frangible tabs is substantially T-shaped.
In some embodiments, the second tab portion is configured to form a hinge configured to increase compression, and prevent inversion of the fastening cap from overshooting or overpressing the fastening cap down onto a working surface.
In some embodiments, the frangible zone may include a thermoplastic material having a molecular alignment integrated into the material through calendering with the continuous roll molder, and the molecular alignment is in the general direction of the first axis.
In some embodiments, the frangible cap strip is not injection molded.
In some embodiments, each of the fastening caps may include a top side and a bottom side opposing the top side, each of the bottom sides including at least one depression, and the at least one depression may include at least one of a kidney shape and a circular shape.
In some embodiments, the thermoplastic material may be high density polyethylene.
In some embodiments, the thermoplastic material may be high density polyethylene and calcium carbonate. In some embodiments, the thermoplastic material may include between about 20% and about 30% calcium carbonate by weight.
The disclosed embodiments will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed embodiments, wherein like designations denote like elements.
Various embodiments of the novel systems, apparatuses, and methods disclosed herein are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein, one skilled in the art would appreciate that the scope of the disclosure may be intended to cover any embodiment of the novel systems, apparatuses, and methods disclosed herein, whether implemented independently of, or combined with, any other embodiment of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the embodiments set forth herein. In addition, the scope of the disclosure may be intended to cover such an apparatus or method that may be practiced using other structure, functionality, or structure and functionality in addition to or other than the various embodiments of the disclosure set forth herein. It should be understood that any embodiment disclosed herein may be implemented by one or more elements of a claim.
Although particular embodiments are described herein, many variations and permutations of these embodiments fall within the scope of the disclosure. Although some benefits and advantages of certain embodiments are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, and/or objectives. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof.
It will be recognized that while certain embodiments of the disclosure are described in terms of a specific sequence of steps of a method, these descriptions are only illustrative of the broader methods of the disclosure, and may be modified as required by the particular application. Certain steps may be rendered unnecessary or optional under certain circumstances. Additionally, certain steps or functionality may be added to the disclosed embodiments, or the order of performance of two or more steps permuted. All such variations are considered to be encompassed within the disclosure disclosed and claimed herein.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The disclosure is not limited to the disclosed embodiments. Variations to the disclosed embodiments and/or implementations may be understood and effected by those skilled in the art in practicing the claimed disclosure, from a study of the drawings, the disclosure and the appended claims.
The systems and methods described herein are for improved manufacturing of parts. In some embodiments, the parts are made from thermoplastics. In still further embodiments, the parts include thermoplastic parts molded from a thermoplastic sheet. In other embodiments, the thermoplastic parts have certain 3-dimensional features. In some embodiments, the parts include a frangible cap strip. In certain embodiments, the manufacturing process may be a continuous roll molding process that may include conveying a thermoplastic material through a sheet die to form a thermoplastic sheet material, conveying the thermoplastic sheet material through a calendering system, and then conveying the thermoplastic sheet material through a continuous roll molder to form the thermoplastic sheet material into a part. In certain embodiments, the continuous roll molding process may include conveying the thermoplastic sheet material through a continuous roll molder to form the thermoplastic sheet material into a part, the thermoplastic sheet material being spooled, or otherwise stored, before being conveyed through the continuous roll molder.
Some systems and methods for producing parts may utilize injection molding and other more complex part capable processes. In certain embodiments, the manufacturing process according to embodiments of this disclosure provides improved systems and methods for producing parts, such as a frangible cap strip that may be more easily sheared. In additional embodiments, the continuous roll molding process may allow for dimensionally complex engineered part production. As described, embodiments of continuous roll molding may use a combination of material temperature, material handling, pressure, line speed, die shapes, and macromolecular flow directions to achieve high-speed production of dimensionally complex thermoplastic parts. Continuous roll molding may also have an even flow of parts constantly being produced at high speeds on multiple continuous roll molds through which thermoplastic material is conveyed, as described herein.
The frangible cap strip described herein may include a plurality of caps arranged consecutively along the frangible cap strip. The frangible cap strip may also include a plurality of frangible tabs, each of the frangible tabs configured to join adjacent fastening caps. Each frangible tab may be sheared more easily to allow for release of a cap from the frangible cap strip.
The systems and methods described herein will now be described with reference to the figures. The continuous roll mold system and method will be described first with reference to
The thermoplastic material may be formed into a sheet during the continuous roll molding method 1000. The thermoplastic material may be formed into other shapes or profiles instead of sheet structures. For example, the thermoplastic material may form shapes or profiles having rod, square, or rectangle cross-sections, etc.
Other embodiments include two or more thermoplastics of the same material being coextruded at different temperatures to assist in the flow of the thermoplastic sheet material 300 through the continuous roller molds of the continuous roll molder at different rates for part formation. The coextruded thermoplastic material at two different temperatures allows for the material above the melt temperature on the top of the sheet to flow more quickly and mold more rapidly in the continuous roller molds, where the mold cavities have greater depth and more volume to fill than the molds on the other side of the sheet. This allows for the mold with more volume needed in it to fill at the same rate of speed as the one below.
In certain embodiments, the sheet material passes through the continuous roller molds at a speed of about 30 to about 1,000 linear feet per minute (min), such as about 40 to about 500 linear feet per min, such as about 50 to about 200 linear feet per minute, such as about 100 linear feet per min.
In some embodiments, before step 1020, method 1000 may include inserting raw thermoplastic material into a hopper to mix and dose the raw thermoplastic material into the extruder, and conveying the thermoplastic material through an extruder by an extruder screw to the sheet die.
In other embodiments, before step 1020, method 1000 may include inserting recycled material into a hopper configured to mix and dose the recycled material into an extruder, and conveying the thermoplastic material through an extruder by an extruder screw to a sheet die. The recycled material may be ground for re-use and mixed with colorants, any additives, and raw material in a hopper for mixing and dosing into the extruder.
In some embodiments, before step 1020, method 1000 may include adding additives to the thermoplastic material. Colorant may be the primary additive, along with ultraviolet radiation (UV) protection additives. In some embodiments, secondary additives may be added, such as talc and calcium, which may increase the rigidity of the thermoplastic material, and facilitate shearing. For example, talc increases rigidity, and decreases shear strength, while calcium increases the impact strength of the thermoplastic material. In some embodiments, processing additives may be added to improve material flow. In some embodiments, stabilizers may be added to raw thermoplastic material to help prevent material degradation.
As will be discussed further below, thermoplastic sheet material 300 may include high density polyethylene (HDPE). In some embodiments, the thermoplastic material includes HDPE, and the HDPE includes calcium carbonate added to the HDPE. In one embodiment, a mixture of HDPE and calcium carbonate to form thermoplastic sheet material 300 may include between about 20% and about 30% calcium carbonate by weight. The addition of calcium carbonate may allow for thermoplastic sheet material 300 to be introduced to the continuous roll molding process at an ambient temperature, without requiring heating or cooling.
Calcium carbonate may have a rounded structure, which may improve flow of thermoplastic sheet material 300 while maintaining shape and rigidity for part formation. In one embodiment, the HDPE may have a density of 0.955 grams per centimeters cubed, a melt mass-flow rate of 0.35 grams per 10 minutes, an environmental stress-cracking resistance of 25.0 hour, a tensile modulus of 185000 pound per square inch, a tensile strength of 4000 pound per square inch, and a tensile elongation of greater than 500%. In one embodiment, the calcium carbonate may have a melt index of 2 grams per 10 minutes, a density of 1.95 gram per cubic centimeter, a moisture of less than 1000 parts per million, and a particle size of 3 micron.
