Patent Application
20220395962
The invention relates to methods of manufacturing abrasive rotary tools.
Handheld electronics, such as touchscreen smartphones and tablets, often include a cover glass to provide durability and optical clarity for the devices. Production of cover glasses may use computer numerical control (CNC) machining for consistency of features in each cover glass and high-volume production. The edge finishing of the perimeter of a cover glass and various other features, such as a camera hole, is important for strength and cosmetic appearance. Typically, diamond abrasive tools, such as metal bonded diamond tools, are used to machine the cover glasses. These tools may last a relatively long time and may be effective at high cutting rates. However, the tools may leave microcracks in the cover glass that become stress concentration points, which may significantly reduce the strength of the glass. To improve the strength or appearance of the cover glasses, the edges may be polished. For example, a polishing slurry, such as cerium oxide, is typically used to polish the glass covers. However, slurry-based polishing may be slow and require multiple polishing steps. Additionally, slurry polishing equipment may be large, expensive, and unique to particular features being polished. Overall, the slurry polishing systems themselves may produce low yields, create rounded corners of the substrate being abraded, and increase labor requirements.
The disclosure is generally directed to durable molded abrasive rotary tools that may be manufactured quickly and/or inexpensively. Exemplary abrasive rotary tools may include an elastic layer formed in a mold between a spindle and an abrasive sheet without the use of adhesive layers. In this way, an abrasive rotary tool may resist delamination and require reduced post-processing for concentricity.
In one embodiment, the present disclosure provides a method of making an abrasive rotary tool includes providing a mold having a cavity with a peripheral surface and providing an abrasive sheet having a working surface and an opposed surface, in which the working surface is adjacent to and along at least a portion of the peripheral surface of the mold. The method includes providing a spindle having an exterior surface within the mold and creating a region between the exterior surface of the spindle and the peripheral surface of the mold. The method includes injecting an elastomeric precursor material into the region and solidifying the elastomeric precursor material to form an elastic layer, such that the elastic layer is in contact with at least a portion of the opposed surface of the abrasive sheet and at least a portion of the exterior surface of the spindle.
In another embodiment, the present disclosure provides an abrasive rotary tool comprising an abrasive sheet having a working surface and an opposed surface; a spindle having an exterior surface; and an elastic layer, wherein the elastic layer is in contact with at least a portion of the opposed surface of the abrasive sheet and at least a portion of the exterior surface of the spindle, wherein the abrasive sheet is coupled to the elastic layer by only adhesive forces at the contact between the at least a portion of the opposed surface of the abrasive sheet and the elastic layer. In some embodiments, the elastic layer is a unitary body.
The details of one or more embodiments of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like symbols in the drawings indicate like elements. Dotted lines indicate optional or functional components, while dashed lines indicate components out of view.
The present disclosure describes abrasive rotary tools that feature an elastic layer formed in a mold and bonded to adjacent surfaces without an adhesive layer and/or fastening means.
Conventional abrasive rotary tools may include a rod, a support layer, an abrasive sheet, and one or more adhesive layers between the support layer and the rod and/or abrasive sheet. For example, to form such conventional abrasive rotary tools, a support layer may be formed as a sheet and wrapped around the rod. An abrasive sheet that includes an adhesive backing layer on an inner surface of the abrasive sheet may be wrapped around the preformed support layer.
The aforementioned abrasive rotary tools may be relatively time-consuming to assemble. For example, each of the abrasive sheet, support layer, and adhesive layers may be precisely placed on a preceding surface such that the respective layers substantially align. The rod may be machined prior to positioning of the support layer on the rod to improve a conformal fit of the preformed support layer. Once positioned on the rod, the support layer may be further machined to improve concentricity prior to positioned the abrasive sheet on the support layer. The aforementioned abrasive rotary tools may also be relatively weak and susceptible to delamination between the support layer and adjacent layers. Each adhesive layer in the abrasive rotary tool may be a weak point of the abrasive rotary tool. For example, a support layer formed from rubber may have a relatively low surface energy, such that the support layer may be difficult to securely bond to the abrasive sheet through an adhesive layer. During operation, an interface between the support layer and the abrasive sheet may repeatedly deform to conform to an edge of a substrate, which may create delamination forces between the adhesive layer and the support layer. Due to the poor bonding between the abrasive sheet and the support layer through the adhesive layer, the abrasive sheet may delaminate from the support layer, reducing a service life of the abrasive rotary tool.
