Patent Application
20180104891
The invention relates to a use of electromagnetic susceptible material for fused deposition modeling, a method of fused deposition modeling and a system for fused deposition modeling.
In fused deposition modeling objects are formed by layering fusible material in a controlled manner such that a desired three dimensional shape can be created. This way of forming objects is sometimes also referred to as additive printing or fused deposition modelling. Very often for fused deposition modeling a fused deposition modeling printer is used. The printer has a three dimensionally moveable print head. The fusible material is usually fed in the print head in the form of filaments. The print head heats up fusible filament which is subsequently melted, extruded from the print head and deposited on the object on previously deposited layers where it is allowed to cool down and solidify. Thus a fused deposition modeled object grows with each deposited layer and gradually attains its desired shape.
Fusible materials used in the fused deposition modeling can have different thermal expansion coefficients in different production stages of the fused deposition modeled object. This causes mechanical tensions and warping during the printing and cooling down of the fused deposition modeled object.
The mechanical tensions and warping can be prevented by thermal conditioning of the fused deposition modeled object. The fused deposition modeled object can be held in a thermally conditioned space such as an oven, where it is held at a predefined temperature higher than the ambient temperature during the printing. After the printing the finished printed object is allowed to gradually cool off, thus maintaining its original shape without warping.
Holding a fused deposition modeled object in a thermally conditioned space may involve holding the fused deposition modeled object and a three dimensionally moveable fused deposition modeling print head in the thermally conditioned space together to allow the print head to form the fused deposition modeled object. The thermally conditioned space has to be large enough to accommodate both moveable print head and fused deposition modeled object. Substantially the same constant temperature has to be maintained throughout the space which is problematic in larger spaces. Furthermore sufficient printing accuracy has to be maintained in a temperature range sufficiently high for the printing process. Higher temperature ranges require large ovens involving high costs and as the deposition modeling printer is enclosed in the oven, accessibility to deposition modeling printer and fused deposition modeled object is reduced. Higher temperatures also accelerate the aging process of the deposition printer.
It is therefore an object of the invention to prevent mechanical tension and warping of a fused deposition modeled object during fused deposition modeling of the fused deposition modeled object.
The object is achieved according to an aspect of the invention in a method of fused deposition modeling an object comprising
The fusible materials of the object and heating element can be heated, melted and extruded using a fused deposition modeling (FDM) printer which can deposit the fusible on the object and heating element respectively. The FDM printer can use two FDM printheads for alternatively depositing the layers of fusible material for the object and heating element. The fused deposition modeled object formed as described by deposition printing can be heated by means of irradiating the heating element, i.e. applying an alternating electromagnetic field to the heating element, which transfers its heat to the object to maintain the object at an elevated temperature.
This allows the creation of fused deposition modeled objects, at least portions of which can be heated such that warping and tensile stress in the object can be relieved. The fused deposition modeled objects can gradually cool down after the fused deposition modeling process has ended. In an embodiment, the gradual cooling down can be facilitated by gradually reducing a strength of the electromagnetic radiation. When the object is cooled down, the heating element can be removed to expose and free the object.
In an embodiment, the exposing the heating element to electromagnetic radiation is performed during the fused deposition modeling the object and the fused deposition modeling the at least one heating element. This will heat up the object while the deposition of the object is on-going.
In an embodiment, the electromagnetic radiation comprises high frequency electromagnetic field (RF), and the electromagnetic radiation absorptive material comprises electromagnetically susceptive material. This electromagnetically susceptive material can be applied as a filler material in a FDM thermoplastic matrix, such that is can be fused deposition modeled in combination with the object.
This allows the heating element to be heated contactless with an RF electromagnetic field applied at a distance from the heating element and the object.
In an embodiment, the filler material can be a ferromagnetic material. The heating is caused by the remanence of the ferromagnetic material in which causes absorption of energy from the alternating electromagnetic field. In another embodiment, the filler material can be a low conductive material. In this case, the heating is caused by eddy currents in the low conductive material induced by the alternating electromagnetic field.
In an embodiment according to the invention the method further comprises fused deposition modeling the object around the heating element comprising electromagnetically susceptive fusible material. This allows the fused deposition modeled object to be heated from within the object, while the RF electromagnetic field permeates the object.
