ELECTRON BEAM SYSTEM, AND METHOD FOR THE ADDITIVE MANUFACTURE OF A WORKPIECE

Abstract

An electron beam system for the additive manufacture of a workpiece having a process chamber which can be evacuated and comprising an electron beam generator which is designed to direct an electron beam onto laterally different locations of a powder bed made of a pulverulent material to be processed in the process chamber. In order to improve the throughput of the electron beam system, the system has at least one prechamber which can be evacuated and which is constantly connected to the process chamber during the operation of the electron beam system in a vacuum-tight manner via a sluice door. Furthermore, at least one movable receiving device for receiving the powder bed and a transport device are provided, said transport device allowing the at least one receiving device to be transported from the prechamber into the process chamber.

Claims

1. An electron beam system for the additive manufacture of a workpiece, comprising: a) a process chamber which can be evacuated; b) an electron beam generator which is set up in the process chamber directing an electron beam onto laterally different locations of a powder bed made of a powdery material to be processed; wherein c) at least one prechamber which can be evacuated and which can be used during operation of the electron beam system, is continuously connected to the process chamber in a vacuum-tight manner via a sluice door; d) at least one movable receiving device for receiving the powder bed; and a transport device with which the at least one receiving device can be transported from the prechamber into the process chamber.

2. The electron beam system according to claim 1, wherein the movable receiving device has a construction container which is set up to receive the powder bed, and in which the workpiece can be produced additively.

3. The electron beam system according to claim 2, wherein the movable receiving device has a storage container for the powdery material.

4. The electron beam system according to claim 3, wherein the movable receiving device has a powder application device which is set up to remove the powdery material from the storage container to be transferred into the construction container in order to generate the powder bed there for the additive manufacture of the workpiece.

5. The electron beam system according to claim 1, wherein wherein the transport device is set up to exchange a first movable receiving device, which is initially located in the prechamber, for a second movable receiving device, which is located in the process chamber.

6. The electron beam system according to claim 1, wherein wherein the transport device has at least two transport tracks, along which at least two movable receiving devices are transportable back and forth past one another between the prechamber and the process chamber.

7. The electron beam system according to claim 1, wherein wherein the prechamber and/or the receiving device has at least one temperature measuring device.

8. The electron beam system according to claim 1, wherein wherein a loading and unloading station is connected to the prechamber, via which the at least one movable receiving device is introduced into the electron beam system or can be removed from this.

9. A method for additive manufacture of a workpiece comprising the following steps: a) providing an electron beam system according to any one of the preceding claims; b) producing a first workpiece in a first movable receiving device by processing the powdery material in the powder bed by means of an electron beam in the process chamber; c) equipping the prechamber with a second movable receiving device and then evacuating the prechamber; d) transporting the first movable receiving device from the process chamber into the prechamber or into another prechamber; e) transporting the second movable device from the prechamber into the process chamber; f) producing a second workpiece in the second movable receiving device by processing the powdery material in the powder bed by means of an electron beam in the process chamber; and g) cooling of the first workpiece in the first movable receiving device in the prechamber.

10. The method according to claim 9, further comprising the step of: a) removing the first movable device together with the workpiece from the prechamber.

11. A system for the additive manufacture of a workpiece comprising: a) a process chamber which can preferably be evacuated; b) a construction container in which the workpiece can be produced; c) a storage container for powdery material; d) a powder application device which is set up to transfer the powdery material from the storage container into a powder bed in the construction container to transfer; e) a beam generator which is set up to direct an energy beam, in particular an electron beam, onto laterally different locations of the powder bed in the process chamber; wherein f) the powder application device can be removed from the process chamber.

12. The system according to claim 11, wherein the system comprises at least one movable receiving device having the construction container (40), the storage container and the powder application device.

13. The system according to claim 12, wherein the at least one movable receiving device can be transported from the process chamber into the process chamber and out of it.