According to embodiments of the present disclosure, an abrasive rotary tool may include an elastic layer formed in a mold and directly coupled to a spindle and an abrasive sheet without the use of an adhesive layer. When forming the abrasive rotary tool, the spindle may be positioned at a center of a cavity of the mold to form a core within the cavity, while the abrasive sheet may be positioned along a peripheral surface of the cavity to form a surface around the cavity, thereby creating a void region between an exterior surface of the spindle and an opposed surface of the abrasive sheet. An elastomeric precursor material may be injected into the void region between the spindle and the abrasive sheet and solidified to form an elastic layer. As a result of this solidification in the presence of the abrasive sheet and the spindle, the elastic layer is in direct contact with at least a portion of the opposed surface of the abrasive sheet and at least a portion of the exterior surface of the spindle. Further, the abrasive sheet is coupled to the elastic layer by only adhesive forces at the contact between the at least a portion of the opposed surface of the abrasive sheet and the elastic layer, i.e. the abrasive rotary tool is free of one or more adhesive layers (e.g. a pressure sensitive adhesive, a thermoset adhesive and/or a hot melt adhesive) disposed between the opposed surface of the abrasive sheet and the elastic layer and the rotary tool is free of one or more fastening means (e.g. a clip, clamp, and/or band) suitable for attaching the abrasive sheet to the elastic layer. In some embodiments, the spindle is coupled to the elastic layer by only adhesive forces at the contact between the at least a portion of the exterior surface of the spindle and the elastic layer, i.e. the abrasive rotary tool is free of one or more adhesive layers (e.g. a pressure sensitive adhesive, a thermoset adhesive and/or a hot melt adhesive) disposed between the exterior surface of the spindle and the elastic layer and the rotary tool is free of one or more fastening means (e.g. a clip, clamp, and/or band) suitable for attaching the spindle to the elastic layer. In this way, the resulting abrasive rotary tools may have improved resistance to delamination without the use of adhesive layers and/or fastening means for combining the abrasive sheet and/or spindle to the elastic layer and may be quickly manufactured without concentric machining. In some embodiments, the abrasive rotary tool is free of a primer layer capable of facilitating bonding between the at least a portion of the opposed surface of the abrasive sheet and the elastic layer. In some embodiments, the abrasive rotary tool is free of a primer layer capable of facilitating bonding between the at least a portion of the exterior surface of the spindle and the elastic layer.
Substrate 16 is mounted and secured to substrate platform 22 in a manner that facilitates precise machining of substrate 16 by machining system 12. Substrate holding fixture 24 secures substrate 16 to substrate platform 22 and precisely locates substrate 16 relative to machining system 12. Substrate holding fixture 24 may also provide a reference location for control programs of machining system 12. While the techniques disclosed herein may apply to workpieces of any materials, substrate 16 may be a component for an electronic device. In some embodiments, substrate 16 may be a display element, e.g., a transparent display element, of an electronic device, such as a cover glass for an electronic device or, more particularly, a cover glass of a smartphone touchscreen. For example, such cover glasses, back covers, or back housings may include edges for which a high degree of planarity and angularity is desired.
In some embodiments, substrate 16 may include a first major surface 2 (e.g. a top of substrate 16), a second major surface 4 (e.g. a bottom of substrate 16), one or more edge surfaces 6 (e.g. sides of substrate 16), and one or more holes 7 having an edge around a circumference of each of holes 7. The area of edge surface 6 of substrate 16 is typically less than the area of the first major surface and/or second major surface of substrate 16. In some embodiments, the ratio of edge surface 6 of substrate 16 to the area of first major surface 2 of substrate 16 and/or the ratio of edge surface 6 of substrate 16 to the area of second major surface 4 of substrate 16 may be greater than 0.00001, greater than 0.0001, greater than 0.0005, greater than 0.001, greater than 0.005 or even greater than 0.01; less than 0.1, less than 0.05 or even less than 0.02. In some embodiments, a thickness of edge surface 6 measured normal to first and/or second major surfaces 2, 4, is no greater than 15 mm, no greater than 4 mm, no greater than 3 mm, no greater than 2 mm or even no greater than 1 mm. Edge surface 6 intersects first major surface 2 to form a first corner 3 and intersects second major surface 4 to form the second corner 5. In some embodiments, edge surface 6 may be substantially perpendicular to each of major surfaces 2, 4, while in other examples, edge surface 6 may include more than one edge surface, wherein at least one of the more than one edge surfaces is not perpendicular (e.g., a chamfered edge, rounded edge, curved edge or combination of edge shapes).
In the embodiment of
In accordance with embodiments discussed herein, abrasive rotary tool 18 may be configured with increased resistance to delamination.
