Device and method for rendering inert a process chamber for the additive manufacture of a workpiece

Abstract

The invention relates to a device (10) for the additive manufacture of a workpiece (44). The device (10) has at least one fluidizing cushion (20) in order for inert gas (16) to flow uniformly and as a block into the interior of a process chamber (12). This allows the process chamber (12) to be effectively rendered inert. A gas outlet (18) is preferably arranged opposite a gas inlet (14) with the fluidizing cushion (20). The invention also relates to a method (34) for operating such a device (10). In the method (34), the process chamber (12) is preferably rendered inert by the fluidizing cushion (20) before the additive manufacture of the workpiece (44) begins, while a pump (52) makes inert gas (16) flow through the process chamber (12) during the additive manufacture.

Description

[0001] Device and method for inerting a process chamber for the additive manufacturing of a workpiece

[0002] Background of the invention

[0003] The invention relates to a device for the additive manufacturing of a workpiece. The device comprises a process chamber in which the workpiece can be additively built. The device further comprises a gas inlet and a gas outlet at the process chamber for passing protective gas through the process chamber to inertize the process chamber and / or achieve gas flow during the manufacturing process.

[0004] WO 2019 / 162190 A1 discloses such a device, in which a process chamber for the additive manufacturing of three-dimensional structures is flowed through with a protective gas. According to WO 2019 / 162190 A1, the protective gas is introduced into the process chamber at specific points.

[0005] WO 2018 / 086887 A1 teaches the use of a porous wall for gas inlet into a process chamber.

[0006] Object of the invention

[0007] The object of the invention is to provide a device and a method that enable significantly more effective inerting of a process chamber. Description of the invention

[0008] This object is achieved according to the invention by a device according to claim 1 and a method according to claim 8. The subclaims give preferred developments.

[0009] The object of the invention is thus achieved by a device as described above, in which the gas inlet has a fluidization pad. The fluidization pad has a plate with several grids arranged one behind the other with respect to the flow direction of the fluidization pad. The fluidization pad enables a particularly uniform, essentially laminar, and turbulence-free gas flow. This allows the gas in the process chamber to be displaced by a block-like inflow of shielding gas. In contrast to the prior art, there is virtually no turbulence or dilution of the gas in the process chamber with shielding gas; instead, the gas in the process chamber is effectively and quickly pushed out of the process chamber by the front "wall" of the shielding gas block. Inerting the process chamber can thus be achieved very quickly and with very little shielding gas.

[0010] The plate of the fluidization cushion can be designed in the form of a wire mesh composite plate. The outer mesh or outer wire mesh layers can have flattened peaks to optimize the outflow behavior. The fluidization cushion preferably has a pore size between 5 μm and 500 μm.

[0011] The plate of the fluidization cushion can be curved to achieve a particularly laminar gas flow adapted to the design of the process chamber.

[0012] The fluidization cushion can be used to inertize a portion, particularly a large portion, of the piping in / to the process chamber. The gas inlet can have a T-shaped stirrer. In a particularly preferred embodiment of the invention, the gas inlet has a Y-shaped pipe section. The stem (lower part of the Y-shape) preferably faces the process chamber. The fluidization cushion can be arranged on a first branch of the Y-shape, so that protective gas can flow into the process chamber in a substantially straight line.

[0013] The second branch of the Y-shaped tube can lead to a pump of the device. The pump can be fluidically arranged between the gas outlet and the second branch. A filter can be arranged on the pump.

[0014] To achieve a particularly linear flow through the process chamber, the gas inlet and outlet can be arranged opposite each other. The additive structure can be provided between the gas inlet and outlet, particularly in a construction cylinder.

[0015] The inerting of the process chamber can be carried out even more effectively if the device has at least one additional fluidization pad for flowing protective gas into the process chamber. The at least one additional fluidization pad can be arranged on the inside of a first chamber wall of the process chamber. The at least one additional fluidization pad comprises a plate with multiple grids.

[0016] A further gas outlet can be provided opposite the at least one further fluidization cushion, so that protective gas can flow into the process chamber essentially in a straight line from the at least one further fluidization cushion through the process chamber and out of the further gas outlet.

[0017] The plate of the at least one further fluidization cushion can be curved in order to achieve a particularly laminar gas flow adapted to the design of the process chamber. The at least one further fluidization cushion and the fluidization cushion can be designed identically. The at least one further fluidization cushion preferably covers the inside of the first chamber wall predominantly, in particular almost completely, particularly preferably completely. Alternatively, the inside of the first chamber wall can be covered predominantly, in particular almost completely, particularly preferably completely, by several further fluidization cushions. The several further fluidization cushions each have a plate with several grids. The several further fluidization cushions can be designed identically, in particular the same as the fluidization cushion.