In a preferred embodiment according to the invention the method further comprises fused deposition modeling the heating element comprising electromagnetically susceptive fusible material around the at least one second part of the object modeled from fusible material in a heating layer or mantle. This allows the low-susceptive material inside to be kept warm at its periphery, where otherwise the greatest tension and warping would occur due to cooling down.
The heating element may comprise insulating material as a matrix, which allows the object to be thermally insulated.
In an embodiment according to the invention the exposing the heating element to electromagnetic radiation comprises
In a further embodiment according to the invention, the arranging an induction coil near the fused deposition modeled object comprises arranging an induction coil having its windings below the fused deposition modeled object. This allows easy access of the fused deposition modeled object from above the induction coil.
In another embodiment the arranging an induction coil near the fused deposition modeled object comprises arranging an induction coil having its windings laterally arranged with respect to the fused deposition modeled object. This allows easy access of the fused deposition modeled object from a side of the induction coil.
In another embodiment, the exposing the heating element to electromagnetic radiation comprises irradiating the heating element using infrared radiation, and the electromagnetic radiation absorptive material comprises infrared radiation absorptive material.
This allows efficient contactless heating of the heating element using Infrared (IR) lamps or similar sources arranged at a distance from the object and heating element.
In an embodiment, the infrared radiation absorptive material comprises a filler having a emissivity of at least 0.7. Preferably the emissivity of the filler is greater than 0.8. Even more preferably the emissivity is greater than 0.9.
In an embodiment, the method comprises fused deposition modeling the at least one heating element as a heating layer or mantle around the fused deposition modeled object.
In a further embodiment, the method comprises leaving an air gap between the object and the heating layer. This allows air or a gas to be introduced between the heating layer or mantle and the object. The heating layer is heated by the infrared radiation, which causes the heating layer to heat up. The so heated heating layer in its turn irradiates the object in the space within the heating layer or mantle by means of thermal, infrared radiation. Moreover, the inner wall of the heating layer or mantle causes the air within the inner space to heat up which causes heating of the object by convection of the air within that space.
In a further embodiment, the method comprises fused deposition modeling an infrared radiation transparent layer between the object and the heating layer. This allows the infrared radiation from the inner wall of the heating layer or mantle to be passed on to the object while preventing any air in the inner space between the heating layer or mantle and the object to flow. Such heated air would escape from the inner space in the clearing between the upper rim of object and heating layer by convection, causing an undesired drop in the temperature of the inner pace and thus of the object.
As an alternative embodiment, the method further comprises fused deposition modeling a heat conducting layer between the object and the heating layer. This allows heat from the heating layer or mantle to flow to the objet to be heated using heat conductivity, whilst heat loss of the object due to convection is prevented.
As a further embodiment, the method can further comprise covering the fused deposition modeled heating layer or mantle rim and the object rim. This prevents air flow and convection within the inner space between the heating layer or mantle and the object, thus heat loss of the object is prevented.
The object is also achieved according to another aspect of the invention by a system for fused deposition modeling an object, comprising a deposition modeling printing assembly comprising at least two deposition print heads, positioning means for positioning the deposition modeling printing assembly, at least one electromagnetic radiation source, and a stage for the object to be printed.
In an embodiment, the at least electromagnetic field generation device is an induction coil connected to a high frequency voltage supply. By applying an alternating voltage to the induction coil an alternating electromagnetic field is generated which can be used for heating electromagnetic susceptive material used in fused deposition modeling as described.
In another the induction coil is an induction coil having windings in a flat surface. This allows the induction coil to be arranged near the object to be formed by the system for fused deposition modeling, i.e. three dimensional printed, without occupying much space, keeping the system for fused deposition modeling compact.
In another embodiment, the induction coil is arranged underneath the object to be fused deposition modeled. Thereby the object is easily accessible and where necessary separated from the induction coil by the stage, platform and the like.
In another embodiment, the induction coil is arranged lateral to the object to be fused deposition modeled. Thereby the object is easily accessible from a side of the object.
In another embodiment, the two induction coils are laterally arranged on opposite sides of an object to be fused deposition modeled. This allows fused deposition modeled objects to be placed between the induction coils for better capture of the electromagnetic field generated by the coils.
In an embodiment, the at least one electromagnetic field source comprises an infrared radiation source.