In step 1040, method 1000 may include conveying thermoplastic sheet material 300 through a calendering system. In step 1060, method 1000 may include conveying thermoplastic sheet material 300 through a continuous roll molder. In step 1080, method 1000 may include collecting the part from the continuous roll molder in a collection system. In some embodiments, the continuous roll molder may include one or more molds to form the thermoplastic sheet material into the part.
In one embodiment, continuous roll molder may make one or more strips of parts from thermoplastic sheet material 300, or any other material. In some embodiments, the parts may be separated by frangible zones to allow for separation of parts from one another. In another embodiment, the parts may be cut by a cutting machine before or after conveyance through the continuous roll molder. In another embodiment, the parts may be cut by the continuous roll molder and collected.
As will be discussed, the continuous roll molder may include one or more molds, such as an upper mold and a lower mold, between which the thermoplastic sheet material 300, or any other material, is conveyed. At least one of the molds may include a knife, or sharp edge, for cutting parts. For example, the upper mold may include a series of shapes, each shape having knives, such as a sharp edge on either end of the shape. The lower mold may also include a series of shapes, each shape forming at least part of an anvil surface upon which the knives cut parts. The upper mold and the lower mold may rotate towards one other during the continuous roll molding process, allowing the upper mold shapes and the lower mold shapes to roll towards one another, a pair of one upper mold shape and one lower mold shape contacting the material at substantially the same time to form a part. The cutting process may include kiss cutting, in which the upper mold knives cut the part by landing on the same plane as the surfaces of the lower mold shape. In this way, the overall shape of the part may be imparted onto the material. Another cutting process may be implemented and may include crush cutting, in which the knives fully lower into or beyond surfaces of the lower mold shape. The crush cutting may cut and compress the material to form parts.
In some embodiments, the molds may cut openings in the parts. In some embodiments, the parts do not have any openings and are devoid of openings. The molds may cut create one or more shapes on the parts, such as a shape surrounded by a frangible zone to be removed in a larger process. The parts, after cutting, may be separated from waste material by the molds. After cutting, the parts may be coupled to the molds, allowing release of waste material. Downstream of the molds, one or more components may provide tension to release parts and waste material from the molds along separate streams. The parts may continue along a stream separate from a stream of waste material. In this way, parts are formed without residual waste coupled to parts. The components for creating the separate streams may include nip rollers or bars.
In step 2100, method 2000 may include conveying thermoplastic sheet material 300 through a calendering system with one or more temperature-controlled rolls. In one embodiment, the calendering system may include five heating and cooling nip rollers. In step 2120, method 2000 may include conveying thermoplastic sheet material 300 through a material slitter to trim and even edges of thermoplastic sheet material 300 before entering the continuous roll molder. In step 2140, method 2000 may include conveying thermoplastic sheet material 300 through a secondary heating or cooling system to be heated and/or cooled, respectively. In some embodiments, thermoplastic sheet material 300 may be heated in a tenter oven. In some embodiments, thermoplastic sheet material 300 may be cooled by a chiller.
In step 2160, method 2000 may include conveying thermoplastic sheet material 300 through a continuous roll molder infeed system, which may feed thermoplastic sheet material 300 to a continuous roll molder. In some embodiments, the infeed system may be a conveyor that leads thermoplastic sheet material 300 to the continuous roll molder.
In step 2180, method 2000 may include conveying thermoplastic sheet material 300 through a continuous roll molder, which may intake thermoplastic sheet material 300 from the continuous roll molder infeed system from step 2160.
In step 2200, method 2000 may include conveying thermoplastic sheet material 300 through a continuous roll molder outfeed system. The outfeed system may output parts molded by the continuous roll molder from step 2180. In some embodiments, the outfeed system may be a conveyor that leads parts away from the continuous roll molder from step 2180.
In step 2220, method 2000 may include collecting parts from the continuous roll molder outfeed system from step 2200. Additionally or alternatively, parts may be collected from an exit stream of parts from the continuous roll molder. The parts may be guided away from the continuous roll molder along a stream separate from a stream of waste thermoplastic sheet material. These exit streams will be discussed further below with reference to
In another embodiment, parts may be collected at a product accumulator station. In some embodiments, the product accumulator station may be a vertical accumulation station for handling multiple lanes containing roller bars that lift up and lower down on an elevator. Continuous strands of parts or discrete parts may be weaved through the roller bars of the product accumulation station. The product accumulation station may balance the speed differences in the production line and the accumulation processing of the parts, creating a time delay and a time buffer that supports the intermittent process of spooling continuous strands of parts.
In step 2240, method 2000 may include conveying parts through an automatic core feed station. In some embodiments, the automatic core feed station may pull a continuous strands of parts from the product accumulator station in step 2220. In some embodiments, the automatic core feed station may then convey continuous strands of parts for spooling, wind-up, and taping in step 2260 via a track that runs down to a position in line with the spooling station.
In step 2260, method 2000 may include conveying parts through an automatic spooling, wind-up, and taping station. The parts may be lowered onto a spool from a track above, pinched onto the spool, and rotated. In some embodiments, parts may go to a winding station, where they are spun onto cores, counted, cut, sealed, and ejected as a finished spool for packaging. This spooler may act not only to spool the parts, but also acts to add a few last elements to the product. In certain embodiments, the speed of the spooler may be set higher than the continuous roll molder, the spooler acting to stretch out frangible elements of parts, thinning them further to reduce the shear pressure needed to cut them. In other embodiments, the spooler may be set to a speed slower than the continuous roll molder, the spooler acting to thicken frangible elements to increase the shear pressure needed to cut them. Accordingly, this spooler may be used to adjust the shear properties of frangible elements of parts. An end of the parts may be cut and taped to the spool.
In step 2280, method 2000 may include conveying parts through a staging location. The staging location may receive and setup spools of parts for packaging and palletizing in step 2300. In some embodiments, a staging table may have a pick and place robot to lift the spools and place them in a box. In certain embodiments, the robot includes visual sensors.
In step 2300, method 2000 may include conveying parts for automated packaging and palletizing. In some embodiments, spools of parts may be packaged together and secured to pallets for transportation.
Referring to
Referring to
In certain embodiments, continuous roll molding may produce parts with material that is either highly crystalline and/or amorphous. As described herein, a thermoplastic material may be used. In some embodiments, the thermoplastic material may be selected from the group consisting of, but not limited to, polyethylenes, HDPE, polypropylene, low density polyethylene, acrylonitrile butadiene styrene, polystyrene, high impact polystyrene, polyvinylchloride, polyethylene terephthalate, aliphatic polyamides, polylactic acid, and high-impact polystyrene. In some embodiments, the thermoplastic material may additionally or alternatively be selected from the group consisting of polyamides, polyethylene terephthalate, polyimide, polyolefin, perfluoroalkoxy alkane, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, fluorinated ethylene propylene, and polyphenylene sulfide. In other embodiments, the thermoplastic material includes polyethylene, PVC, polystyrene, and polyamides. In other embodiments, the thermoplastic material may include a thermoplastic elastomer, copolymers, and polymer blends. In other embodiments, additives may be added to the thermoplastic material in order to improve certain properties.