[0018] In a particularly preferred embodiment of the invention, the device is designed for additive manufacturing of the workpiece in a powder bed. The device is preferably designed for powder-bed-based laser melting (laser metal fusion process).

[0019] The object of the invention is further achieved by a method for inerting a device described herein, comprising the following method step: A1) Inflow of protective gas into the process chamber via the fluidization cushion and outflow of gas (air) from the process chamber via the gas outlet. During this method step, preferably no additive manufacturing of the workpiece takes place and / or the pump is switched off.

[0020] Process step A1 therefore preferably represents a step for inerting the process chamber before the actual construction of the workpiece.

[0021] The method preferably comprises the following method step: B) Switching on the pump and additive construction of the workpiece.

[0022] During process step B, protective gas preferably does not flow through the fluidization pad. However, inerting can preferably be performed before the process starts while the pump is running, and / or temporarily re-inerting can be performed during the additive build-up of the workpiece. The following process step preferably takes place before or after process step A1 and before process step B:

[0023] A2) Inflow of protective gas via the at least one, in particular several, further fluidization cushions and outflow of gas via the further gas outlet. During this process step, additive manufacturing of the workpiece preferably does not occur and / or the pump is switched off.

[0024] Process step A1 therefore preferably represents a step for inerting the process chamber before the actual construction of the workpiece.

[0025] Noble gas and / or nitrogen are preferably used as protective gas (inert gas).

[0026] Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further-described features can be used individually or in combination in any desired manner. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention.

[0027] Detailed description of the invention and drawing

[0028] Fig. 1 shows schematically a device for the additive manufacturing of a workpiece in a process chamber, wherein Fig. 1 shows the inerting of a part of the process chamber through which flow is actively carried out during the construction of the workpiece.

[0029] Fig. 2 shows schematically the device from Fig. 1, wherein Fig. 2 shows the inerting of a part of the process chamber through which no active flow occurs during the construction of the workpiece.

[0030] Fig. 3 shows schematically the device from Figs. 1 and 2, wherein Fig. 3 shows the active flow through the process chamber during the construction of the workpiece.

[0031] Figs. 1-3 further represent an embodiment of a method according to the invention. Fig. 1 shows a device 10 for additive manufacturing with a process chamber 12, a gas inlet 14 for introducing protective gas 16 and a gas outlet 18 for discharging the protective gas 16. The protective gas 16 or inert gas is preferably in the form of noble gas or nitrogen.

[0032] The shielding gas 16 flows in through a fluidization pad 20, which has a plate 22 with several grids 24. The grids 24 create a very laminar gas flow with very little turbulence. As a result, the shielding gas 16 flows out in a block shape and pushes the gas 26 present in the process chamber 12 out of the process chamber 12 via the gas outlet 18. A first valve 28, possibly with a filter 30, can be provided to the ambient atmosphere 32.

[0033] Fig. 1 shows a first method step of a method 34 for inerting the process chamber 12. Further method steps are shown in Figs. 2 and 3.

[0034] Fig. 2 shows the device 10 or the method 34 with the process chamber 12, wherein it can be seen from Fig. 2 that no protective gas flow occurs from the fluidization cushion 20.

[0035] The process chamber 12 has a first chamber wall 36, the interior of which is completely covered with additional fluidization pads 38a, 38b. The additional fluidization pads 38a, 38b each have a plate 22 with several grids 24. Shielding gas 16 flows in blocks from the additional fluidization pads 38a, 38b to force gas 26 out of the process chamber 12 in blocks through an additional gas outlet 40 and possibly an additional filter 42.

[0036] Fig. 3 shows the device 10 or the method 34 during the production of a workpiece 44 by melting a powder layer 46 in certain areas with a laser beam 48. Additive manufacturing preferably takes place in a build cylinder 50. During the additive manufacturing of the workpiece 44, a pump 52 circulates protective gas 16—optionally through a prefilter 54. The prefilter 54 can be designed in the form of a filter unit.

[0037] Generally speaking, a filter fluidization pad (not shown) may be provided on the pre-filter 54, which is in particular designed identically to the fluidization pad 20.

[0038] The fluidization cushion 20 and the further fluidization cushions 38a, b are preferably switched off unless an oxygen sensor (not shown) measures a significant increase in the oxygen content.

[0039] From Fig. 3, it can be seen that the gas inlet 14 is Y-shaped, with a stem 56, a first branch 58, and a second branch 60. The fluidization pad 20 is arranged in the first branch 58. The second branch 60 leads to the pump 52. The stem 56 leads—here via a honeycomb-shaped distributor 62—into the interior of the process chamber 12.