Instead of coupling elastic layer 36 to abrasive sheet 38 and spindle 34 through adhesive layers, layer 36 is in direct contact with at least a portion of opposed surface 42 of abrasive sheet 38 and at least a portion of exterior surface 40 of spindle 34. For example, an elastic precursor material, which will form elastic layer 36, may contact opposed surface 42 and exterior surface 40 as a fluid and cure into a solid or foam so that the resulting elastic layer 36 is in direct contact with at least a portion of opposed surface 42 and at least apportion of exterior surface 40. In this way, abrasive rotary tool 18 may be quickly manufactured without the use of adhesive layers or significant post-machining processes.
In operation, abrasive rotary tool 18 may have increased durability for greater longevity. For example, spindle 34 may be configured to receive an applied force from a rotary tool holder, such as a rotational force around the axis of rotation of spindle 34 and, optionally, a directional force along at least one of an x-, y-, or z-axis, and transmit at least a portion of the applied force to abrasive article 32. Abrasive article 32 may be configured to receive the applied force from spindle 34, such as a rotational force around the axis of rotation of spindle 34 and, optionally, a directional force along at least one of an x-, y-, or z-axis, and transmit at least a portion of the applied force to abrasive sheet 38. This rotational applied force may pull abrasive sheet 38 from elastic layer 36 and elastic layer 36 from spindle 34. Directly coupling abrasive sheet 38 to elastic layer 36 and/or elastic layer 36 to spindle 34 may create a stronger bond between adjacent layers than if an adhesive layer was used to bond adjacent layers. In this way, abrasive rotary tool 18 may have improved resistance to delamination of abrasive sheet 38 from elastic layer 36 and/or elastic layer 36 from spindle 34. In some embodiments, the elastic layer is a unitary body. A unitary body refers to a construction that does not have any internal interfaces, joints, or seams. In some cases, a unitary body is capable of being formed in a single forming step such as casting or molding A unitary body is not formed by bonding components parts together. In some embodiments the elastic layer may be multiple elastic layers, either in the radial direction and/or the axial direction (e.g. axis 48).
Additionally, or alternatively, abrasive rotary tool 18 may have high conformability for consistent abrading. For example, a preformed support layer formed from a sheet of support material may require a higher diameter spindle so that the support layer can wrap around the spindle without significant deformation due to compression at an inner surface of the preformed support layer. In contrast, elastic layer 36 may not be inhibited by a minimum diameter of spindle 34. As such, spindle 34 may have a reduced diameter and elastic layer 36 may have a greater thickness for a particular diameter of abrasive rotary tool 18, resulting in a more conformable working surface 46.
In addition or alternative to improved performance, abrasive rotary tools discussed herein may be manufactured faster and/or less expensively than abrasive rotary tools that do not include an elastic layer formed in a mold.
Cavity 202 includes a peripheral surface 204. A portion of peripheral surface 204 may be configured to position abrasive sheet 206 within cavity 202. For example, abrasive sheet 206 may be a sheet or film, such that a portion of peripheral surface 204 contacts an outer surface of abrasive sheet 206, e.g. a working surface. In some examples, peripheral surface 204 may correspond to at least a portion of an outer shape or size (e.g. circumference, diameter, or length) of abrasive rotary tool 224 or components of abrasive rotary tool 224. For example, cavity 202 may be cylindrical shaped, such that a diameter of cavity 202 is approximately equal to a diameter of abrasive rotary tool 224 once formed and a circumference of cavity 202 is approximately equal to a length of abrasive sheet 206 positioned within cavity 202. In some examples, abrasive sheet 206 has a length within ±5% of a circumference of cavity 202. In some examples, abrasive sheet 206 has a width within ±5% of a depth of cavity 202.
In the example of
Abrasive sheet 206 includes a working surface 208 and an opposed surface 210. Working surface 208 is positioned adjacent to and along at least a portion of peripheral surface 204 of mold 200. Opposed surface 210 is positioned facing a center of cavity 202. Working surface 208 is configured to contact and abrade one or more surfaces of a substrate, such as substrate 16 of
Abrasive sheet 206 is not particularly limited and may include, but is not limited to, traditional coated abrasives and structured abrasives (e.g. 3M TRIZACT ABRASIVE, available from 3M Company, St. Paul, Minn.). Abrasive sheet 206 may include a base layer, e.g. backing layer having first and second major surfaces. In some embodiments, one of the first and second major surfaces of the base layer may include the opposed surface 210 of abrasive sheet 206. The base layer may be formed from a polymeric material. For example, the base layer may be formed from thermoplastics, such as polypropylene, polyethylene, polyethylene terephthalate and the like; thermosets, such as polyurethanes, epoxy resin, and the like; or any combinations thereof. The base layer may include any number of layers. In some examples, the base layer may be an elastic base layer, such that the abrasive sheet is capable of stretching in response to a tensile force applied to the abrasive sheet. The thickness of the base layer (i.e., the dimension of the base layer in a direction normal to the first and second major surfaces) may be less than 10 mm, less than 5 mm, less than 1 mm, less than 0.5 mm, less than 0.25 mm, less than 0.125 mm, or less than 0.05 mm.