14. The system according to claim 12, wherein the at least one movable receiving device is designed to accommodate construction containers and/or storage containers with different dimensions, in particular of different volumes.

15. The system according to claim 11, wherein all components coming into contact with the process can be removed from the process chamber.

16. A movable receiving device for a system for the additive manufacture of a workpiece from a powdery material, comprising: a construction container in which the workpiece can be produced in layers, wherein a) the movable receiving device has a powder application device which is set up to transfer the powdery material from a storage container into a powder bed to be transferred in the construction container.

17. The movable receiving device according to claim 16, wherein the storage container for the powdery material is part of the movable receiving device.

18. The movable receiving device according to claim 16, wherein the receiving device comprises a support frame which has at least two thermally decoupled sections.

19. The movable receiving device according to claim 16, wherein the construction container and the powder application device are attached to different sections of the support frame.

20. A method for the additive manufacture of a workpiece, comprising the steps of: a) providing a beam system according to claim 11; b) producing a workpiece by processing the powdery material by means of an energy beam in the process chamber; and c) removing the powder application device from the process chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings, in which:

[0094] FIG. 1 shows a schematic view of an electron beam system according to the invention for the additive manufacture of a workpiece;

[0095] FIG. 2 shows a side view of the electron beam system;

[0096] FIG. 3 shows a plan view of the electron beam system;

[0097] FIG. 4 shows an isometric view of a receiving device for the electron beam system;

[0098] FIG. 5 shows a side view of an electron beam system according to another exemplary embodiment with two prechambers;

[0099] FIGS. 6a-6d are plan views of various embodiments of the electron beam system with different arrangements of the prechamber;

[0100] FIG. 7a shows a side view of an electron beam system with a vertical arrangement of the prechamber;

[0101] FIG. 7b shows a side view of an electron beam system with a vertical arrangement of the prechamber;

[0102] FIG. 8a shows an isometric view of an embodiment of the receiving device for the electron beam system,

[0103] FIG. 8b shows an isometric view of a system for the additive manufacture of a workpiece with a movable receiving device.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

[0104] FIG. 1 schematically shows the principle of an electron beam system 10 according to the invention, which comprises a process chamber 12 and a prechamber 14 which is connected to the process chamber 12 via a sluice door 16.

[0105] Both the process chamber 12 and the prechamber 14 are defined by vacuum housings which can be evacuated to pressures in the range from 10.sup.−5 to 10.sup.−2 mbar by means of generally known suction devices and vacuum pumps, which are not shown in detail. When the sluice door 16 is closed, the process chamber 12 and the prechamber 14 can, however, be evacuated and ventilated separately from one another. For this purpose, the electron beam system 10 can have a gas inlet, not shown here, for an inert gas, for example, on the process chamber 12 and/or the prechamber 14.

[0106] In addition, a further sluice door 18 is provided on the prechamber 14 to an optional loading and unloading station 20 arranged outside the prechamber 14 (see also FIG. 2).

[0107] Usually arranged on a flange of the vacuum housing, the electron beam system 10 has an electron beam generator 22 together with a deflection device 24, with the aid of which an electron beam 26 can be generated and deflected in the process chamber 12.

[0108] As can be seen from FIGS. 1 and 3, in the exemplary embodiment shown here, rails 34a, 34b, 36a, 36b are provided as a transport device 30 for a movable receiving device 32 in the process chamber 12, in the prechamber 14 and as part of the loading and unloading station 20, 38a, 38b.

[0109] The rails 34a, 34b, 36a, 36b, 38a, 38b are interrupted in the area of the two sluice doors 16 and 18, so that when the sluice doors 16 and 18 are closed, the rails 34a, 34b are arranged fully in the process chamber 12 and the rails 36a, 36b fully in the prechamber 14.

[0110] The transport device 30 makes it possible to transport the movable receiving device 32 back and forth between the prechamber 14 and the process chamber 12 and if necessary the loading and unloading station via actuators 40, which are not detailed here, such as driven rollers.