In certain embodiments, the thermoplastic material may be amorphous, crystalline, or semi-crystalline. Amorphous thermoplastic materials may have a melt temperature TM, and a glass transition temperature TG. Semi-crystalline and crystalline materials may form crystalline regions in between TM and TG.
In certain embodiments, during extrusion, the continuous roll molding process may have greater control over the direction of the macromolecules compared to other manufacturing methods, as extrusion may align the direction of the polymer strands. Polymers, when extruded and calendered through the calendering process, may allow for setting the molecular direction in the feed flow direction. In this way, part production by the continuous roll molder may be improved, as the molds may be filled more evenly.
As shown in
In other embodiments, as shown in
In some embodiments, different zones of thermoplastic sheet material 300 (
In the embodiments of
The feed flow direction A of an embodiment of the thermoplastic material may be seen in
Extrusion may align the direction of the polymer strands. In sheet die 320, HDPE macromolecules, for example, may be aligned as they extrude through sheet die 320. With reference to
When the thermoplastic material is being mixed by the extruder screw and the melt pump, the molecules of thermoplastic sheet material 300 may be oriented randomly due to mixing and shearing. As the melted material is forced through thinner and wider openings in sheet die 320, the molecules begin to align along themselves, due to flow, friction, and being forced into a sheet profile.
In some embodiments, thermoplastic sheet material 300 may flow out of sheet die 320, thermoplastic sheet material 300 may be extruded directly into a nip gap 331 of calendering nip rollers 332, shown in
In some embodiments, the thickness of thermoplastic sheet material 300 before entering sheet die 320 may be between about 0.045 inches and about 0.06 inches. In some embodiments, thermoplastic sheet material 300 may thin by between about 0.05 inches and about 0.55 inches. In effect, the nip rollers 332 may thin the thermoplastic sheet material 300 by stretching it. Thinning of thermoplastic sheet material 300 may also further pull and align the macromolecular structures of thermoplastic sheet material 300 in feed flow direction A. In some embodiments, the maximum thickness of thermoplastic sheet material 300 after exiting sheet die 320 may be between about 0.5 inch and about 2 inches, such as about 1 inch.
In certain embodiments, crystallization by stretching may increase the crystallization of a thermoplastic material beyond melt crystallization, or may cause crystallization to occur more rapidly. In this process, the polymer is forced through, e.g., a nozzle that creates tensile stress which partially aligns its molecules. Such alignment may be considered as crystallization and it affects the material properties. For example, the strength of the fiber is greatly increased in the longitudinal direction. Some elastomers which are amorphous in the unstrained state undergo rapid crystallization upon stretching. In certain embodiments, use of sheet die 320 and nip rollers 332 may enhance crystallization of the thermoplastic sheet material 300 over the same thermopolymer that is injection molded, or over an extrusion process not using a sheet die 320 and/or nip rollers 332.
In some embodiments, the thickness of thermoplastic sheet material 300 after exiting sheet die 320 may be between about 0.04 inches and about 0.06 inches. Thermoplastic sheet material 300 after being conveyed through sheet die 320 may have aligned molecules 204 and may be more crystalline and less amorphous, for example, compared to a similar part that is injection molded. Crystallinity may depend on the thermoplastic material used. In some embodiments, thermoplastic sheet material 300 may have a crystallinity of between about 60% and about 85%. In some embodiments, the thermoplastic material is HDPE. Crystallinity may increase through the continuous roll molding process as the molecules are aligned and as the temperature is manipulated.
In some embodiments, the thermoplastic material may be heated in extruder 310 and sheet die 320, which may mix the thermoplastic material for extrusion into thermoplastic sheet material 300 that is at or above its melt temperature TM. In certain embodiments, e.g., for HDPE, TM may be between about 60 degrees Celsius and about 330 degrees Celsius, such as between about 100 and about 250 degrees Celsius, such as between about 190 and about 210 degrees Celsius. The melt temperature may be measured on a surface of thermoplastic sheet material 300 immediately upon exiting sheet die 320.
In some embodiments, method 1000 (
In some embodiments, after conveying thermoplastic sheet through sheet die 320 and before conveying thermoplastic sheet material 300 (
Calendering may cool thermoplastic sheet material 300 to a temperature below its melt transition point TM, or below the temperature at the exit of sheet die 320 (
Calendering system 330 may reduce or increase the temperature of one or more parts of thermoplastic sheet material 300 via one or more temperature-controlled nip rollers 332, 336. In addition, in some embodiments, thermoplastic sheet material 300 may be cooled and heated in different stages, dependent on the material properties needed for specific part formation in continuous roll molder 360 (e.g.,
In some cases, for example regarding HDPE, even if the sheet material is cooled quickly, the molecules of HDPE thermoplastic sheet material 300 may become more ordered and compact within the polymer chain, reducing the free volume of thermoplastic sheet material 300 and increasing crystallinity within the polymer chain. HDPE may have a glass transition temperature TG of between about −100 degrees Celsius and about −130 degrees Celsius, such as about −110 degrees Celsius, allowing HDPE thermoplastic sheet material 300 a broader working range for cooling such that the molecules may crystallize. Increasing order and compactness of the molecules via crystallization may result in a more stable, resistant, and strong material and may improve the chemical resistance, moisture resistance, and electrical insulation properties of the material more resistant to chemical attack and moisture absorption. In addition, the more ordered and compact structure of the molecules may improve the impact resistance, dimensional stability, and tensile strength of the material, as the more closely packed and stable structure of the molecules may make the material more resistant to deformation and more able to withstand external forces. The more ordered and compact structure may indicate crystallinity, which may be measured with differential scanning calorimetry, thermogravimetric analysis, and thermomechanical analysis.
In certain embodiments, the calendering process may control heat dissipation as thermoplastic sheet material 300 is fed through a plurality of temperature-controlled nip rollers 332, 336. Calendering in the continuous roll molding process, therefore, may create a constant and even contact with thermoplastic sheet material 300 to create even heat dissipation and prevent or limit warping. In contrast, quick cooling in injection molding may be uncontrolled. Accordingly, the crystallinity and form of parts as injection molded parts often shrink in the mold and at least some part elements do not contact the cavity in the mold, creating uneven cooling that may warp parts.
According to embodiments, the calendering process may introduce additional macromolecular alignment in the direction of material flow, as the process pulls and squeezes thermoplastic sheet material 300 in one feed direction. The macromolecular alignment from the calendering process may increase tensile strength and density of thermoplastic sheet material 300 to strengthen the material and improve part formation. In some embodiments, referring to
In an embodiment, calendering system 330 may reduce the thickness of thermoplastic sheet material 300 by adjusting the gap distance, speed and temperature of nip rollers 332, 336. In some embodiments, nip rollers 332, 336 may be arranged adjacent one another. In one embodiment, nip rollers 332 may be positioned along an axis 333 without intermediate structures such that they are adjacent. Similarly, nip rollers 336 may be positioned along an axis 337 without intermediate structures such that nip rollers 336 are adjacent. In some embodiments, two adjacent nip rollers 332, 336 may form a nip roller pair. Two or more adjacent nip rollers 332, 336 may be adjacent and proximate one another such that thermoplastic sheet material 300 may be conveyed through a nip gap 331 between two adjacent nip rollers 332, 336. In some embodiments, nip rollers 332, 336 may be arranged in a series, or linearly. Accordingly, nip rollers 332 may be positioned along axis 333 such that they are aligned. Similarly, nip rollers 336 may be positioned along axis 337 such that they are aligned. In some embodiments, nip rollers 332, 336 may be arranged vertically with respect to a surface plane P. In other words, nip rollers 332 may be aligned on axis 333, which may be perpendicular to surface plane P. Similarly, nip rollers 336 may be aligned on axis 337, which may be perpendicular to surface plane P.