In some embodiments, working surface 208 includes a microstructured surface comprising a plurality of three-dimensional features (or “microstructures”). In some examples, the plurality of three-dimensional features includes a plurality of three dimensional microreplicated features. The three-dimensional features of the microstructured surface may be configured to increase a contact pressure of working surface 208 on one or more surfaces of a substrate. In some embodiments, the microstructured surface of working surface 208 may include a plurality of cavities. The shape of the cavities may be selected from among a number of geometric shapes such as a cubic, cylindrical, prismatic, hemispherical, rectangular, pyramidal, truncated pyramidal, conical, truncated conical, cross, post-like with a bottom surface which is arcuate or flat, or combinations thereof. Alternatively, some or all of the cavities may have an irregular shape. In various embodiments, one or more of the side or inner walls that form the cavities may be perpendicular relative to the top major surface or, alternatively, may be tapered in either direction (i.e., tapered toward the bottom of the cavity or toward the top of the cavity—toward the major surface). The angle forming the taper can range from about 1 to 75 degrees, from about 2 to 50 degrees, from about 3 to 35 degrees, or from between about 5 to 15 degrees. The height, or depth, of the cavities can be at least 1 micron, at least 10 micron, or at least 500 micron, or at least 1000 micron; less than 10 mm, less than 5 mm, or less than 1 mm. The height of the cavities may be the same, or one or more of the cavities may have a height that is different than any number of other cavities. In some embodiments, the cavities can be provided in an arrangement in which the cavities are in aligned rows and columns. In some instances, one or more rows of cavities can be directly aligned with an adjacent row of cavities. Alternatively, one or more rows of cavities can be offset from an adjacent row of cavities. In further embodiments, the cavities can be arranged in a spiral, helix, corkscrew, or lattice fashion. In still further embodiments, the composites can be deployed in a “random” array (i.e., not in an organized pattern).
In some embodiments, the microstructured surface of working surface 208 includes a plurality of precisely shaped abrasive composites. “Precisely shaped abrasive composite” refers to an abrasive composite having a molded shape that is the inverse of the mold cavity which is retained after the composite has been removed from the mold; preferably, the composite is substantially free of abrasive particles protruding beyond the exposed surfaces of the shape before the abrasive sheet has been used, as described in U.S. Pat. No. 5,152,917 (Pieper et al.), which is incorporate herein by reference in its entirety. The plurality of precisely shaped abrasive composites may include a combination of abrasive particles and resin/binder forming a fixed abrasive. In some embodiments, working surface 208 may be formed as a two-dimensional abrasive material, such as an abrasive sheet with a layer of abrasive particles held to a backing by one or more resin or other binder layers. Alternatively, working surface 208 may be formed as a three-dimensional abrasive material, such as a resin or other binder layer that contains abrasive particles dispersed therein and is formed into a three-dimensional structure (forming a microstructured surface) via a molding or embossing process, for example, followed by curing, crosslinking, and/or crystallizing of the resin to solidify and maintain the three-dimensional structure. The three-dimensional structure may include a plurality of precisely shaped abrasive composites. In either embodiment, working surface 208 may include an abrasive composite which has appropriate height to allow for the abrasive composite to wear during use and/or dressing to expose a fresh layer of abrasive particles. The abrasive sheet may comprise a three-dimensional, textured, flexible, fixed abrasive construction including a plurality of precisely shaped abrasive composites. The precisely shaped abrasive composites may be arranged in an array to form the three-dimensional, textured, flexible, fixed abrasive construction. The abrasive sheet may comprise abrasive constructions that are patterned. Abrasive sheets available under the trade designation TRIZACT abrasives available from 3M Company, St. Paul, Minn., are exemplary patterned abrasives. Patterned abrasive sheets may include monolithic rows of abrasive composites precisely aligned and manufactured from a die, mold, or other techniques.
