Additive Manufacturing

Abstract

In one example, a processor-readable medium having instructions thereon that, when executed, cause a fusing system for an additive manufacturing machine to: preheat build material in a layer of unfused build material during a first slide pass; dispense liquid flux onto the preheated unfused build material in the layer during the first slide pass and / or during a second slide pass, and subsequently, during the second slide pass, irradiate the build material in the layer with the flux dispensed thereon with fusing light; and during a third slide pass, irradiate the fused build material with the fusing light; and during a fourth slide pass, irradiate the fused build material with the fusing light, and subsequently, actively cool the fused build material.

Description

[0001] This application is a divisional application of the Chinese patent application entitled “Additive Manufacturing” and application number 201780086684.3 filed on August 15, 2019. Background Art

[0002] Additive manufacturing machines produce 3D objects by building up layers of material. Some additive manufacturing machines are often referred to as "3D printers". 3D printers and other additive manufacturing machines make it possible to transform a CAD (computer-aided design) model or other digital representation of an object into a physical object. The model data can be processed into slices that each define a portion of the object to be formed from one or more layers of build material. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 and Figure 2 2 are a front view and a plan view, respectively, illustrating one example of a fusion system for an additive manufacturing machine.

[0004] Figure 3-28 A series of views are presented that illustrate the use of Figure 1 and Figure 2 An example of a four-way fusion cycle of a fusion system.

[0005] Fig.29 is a diagram illustrating one example of a spool fusion cycle.

[0006] Fig.30 and Fig.31 is a flow chart illustrating an example of a fusion process for additive manufacturing, which may be used, for example, Figure 1 and Figure 2 The fusion system is implemented.

[0007] Fig.32 is a block diagram illustrating one example of a processor readable medium having fusing instructions to fuse build materials during additive manufacturing of a 3D object.

[0008] Fig.33 is a block diagram illustrating one example of a fusing system for an additive manufacturing machine implementing a controller with fusing instructions for fusing build materials during additive manufacturing of a 3D object.

[0009] Throughout the drawings, the same reference numerals designate the same or similar parts. The drawings are not drawn to scale. The proportions of the layers of building materials and the slices of the objects are greatly exaggerated in the drawings. For example Figure 3-28 Each layer of building material in the fusion process shown in FIG can be less than 100 µm, while objects can be manufactured in thousands of layers. DETAILED DESCRIPTION

[0010] In some additive manufacturing processes, heat is used to fuse particles in a powdered build material together to form a solid object. For example, the heat to fuse the build material can be generated by applying a liquid flux to a thin layer of the powdered build material in a pattern based on a slice of the object, and then exposing the patterned area to a fusing light. The light absorbing component in the flux absorbs the light energy to help heat the patterned build material above the fusing temperature to sinter, melt, or otherwise fuse the build material. Other liquid reagents can be used to produce the desired properties of the object. For example, a refiner can be used to enhance or inhibit fusing in certain areas of the object, a colorant can be used for objects of different colors or different colors in a single object, and other reagents can be used to affect physical properties such as ductility and conductivity. The process is repeated layer by layer and slice by slice to complete the object.

[0011] New fusing techniques have been developed to help improve the ductility of plastic objects. In one example, a four-pass fusing process is used to heat the build material to above the fusing temperature and keep it there in a molten state long enough for reptation, and then the fused build material is cooled to below the crystallization temperature and left there briefly to help lock the polymer into an amorphous state while inhibiting crystallization. In one such four-pass fusing process, for example, during the first carriage pass, the build material in the unfused build material layer is preheated, and then, liquid flux is selectively dispensed onto the preheated unfused build material. During the second carriage pass, the build material on which the flux has been dispensed is irradiated with a fusing light to heat the build material to above the fusing temperature to form a fused build material. Although the fusing light is typically applied to the entire work area, thereby irradiating the build material treated with the flux as well as the untreated build material, selective illumination can also be used for the treated build material. During the third carriage pass, the fused build material is illuminated with the fusing light, and during the fourth carriage pass, the fused build material is illuminated with the fusing light again to maintain the fused build material above the fusing temperature during the desired creep period. Then, also during the fourth carriage pass, the fused build material is rapidly cooled to below the crystallization temperature by spreading the next layer of unfused build material over the hot build material. The sequence then immediately begins again with the first carriage pass. Preheating the new layer of unfused build material in the first carriage pass warms the underlying fused build material above the crystallization temperature to limit the duration of "extreme" cooling and, therefore, inhibit crystallization and edge curling along the perimeter.