As shown in
In some embodiments, calendering in calendering system 330 may impart a surface finish onto thermoplastic sheet material 300. In one embodiment, imparting a surface finish may be used to either increase or decrease material flow speeds in continuous roll molder 360 (
In some embodiments, nip rollers 332, 336 may have a gloss chrome, satin, or matte finish. In some embodiments, finishes from a gloss chrome surface may be between about 5 Ra and about 30 Ra, such as about 10 Ra, finishes from a matte surface may be between about 20 Ra and about 40 Ra, such as about 30 Ra, and finishes from a satin finish may be between about 70 Ra and about 130 Ra, such as about 100 Ra.
In some embodiments, each successive temperature-controlled pair of nip rollers 332, 336 in feed flow direction A (
In some embodiments, nip rollers 332, 336 may be set between about 30 degrees Fahrenheit and about 500 degrees Fahrenheit. In some embodiments, first nip roller 332a may approximately match the temperature of thermoplastic sheet material 300 (
In some embodiments, with reference to
In some embodiments, at the first stage of calendering in calendering system 330, nip rollers 332 may be at a greater temperature than secondary nip rollers 336 in the second stage of calendering in calendering system 330, dependent on the temperature and type of sheet material. In some embodiments, nip rollers 332, 336 may progressively cool from one nip roller 332, 336 to the next until thermoplastic sheet material 300 is cooled down enough to be below its melt transition TM, or reaches a desirable temperature for further processing.
In one embodiment, in setting secondary nip rollers 336 to be cooler than nip rollers 332, secondary nip rollers 336 may be referred to as chiller rolls, and may create a cooler upper surface 302 (
Instead of being arranged vertically as in
In some embodiments, the cooling of upper surface 302 (
Certain embodiments may provide for the reduction of memory in thermoplastic sheet material 300 through the pressurizing, heating and cooling of thermoplastic sheet material 300 through the continuous roller molds process. In other words, pre-cooled and/or pre-formed and spooled thermoplastic sheet material 300 that is in the format of a large spool maintains a memory of the shape of itself in the spool form, and e.g., may have a curve shape to the sheet. To remove this memory and prevent parts from being curved in the same way thermoplastic sheet material 300 is spooled, thermoplastic sheet material 300 may be heated to or above its melting point TM such that it is molten, and then chilled back down under its melting point TM, or its glass transition point TG again, thereby giving it a new memory and/or shape. In certain embodiments, this process may be achieved through temperature control stations 340.
In certain embodiments, as shown in
In some embodiments, a temperature control station 340 may be a heating station 342, e.g., a tenter oven, to provide heating. In some embodiments, a temperature control station 340 may be a cooling station 346, e.g., a cryogenic cooling station, to provide cooling. In some embodiments, a temperature control station 340 may be a cooling station 348, e.g., a water bath, to provide cooling.
In certain embodiments, heating and cooling temperature control stations 340 may be used or not used depending on what operations are required. If both heating and cooling are required, both heating station 342 and cooling station 348 may be used. For example, both heating and cooling may be required if upper surface 302 (
In some embodiments, if only heating is required, cooling station 348 may be offline. Similarly, if only cooling is required, heating station 342 may be taken offline. Temperature control stations 340 that are offline may convey thermoplastic sheet material 300 without active heating or cooling. In other words, temperature control stations 340 that are not used may be bypassed, or the thermoplastic sheet may traverse the temperature control station 340 without active cooling or heating being performed.
In some embodiments, the cooling of upper surface 302 (
In other embodiments, secondary heating or cooling by temperature control stations 340 may prepare thermoplastic sheet material 300 for part formation. Calendering may facilitate setting the temperatures and introduce lower pressure levels in a manner that begins to affect the polymer chain rotation and reptation of the macromolecules of the thermoplastic sheet and either reduce or increase free volume of the material. In some embodiments, this may help preset the macromolecular flow direction within thermoplastic sheet material 300 which may assist in optimizing the process of part formation in the continuous roll molders by creating more predictable material flow rates and enabling more accurate part shaping.
In other embodiments, secondary heating or cooling may adjust rotational speed of the polymer chains of the macromolecules of thermoplastic sheet material 300 (
In some embodiments, parts of calendering rolls may be configured to have slots, e.g., gaps 334, to limit or prevent temperature change, for example. In some embodiments, parts of thermoplastic sheet material 300 (
In certain embodiments, calendering HDPE thermoplastic material 300 may reduce the free volume and increase density. In some embodiments, free volume may decrease by up to about 40% to about 50%. In some embodiments, the HDPE thermoplastic material 300 may be calendered under pressure between about 8,000 psi and about 30,000 psi. The increased density may limit warp and shrinkage in part formation. In certain embodiments, experimental shrinkage rates may be between about 0.1% and 1% at temperatures between about 70 degrees Celsius and about 120 degrees Celsius and pressures between about 2,500 psi and about 80,000 psi.
Prior to being conveyed into continuous roll molder 360, in some embodiments, HDPE thermoplastic sheet material 300 may be stored and later reintroduced into the continuous roll molding process. For example, after calendering, HDPE thermoplastic sheet material 300 may be stored. HDPE thermoplastic sheet material 300 may be stored at any step before calendering alternative. HDPE thermoplastic sheet material 300 may spooled, for example, for storage.
In some embodiments, after calendering, thermoplastic sheet material 300 may be conveyed into continuous roll molder 360, shown in
In some embodiments, thermoplastic sheet material 300 may include a first density when exiting sheet die 320 (
With reference to
Referring again to
In some embodiments, thermoplastic sheet material 300 may be at a second temperature when entering continuous roll molder 360. In some embodiments, the second temperature may be lower than the first temperature of thermoplastic sheet material 300 after exiting sheet die 320 (
In some embodiments, continuous roll molder 360 may include heating and cooling lines 386 for a first mold, such as an upper mold 362. In some embodiments, continuous roll molder 360 may include heating and cooling lines 386 for a second mold, such as lower mold 388. In this way, upper mold 362 and lower mold 388 may be heated or cooled, thereby heating or cooling thermoplastic sheet material 300.
In an embodiment, intermediate portion 306 (
In some embodiments, continuous roll molder 360 may include a surface at a fifth temperature lower than the second temperature of upper surface 302 (
In some embodiments, one or more metal tracks and guides may align thermoplastic sheet material 300 to direct it through infeed roller guides 384 or nip rollers 383 in front of continuous roll molder 360 such that thermoplastic sheet material 300 enters continuous roll molder 360 evenly without buckling the sheet. Nip rollers 383 in front of continuous roll molder 360 may be matched to the speed of continuous roll molder 360 to provide for an even flow upon entry. In certain embodiments, the speed of nip rollers 383 may be set as low as about 20 feet per min after startup, and may be ramped up to over about 1,000 feet per min upon entry of thermoplastic sheet material 300.
