METHOD AND APPARATUS FOR THE ADDITIVE MANUFACTURING OF A WORKPIECE

Abstract

The invention is directed to a method and an apparatus for building up a workpiece layer by layer in the course of an additive manufacturing process, in particular in the form of a powder-bed process, wherein grains of a powder are fused to one another by using a binder, wherein the binder used is a heat-curable adhesive which is not applied selectively but layer by layer and which is activated and cured by a controlled energy source, in particular a laser with a controlled laser beam, and thereby fuses respectively adjacent grains of the powder.

Claims

1. An additive manufacturing process for building up a workpiece (2) layer by layer, in particular in the form of a powder-bed process, wherein grains of a powder (3) are fused to one another by using a binder (9), characterized in that the binder (9) used is an adhesive that can be cured under the influence of heat or an adhesive that can be melted under the influence of heat and that solidifies during subsequent cooling, which is not applied selectively but layer by layer and, after the application of every layer, is selectively activated and cured or selectively melted and cured during cooling, and thereby fuses respectively adjacent grains of the powder (3).

2. The additive manufacturing process according to claim 1, characterized in that the energy input in/on the heat-curable adhesive or the hot-melt adhesive takes place by means of one or more masks and/or apertures, in particular by means of an unfocused beam, whereby, through the masks and/or apertures for each layer, a region of the uppermost powder layer is selectively masked out.

3. The additive manufacturing process according to claim 1, characterized in that the energy input in/on the heat-curable adhesive or the hot-melt adhesive takes place by means of one more beams, in particular by a focused beam, preferably by means of a beam that is individually focused and/or controlled for each layer, for example an x-ray or a gamma ray.

4. The additive manufacturing process according to claim 1, characterized in that the energy input in/on the heat-curable adhesive or the hot-melt adhesive takes place by means of waves, in particular by means of electromagnetic waves, for example for example by means of microwaves, UV radiation, light, polarized light, monochromatic light, or the like.

5. The additive manufacturing process according to claim 4, characterized in that the energy input in/on the heat-curable adhesive or the hot-melt adhesive takes place by means of at least one laser (11), in particular by means of a controlled or controllable laser beam (12, 15).

6. The additive manufacturing process according to claim 5, characterized in that the introduced thermal energy or the power of the laser (11) is controlled, in particular limited, in such a way that the grains of the powder (3) are neither melted nor starting to melt nor sintered.

7. The additive manufacturing process according to claim 1, characterized in that a hot or hot-melt adhesive is used as the adhesive that can be melted under the influence of heat and that solidifies during subsequent cooling, preferably a thermoplastic or a thermoplastic elastomer.

8. The additive manufacturing process according to claim 7, characterized in that the hot or hot-melt adhesive is selected from the group consisting of polyamides (PA), polyethylene (PE), amorphous polyalphaolefines (APAO), ethylene vinyl acetate copolymers (EVAC), polyester elastomers (TPE-E), polyurethane elastomers (TPE-U), copolyamide elastomers (TPE-A), and vinyl pyrrolidone/vinyl acetate copolymers as well as mixtures thereof.

9. The additive manufacturing process according to claim 1, characterized in that a reactive hot-melt adhesive is used as the heat-curable adhesive.

10. The additive manufacturing process according to claim 9, characterized in that the heat-curable adhesive is selected from the group consisting of polyurethane (PUR), epoxy and polysiloxanes (SI) as well as mixtures thereof.

11. The additive manufacturing process according to claim 1, characterized in that a powder (3) of particles is used, which are coated with the binder (9), in particular said heat-curable adhesive.

12. The additive manufacturing process according to claim 1, characterized in that particulate matter from the binder (9), in particular said heat-curable adhesive, is admixed with the powder (3).

13. The additive manufacturing process according to claim 1, characterized in that after applying a powder layer on this, a binder (9) in liquid form is sprayed on.