[0012] For additively manufactured plastic objects, this and other examples of the new fusion technology enable polymers in the build material to form and maintain an amorphous structure that exhibits higher ductility and lower brittleness compared to other additive manufacturing techniques. However, the examples are not limited to additively manufactured plastic objects. In other examples, other types of build materials can be used to make objects.

[0013] These and other examples described below and shown in the accompanying drawings illustrate but do not limit the scope of the patent, which is defined in the claims that follow this specification.

[0014] As used in this document: "and / or" means one or more of the associated things; "flux" means a substance that causes or helps to cause the building materials to sinter, melt or otherwise fuse; "fine agent" means a substance that inhibits or prevents or enhances the fusing of building materials, for example by changing the effect of the flux; "irradiation" means exposure to radiation, including heat and light; "light" means electromagnetic radiation of any wavelength; "liquid" means a fluid that is not primarily composed of one or more gases; "processor-readable medium" means any non-transitory tangible medium that can implement, contain, store or maintain instructions and other information for use by a processor, and may include, for example, circuits, integrated circuits, ASICs (application specific integrated circuits), hard drives, random access memory (RAM), read-only memory (ROM) and flash memory; and "working area" means any suitable structure that supports or contains building materials for fusing, including underlying layers of building materials and slices and other object structures being processed.

[0015] Figure 1 and Figure 2 1 and 2 are elevation and plan views, respectively, illustrating one example of a fusion system 10 for an additive manufacturing machine. Figure 3-28 A series of views are presented that illustrate one example of a spool fusion process using system 10. Figure 1 and Figure 2 , the fusing system 10 includes a first "fuser" carriage 12 and a second "dispenser" carriage 14. The carriages 12 and 14 move back and forth on a track 16 above a work area 18. The fuser carriage 12 carries a laminating device 22, a heater 24, and a fusing lamp 26. The dispenser carriage 14 carries an inkjet printhead assembly or other suitable liquid dispensing assembly 28 to dispense liquid flux. In the example shown, the dispensing assembly 28 includes a first dispenser 30 that dispenses flux and a second dispenser 32 that dispenses another agent, such as a fine agent.

[0016] exist Figure 1 and Figure 2In the example shown in FIG. 1 , laminating device 22 is implemented as roller 22 which is arranged in an extended position for laminating building material when carriage 12 moves over work area 18 and in a retracted position ( FIG. 2 ) for not laminating building material when carriage 12 moves over work area 18 . Fig. 9 Other embodiments of laminating device 22 are possible, including, for example, a blade or device that dispenses the building material as a layer directly over the work area.

[0017] Heater 24 may be implemented as a "warming" lamp or other radiant heating device 24. "Warming" in this context refers to the pre-heating function of heater 24 that heats unfused build material in work area 18 to a temperature closer to the fusing temperature. Although a single device 24 is shown, multiple warming lamps or other radiant heating devices 24 may be used. Likewise, although a single fusing lamp 26 is depicted, multiple fusing lamps may be used, for example to enable a wider range of fusing lights.

[0018] Although the characteristics of warming lamps 24 and fusing lamps 26 may vary depending on the characteristics of the build material and flux (as well as other fusing process parameters), generally lower color temperature warming lamps 24 and higher color temperature fusing lamps 26 will be desirable to better match the spectral absorption of the untreated and treated build materials, respectively, in order to increase energy transfer from the lamps to the build materials. For example, a desired power absorption level may be achieved using warming lamps 24 operating in the range of 800K to 2150K to effectively preheat an untreated white or other light-colored build material, and a desired power absorption level may be achieved using fusing lamps 26 operating in the range of 2400K to 3500K to effectively fuse the same build material treated with a black or highly absorptive low tint liquid flux without significantly heating the surrounding untreated build material. The black flux, which absorbs substantially all of the radiant energy emitted by the higher color temperature fusing lamp, fuses the treated build material without also fusing the surrounding untreated build material.