With reference to
In some embodiments, with reference to
Referring to
In some embodiments, the continuous roll mold process using continuous roll molder 360 may limit complexity by shaping a part, e.g., a frangible cap strip, after an extrusion process. In other words, continuous roll molding is a post material processed part formation manufacturing process such that the thermoplastic material has already been processed through a sheet extrusion phase, prior to being formed into parts. In contrast to injection molding, continuous roll molding does not produce a part by forcing molten thermoplastics into a die to cool. In certain embodiments, continuous roll molding may allow thermoplastic sheet material 300 (
In certain embodiments, as shown in
In certain embodiments, continuous roll molder 360 may include one or more molds circuitously aligned around a roller. As shown in
In some embodiments, roll molder nip gap 382, shown in
In some embodiments, upper mold 362 may include one or more shapes 364. Shapes 364 as shown in
With reference to
In some embodiments, lower mold 362 may include one or more shapes 374 to impart a shape onto a part. In some embodiments, shapes 374 may include one or more surfaces to provide surfaces against which knives 366 of upper mold 362 may cut against. In this way, lower mold 362 may be an anvil against which knives 366 cut.
In addition, shapes 374 of lower mold 372 may be made of a less hard steel or aluminum in comparison to knives 366 of upper mold 362. Upper mold 362 and lower mold 372 may have between about a Rockwell B 30 to 105 hardness and about a Rockwell C 10 to 70 hardness. In certain embodiments as shown with reference to
In some embodiments, production tolerances may be within about 0.005 millimeters (mm). In other embodiments, depths within molds of continuous roll molder 360 may depend on part dimensions and material temperatures. In some embodiments, depths of walls that may be formed from thermoplastic sheet material 300 may be up to about 3 inches deep with an about 0.5 inch thick sheet. In other embodiments, the thermoplastic sheet material 300 may be stretched, moved, and thinned through the molds up to about 650% its original thickness, such as between about 300% and about 650%. In certain embodiments, thermoplastic sheet material 300 may be thinned between about 0.005 inch and about 4 inches.
In some embodiments, surface finishes may affect the part formation by increasing or decreasing surface contact between the finish on continuous roll molder 360 (FIG. 14), and the surfaces of thermoplastic sheet material 300, which may affect how thermoplastic sheet material 300 flows and forms in continuous roll molder 360. In certain embodiments, the gloss surface finish between about 0.2 Ra and about 16 Ra on continuous roll molder 360 may reduce the resistance to flow of thermoplastic sheet material 300, allowing it to flow more easily and uniformly into and through continuous roll molder 360. In other embodiments, a rougher matte surface finish from about 16 Ra to about 60 Ra may increase the resistance to flow of thermoplastic sheet material 300, leading to flow changes, allowing for increasing back pressure or a slowing of the flow, which is used for thickening and thinning particular dimensions in the final part. In still further embodiments, the rough satin finish between about 60 Ra and about 300 Ra may increase even more the resistance to flow of the material, leading to flow changes, allowing for increasing back pressure or a slowing of the flow, which is used for thickening and thinning particular dimensions in the final part.
In embodiments, the speed of the flow of thermoplastic sheet material 300 may be increased with the presence of larger, or more complex dimensions due to reduced surface contact, or the speed of the flow of the material may be reduced in simpler dimensions due to an increase in surface contact. In other words, the speed of flow of thermoplastic sheet material 300 may be slower across simpler dimensions having a lower surface roughness in comparison to larger or more complex dimensions having a higher surface roughness. Simpler dimensions may include the smooth or polished surfaces of continuous roll molder 360 or thermoplastic sheet material 300 while more complex dimensions may include first shape 364 and second shape 374 and rougher thermoplastic sheet material 300. Varying roughness may facilitate shaping and balancing features on the shapes on the part, as well as speed of exit from continuous roll molder 360 of the part and waste, which will be discussed further below.
In certain embodiments, as thermoplastic sheet material 300 (
Turning to
In some embodiments, shape 364 and shape 374 may be separated by a gap 379. Gap 379 may be between about 3 micron and about 7 micron, such as between about 4 micron and about 6 micron, such as about 5 micron. Gap 379 may facilitate kiss cutting, or cutting parts between upper mold 362 (
Nip gap 382 may be at least the same size as the larger of gap 379 and gap 381. Nip gap 382 may allow conveyance of thermoplastic sheet material 300 (
In some embodiments, upper mold 362 (
In some embodiments, upper mold 362 may include one or more shapes 364 and lower mold 372 may include one or more inserts 373 to form thermoplastic sheet material 300 (
In some embodiments, insert 373 may include material that expands at a greater rate under heat in comparison to the material of shape 364 (
In certain embodiments, insert 373 may include a mixture of aluminum and other materials, in other embodiments, insert 373 may include non-aluminum materials. These materials, like aluminum, may expand at a greater rate in comparison to steel such that insert 373 may act as a bumper between shape 374 of upper mold 362 and shape 374 of lower mold 372. As a bumper, insert 373 may lift upper mold 362 away from lower mold 372 to maintain a gap therebetween. In some embodiments, insert 373 may be within shape 374 of lower mold 372. Alternatively, insert 373 may be disposed adjacent a respective shape 374. In some embodiments, multiple inserts 373 may be disposed along lower mold 372 such as both within and next to shapes 374 of lower mold 372. In some embodiments, insert 373 may be outside of continuous roll molder 360 and may extend between upper mold 362 and lower mold 372 to act as a bumper.
In certain embodiments, heat from the operations of the continuous roll molder 360 may cause the upper mold 362, lower mold 372, and frame 393 and other components to expand. This may result in a decrease in gap distances, e.g., gap 379 (
In some embodiments, during the continuous roll molding process, continuous roll molder 360 (
In some embodiments, temperature control may maintain certain temperatures of one or more individual components of continuous roll molder 360 (
In some embodiments, temperature control unit 404 may be coupled to chiller 402. Chiller 402 may distribute the temperature-controlled mixture to temperature control unit 404, which may adjust the temperature of the temperature-controlled mixture. In some embodiments, temperature control unit 404 may warm the temperature-controlled mixture. In some embodiments, the temperature of the temperature-controlled mixture is set to between about 5 and about 15 degrees above the temperature of a frame 393 (
Referring to
As shown, the temperature-controlled mixture may flow through bearing block 365 and through one or more molds, e.g., upper mold 362 lower mold 372. In one embodiment, the temperature-controlled mixture may flow through upper mold 362 and through lower mold 372 in series, and exit through bearing block 365 to return to chiller 402. In another embodiment, the temperature-controlled mixture may flow through upper mold 362 and lower mold 372 in parallel, and exit frame 393 to return to chiller 402. A series of channels 379 may extend through each of upper mold 362 and lower mold 372 to circulate the temperature-controlled mixture through upper mold 362 and lower mold 372.
With reference to
One or more parts of continuous roll molder 360 may be monitored to maintain gap distances. For example, with reference to
Differing speeds of the material flow through continuous roll molder 360 and components thereof, such as shape 364 of upper mold 362 and shape 374 of lower mold 372, may create specific challenges to consistent part formation. Increasing the pressure on upper mold 362 and lower mold 372 directs material flow through differing geometric shapes, such as such as shape 364 and shape 374. However, in certain embodiments, increasing pressure may create back pressure and forward pressure which causes material to move at different speeds through continuous roll molder 360. Referring to
In some embodiments, waste and product diverter 394 may be mounted directly inside of the frame of continuous roll molder 360. In some embodiments, switchable product and waste guide tooth 395 may be adjacent to the face of continuous roll molder 360, or mounted outside of the frame, where the product and waste thermoplastic sheet material 308 enter further from the face of continuous roll molder 360. When continuous roll molder 360 forms product 100, the product and waste thermoplastic sheet material 308 may come out of continuous roll molder 360 at different speeds. Waste and product diverter 394 may act to separate the two streams.