In a further embodiment, the at least one infrared radiation source is arranged laterally of a heating element surrounding the object.
In an embodiment, the at least one infrared radiation source further comprises an infrared reflector arranged laterally of the heating element.
In another embodiment, the system further comprises a heater for heating a bottom part of the object to be fused deposition modeled. In a further embodiment, the heater is comprised in the stage.
In an embodiment, the system further comprises a heat cover connected to the at least two deposition print heads.
In a further embodiment, the heat cover comprises a heater.
The object is also achieved according to another aspect of the invention in a use of electromagnetic radiation absorptive fusible material in fused deposition modeling.
In an embodiment, the electromagnetic radiation absorptive fusible material comprises electromagnetic susceptive material.
In a further embodiment, the electromagnetic susceptive material comprises a filler comprising an ferromagnetic material.
In another embodiment, the electromagnetic radiation absorptive fusible material comprises a filler comprising infrared radiation absorptive material.
In an embodiment, the infrared radiation absorptive material comprises a filler having a emissivity of at least 0.7. Preferably the emissivity of the filler is greater than 0.8. Even more preferably the emissivity is greater than 0.9.
Fused Deposition Modeling Material
Fused deposition modeling filament for fused deposition modeling or three-dimensional additive printing can be made from fusible materials such as thermoplastic materials including ABS, HIPS, PLA, PVA, TPE, PA, PET, PK. Other fusible materials include for example metal alloys with low melting temperature such as tin, indium or bismuth alloys. In the art fused deposition modeling filaments made from these materials are heated and melted in a deposition modeling print head in a fused deposition modeling printer and extruded and deposited in a deposition modeling printer in layers to form a fused deposition modeled object. In order for fused deposition modeled objects or parts thereof made from these materials to be heated during the fused deposition modeling, heatable material can be arranged within or outside the fused deposition modeled object where heating is required, to prevent tension and/or warping.
WO2009002528 A1 describes method and material for inductively heating a composition of polymer and an electromagnetically susceptive filler, the filler comprising i.e. electrically conductive and/or ferromagnetic particles. The electromagnetically susceptive particles heat up when exposed to an alternating magnetic field due to hysteresis of ferromagnetic properties of the particles or in case of conductive material, by eddy currents in the material.
This type of electromagnetically susceptive material is used for induction welding of objects. In induction welding two parts made of this electromagnetically susceptive material are brought into contact with each other and the overlapping part is locally heated under pressure by means of a locally applied alternating high frequency electromagnetic field. The electromagnetically susceptive material melts where the electromagnetic field is applied and locally and bonds the parts together.
The fusible material can for example be the thermoplastics poly(etheretherketone), polyetherketoneketone, poly(etherim ide), polyphenylene sulfide, poly(sulfone), polyethylene terephthalate, polyester, polyamide, polypropylene, polyurethane, polyphenylene oxide, polycarbonate, polypropylene/polyamide, polypropylene/ethylene vinyl alcohol, polyethylene, polyolefin oligomers, liquid modified polyolefins or combinations thereof. From U.S. Pat. No. 6,048,599, cited in WO 2009002528 A1, electromagnetic susceptive additives, i.e. conductive and ferromagnetic particles known for electromagnetic fusion bonding include NiFe alloys and iron. Also ferromagnetic materials can be considered. Furthermore also fusible metal alloys with low melting temperature can be used such as tin, indium or bismuth alloys, enriched with electromagnetic susceptive additives as described.
This electromagnetically susceptive material can advantageously be made in for example a filament such that it can be used in known fused deposition modeling printers, i.e. three dimensional printers. The electromagnetically susceptive material can also be supplied for example in the form of rods or grains, depending on the requirements and capabilities of the fused deposition modeling printer used. The electromagnetic susceptive material can be deposited and arranged by fused deposition modeling into objects as required, which are inductively heatable during creation of once created by subjecting the objects to an alternating electromagnetic field.
Fused Deposition Modeling
The electromagnetic susceptive material can be used in creating objects from the electromagnetic susceptive material or from a combination of electromagnetic susceptive material and low susceptive fusible material. A fused deposition modeled object from electromagnetic susceptive material alone can be partly or wholly subjected to the alternating electromagnetic field. The alternating electromagnetic field has a certain limited penetration depth into the material, so it is preferred to also use low-susceptive fused deposition printing material and limit the use of the electromagnetic susceptive material. Below examples of objects made of such a combination of materials are described.