[0019] As described above, working area 18 represents any suitable structure that supports or contains build material for fusion, including underlying build material layers and slices and other object structures in process. For example, for a first layer of build material, working area 18 may be formed on the surface of platform 34, which moves up and down to accommodate the lamination process. For subsequent layers of build material, working area 18 may be formed on underlying structure 36. Figure 1 In the example, the underlying structure 36 is a layer of unfused building material 38. Fig.15 In the embodiment of the present invention, the underlying structure 36 is an object structure including unfused building material and building material that has been fused into the object slice.

[0020] exist Figure 1 and Figure 2 , ribbon 40 of unfused build material 38 is deposited along platen 42 adjacent work area 18, laminating roller 22 is unwound, heating lamps 24 and fusing lamps 26 are turned on, and fuser carriage 12 moves to the right in a first pass, as indicated by motion arrow 44. Figure 3 and Figure 4 , as fuser carriage 12 continues to move to the right, warming lamps 24 heat lower layer 36 while rollers 22 laminate unfused build material into layer 46 over lower layer 36. Fusing lamps 26 may contribute a small amount of heat to the unfused build material in lower layer 36. However, as described above, in this example, the fusing lamps are configured to optimize heating of build material that has been processed with flux, and therefore, do not sufficiently heat unprocessed build material.

[0021] exist Figure 5 and Figure 6 , fuser carriage 12 moves to the left in the first pass of the fusing sequence, represented by motion arrow 48. Lamination rollers 22 are unrolled to re-laminate any excess build material in layer 46, and warming lamps 24 are turned on to pre-heat the build material in layer 46. Excess build material may be desirable, for example, to help ensure complete coverage of the underlying structure, including cavities that may be formed during fusing. Figure 3 and Figure 4 Roller 22 moving to the right in the middle can be retracted to skip over any excess build material accumulated on the left platen 42 in preparation for Figure 5 and Figure 6 The excess build material is restacked in the first pass of the fusing cycle shown in FIG.

[0022] exist Figure 7 and Figure 8 , dispenser carriage 14 follows fuser carriage 12 over work area 18 in a first pass, and dispenser 30 dispenses flux 52 onto build material 38 in layer 46 in a pattern 54 based on the desired object slice. In this example, dispenser 32 also dispenses a fine agent or other agent 56 onto patterned build material 54 and / or unpatterned build material in layer 46 in the first pass.

[0023] exist Fig. 9 and Fig.10 , as dispenser carriage 14 moves to the right in a second pass as indicated by motion arrow 44, dispensers 30 and 32 dispense reagents 52 and 56, respectively, onto patterned and / or unpatterned build materials in layer 46. Fig.11 and Fig.12In the example, fuser carriage 12 follows dispenser carriage 14 over work area 18 in a second pass, and fusing lamps 26 are turned on to illuminate patterned build material 54 with fusing light to fuse the patterned build material. Fused build material 58 forms first object slice 60. In this example, warming lamps 24 are turned on in the second pass, for example, to slow cooling of fused material 58.

[0024] exist Fig.13 and Fig.14 , dispenser carriage 14 remains parked while fuser carriage 12 moves to the left in a third pass as indicated by motion arrow 48, with warming lamps 24 and fusing lamps 26 turned on to illuminate fused build material 58. Nearly continuous exposure to both heat from heater 24 and light from lamps 26 helps to maintain fused build material 58 at or above the fusing temperature. Fig.15 and Fig.16 , fuser carriage 12 moves to the right in a fourth pass, with warming lamps 24 and fusing lamps 26 turned on to illuminate fused build material 58. Rollers 22 follow these lamps, spreading unfused build material 38 into a next layer 64 over underlying structure 62 to cool fused build material 58.

[0025] The sequence then begins again with a first carriage pass to preheat layer 64 and warm the underlying fused build material 58, as Fig.17 and Fig.18 The four-pass fusion cycle for the next layer 64 is shown in Figure 17-28 6 to form a second slice 68 covered by the next subsequent layer 70. The fusing process continues layer by layer and slice by slice to complete the object. The sequence of four carriage passes represents a continuous cycle during manufacturing, and therefore, the first, second, third and fourth pass numbering in the above example does not necessarily mean the beginning and end. For example, the beginning of the sequence for one layer may be the end of the sequence for another layer. These passes may be numbered differently than the passes.

