ADDITIVE PRODUCTION DEVICE AND ASSOCIATED ADDITIVE PRODUCTION METHOD

Abstract

An additive manufacturing apparatus for manufacturing a three-dimensional object comprises a layer application device (16) for applying a building material layer by layer, an energy input unit (20) which comprises a carbon monoxide laser (21) and a radiation supply unit for supplying laser radiation of the carbon monoxide laser to positions in each layer that are assigned to the cross-section of the object in this layer, and a laser power modification device (27) adapted to effect an increase of the power per unit area incident on the building material within a time period that is smaller than 300 μs and/or larger than 50 ns, when the laser power is increased and/or to effect a reduction of the power per unit area incident on the building material within a time period that is smaller than 100 μm and/or larger than 100 ns, when the laser power is decreased.

Claims

1. An additive manufacturing apparatus for manufacturing a three-dimensional object comprises: a layer application device for applying a building material layer by layer, an energy input unit which comprises a carbon monoxide laser and a radiation supply unit for supplying laser radiation of the carbon monoxide laser to positions in each layer that are assigned to the cross-section of the object in this layer, and a laser power modification device adapted to effect an increase of the power per unit area incident on the building material within a time period that is smaller than 300 μs and/or larger than 50 ns, when the laser power is increased and/or to effect a reduction of the power per unit area incident on the building material within a time period that is smaller than 100 μm and/or larger than 100 ns, when the laser power is decreased.

2. The additive manufacturing apparatus of claim 1, wherein the laser power modification device is an acousto-optic or electro-optic modulator.

3. The additive manufacturing apparatus of claim 2, wherein the zeroth order laser radiation penetrating the laser power modification device is supplied to the positions in each layer that are assigned to the cross-section of the object in this layer in order to solidify the building material.

4. The additive manufacturing apparatus of claim 1, wherein the radiation supply unit comprises a deflection unit adapted to direct laser radiation of the carbon monoxide laser to positions in each layer that are assigned to the cross-section of the object in this layer and/or a focusing unit adapted to focus laser radiation of the carbon monoxide laser on the surface of a building material layer, wherein a characteristic dimension is equal to or smaller than approximately 50 mm and/or equal to or larger than 5 mm.

5. The additive manufacturing apparatus according to claim 4, comprising a focusing unit adapted to generate a focus diameter equal to or smaller than 500 μm on the surface of a building material layer.

6. The additive manufacturing apparatus according to claim 4, wherein the deflection unit is adapted to move the laser beam focus with a speed across the surface of the building material that is equal to or larger than 2 m/s and/or equal to or smaller than 50 m/s.

7. The additive manufacturing apparatus according to claim 1 in which the laser beam focus can be moved across the surface of the building materials in hatch lines that are parallel to each other with a distance to one another that is smaller than 0.18 mm and/or in which a beam offset can be set that is smaller than 0.18 mm.

8. An additive manufacturing method for manufacturing a three-dimensional object, wherein a building material is applied layer on layer and by means of an energy input unit that comprises a carbon monoxide laser and a radiation supply unit laser radiation of the carbon monoxide laser is supplied by the radiation supply unit to positions in each layer that are assigned to the cross-section of the object in this layer, and by means of a laser power modification device an increase of the power per unit area incident on the material is effected within a time period that is smaller than 300 μs and/or larger than 50 ns, when the laser power is increased, and/or a reduction of the power per unit area incident on the building material is effected within a time period that is smaller than 300 μs and/or larger than 50 ns, when the laser power is reduced.

9. The additive manufacturing method according to claim 8, wherein the building material is substantially free from absorbers.

10. The method according to claim 8, wherein the building material contains a polymer and/or coated sand and/or a ceramic material.

11. The method according to claim 8, wherein the building material includes at least one member from the group consisting of a polyamide, polypropylene (PP), polyether imide, polycarbonate, polyphenylene sulfone, polyphenylene oxide, polyether sulfone, acrylonitrile butadiene styrene copolymerisate, polyacrylate, polyester, polyurethane, polyimide, polyamide imide, polyolefin, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyamide elastomer, polyether ether ketone (PEEK) and polyaryletherketone (PAEK).

12. The method according to claim 8, wherein a solidified area in the area of incidence of the laser radiation on the building material has a dimension in the layer plane that is less than approximately 300 μm.

13. The method according to claim 8, wherein the layers of the building material are applied with a thickness of less than 80 μm and/or a thickness of 10 μm or more.

14. An article that has been manufactured by the methods according to claim 8 from a building material that is substantially free from absorbers, wherein at least one dimension of a detail is equal to or smaller than 150 μm and/or equal to or larger than 50 μm.

15. The article according to claim 14, which is made from at least member from the group consisting of polyamide, polypropylene (PP), polyether imide, polycarbonate, polyphenylene sulfone, polyphenylene oxide, polyether sulfone, acrylonitrile butadiene styrene copolymerisate, polyacrylate, polyester, polyurethane, polyimide, polyamide imide, polyolefin, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyamide elastomer, polyether ether ketone (PEEK) and polyaryletherketone (PAEK), and comprises less than 0.01 wt.-% absorber material.

Description

[0054] Further features and practicalities of the invention will arise from the description of embodiments based on the attached drawings.

[0055] FIG. 1 shows a schematic, partially sectional view of an exemplary apparatus for an additive manufacture of a three-dimensional object according to the invention.

[0056] FIG. 2 is for the purpose of schematically illustrating the manner of use of an acousto-optic modulator used as laser power modification device in the context of the present invention.