The shape of each precisely shaped abrasive composite may be selected for the particular application (e.g., workpiece material, working surface shape, working surface shape, temperature, resin phase material). The shape of each precisely shaped abrasive composite may be any useful shape, e.g., cubic, cylindrical, prismatic, right parallelepiped, pyramidal, truncated pyramidal, conical, hemispherical, truncated conical, cross, or post-like sections with a distal end. Composite pyramids may, for instance, have three, four sides, five sides, or six sides. The cross-sectional shape of the abrasive composite at the base may differ from the cross-sectional shape at the distal end. The transition between these shapes may be smooth and continuous or may occur in discrete steps. The precisely shaped abrasive composites may also have a mixture of different shapes. The precisely shaped abrasive composites may be arranged in rows, spiral, helix, or lattice fashion, or may be randomly placed. The precisely shaped abrasive composites may be arranged in a design meant to guide fluid flow and/or facilitate swarf removal.
The precisely shaped abrasive composites may be set out in a predetermined pattern or at a predetermined location within the abrasive sheet. For example, when the abrasive sheet is made by providing an abrasive/resin slurry between a backing and mold, the predetermined pattern of the precisely shaped abrasive composites will correspond to the pattern of the mold. The pattern is thus reproducible from abrasive sheet to abrasive sheet. The predetermined patterns may be in an array or arrangement, by which is meant that the composites are in a designed array such as aligned rows and columns, or alternating offset rows and columns. In another embodiment, the abrasive composites may be set out in a “random” array or pattern. By this is meant that the composites are not in a regular array of rows and columns as described above. It is understood, however, that this “random” array is a predetermined pattern in that the location of the precisely shaped abrasive composites is predetermined and corresponds to the mold.
An abrasive material forming working surface 208 of abrasive sheet 206 may include a polymeric material, such as a resin. In some embodiments, the resin phase may include a cured or curable organic material. The method of curing is not critical, and may include, for instance, curing via energy such as UV light or heat. Examples of suitable resin phase materials include, for instance, amino resins, alkylated urea-formaldehyde resins, melamine-formaldehyde resins, alkylated benzoguanamine-formaldehyde resins, acrylate resins (including acrylates and methacrylates), phenolic resins, urethane resins, and epoxy resins.
Examples of suitable abrasive particles for the abrasive sheet include cubic boron nitride, fused aluminum oxide, ceramic aluminum oxide, heat treated aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, silicon nitride, tungsten carbide, titanium carbide, diamond, cubic boron nitride, hexagonal boron nitride, alumina zirconia, iron oxide, ceria, garnet, fused alumina zirconia, alumina-based sol gel derived abrasive particles and the like. The alumina abrasive particle may contain a metal oxide modifier. The diamond and cubic boron nitride abrasive particles may be mono crystalline or polycrystalline. Other examples of suitable inorganic abrasive particles include silica, iron oxide, chromia, ceria, zirconia, titania, tin oxide, gamma, alumina, and the like. The abrasive particles may be abrasive agglomerate particles. Abrasive agglomerate particles typically comprise a plurality of abrasive particles, a binder, and optional additives. The binder may be organic and/or inorganic. Abrasive agglomerates may be randomly shaped or have a predetermined shape associated with them.
Spindle 212 may be formed from a variety of materials including, but not limited to: metals, such as aluminum and steel; polymers; and the like. Spindle 212 may have a variety of dimensions and sizes. For example, due to formation of elastic layer 220 from an elastomeric precursor material 218 (shown in
Positioning spindle 212 in spindle cavity 209 creates a region 216 between exterior surface 214 of spindle 212 and opposed surface 210 of abrasive sheet 206. Region 216 may represent a volume corresponding to an eventual elastic layer 220 (shown in
A variety of elastomeric precursor materials and, correspondingly, elastomeric materials may be used to form elastomeric precursor material 218 and elastic layer 220, respectively. Elastomeric precursor materials may be at least one of a c and a thermoplastic material. In some embodiments, the elastomeric precursor material may be a polymerizable composition which includes at least one of monomer, oligomer and curable resin, which can be solidified by polymerizing and/or curing the polymerizable composition. Polymerizing/curing may be conducted thermally or by exposer to actinic radiation. In some embodiments, the elastomeric precursor material is a molten thermoplastic material. Thermoplastic materials become molten (capable of flow), when raised to a temperature above their melting temperature. Thermoplastic materials can solidify upon cooling below their melting temperature. Thermoplastic materials that may be used as the elastomeric precursor