[0026] Other processing and system configurations are also possible. For example, the laminating roller 22 can be used throughout the second pass ( Figure 5 and Figure 6), for example, when it is not desired to re-stack the building material. More or less reagent dispensers are possible to distribute more or less reagents, and more or less carriages can be used to carry the movable parts. In addition, the order of dispensing reagents may also be different from the order shown, and although one carriage follows another carriage in some passes, these carriages may be staggered as part of the same pass. In some system configurations, fixed heaters and / or fusion lamps may be used to continuously irradiate the working area with fusion light (except when blocked by the carriage), rather than intermittently irradiating as the parts mounted on the carriage.

[0027] Fig.29 is a diagram illustrating an example of a spool fusion cycle, such as that described above with reference to Figure 3-28 Four-way fusion cycle as described. Fig.29 The temperatures in refer to the processing temperatures for polyamide building material powders such as PA-12 powder. Fig.29 , during the first carriage pass (indicated by "1" along the timeline), e.g. Figure 17-20 As shown in , the unfused build material in the next layer is preheated, as shown by the steeply rising temperature curve in 1, and then the liquid reagent is dispensed onto the preheated unfused build material in that layer, as shown by the steeply falling temperature curve in 1. The heat from the slice below warms the build material in the next layer, as shown by the gradually rising temperature curve in 1.

[0028] During the second carriage pass (indicated by "2" along the timeline), e.g. Figure 21-24 As shown in , more reagent is dispensed onto the build material in this layer, and then the build material having at least flux dispensed thereon is illuminated with a fusing light to heat the build material above the fusing temperature, as shown by the sharp rise in the temperature profile to "Fuse 1". The now fused build material can be cooled slightly before the next carriage pass, as shown by the gradually falling temperature profile after Fuse 1 in Pass 2.

[0029] During the third carriage pass (indicated by "3" along the timeline), e.g. Fig.25 and Fig.26 As shown in , the fused building material is illuminated with a fusing light to maintain the fused building material above the fusing temperature, as shown by the sharp rise in the temperature curve to "Fuse 2". The fused build can be cooled before the next slide pass, as shown by the gradually falling temperature curve after Fuse 2 in Pass 3.

[0030] During the fourth carriage pass (indicated by "4" along the timeline), e.g. Fig. 27 and Fig.28As shown in , the fused build material is again illuminated with the fusing light to maintain the fused build material above the fusing temperature, as shown by the sharp rise in the temperature curve to "Fuse 3", and then rapidly cooled by spreading the next layer of unfused build material over the fused build material, as shown by the sharp drop in the temperature curve after Fuse 3 in Pass 4. Prior to Pass 1 for the next fusion cycle, heat from the new underlying slice warms the next layer of build material, as shown by the gradually rising temperature curve in Pass 4.

[0031] Still refer to Fig.29 , the unfused build material is preheated to a neutral zone above the crystallization temperature and below the fusion temperature in passes 1 and 2, which in this example are about 145°C and about 180°C, respectively. Beginning at about fusion 1 during the second pass, the temperature of the fused build material is raised to a fusion zone above the fusion temperature and below an upper temperature, which in this example is about 215°C. Fig.29 The polyamide build materials such as PA-12 presented in do not fuse at a single temperature. Instead, the polymer enters a molten state when the particles begin to fuse at a "fusion" temperature that defines the lower end of the fusion zone, and then, as the temperature increases in the fusion zone, the fusion continues. For example, PA-12 powder may enter a molten state at about 180°C and be completely melted at about 187°C. The fused material may be held in a molten state in the fusion zone for 1.0-3.0 seconds to allow sufficient time for the desired creep, and then, cooled to a crystallization zone for less than 0.75 seconds to help lock the polymer into an amorphous state while inhibiting crystallization. The cooled fused build material is then warmed into the neutral zone to stabilize for 2-3 seconds, such as when preheating a new layer of unfused build material for the next fusion cycle.