[0057] For building an object 2, the laser sintering or laser melting apparatus 1 comprises a process chamber or build chamber 3 having a chamber wall 4. A build container 5 which is open at the top and which has a container wall 6 is arranged in the process chamber 3. The top opening of the container 5 defines a working plane 7, wherein the area of the working plane 7 located within the opening, which area can be used for building the object 2, is referred to as build area 8.

[0058] In the build container 5, a support 10 is arranged that can be moved in a vertical direction V and to which a base plate 11 is attached which seals the container 5 at the bottom and thus forms the bottom thereof. The base plate 11 can be formed as a plate separately from the support 10, which plate is fixed to the support 10, or it can be integrally formed with the support 10. Depending on the powder and process used, a building platform 12 as building support can be additionally arranged on the base plate 11, on which building platform 12 the object 2 is built. However, the object 2 can also be built on the base plate 11 itself, which then serves as a building support. In FIG. 1, the object 2 to be formed in the container 5 on the building platform 12 is shown below the working plane 7 in an intermediate state with several solidified layers, surrounded by building material 13 that remained unsolidified.

[0059] The laser sintering or melting device 1 further comprises a storage container 14 for a building material 15, in this example a powder that can be solidified by electromagnetic radiation, and a recoater 16 as material application device that can be moved in a horizontal direction H for applying the building material 15 within the build area 8. Optionally, a heating device, e.g. a radiant heater 17, can be arranged in the process chamber 3, which heating device serves for a heating of the applied building material. For example, an infrared heater may be provided as radiant heater 17.

[0060] The exemplary additive manufacturing apparatus 1 further comprises an energy input unit 20 having a carbon monoxide laser 21 generating a laser beam 22 that is deflected by a deflection device 23 and is focused on the working plane 7 through a coupling window 25 that is arranged at the top side of the process chamber 3 in the chamber wall 4 by a focusing device 24. For example, the laser distributed by the company Coherent under the name “DIAMOND J-3-5 CO Laser” can be used as carbon monoxide laser.

[0061] The deflection device 23 substantially consists of a galvanometer mirror for a deflection into each of the X direction and the Y direction, wherein it is assumed that the working plane 7 extends in the X direction and Y direction. In particular, a laser power modification device 27, which in the present example is an acousto-optic modulator, is located in the beam path between the carbon monoxide laser 21 and the deflection device 23. Such modulators are for example distributed by the company Gooch & Housego PLC in Ilminster UK. For example, the model I-MOXX-XC11B76-P5-GH105 can be driven with up to 60 MHz.

[0062] FIG. 2 shows in detail the manner of use of the acousto-optic modulator in the present example. The laser beam 22 emitted by the carbon monoxide laser 21 is split up in the acousto-optic modulator 27 into a beam 22a supplied to the deflection device 23 and a beam 22b. In the present example, the beam 22a is the zeroth order of the diffraction pattern and the beam 22b is the first order of the diffraction pattern. Of course, also higher orders occur. However, these are not shown in order to simplify the drawing. It can be seen that in the present example the laser power modification device 27 serves for attenuating the beam 22 emitted by the carbon monoxide laser 21 in order to modulate thereby its power. Here, the beam 22a supplied to the deflection device 23 propagates in the same direction as the beam 22 emitted by the carbon monoxide laser 21. Thus, even if variations of the environmental conditions lead to variations in the behavior of the acousto-optic modulator, this has no effect on the direction of the beam supplied to the deflection device 23. By means of the shown arrangement, the power in the beam 22 is substantially deflected into the higher orders for switching off the beam in order to obtain as few power as possible in the zeroth order. Thus, by a control of the acousto-optic modulator 27, the beam supplied to the deflection device 23 is substantially switched on and off. The power still remaining in the zeroth order in a switch-off lies in the range of few percent and can be tolerated as it is usually not able to effect an undesired solidification of the building material. The presence of residual light of the beam source used for the solidification is known in the prior art and is named there “bleeding”.

[0063] Furthermore, the laser sintering apparatus 1 comprises a control unit 29 by which the individual components of the apparatus 1 can be controlled in a coordinated manner in order to implement the building process. Alternatively, the control unit can also be arranged partially or completely outside of the additive manufacturing apparatus. The control unit can comprise a CPU, the operation of which is controlled by a computer program (software). The computer program can be stored separately from the additive manufacturing apparatus on a storage device from where it can be loaded (e.g. via a network) into the additive manufacturing apparatus, in particular into the control unit.

[0064] In operation, the control unit 29 lowers the support 10 layer by layer, it activates the recoater 16 for applying a new powder layer and the laser power modification device 27, the deflection device 23 and, if necessary, also the laser 21 and/or the focusing device 24 for solidifying the respective layer at the positions corresponding to the respective object by means of the laser by scanning these positions with the laser.

[0065] In the additive manufacturing apparatus just described as an example, a manufacturing process is carried out in such a way that the control unit 29 processes a control data set.

[0066] For each point in time during the solidification process, the control data set instructs an energy input unit, in the case of the above laser sintering or laser melting apparatus specifically the deflection device 23, to which position on the working plane 7 the radiation is to be directed.

[0067] As mentioned further above, instead of the acousto-optic modulator also a different optical device can be used as laser power modification device provided that it is adapted to change the laser power supplied to the building material, meaning in particular the power impinging per unit area onto the building material, within a short period of time. For example, also a photo-elastic modulator (PEM) that can be controlled correspondingly fast or an adequate wave plate (e.g. λ/2 plate) together with a polarizer can be used.