[0111] In addition, it can be seen from FIG. 3 that the transport device 30 with the rails 34a, 36a, 38a and the rails 34b, 36b, 38b has two parallel transport tracks, so that two movable receiving devices 32 can be transported past one another from the prechamber 14 into the process chamber 12 and back.

[0112] In the process chamber 12, a coordinate table 39 adjoins the transport device 30, which can laterally position and move the receiving device 32 in the process chamber 12.

[0113] Such a movable receiving device 32 is shown in FIG. 4.

[0114] The receiving device 32 firstly has a support frame 33 as a basic component, with which the transport device 30 interacts.

[0115] The receiving device 32 also has a construction container 40 in which a powder bed 42 (see FIG. 1) can be received, from which a workpiece 43 can be produced in an additive manufacturing process (3D printing).

[0116] Furthermore, the receiving device 32 comprises a storage container 44, which is arranged here next to the construction container 40, in which powdery material 46 is stored.

[0117] Both the construction container 40 and the storage container 44 are used as separate components in the support frame 33 and can thus be selected individually for each manufacturing process, i.e. in particular with different sizes. Alternatively, the support frame 33 and the containers 40, 44 can also be permanently attached or even designed as a single piece, so that the receiving device 32 is exchanged in its entirety depending on the manufacturing process.

[0118] The construction container 40 for its part comprises a movable base plate 48 which can be raised and lowered via a reciprocating piston 50 arranged in the process chamber 12.

[0119] The same applies to the storage container 44, which also has a movable base plate 52 which can be raised and lowered via a second reciprocating piston 54.

[0120] Above the two containers 40, 44 a squeegee 56 is provided as a powder application device, with which the powdery material 46 as the uppermost loose layer can be doctored from the storage container 44 to the construction container 40 and evenly applied to a powder bed 42.

[0121] The two base plates 48 and 52 are moved in opposite directions, layer by layer, so that the construction container 40 gradually becomes larger and the storage container 44 becomes smaller according to the amount of powder required.

[0122] In the simplest design, the two containers 40, 44 have the same overall cross-section. In the case of different overall cross-sections, the movement of the base plate 52 of the storage container 44 must be adapted accordingly to the required amount of powder.

[0123] Both the storage container 44 and the powder application device can alternatively also be arranged in the process chamber 12 independently of the receiving device 32. Furthermore, the receiving device 32 can have a powder overflow 58 and a heat shield above the construction container 44.

[0124] A control unit 60 is connected to the essential components of the electron beam system 10, in particular to the electron beam generator 22, the actuators of the transport device 30, the sluice doors 16, 18 and the reciprocating pistons 50, 54 in order to control the entire manufacturing process.

[0125] The manufacturing process according to the invention works as follows:

[0126] To produce a workpiece 43 in the electron beam system 10 according to the invention, a receiving device 32 with a construction container 40 for receiving a powder bed 42 is positioned in die process chamber 12 via the transport device 30.

[0127] The powdery material 46 is arranged in the storage container 44.

[0128] In the next step, the process chamber 12 is evacuated. After the target pressure has been reached, the manufacturing process of the workpiece 43 begins. For this purpose, the powder application device is used to apply layer by layer of the powdery material 46 in the construction container 40, and each layer is partially solidified with the electron beam 26.

[0129] The movement of the electron beam 26 relative to the powder bed 42 can take place by deflecting the electron beam 26 with the deflection device 24 or by moving the coordinate table 39.

[0130] Optionally, the powdery material 46 is preheated in a preheating step before the melting step in order to avoid powder losses and process interruptions due to electrostatic blowing of the material 46.

[0131] While the first workpiece 43 is being manufactured in the evacuated process chamber 12, the next construction container 40 and possibly the next storage container 44 can be prepared in a further receiving device 32 outside the electron beam system 10. This second receiving device 32 is then placed in the prechamber 14, it being possible for the sluice door 16 to the process chamber 12 to remain closed. Then the prechamber 14 is also evacuated.