[0032] Fig.30 An example of a fusion process 100 for additive manufacturing is shown. The fusion process 100 may be used, for example, Figure 1 and Figure 2 The fusion system 10 shown in FIG. Fig.30 During a first carriage pass, the building material in the layer of unfused building material is warmed to a desired preheating temperature, and then liquid flux is dispensed onto the warmed unfused building material in the layer (block 102), such as Figure 5-8 During the second carriage pass, liquid flux or other reagent is dispensed onto the unfused build material in the layer, and then the build material in the layer having the flux dispensed thereon is illuminated with a fusing light to form a fused build material (block 104), e.g., as Figure 9-12 as shown in .

[0033] During the third carriage pass, the fused building material is illuminated with fusing light (block 106), such as Fig.13 and Fig.14 During the fourth carriage pass, the fused build material is again illuminated with the fusing light, and then the fused build material is briefly cooled to a temperature at or below the crystallization temperature of the build material (block 108), e.g., as shown in FIG. Fig.15 and Fig.16 The sequence of warming and dispensing in a first carriage pass, dispensing and irradiating in a second carriage pass, irradiating in a third carriage pass, and irradiating and cooling in a fourth carriage pass is repeated for multiple successive layers of build material.

[0034] Fig.31 Another example of a fusion process 120 for additive manufacturing is shown. The fusion process 120 may be used, for example, Figure 1 and Figure 2 The fusion system 10 shown in FIG. Fig.31 , process 120 includes: forming a first layer of unfused build material (block 122), such as Figure 3 and Figure 4 as shown in; fusing the building material in the first layer in a pattern based on the first object slice (block 124), for example Fig.11 and Fig.12 The temperature of the fused building material in the molten state is maintained at or above the fusion temperature of the building material for at least 1 second (block 126), for example, Figure 13-16 and Fig.29 and then, cooling the fused building material to a temperature at or below the crystallization temperature of the building material for less than 0.75 seconds to form a first object slice (block 128), such as Figure 15-16 and Fig.29 as shown in .

[0035] Fig.31 The fusing process 120 in the embodiment further includes: forming a second layer of unfused building material on the first object slice (block 130), for example, Fig.15 and Fig.16 as shown in; fusing the building material in the second layer in a pattern based on the second object slice (block 132), for example Fig.23 and Fig.24 The temperature of the fused building material in the second layer in the molten state is maintained at or above the fusion temperature of the building material for at least 1 second (block 134), for example, Figure 25-28 and Fig.29and then, cooling the fused build material in the second layer to a temperature at or below the crystallization temperature of the build material for less than 0.75 seconds to form a second object slice (block 136), such as Figure 27-28 and Fig.29 The forming, fusing, maintaining and cooling described above are repeated for a plurality of subsequent layers and slices (block 138 ).

[0036] Fig.32 is a block diagram illustrating a processor readable medium 72 having fusing instructions 74 to fuse build materials and form object slices during additive manufacturing of a 3D object. For example, the fusing instructions 74 may include executing Fig.30 100. As another example, the fusion instructions 74 may include executing Fig.31 The instructions for process 120 are shown in FIG.

[0037] The processor-readable medium 72 having the fusing instructions 74 may be implemented, for example, in a CAD computer program product, in an object model processor, and / or in a controller for a fusing system in an additive manufacturing machine (which may be part of a controller for an additive manufacturing machine). For example, control data for fusing build materials using a four-pass sequence, such as a four-pass sequence, may be generated by processor-readable instructions on a source application, typically a CAD computer program product, in an object model processor, and / or by processor-readable instructions on a controller for a fusing system in an additive manufacturing machine. Figure 3-28 The four-way sequence shown in .

[0038] Fig.33 is a block diagram illustrating one example of a fusion system 10 for an additive manufacturing machine implementing a controller 76 having fusion instructions 74. Fig.33 , fusion system 10 includes controller 76, work area 18, build material stacking device 22, flux dispenser 30, another reagent dispenser 32, heater 24, and fusion lamp 26. Stacking device 22 stacks build material on work area 18, and may include, for example, a device for dispensing build material and a scraper or roller that spreads the build material for each layer. Flux dispenser 30 and another reagent dispenser 32 selectively dispense their respective reagents as commanded by controller 76, for example, as described above with reference to Figure 7-10 While any suitable dispenser 30, 32 may be used, inkjet printheads are sometimes used in additive manufacturing machines because of the precision with which they can dispense reagents and their flexibility in dispensing different types and formulations of reagents.