material include, but are not limited to, polyethylene, polypropylene, polyurethane (e.g. thermoplastic polyurethanes), polyethylene terephthalate, polyethylene oxide, polypropylene oxide, polyamides, polystyrene, polyacrylates, polymethacrylates and combinations thereof. Thermoplastic materials include thermoplastic elastomers. Thermoplastic elastomers may include block copolymers. Di, tri and even higher order block copolymer having at least one soft segment (e.g. a segment having a glass transition temperature below room temperature) and at least one hard segment (e.g. a crystallizable segment) are particularly useful. In some examples, elastic layer 220 is an elastomeric foam. Foams that may be used include, but are not limited to, synthetic or natural foams, thermoformed foams, polyurethanes, polyesters, polyethers, filled or grafted polyethers, viscoelastic foams, melamine foam, polyethylenes, cross-linked polyethylenes, polypropylenes, silicone, ionomeric foams, etc., and blends of these materials. In some embodiments, elastic layer 220 is a thermoplastic elastomer. Thermoplastic elastomers that may be used include, but are not limited to, polypropylene, polyethylene, polyethylene terephthalate and the like; thermosets, such as polyurethanes, epoxy resin, etc., and blends of these materials. In some examples, the elastic layer is a thermosetting elastomer. Thermosetting elastomers that may be used include, but are not limited to, nitriles, fluoroelastomers, chloroprenes, epichlorohydrins, silicones, urethanes, polyacrylates, EPDM (ethylene propylene diene monomer) rubbers, SBR (styrene butadiene rubber), butyl rubbers, nylon, polystyrene, polyethylene, polypropylene, polyester, polyurethane, etc., and blends of these materials.
In some embodiments, elastic layer 220 may be configured to deform in response to a contact pressure of abrasive rotary tool 224 against a substrate. Elastic layer 220 may deform by receiving a radial force, such as from abrasive sheet 206, and compressing at least a portion of elastic layer 220.
In some embodiments, elastic layer 220 may be composed of a material selected according to hardness. Hardness may represent a measure of elastic layer 220 to deform in response to a force. In some cases, the hardness may be most appropriately measured using different scales for elastic layer 220 (e.g., Shore A durometer). In some embodiments, elastic layer 220 has a sufficiently low hardness, such that elastic layer 220 deforms against a substrate under normal operating conditions. Elastic layer 220 may have a hardness of less than 70 Shore A and greater than 10 Shore A (e.g., as measured using ASTM D2240, Revision 15, using Durometer Gauge from Rex Gauge Company, Buffalo Grove, Ill.).
In some embodiments, elastic layer 220 may be composed of a material selected according to compressibility. Compressibility may represent a measure of the relative change of a material of elastic layer 220 in response to a pressure, while the terms “compressible” or “incompressible” may refer to a material property of compressibility. For example, the term “substantially incompressible” refers to a material having a Poisson's ratio greater than about 0.45. Compressibility of a material may be expressed as a particular pressure required to compress the material to a reference deflection (e.g., 25% deflection). In some embodiments, the compressibility of the elastic layer may be measured via Compression Force Deflection Testing per ASTM D3574 or a modified version thereof, when elastic layer 220 is foam; and via Compression-Deflection Testing per ASTM D1056 when elastic layer 220 is a flexible cellular material such as, for example, sponge or expandable rubber.
In some embodiments, the compressibility of elastic layer 220 may be relatively high for operating conditions encountered during abrading. In some embodiments, elastic layer 220 may have a compressibility at 25% deflection of less than about 1.5 MPa (220 psi), less than about 1.1 MPa (160 psi), less than about 0.31 MPa (45 psi) and/or a Poisson's ratio less than about 0.5, less than about 0.4, less than 0.3 or preferably less than about 0.1. In some embodiments, elastic layer 220 has a sufficiently high elasticity, such that elastic layer 220 compresses against the substrate under normal operating conditions. In some embodiments, elastic layer 220 may have a Young's Modulus of less than about 6.0 MPa (870 psi), less than about 3.4 MPa (500 psi), less than about 1.0 MPa (150 psi) and/or a Poisson's ratio less than about 0.5, less than about 0.4, less than 0.3 or preferably less than about 0.1.
In some embodiments, elastic layer 220 may be composed of a material selected according to elasticity. Elasticity (or stiffness) may represent a measure of the relative deformation (strain) of a material of elastic layer 220 in response to a pressure (stress), while the terms “elastic” or “inelastic” may refer to a material property of elasticity. For example, the term “substantially inelastic” refers to a material having a Poisson's ratio greater than about 0.45. Elasticity of a material may be expressed as a tensile modulus, Young's modulus, or elastic modulus. In some embodiments, the elasticity of the layer may be measured via Standard Test Method for Young's Modulus, Tangent Modulus, and Chord Modulus per ASTM E111-17.