[0132] Since each movable receiving device 32 can be prepared individually, the storage container 44 can also be filled with a different material 46 in each case. Thus, different workpieces 43 made of different materials can be produced one after the other.

[0133] In order to minimise powder consumption, construction containers 40 are provided with different volumes, which are selected depending on the size of the workpiece 43 and can be introduced into the electron beam system 10 by means of the receiving device 32.

[0134] After completion of the first workpiece 43, the sluice door 16 between the prechamber 14 and the process chamber 12 is opened. The finished workpiece 43 is transported into the prechamber 14 on a transport track of the transport device 30. The second receiving device 32 is transported into the process chamber 12 on the second transport track.

[0135] While the manufacturing process of the second workpiece 43 now begins in the process chamber 12, the first workpiece 43 can cool down in the prechamber 14. This process can be accelerated or precisely defined by introducing an inert gas such as helium. The cooling process of the workpiece 43 is monitored by temperature measuring devices 62 placed in the electron beam system 10 and/or on the receiving device 32.

[0136] In order to monitor the process, in particular the cooling process, the temperature is measured at various points in the electron beam system 10 and at the receiving device 32 by means of temperature measuring devices 62. Preferred measuring points include on the base plate 48 of the construction container 40, on the walls of the construction container 40, the storage container 44 and/or the powder overflow 58, on the doctor blade 56, in particular a doctor blade carrier and/or along the doctor blade rail, and combinations of these. Temperature measuring devices 62 can also be attached in the chambers, for example on a side wall or ceiling of the prechamber 14 or process chamber 12.

[0137] In one embodiment of the invention, the control unit 60 is designed to monitor the cooling down and automatically flood the prechamber 14 when a certain temperature is reached, to open the sluice door 18 and to transport the receiving device 32 out of the prechamber 14.

[0138] A receiving device 32 can then be prepared again and placed in the prechamber 12.

[0139] FIG. 5 shows an embodiment of the electron beam system 10 with two prechambers 12. In this embodiment, the transport device 30 can have one, two or four transport tracks. With this system, it is possible to further reduce the time required for cooling per workpiece 43, since several workpieces 43 can cool down in several receiving devices 32 at the same time.

[0140] When using two prechambers 14, the transport device 30 can also be equipped with only one transport track, so that, in the continuous flow principle, one prechamber 14 is always used for loading and the other prechamber 14 is always used for cooling and unloading. This reduces the complexity of the transport device 30.

[0141] FIGS. 6a-d and 7 show embodiments of the electron beam system 10 with a reduced volume of the process chamber 12 and optimised transport routes of the receiving device 32.

[0142] The process chamber 12 of the embodiments shown in FIGS. 6a-d and 7 is designed to accommodate precisely one movable receiving device 32.

[0143] FIG. 6d shows an embodiment of the electron beam system 10 with a turntable in the prechamber.

[0144] The loading and unloading station 20 can, as shown in FIG. 7, be designed in the form of a closed workspace. The loading and unloading station 20 is preferably a glove box with a powder suction system for the safe unpacking of the workpiece. The loading and unloading station 20 can be designed in the form of a transport unit that can dock with the prechamber.

[0145] FIG. 7 shows an embodiment of the electron beam system 10 with a vertical arrangement of the prechamber 14. The prechamber 14 is provided with an elevator 15. The elevator is designed to accommodate at least two movable receiving devices 32 arranged vertically one above the other. The prechamber shown in FIG. 7 has two holding positions for the elevator. In FIG. 7 the elevator 15 is in the lower position and enables the transport from the loading and unloading station 20 to the second loading level 15b of the elevator. The first loading level 15a of the elevator is also designed to accommodate a movable receiving device 32. The upper holding position has the reference symbol 17 in FIG. 17.