The conformal heating layer 105 of susceptive filament material can be printed adjacent to the fused deposition modeled object body 104 without contacting the fused deposition modeled object body material. After completing fused deposition modeling of the fused deposition modeled object, the conformal heating layer 105 can be easily removed. Furthermore, the conformal heating layer 105 can be additionally covered with a thermal insulation layer for preventing thermal losses during the fused deposition modeling and heating of the fused deposition modeled object 103. The conformal heating layer 105 and thermal insulation layer thus form a mantle around the fused deposition modeled object which may also provide structural support to the fused deposition modeled object 103 during the fused deposition modeling of the object 103.
When the induction coil 101 is excited, heat is generated inside the fused deposition modeled object causing an increased temperature. In this example, since the susceptive filament material is distributed over the entire fused deposition modeled object body 104, the increased temperature is also available throughout the entire fused deposition modeled object body 104.
The object 103 with the susceptive portions 105, 106 and 107 as described in the examples of
A first deposition print head 203a can for example be used for forming the conformal heating layer 105 of electromagnetically susceptive fusible material as described under
After forming the conformal heating layer 105, it can for example be subjected to an alternating magnetic field, generated by an induction coil 101 positioned underneath a stage 108 on which the fused deposition modeled object 103 is placed. The induction coil 101 can be inductively excited by a power supply 102 connected to the induction coil 101. The induction coil 101 can be made from conductive windings which are arranged in for example a flat surface. Such an induction coil can also be referred to as a ‘pancake’ coil. The conductive windings of the induction coil 101 can also be in an annular fashion below the fused deposition modeled object 103. The induction coil windings can be flat, annularly shaped or any other form is possible, including a rectangular shape or polygon shape.
Alternatively to inductively heating the heating layer with a high frequency electromagnetic field, the heating layer can be heated using infrared electromagnetic radiation.
For the purpose of heating, the fused deposition modeling system 300 has infrared sources 304 posted laterally from the heating layer 301. The infrared sources 304 can for example be tubular infrared lamps, coiled filament lamps or heaters and the like for irradiating the infrared radiation having wave lengths in a mid-infrared wavelength range of 2 to 30 μm. The infrared radiation absorbed by the outer surface of the heating layer 301 heats up this heating layer or mantle 301 to a high temperature. Temperatures exceeding 100° C. or even 200° C. may be achieved for adequately heating and the object 302. The heat accumulated in the heating layer 301 is subsequently passed on to the fused deposition modeling object 302.
The material of heating layer 301 may contain an infrared absorbent filler such as outlined in Table 1 below:
The filling grade of the filler must be sufficient to obtain an effective emissivity of at least 0.8 and preferably at least 0.9 which is sufficient for use as heating element 301 or mantle.
As a thermoplastic matrix a material can be used which has its VICAT temperature above 170° C. This allows a structure deposited as heating element to maintain its shape at a workable temperature. Exemplary materials are PET, PA6 and PA66, which are also non-toxic and relatively cheap. Recyclates of these materials are well suited for use in heating elements as described.
The infrared radiation can be combined with heating the stage 305 of the fused deposition modeling object 302 from below the stage 305 on which the object 302 is positioned using a heater.
The fused deposition modeling printhead 303 can be equipped with a heat cover 306 attached to the printhead 303. The heat cover 306 is provided with a passage for the printhead 303 and can be adjustable in height relative to the printhead nozzle. As printing progresses, the fused deposition modeling object 302 and heating layer 301 have an increasing height. Since the heat cover 306 is attached to the printhead 303, the heat cover has a fixed distance to the top of the fused deposition modeling object 302 and heating layer 301 respectively. This distance or gap 308 can be chosen in a small distance range d such as 0.1 mm to a few mm. The smaller the gap 308 the better the heat cover 306 prevents air convection from the space 307 between the fused deposition modeling object 302 and heating layer 301, cooling down an inner side of the heating layer 301 and the object 302.
The above embodiments are described by way of example only. Variations thereof are possible without departing from the scope of protection as defined by the claims set out below.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014678 | Apr 2015 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/058787 | 4/20/2016 | WO | 00 |