In some embodiments, elastic layer 220 may be composed of a material selected according to elastic deformation. Elastic deformation may represent an ability of a material of elastic layer 220 to recover to its original state after being deformed. The material may be elastically deformable, e.g., being capable of substantially 100% (e.g., 90% or more, 95% or more, 99% or more, 99.5% or more, or 99.9% or more) recovering to its original state after being deformed.
In some embodiments, elastic layer 220 may be selected according to its relaxation modulus, e.g. stress relaxation modulus. Relaxation modulus may represent a measure of a time-dependent viscoelastic property. In this disclosure, relaxation modulus is expressed in percentage and is determined from the relaxation modulus versus time curve provided from a stress relaxation test (e.g., as measured using ASTM D6048) using the following equation:
Relaxation modulus (%)=(instantaneous modulus−modulus after 2 minutes relaxation under a constant compressive strain)/instantaneous modulus×100.
In some embodiments, elastic layer 220 has a relaxation modulus of less than 25%.
In some embodiments, elastic layer 220 may be configured for various thicknesses. For example, a thickness of elastic layer 220 may correlate with a force or distance of rebound of elastic layer 220, such that elastic layer 220 may have a thickness that provides a particular range or distance of movement relative to the force produced or absorbed by the elastic layer. As an example, elastic layer 220 of abrasive rotary tool 224 intended for substrates with a relatively high degree of planarity may be thinner than elastic layer 220 of abrasive rotary tool 224 intended for substrates with a relatively low degree of planarity, as a higher degree of planarity may result in less compression or travel of elastic layer 220. In some embodiments, the elastic layer thickness may be less than 3 mm, less than 2 mm, or less than 1 mm.
In some embodiments, elastic layer 220 may have a substantially uniform (e.g., less than about 5% variation) radial density (i.e., in a radial direction from a central axis of spindle 212 to an outer edge of abrasive rotary tool 224). For example, in an elastic layer formed from a sheet or tube, a density may be higher at an inner surface of the elastic layer than an outer surface of the elastic layer due to a smaller diameter of the elastic layer at the inner surface than the outer surface. However, elastic layer 220 formed in mold 200 may have a relatively constant density in a radial direction from spindle 212 to abrasive sheet 206, as elastic layer 220 is not deformed from a sheet. In some embodiments, the density of elastic layer 220 may be greater than 0.2 g/cm3, greater than 0.4 g/cm3, greater than 0.6 g/cm3, greater than 0.8 g/cm3, greater than 0.85 g/cm3, greater than 0.9 g/cm3, greater than 0.95 g/cm3, greater than 1.0 g/cm3, greater than 1.1 g/cm3 or even greater than 1.2 g/cm3; less than 2.0 g/cm3, less than 1.8 g/cm3, less than 1.6 g/cm3, less than 1.4 g/cm3 or even less than 1.2 g/cm3.
In addition to the processes described above, method of manufacturing rotary tools as discussed herein may include other processes before, during, or after the processes described above. As one example, after elastomeric precursor material 218 is injected into cavity 202, elastomeric precursor material 218 may be foamed to provide particular compression properties to the solidified elastic layer 220. As another example, after solidification of elastomeric precursor material 218 into elastic layer 220, excess elastomeric precursor material outside a desired boundary of abrasive rotary tool 224 may be removed, such as by cutting. As yet another example, prior to injection of elastomeric precursor material 218, one or more additional materials may be injected or positioned into region 216. For example, an intermediate ring (not shown in
In some examples, molds used to form abrasive rotary tools discussed herein may be configured to form a plurality of abrasive rotary tools at a same time.
Select embodiments of the present disclosure include, but are not limited to, the following:
In a first embodiment, the present disclosure provides a method of making an abrasive rotary tool comprising:
providing a mold having a cavity with a peripheral surface;
providing an abrasive sheet having a working surface and an opposed surface, wherein the working surface is adjacent to and along at least a portion of the peripheral surface of the cavity;
providing a spindle having an exterior surface within the mold and creating a region between the exterior surface of the spindle and opposed surface of the abrasive sheet;
injecting an elastomeric precursor material into the region; and
solidifying the elastomeric precursor material to form an elastic layer, wherein the elastic layer is in contact with at least a portion of the opposed surface of the abrasive sheet and at least a portion of the exterior surface of the spindle.
In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the elastic layer fills at least 50% by volume of the region.