[0146] According to one possible operating mode, the elevator 15 is equipped with a receiving device 32 and the prechamber 14 is evacuated. The sluice door 16 is then opened and the receiving device 32 is transported into the process chamber. Sluice door 16 is closed again. During the processing of the powder with the electron beam in the process chamber, the sluice door 18 of the prechamber 14 is opened and the elevator 15 is equipped with a further movable receiving device 32. The sluice door 18 is then closed and the prechamber 14 is evacuated.

[0147] Alternatively, the elevator 15 can already be equipped with two receiving devices when loading. For this purpose, the elevator is moved from the first to the second stop position or vice versa.

[0148] Before finishing the powder processing step, the elevator is brought into a position in which the still vacant loading level and the sluice door 16 are connected. After completion of the powder processing step, the sluice door 16 is opened and the receiving device with the processed powder is transported from the process chamber 12 into the vacant position of the elevator. The elevator is then moved, and the receiving device 32 is transported with the unprocessed powder into the process chamber and processed with the electron beam.

[0149] During the powder processing step of the second receiving device, the hot receiving device 32 with the processed powder remains in the prechamber and cools down. In the case of supported cooling processes, the receiving device is brought into an advantageous position, e.g. in the upper area of the prechamber or near the inlet of the coolant.

[0150] When the desired temperature is reached, or before the end of the powder processing step of the second receiving device, the elevator is brought into a suitable position, the sluice door 18 is opened and the receiving device is transported out of the prechamber. Then a third receiving device can be brought into the prechamber, the sluice door 18 closed and the prechamber evacuated. The exchange with the receiving device with the processed powder takes place in the same way as described above. The process can be repeated any number of times.

[0151] The vertical embodiment of the prechamber is particularly advantageous because in addition to the improved use of the electron beam system with regard to the dwell time and evacuation problems, the space requirement, especially with regard to the footprint of the system, is reduced.

[0152] As an alternative to this, the electron beam system 10 can be designed with two prechambers 14 and two transport tracks. In one embodiment of the invention, the electron beam system 10 comprises a multiplicity of process chambers 12 and prechambers 14, between which the movable receiving devices 32 according to the invention are moved back and forth with the aid of the transport device 30.

[0153] By parallelizing the manufacturing and cooling process, the dwell time of the workpiece 43 in the process chamber 12 can be significantly reduced and thus the utilisation of the electron beam system 10 can be optimised.

[0154] FIG. 8a shows an isometric view of a preferred embodiment of the movable receiving device 32 for the electron beam system.

[0155] This movable receiving device 32 comprises a support frame 33 on which a construction container 40, a storage container 44 and a powder overflow 58 as well as a doctor unit as a powder application device 56 are received.

[0156] The doctor unit here has one or more squeegees 45 which can be moved along rails via a squeegee carrier. Actuators for moving the doctor blade 45, on the other hand, are arranged in the interior of the process chamber 12 and are not shown in the figures.

[0157] It is also not evident in the figures that the support frame 33 has two sections which are thermally decoupled from one another. The doctor blade system 45 and the construction container 40 are not attached to the same section, so that they are thermally decoupled.

[0158] FIG. 8b shows an isometric view of a system 10 for the additive manufacture of a workpiece with a movable receiving device 32.

[0159] The movable receiving device 32 can be completely removed from the system 10 through the door 16. In this embodiment, the device 32 can be pushed out of the process chamber 12 along rails. No conversion steps whatsoever are necessary in order to remove the movable receiving device 32.

[0160] The actuators for the reciprocating pistons 50 and 54 (see FIG. 1), for moving the doctor blade 45 and optionally for a transport device, remain in the process chamber 12 and have a suitable interface to the movable receiving device 32.

[0161] An evacuable prechamber as well as a loading and unloading station are optional here, but they make handling easier and shorten non-productive times in the manufacturing process.

[0162] Due to the complete removal of the movable receiving device 32 service activities such as cleaning, repair, etc. are significantly simplified. The better accessibility reduces the risk of contamination with foreign particles when changing materials.