In some embodiments, waste and product diverter 394 may capture waste thermoplastic sheet material 308 as it exits continuous roll molder 360, since it is located by the face of continuous roll molder 360. In some embodiments, waste thermoplastic sheet material 308 may be sent to a grinder for chopping and reintroduction into the extruder hopper as recycled material.
In some embodiments, waste diverter guide tooth 399 may be positioned adjacent to continuous roll molder 360 to feed exiting product into outfeed track guide 396. In some embodiments, outfeed track guide 396 may separate each stream of product 100 into individual lanes away from other product streams to avoid product streams from intersecting. Product may then be accumulated and spooled.
In some embodiments, at least one of product 100 and waste guide tooth 395 and waste diverter guide tooth 399 are switchable. Accordingly, the product guide teeth may switch up or down via an air cylinder, and may change the direction of the product stream from going towards the accumulator and send it into the waste and regrind streams instead. In other embodiments, rejecting the product lines into the waste stream may occur after product 100 stream passes through outfeed track guide 396.
In some embodiments, once parts 100 exit continuous roll molder 360, they may be conveyed by nip roller guide 398 on the other side that may have adjustable speeds. In some embodiments, nip roller guide 398 may be set to the same speed as molds of continuous roll molder 360. Nip roller guide 398 may not only feed the parts out and into a guided rail, but may also add a few last elements to the product. In some embodiments, with speeds set higher than speeds of continuous roll molder 360, nip roller guide 398 may also thin parts 100, particularly in frangible areas, or with speeds set lower than speeds of continuous roll molder 360, nip roller guide 398 may thicken parts. Accordingly, nip roller guide 398 may be used to adjust the shear force values of parts, particularly in frangible areas.
Referring to
In some embodiments, nip rollers 387, which may be lower nip rollers, may receive stream 408 of waste thermoplastic sheet material 308 from continuous roll molder 360. Stream 408 may be conveyed through the pair of nip rollers 387, which may convey stream 408 to continue the stream of waste thermoplastic sheet material 308 away from parts 100. In some embodiments, stream 408 may be angled downward via nip rollers 387 to separate from stream 406 of parts 100. In other embodiments, stream 406 may be angled upward via a bar 389, which may be an upper bar. In one embodiment shown in
Surface roughness of one or more of thermoplastic sheet material 300 (
According to an embodiment with reference to
As shown, lower mold 372 may include a plurality of shapes 374. In some embodiments, shapes 374 may be arranged in pairs, the pairs being arranged in a first series 378 and a second series 380. In some embodiments, first series 378 and second series 380 are adjacent. In some embodiments, first series 378 and second series 380 are adjacent and offset such that pairs of shapes 374 of first series 378 are offset from pairs of shapes 374 of second series 380. In some embodiments, shapes 374 may be arranged in pairs arranged in a third series 381. In some embodiments, first series 378 and second series 380 are adjacent and offset from third series 381 such that pairs of shapes 374 of first series 378 and second series 380 are adjacent and offset from pairs of shapes 374 of third series 380. In other embodiments, the shapes 374 of the first, second, and third series may be arranged as a single, triple, quadruple, or any number of shapes aligned in a row, and the lower mold may include more than three series.
Certain embodiments provide for the use of roller deflection to accommodate the roller deflection for the purposes of even product formation and production. If a roller is designed such that all shapes align and are not offset, the roller pressure may peak and valley as the roller turns. When the roller reaches the portion of the shape corresponding to the highest pressure on the part, the roller pressure may peak. When the roller reaches the portion of the shape corresponding to the lowest pressure on the par, the roller pressure may valley. In embodiments where the molds shapes are offset, the portions of each shape corresponding to the highest pressure on the part are out of phase, which even out the roller pressure, and may help prevent roller deflection, which may result in more even product formation.
Certain embodiments provide for the use of waste trenches in continuous roll molder 360 for pressure relieving on the parts and waste. The waste trenches may exist in between each row of product strips, and include zones that are milled down into the face of the molds, creating a continuous gap that allows for the waste to slide into the gap as it moves through continuous roll molder 360. Accordingly, pressure on continuous roll molder 360 is reduced as waste is not pressed upon by the molds, the roller pressure being generated by the pressure on the shapes only.
Referring to
Draft angles are needed in injection molding for part release due to vacuum, as shown in
In one embodiment, upper mold 362 and lower mold 372 of continuous roll molder 360 are shown in
In addition, because the part shape is incorporated along a circumference, the molds of continuous roll molder 360 (
In embodiments, roller molder 360 does not introduce a vacuum into upper mold 362 and lower mold 372 cavities. In other embodiments, roller molder 360 does not include ejector pins, air pressure, or other means of releasing the parts from the upper mold 362 and lower mold 372 cavities.
In some embodiments, minimal or no draft designs are created in the part from continuous roll molding due to no vacuum being present since molds of continuous roll molder 360 are in an open position 361 with respect to the atmosphere. Being in open position 461 may allow for inverse draft/draw designs, as the parts still flow. Open position 461 of the molds may prevent the forming of a mold vacuum, which may form along vertical mold side walls or surfaces in injection molding. Accordingly, in embodiments of continuous roll molding, the molded parts, unbounded by vertical mold walls or surfaces, may not need to break a mold vacuum for release
In certain embodiments, use of thermoplastic sheet material 300 (
In certain embodiments, the pressures of continuous roll molder 360 (
In certain embodiments, the continuous roll mold process described herein may improve speed and volume for producing parts, e.g., a frangible cap strip. For example, according to some embodiments, six lanes running on the continuous roll molder at about 60 linear feet per minute, may produce about 4,320 caps per minute. In some embodiments, the continuous roll molder at about 1,200 linear feet per minute may produce about 86,400 caps per minute. In contrast, injection molding with six lanes at about 15 second cycles may produce about 360 caps per minute.
In certain embodiments, continuous roll molding may produce complex parts with certain benefits over injection molded parts, including but not limited to greater depths, the formation of geometric elements having tightly engineered tolerances and low shrinkage rates. The continuous roll molding process may produce within a tolerance of about 0.001 inches, or within about 0.0762 mm, and may not require draft angles in parts. In contrast, injection molding may have tolerances within about 0.005 inches with an approximate 0.5-degree draft angle minimum. In addition, injection molding requires adding about one degree of draft for about every one inch of depth. In some embodiments, the shrinkage rate of the continuous roll molding process is between about 0.5% and about 1%. In contrast, the injection mold process has a shrinkage rate of about 2% and about 4%.
Manufacturing a frangible cap strip product by the continuous roll molding system and method will now be described with reference to
Referring to
In an embodiment, the HDPE may have a tensile strength of between about 3,500 psi and about 6,600 psi, such as about 3,900 psi. After processing the HDPE may have a tensile strength of between about 4,600 psi and about 4,800 psi. In an embodiment, the HDPE may have a shear strength of between about 4,600 psi and about 4,800 psi. In an embodiment, the HDPE may have a shear strength of about 4,800 psi. In an embodiment, the HDPE may have a tensile strength of between about 0.93 g/cm3 and about 0.97 g/cm3, or between about 27 megapascal (MPa) and about 33 MPa, or between about 1,700 psi and about 8,400 psi, such as about 5,000 psi. In an embodiment, the HDPE may have a tensile modulus of between about 600 MPa and about 1,550 MPa, such as about 1,280 MPa. In an embodiment, the HDPE may have a tensile elongation of between about 450% and about 600%, such as between about 450% and about 500%. In an embodiment, the HDPE may have a melt flow rate between about 0.3 g/10 min and about 30 g/10 min, such as about 0.35 g/10 min.