14. The additive manufacturing process according to claim 1, characterized in that a powder (3) of an organic material is used.

15. The additive manufacturing process according to claim 1, characterized in that a powder (3) of an inorganic material is used, in particular also metal.

16. The additive manufacturing process according to claim 15, characterized in that a powder (3) with particles of an inorganic material or of a metal is used, wherein the particles are coated with an organic binder (9).

17. An additive manufacturing process (1) for building up a workpiece (2) layer by layer, in particular in the form of a powder-bed process, wherein grains of a powder (3) are fused to one another by using a binder (9), characterized by a controllable thermal energy source, whereby a binder (9), in particular an adhesive that can be cured under the influence of heat or an adhesive that can be melted under the influence of heat and that solidifies during subsequent cooling, is activated and cured layer by layer in selected regions, wherein respectively adjacent grains of the powder (3) are fused.

18. The additive manufacturing process (1) according to claim 17, characterized by a light source for light or infrared rays, whose rays of light are selectively controlled by means of a mask on selected regions of the uppermost powder layer.

19. The additive manufacturing process (1) according to claim 18, characterized by a device to change the mask with the selected regions of the uppermost layer of the workpiece when building up individual, multiple or all layers.

20. The additive manufacturing process (1) according to claim 17, characterized by a laser (11) with a controllable laser beam (12, 15) as a controllable thermal energy source.

21. The additive manufacturing process (1) according to claim 20, characterized in that the power of the laser (11) is controlled, in particular limited, in such a way that the grains of the powder (3) are neither melted nor starting to melt nor sintered.

22. The additive manufacturing process (1) according to claim 20, characterized in that the laser beam (11) can be controlled by means of optics (13), in particular by means of mirrors.

23. The additive manufacturing process (1) according to claim 20, characterized in that the laser beam (12, 15) is controlled by a program in such a way that it selectively heats only the grains of the powder (3) that are to be fused.

24. The additive manufacturing process (1) according to claim 17, characterized by a device for the layer by layer application of powder (3).

25. The additive manufacturing process (1) according to claim 24, characterized in that the device for the layer by layer application of powder (3) has a strewing or rolling mechanism.

26. The additive manufacturing process (1) according to claim 24, characterized in that the device for the layer by layer application of powder has a scraper (7) or a roller in order to level off the uppermost last applied powder layer.

27. The additive manufacturing process (1) according to claim 17, characterized by a heating device to preheat the grains of the powder (3).

28. The additive manufacturing process (1) according to claim 17, characterized by a device for spraying on a liquid or liquefied binder (9) on the uppermost layer of the powder (3).

29. The additive manufacturing process (1) according to claim 28, characterized in that the one device for spraying on a liquid or liquefied binder (9) has a nozzle, preferably an atomizing spray nozzle (8), which sprays the liquid or liquefied binder (9) diffusely on the uppermost layer of the powder (3).

30. The additive manufacturing process (1) according to claim 17, characterized by a device for coating the grains of the powder (3) with the binder (9).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Additional features, properties, advantages, and effects based on the invention are yielded from the following description of preferred embodiments of the invention as well as based on the drawing, which shows:

[0046] FIG. 1A first step of an additive manufacturing process according to the invention for building up a workpiece layer by layer, wherein an additional layer of a powder is applied to a bed;

[0047] FIG. 2A second step of the method from FIG. 1, wherein a binder is sprayed onto the last applied layer of powder; as well as

[0048] FIG. 3A third step of the same method, wherein specific regions of the last applied and sprayed-on powder layer are cured or solidified by selective temperature effects.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] The drawing depicts a preferred apparatus 1 for building up a workpiece 2 layer by layer from a powder 3 using additive manufacturing.

[0050] One can see a horizontal frame 4, inside of which a base plate 5 is arranged so that it is can be displaced vertically, for example by means of a very finely adjustable lifting cylinder or a preferably electrically operated motor such as a stepper motor or a position-controlled electric motor.