[0039] Controller 76 represents the processing and memory resources, instructions, and electronic circuits and components required to control the operating elements of system 10. In particular, in this example, controller 76 includes a processor-readable medium 72 having fused instructions 74 and a processor 78 that reads and executes the instructions 74.

[0040] The examples shown in the drawings and described above illustrate but do not limit the present patent, which is defined in the following claims.

[0041] As used in the claims, "a", "an", "an", and "the" mean at least one. For example, "a fused lamp" means one or more fused lamps, and a subsequent reference to "the fused lamp" means the one or more fused lamps.

Claims

1. A fusion system for an additive manufacturing machine, comprising: a first carriage movable over the work area, the first carriage carrying a fusion lamp; a second carriage movable over the work area, the second carriage carrying a reagent dispenser; a controller operatively connected to the first carriage, the fusing lamp, the second carriage, and the reagent dispenser to: irradiating fused building material in a first layer of building material with the fusing lamp and forming a second layer of unfused building material on the first layer of building material while the first carriage moves over the working area; dispensing liquid flux in a pattern onto the building material in the second layer using the dispenser while the second carriage moves over the working area; With the first carriage moving over the working area, irradiating the patterned building material in the second layer with the fusing lamp to fuse the patterned building material in the second layer; and then while the first carriage moves over the working area, again irradiating the patterned building material in the second layer with the fusing lamp to maintain the fused building material in the second layer at or above the fusing temperature, wherein the first carriage carries a heater, and the controller is operatively connected to the heater to heat unfused building material in the second layer with the heater while the first carriage moves over the working area, and wherein the heater comprises a lamp having an operating color temperature in the range of 800K to 2150K, and the fused lamp comprises a fused lamp having an operating color temperature in the range of 2400K to 3500K.

2. The system according to claim 1, characterized in that: The first carriage carries a stacking device; and The controller is operatively connected to the laminating device to form the second layer of unfused building material on the first layer of building material using the laminating device as the first carriage moves over the working area.

3. The system according to claim 2, characterized in that The controller is operatively connected to the first carriage, the fusing lamp, and the laminating device to illuminate fused building material in a first layer of building material with the fusing lamp and to form a second layer of unfused building material on the first layer of building material with the laminating device in a single pass of the first carriage moving over the work area.

4. The system according to claim 2, characterized in that The controller is operatively connected to the first carriage, the fusing lamp, the second carriage, and the reagent dispenser so as to: dispensing liquid flux in a pattern onto the build material in the second layer using the dispenser in a single pass of the second carriage moving over the work area; irradiating the patterned build material in the second layer with the fusing lamp in a single pass of the first carriage over the working area; and then The fusing lamp is again utilized to illuminate the patterned build material in the second layer in a single pass of the first carriage over the working area.

5. A processor-readable medium having instructions thereon, which when executed cause the fusion system for an additive manufacturing machine according to claim 1 to: preheating the build material in the unfused build material layer during the first carriage pass; dispensing liquid flux onto preheated unfused build material in the layer during the first carriage pass and / or during the second carriage pass, and subsequently, during the second carriage pass, irradiating the build material in the layer with the flux dispensed thereon with fusing light to form a fused build material; as well as during a third carriage pass, irradiating the fused build material with the fusing light; as well as During the fourth carriage pass, the fused build material is illuminated with the fusing light and then actively cooled.

6. The medium according to claim 5, characterized in that The instructions include instructions to repeat the following sequence for multiple consecutive layers of build material, namely: preheating during a first slide pass, dispensing during the first slide pass and / or a second slide pass, irradiating in the second slide pass, irradiating in a third slide pass, and irradiating and cooling in a fourth slide pass.

7. The medium according to claim 5, characterized in that The instructions to actively cool the fused build material during the fourth carriage pass include instructions to layer unfused build material onto the fused build material.

8. The medium according to claim 5, characterized in that The instructions for actively cooling the fused build material during the fourth slide pass include instructions for actively cooling the fused build material during the fourth slide pass at least 1-3 seconds after the build material was irradiated with the fusing light in the second slide pass.

9. The medium according to claim 5, characterized in that The instructions for cooling the fused build material during the fourth carriage pass include instructions for cooling the fused build material in the layer to a temperature at or below a crystallization temperature of the build material for less than 0.75 seconds.

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