As discussed above with reference to
HDPE macromolecules may be aligned as they extrude through sheet die 320. Therefore, HDPE thermoplastic sheet material 300 after being conveyed through sheet die 320 may have aligned molecules 204 of HDPE macromolecules and may be more crystalline and less amorphous. In some embodiments, HDPE thermoplastic sheet material 300 may have a crystallinity of between about 70% and about 80% before entering the roll molder 360.
In some embodiments, the HDPE thermoplastic material may be heated in extruder 310 and sheet die 320, which may mix the HDPE thermoplastic material for extrusion into HDPE thermoplastic sheet material 300 that is at or above its melt temperature TM, which may be between about 60 degrees Celsius and 330 degrees Celsius, such as between about 100 and about 250 degrees Celsius, such as between about 190 and about 210 degrees Celsius. The melt temperature may be measured on a surface of HDPE thermoplastic sheet material 300 immediately upon exiting sheet die 320. In some embodiments, the vicat softening temperature of the HDPE maybe at about 127 degrees Celsius.
With reference to
In some embodiments, intermediate portion 306 (
In some embodiments, HDPE thermoplastic sheet material 300 may include a first density when exiting sheet die 320. In some embodiments, the first density when exiting sheet die 320 may be between about 0 g/cm3 and about 2 g/cm3, such as about 0 g/cm3, as HDPE thermoplastic sheet material 300 is mostly molten at this stage.
As discussed above, in some embodiments, after conveying HDPE thermoplastic material through sheet die 320 and before conveying HDPE thermoplastic sheet material 300 (
With reference to
As calendering in calendering system 330 cools HDPE thermoplastic sheet material 300 below its melt temperature TM, heating and cooling of HDPE thermoplastic sheet material 300 below the melt temperature TM of HDPE thermoplastic sheet material 300 may occur, and within the glass transition temperature (e.g., above TG), but above the ductile brittle transition temperature which may be between about −118 degrees Celsius and about −70 degrees Celsius, such as about −80 degrees Celsius. Nip rollers 332, 336 may be maintained below the melt temperature TM and above the ductile brittle transition temperature, a range of between about 0 degrees Celsius and 220 degrees Celsius for HDPE thermoplastic sheet material 300, such as between about 5 degrees Celsius and about 100 degrees Celsius, such as between about 15 degrees Celsius and about 30 degrees Celsius. For heating or cooling surfaces polyethylene HDPE thermoplastic sheet material 300, one of a pair of nip rollers 332, 336 may be set to a higher temperature, while the other may be set to a lower temperature. As discussed below, nip rollers 332 may be at about the temperature of HDPE thermoplastic sheet material 300 after being conveyed through sheet die 320 (
In some embodiments, first nip roller 332a may be between about 180 and about 200 degrees Celsius, such as about 190 degrees Celsius. In some embodiments, first nip roller 332a may have a gloss finish of between about 10 Ra and about 30 Ra. In some embodiments, second nip roller 332b may be cooler than first nip roller 332a. In some embodiments, second nip roller 332b may be between about 150 and about 170 degrees Celsius, such as about 160 degrees Celsius. In some embodiments, second nip roller 332b may have a satin finish of between about 90 Ra and about 110 Ra, such as about 100 Ra. In some embodiments, third nip roller 332c may be cooler than second nip roller 332b. In some embodiments, third nip roller 332c may be between about 120 and about 140 degrees Celsius, such as about 130 degrees Celsius. In some embodiments, third nip roller 332c may have a gloss finish.
Secondary nip rollers 336 may be cooler than nip rollers 332, rendering the secondary nip rollers 336 chiller rolls to create a cooler upper surface 302 (
In some embodiments, secondary nip rollers 336 may be cooler than third nip roller 332c. In some embodiments, secondary nip rollers 336 may be between about 0 degrees Celsius and about 100 degrees Celsius, such as between about 60 degrees Celsius and about 80 degrees Celsius, such as about 70 degrees Celsius.
In certain embodiments, to have a softer intermediate portion 306, secondary nip rollers 336 may be at about 0 degrees Celsius while nip roller 332a may be at about 190 degrees Celsius, nip roller 332b may be at about 140 degrees Celsius, and nip roller 332c may be at about 100 degrees Celsius.
As, discussed above, the speed of nip rollers 332, 336 may be adjusted in accordance with the temperatures required for achieving a particular thickness of thermoplastic sheet material 300 to be formed. For example, if HDPE thermoplastic sheet material 300 needs to be reduced from about 190 degrees Celsius to about 100 degrees Celsius, and is moving at about 60 linear feet per min, the temperature of nip rollers 332, 336 may be adjusted down in about 30 degrees Celsius increments from about 190 degrees Celsius at nip roller 332a, to about 160 degrees Celsius at nip roller 332b, to about 130 degrees Celsius in nip roller 332c, through guide and tension rollers 338, to nip rollers 336, which may be set at about 100 degrees Celsius. The temperature of nip rollers 332, 336 may be measure on the surface of nip rollers 332, 336.
Referring to
Crystallinity may be represented by density. In some embodiments, the density of HDPE thermoplastic sheet material 300 may be between about 0.93 g/cm3 and about 0.97 g/cm3 after the calendering process. In some embodiments, after being processed in continuous roll molder 360 (
As discussed above, after calendering, HDPE thermoplastic sheet material 300 may be conveyed into continuous roll molder 360, shown in
In some embodiments, the thickness of HDPE thermoplastic sheet material 300 may be between 0.04 inches and 0.05 inches when entering continuous roll molder 360, such as about 0.045 inches.
In some embodiments, HDPE thermoplastic sheet material 300 may include a second density when entering continuous roll molder 360 greater than the first density after exiting sheet die 320 (
In some embodiments, HDPE thermoplastic sheet material 300 may be at a second temperature when entering continuous roll molder 360. In some embodiments, the second temperature of HDPE thermoplastic sheet material 300 may be lower than the first temperature after exiting sheet die 320 (
In some embodiments, upper surface 302 (
In some embodiments, continuous roll molder 360 may include a surface at a fifth temperature lower than the second temperature of upper surface 302 (
As shown in
As discussed above, nip roller guide 398 may stretch out the frangible elements of the cap strip, narrowing them further to reduce the shear force needed to sever them. With set speeds of continuous roll molder 360, nip roller guide 398 may act to compress the frangible elements of the cap strip, thickening them to increase the shear force needed to cut them. Accordingly, nip roller guide 398 may be used to adjust the shear force values of the frangible elements of the cap strips up and down.
As shown in
In some embodiments, the speed of upper mold 362 and lower mold 372 may be between about 1 revolutions per min (rpm) and about 400 rpm, such as about 20 rpm, when product is being conveyed at about 1 foot per second. In some embodiments, for every foot per second increase, the speed of upper mold 362 and lower mold 372 may be increased by 20 rpms.
In some embodiments, upper surface 302 (
With reference to
As HDPE thermoplastic sheet material 300 (
In some embodiments, the density of the frangible cap strip parts after being conveyed through continuous roll molder 360 may be between about 1 g/cm3 and about 2 g/cm3, such as about 1.27 g/cm3.