In a third embodiment, the present disclosure provides a method according to the first or second embodiments, wherein the spindle is centered within the cavity.
In a fourth embodiment, the present disclosure provides a method according any of the first through third embodiments, wherein the mold cavity is at least one of a cylindrical shaped cavity, a conical shaped cavity, or a hemispherical shaped cavity.
In a fifth embodiment, the present disclosure provides a method according to the fourth embodiment, wherein a circumference of the cylindrical shaped cavity is Cm and the abrasive sheet has a length Ca, wherein Ca is at least within ±5% of Cm. (Do we need this limitation)
In a sixth embodiment, the present disclosure provides a method according to any of the first through third embodiments, wherein the elastic layer is an elastomeric foam.
In a seventh embodiment, the present disclosure provides a method according to any of the first through third embodiments, wherein the elastic layer is a thermoplastic elastomer.
In an eighth embodiment, the present disclosure provides a method according to any of the first through seventh embodiments, wherein the elastic layer is a cured elastomer.
In a ninth embodiment, the present disclosure provides a method according to any of the first through seventh embodiments, wherein the working surface of the abrasive sheet includes plurality of three-dimensional features.
In a tenth embodiment, the present disclosure provides a method according to the ninth embodiment, wherein the plurality of three-dimensional features includes a plurality of three dimensional microreplicated features.
In an eleventh embodiment, the present disclosure provides an abrasive rotary tool comprising:
an abrasive sheet having a working surface and an opposed surface;
a spindle having an exterior surface; and
an elastic layer, wherein the elastic layer is in contact with at least a portion of the opposed surface of the abrasive sheet and at least a portion of the exterior surface of the spindle, wherein the elastic layer is a unitary body and wherein the abrasive sheet is coupled to the elastic layer by only adhesive forces at the contact between the at least a portion of the opposed surface of the abrasive sheet and the elastic layer.
In a twelfth embodiment, the present disclosure provides an abrasive rotary tool according to the eleventh embodiment, wherein the elastic layer has a substantially uniform radial density.
In a thirteenth embodiment, the present disclosure provides an abrasive rotary tool according to the eleventh or twelfth embodiments, wherein the abrasive rotary tool has at least one of a cylindrical shape, conical shape and hemispherical shape.
In a fourteenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through thirteenth embodiments, wherein the elastic layer is an elastomeric foam.
In a fifteenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through thirteenth embodiments, wherein the elastic layer is a thermoplastic elastomer.
In a sixteenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through thirteenth embodiments, wherein the elastic layer is a cured elastomer.
In a seventeenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through sixteenth embodiments, wherein the elastic layer has at least one of a Young's Modulus of less than about 6.0 MPa (870 psi) or a Poisson's ratio less than about 0.5.
In an eighteenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through seventeenth embodiments, wherein the elastic layer has a hardness less than about 70 Shore A and greater than about 10 Shore A.
In a nineteenth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through eighteenth embodiments, wherein the elastic layer has a compression set of less than about 25%.
In a twentieth embodiment, the present disclosure provides an abrasive rotary tool according to any of the eleventh through nineteenth embodiments, wherein the working surface of the abrasive sheet includes plurality of three-dimensional features.
In a twenty-first embodiment, the present disclosure provides an abrasive rotary tool according to the twentieth embodiment, wherein the plurality of three-dimensional features includes a plurality of three dimensional microreplicated features.
In a twenty-second embodiment, the present disclosure provides a system for forming an abrasive rotary tool, comprising:
a mold having a cavity with a peripheral surface, wherein the peripheral surface is configured to receive a working surface of an abrasive sheet adjacent to and along at least a portion of the peripheral surface of the mold, and wherein the mold is configured to center a spindle within the cavity to create a region between an exterior surface of the spindle and the opposed surface of the abrasive sheet; and
an injection device configured to inject an elastomeric precursor material into the region.
In a twenty-third embodiment, the present disclosure provides a system according to the twenty-second embodiment, wherein the cavity has at least one of a cylindrical shape, a conical shape, or a hemispherical shape.
The methods and articles of the present disclosure will be further described with regard to the following detailed examples. These examples are offered to further illustrate the various specific and preferred embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present disclosure.
Example 1 is illustrated in
Abrasive sheet 604 was formed from TRIZACT abrasive (578XA from 3M Company, St. Paul, Minn. without pressure sensitive adhesive (PSA) layer). The TRIZACT abrasive was cut into sheets with a razor blade. The sheets were sized to fit along the peripheral surface of cavity 702 and inserted into cavities 702 of
Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/060147 | 10/29/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62930605 | Nov 2019 | US |