[0051] As FIG. 1 shows, to produce a single layer of the workpiece 2 on the base plate 5 or on a semi-finished product 6, which was already previously begun on this base plate 5 and which is still embedded in powder 3, a layer of powder 4 is applied and distributed in such a way that the most recent layer is as level as possible. This can be accomplished for example by means of a scraper 7, which is drawn over the previously strewn powder layer, in order to level it off, or by a roller that is rolled over the previously strewn powder layer. The powder layer itself can be strewn or sprayed on or applied with another technique.

[0052] In a second process step, which is reflected in FIG. 2, a liquid or liquefied binder is sprayed or sputtered on the uppermost powder layer. An atomizing spray nozzle 8 that is used in the process is supposed to ensure that the binder 9 gets sprayed or sputtered as uniformly as possible on the entire the powder layer 3. To this end, the atomizing spray nozzle 8 can be arranged optionally above the base plate 5 or even be horizontally movable, in order to be able to approach different positions above the base plate 5. The atomizing spray nozzle 8 can be arranged either directly beneath a container 10 with the liquid or liquefied binder 9, or be separated therefrom and be connected via hose to the container 10.

[0053] If a powder 3 is used, with which the individual particles are either coated with a binder, or with which binder particles are admixed, it is possible to dispense with said second step.

[0054] While the first two steps of the process were not selective, but are only meant to contribute to the most homogenous possible distribution of the powder and of the binder, the actual shaping now follows in a third step of the process.

[0055] In this case, a thermal energy source is controlled in such a way that the binder 9 or the adhesive is thermally activated selectively in the uppermost, last applied powder layer and cured, so that at the location of the subsequent workpiece 3 respectively adjacent grains of the powder 3 are fused to one another, and namely within the uppermost layer as well as also to an earlier already applied layer that might be beneath it.

[0056] In the case of the depicted embodiment, the energy source is a laser 11, whose laser beam 12 can be directed via controllable optics 13 onto different, selected regions 14 in the uppermost layer of the powder 3, which the deflected laser beam 15 is able recognize.

[0057] As a part of the method according to the invention, the laser can be pulsed so that the optics 13 stop initially always at an almost punctiform region to be cured, and the laser 11 is then briefly pulsed in order to introduce a defined quantity of heat in the punctiform region in question, and then stops at a next almost punctiform region to be cured, etc.

[0058] On the other hand, in the case of contiguous surfaces, the laser 11 can also be operated continuously and the laser beam 12, 15 can be adjusted by means of the optics 13 with a defined speed, which is selected so that a defined quantity of heat per unit of area is in turn introduced in the uppermost powder layer 3.

[0059] The energy of the laser 11 is transferred in split seconds in a sufficient quantity onto the respectively selected surface area and produces immediate curing or melting of the local binder 9, which thereby becomes solid either immediately or after a short cooling phase. Therefore, after adjusting the height of the base plate 5 bearing the workpiece semi-finished product 6, it is possible to immediately apply a subsequent powder layer 3, so as to repeat all of the foregoing processing steps layer by layer until the finished workpiece 2 has been created layer by layer from the semi-finished product 6.

[0060] This can then be removed from the powder bed 3, if applicable, after previously removing the uncured regions of the powder bed 3.

[0061] After that the workpiece can be refined more, either by being cured further by a repeated thermal treatment until all binder portions contained are cured, or it could undergo a surface treatment, for example by polishing or the like.

LIST OF REFERENCE NUMBERS

[0062] 1 Apparatus [0063] 2 Workpiece [0064] 3 Powder [0065] 4 Frame [0066] 5 Base plate [0067] 6 Semi-finished product [0068] 7 Scraper [0069] 8 Atomizing spray nozzle [0070] 9 Binder [0071] 10 Container [0072] 11 Laser [0073] 12 Laser beam [0074] 13 Optics [0075] 14 Selected region [0076] 15 Laser beam