Parts 100, such as frangible cap strip parts 100, may exit continuous roll molder 360 along a separate stream from waste thermoplastic sheet material 308, as shown with reference to
Experimental results from an injection molding process and the continuous roll molding process for forming frangible cap strips described herein will now be described with reference to
In injection molding, there is limited or no control over the direction of macromolecular flow. Accordingly, the plastic macromolecules may tumble, squeeze, and roll through the injection ports and dies, filling cavities and shapes in a random, uncontrolled manner.
As shown, consistent edges 35 are imparted by the continuous roll molding process and the thermoplastic macromolecular flow directions in thermoplastic sheet material 300 (
Embodiments of the frangible cap strip part formed by the continuous roll mold system and method described herein will now be described with reference to
An embodiment of cap 110 of a frangible cap strip product is shown in
In the molds of continuous roll molder 360, thermoplastic sheet material 300 may be flowing in a general direction with the entire production line as indicated by the arrows in
Flow channels 132 shown in
In embodiments, cap 110 may include one or more depressions 117. In some embodiments, bottom side 114 may include a first depression 118. In some embodiments, bottom side may include a second depression 122. In some embodiments, bottom side 114 may include first depression 118 and second depression 122.
In some embodiments, first depression 118 may act as a material anchor or stop to prevent or reduce sliding of thermoplastic sheet material 300 (
In an embodiment, first depression 118 may include a circular shape. In some embodiments, second depression 122 may be a flow channel to facilitate flow of thermoplastic sheet material 300. In an embodiment, second depression 122 may include a kidney shape. In an embodiment, second depression 122 may have a ramped edge to facilitate material flow. In some embodiments, cap 110 may include a plurality of first depressions 118. In some embodiments, cap 110 may include a plurality of second depressions 122. In some embodiments, cap 110 may include a plurality of first depressions 118 and a plurality of second depressions 122.
With reference to the embodiment shown in
Second depression 122 may be positioned along a second axis 125 perpendicular to first axis 101. In some embodiments, a plurality of second depressions 122 may be positioned along second axis 125. As shown in
Each cap 110 may be spaced from one another. In some embodiments, frangible cap strip 100 may include a plurality of frangible tabs 140. Each frangible tab 140 may join adjacent caps 110. In some embodiments, each cap may be between about 0.5 inch by about 0.5 inch and about 2 inches by about 2 inches, such as about 1 inch by about 1 inch. With reference to
In some embodiments, each frangible zone 160 may include thermoplastic sheet material 300 (
Frangible zone 160 may facilitate shearing to allow for release of a cap 110 from frangible cap strip 100. For example,
In some embodiments, frangible zone 160 may include a depression 162, a shear line 176, and a divot 178 disposed at shear line 176. Accordingly, frangible zone 160 may be bounded by depression 162 and divot 178. In some embodiments, divot 178 may be closer along first axis 101 to first one of the pair of adjacent caps 110a than to second one of the pair of adjacent caps 110b. In some embodiments, divot 178 may be perforated to facilitate shearing at shear line 176. Divot 178 may be a depression along shear line 176 that is kiss cut in the continuous roll molding process. As discussed above, in some embodiments, the continuous roll molding process may impart perforation on divot 178. Accordingly, divot 178 may be partially cut along its length to facilitate shearing at shear line 176. In some embodiments, divot 178 may be cut along its entire length such that shear line 176 is partially cut before being sheared.
In some embodiments, each frangible tab 140 may include a first tab portion 150a formed between divot 178 and first one of the pair of adjacent caps 110a. Similarly, in some embodiments, each frangible tab 140 may include a second tab portion 150b formed between divot 178 and second one of the pair of adjacent caps 110b. In some embodiments, first tab portion 150a may be adjacent a second side 126 of second one of the pair of adjacent caps 110b. In some embodiments, second tab portion 150b may be adjacent a second side 128 of first one of the pair of adjacent caps 110a.
With reference to
Referring to
With reference to
In embodiments, depression 162 may extend into hinge element 184, as shown with reference to
Top sides 112 of a cap 110 is shown in
In some embodiments, depression 162 may be substantially T-shaped. As shown, depression 162 may include a first portion 164 and a first portion 172. In some embodiments, first portion 164 and first portion 172 may be the same length. In some embodiments, first portion 164 and first portion 172 may have different lengths. In some embodiments first portion 164 may have a length 166. In some embodiments, first portion 172 may have a length 173 smaller than length 166. In some embodiments, length 166 may be between about 0.2 inch and about 0.4 inch, such as about 0.29 inch. In some embodiments, length 173 may be between about 0.05 inch and about 0.3 inch, such as about 0.15 inch. In some embodiments, first portion 164 may have a width 168. In some embodiments, first portion 172 may have a width 175 equal to width 168. In some embodiments, a transition 174 between first portion 164 and first portion 172 may include a curve.
As shown in
With reference to
An embodiment of bottom side 114 of a cap 100 is shown in
Depression 162 may be disposed between ends of second tab portion 150b. As shown in
In some embodiments, thickness of part shapes is increased over the thickness of thermoplastic sheet material 300 (
With reference to
As discussed, the continuous roll molding process may provide a variety of finishes to parts. With reference to
As shown in
Referring to
As shown in
At the end of the track following feed flow direction A, nail cap strip 1100 may be spooled, in some embodiments. With reference to
Injection molded nail caps, in contrast, create caps individually in single cavity molds. The individual caps are then collected in a bin and transported to an assembly station, where they are dispersed onto a table and manually coupled to nails. The process described herein to produce nail cap strip 1100 (
It should be noted that the use of particular terminology when describing certain features or embodiments of the disclosure should not be taken to imply that the terminology is being re-defined herein to be restricted to include any specific characteristics of the features or embodiments of the disclosure with which that terminology is associated. Terms and phrases used in this application, and variations thereof, especially in the appended claims, unless otherwise expressly stated, should be construed as open-ended as opposed to limiting. As examples of the foregoing, the term “including” should be read to mean “including, without limitation,” “including but not limited to,” or the like; the term “comprising” as used herein is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps; the term “having” should be interpreted as “having at least”; the term “such as” should be interpreted as “such as, without limitation”; the term “includes” should be interpreted as “includes but is not limited to”; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof, and should be interpreted as “example, but without limitation”; adjectives such as “known,” “normal,” “standard,” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass known, normal, or standard technologies that may be available or known now or at any time in the future; and use of terms like “preferably,” “preferred,” “desired,” or “desirable,” and words of similar meaning should not be understood as implying that certain features are critical, essential, or even important to the structure or function of the present disclosure, but instead as merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment.
Likewise, a group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should be read as “and/or” unless expressly stated otherwise. The terms “about” or “approximate” and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range may be ±20%, ±15%, ±10%, ±5%, or +1%. The term “substantially” is used to indicate that a result (e.g., measurement value) is close to a targeted value, where close may mean, for example, the result is within 80% of the value, within 90% of the value, within 95% of the value, or within 99% of the value. Also, as used herein “defined” or “determined” may include “predefined” or “predetermined” and/or otherwise determined values, conditions, thresholds, measurements, and the like.
This application claims priority to U.S. Provisional Application No. 63/454,239, filed Mar. 23, 2023, which is incorporated herein in its entirety by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 63454239 | Mar 2023 | US |