[0040] Taking a summary of all figures of the drawing, the invention relates in summary to a device 10 for the additive manufacturing of a workpiece 44. The device 10 has at least one fluidization cushion 20 for flowing protective gas 16 in a block-like and uniform manner into the interior of a process chamber 12. This allows the process chamber 12 to be effectively inerted. A gas outlet 18 is preferably arranged opposite a gas inlet 14 with the fluidization cushion 20. The invention further relates to a method 34 for operating such a device 10. In the method 34, the process chamber 12 is preferably inerted by the fluidization cushion 20 before the additive manufacturing of the workpiece 44 begins, wherein a pump 52 ensures that the protective gas 16 flows through the process chamber 12 during the additive manufacturing.

[0041] 10 Device 38a, b additional fluidization cushion

[0042] 12 Process chamber 40 Additional gas outlet 14 Gas inlet 42 Additional filter

[0043] 16 Shielding gas 20 44 Workpiece

[0044] 18 Gas outlet 46 Powder layer

[0045] 20 fluidization cushions 48 laser beams

[0046] 22 Plate 50 Construction cylinder 24 Grid 52 Pump

[0047] 26 Gas 25 54 Prefilter

[0048] 28 first valve 56 stem (of the Y-shape)

[0049] 30 Filter 58 first branch (of the Y-shape)

[0050] 32 ambient atmosphere 60 second branch (of the Y-shape) 34 process 62 honeycomb distributor

[0051] 36 first chamber wall

Claims

Patent claims 1. A device (10) for the additive manufacturing of a workpiece (44), the device (10) comprising: a) a process chamber (12) for constructing the workpiece (44); b) a gas inlet (14) for introducing protective gas (16) into the process chamber (12); c) a gas outlet (18) from the process chamber (12) for discharging the protective gas (16); characterized in that the gas inlet (14) has a fluidization cushion (20), the fluidization cushion (20) having a plate (22) with a plurality of grids (24) arranged one behind the other in the flow direction in order to achieve a uniform gas flow.

2. Device according to claim 1, wherein the gas inlet (14) is Y-shaped, wherein the stem (56) of the Y-shape opens directly or indirectly into the process chamber (12) and wherein the fluidization cushion (20) is arranged on a first branch (58) of the Y-shape, so that protective gas (16) can flow into the process chamber (12) via the stem (56) of the Y-shape.

3. Device according to claim 2, wherein the second branch (60) of the Y-shape is connected to a pump (52) of the device (10), the pump (52) being connected at the other end to the gas outlet (18) of the process chamber (12), so that protective gas (16) is sucked out of the gas outlet (18) and can flow into the process chamber (12) via the pump (52) and further the stem (56) of the Y-shape.

4. Device according to one of the preceding claims, in which the gas inlet (14) and the gas outlet (18) are arranged opposite one another, wherein the additive construction of the workpiece (44) can take place between the gas inlet (14) and the gas outlet (18).

5. Device according to one of the preceding claims, in which a further fluidization cushion (38a, b) for the inflow of protective gas (16) into the process chamber (12) is arranged on a first chamber wall (36) of the process chamber (12), wherein the further fluidization cushion (38a, b) has a plate (22) with several grids (24) arranged one behind the other in the flow direction, wherein a further gas outlet (40) is arranged in the process chamber (12) opposite the further fluidization cushion (38a, b) so that protective gas (16) can flow from the further fluidization cushion (38a, b) through the process chamber (12) and further out of the further gas outlet (40).

6. Device according to claim 5, wherein the further fluidization cushion (38a, b) covers the first chamber wall (36) or a plurality of further fluidization cushions (38a, b) are provided, wherein the further fluidization cushions (38a, b) each have a plate (22) with a plurality of grids (24) arranged one behind the other in the flow direction, wherein the plates (22) cover the first chamber wall (36).

7. Device according to one of the preceding claims, in which the device (10) is designed for additive manufacturing of the workpiece (44) in the powder bed.

8. Method (34) for inerting a device (10) according to one of the preceding claims, comprising the following method steps: Al) Inflow of protective gas (16) via the fluidization cushion (20) into the process chamber (12) and outflow of gas (26) from the process chamber (12) via the gas outlet (18), whereby no additive build-up of the workpiece (44) takes place.

9. The method according to claim 8, wherein the method (34) comprises the following method step: B) Switching on the pump (52) and additive construction of the workpiece (44).

10. The method according to claim 9, wherein in method step B no inflow of protective gas (16) occurs via the fluidization cushion (20).

11. Method according to one of claims 8 to 10, in conjunction with claim 5, wherein the method (34) comprises the following method step: A2) Inflow of protective gas (16) via the further fluidization cushion (38a, b) into the process chamber (12) and outflow of gas (26) from the process chamber (12) via the further gas outlet (40), wherein no inflow of protective gas (16) via the fluidization cushion (20) and no additive build-up of the workpiece (44) takes place, wherein process step A2 is carried out before or after process step A1.

12. Method according to one of claims 8 to 11, in which a noble gas and / or nitrogen is used as the protective gas (16).

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