Device for generating electron beam and 3D printing device

Abstract

A device (1) for generating an electron beam (4), the device comprising: an elongated wire-shaped hot cathode from which the electron beam (4) is emitted, the electron beam having an elongated, linear cross-section perpendicular to its propagation direction due to the elongated shape of the hot cathode; a cathode electrode (2) and an anode electrode (3), between which a voltage for accelerating electrons escaping from the hot cathode is applied; and a deflection unit capable of deflecting the electron beam (4) penetrating an opening of the anode electrode (3), wherein during operation of the device, the cross-section of the electron beam (4) is changed by the deflection unit so that the extension in the longitudinal direction of the line is reduced and the extension in the transverse direction of the line is increased, in particular, the extension in the longitudinal direction of the line is approximately the same as the extension in the transverse direction of the line.

Description

Technical Field

[0001] The invention relates to a device for generating an electron beam and a 3D printing apparatus for producing a spatially extended product. Background Art

[0002] Devices for generating an electron beam that can be used for 3D printing are known. In particular, the electron beam is directed onto a starting material that is a rod-shaped material in the form of a metal, which melts the starting material locally. The starting material can then be deposited in a predeterminable position in the working area in order to build up the object to be produced in layers.

[0003] It is often found to be disadvantageous that voltages of up to 100 kV are used to accelerate the electrons, so that when the electrons strike the raw material, X-ray radiation with an energy of up to 100 keV is generated. This radiation can only be shielded with great effort. In addition, the high power density of such electron beams can cause problems, since it can lead to partial evaporation of the metallic raw material. In addition, the magnets usually used to deflect the electron beam only allow low scanning speeds of the electron beam in the working area. Summary of the invention

[0004] The problem of the invention is to create a device of the type mentioned at the outset which generates less harmful radiation and / or is more suitable for 3D printing methods. Furthermore, a 3D printing device of the type mentioned at the outset should be specified which comprises such a device.

[0005] According to the invention, this is achieved by an apparatus according to the invention of the type mentioned in the introduction and by a 3D printing device according to the invention of the type mentioned in the introduction.

[0006] The device for generating an electron beam according to the invention comprises:

[0007] an elongated wire-shaped hot cathode from which, during operation of the device, an electron beam emerges which, due to the elongated shape of the hot cathode, has an elongated, wire-shaped cross section perpendicular to its propagation direction, in which the extension in the longitudinal direction of the wire is significantly greater than the extension in the transverse direction of the wire,

[0008] - cathode electrode,

[0009] an anode electrode, which in particular has an opening through which the electron beam emitted by the hot cathode can penetrate, wherein during operation of the device, a voltage is present between the cathode electrode and the anode electrode for accelerating the electrons escaping from the hot cathode,

[0010] - a deflection unit capable of deflecting an electron beam penetrating an opening of an anode electrode, wherein, when the device is in operation, the cross-section of the electron beam is changed by the deflection unit so that an extension in a longitudinal direction of the line is reduced and an extension in a transverse direction of the line is increased, in particular so that an extension in the longitudinal direction of the line is approximately the same as an extension in a transverse direction of the line, preferably the electron beam has a rotationally symmetric cross-section.

[0011] By using an elongated hot cathode, an electron beam with a linear cross section is generated. In addition, by using an elongated hot cathode, the current of the electron beam emitted from the hot cathode can be significantly greater than the current in the case of a substantially point-shaped hot cathode. For example, a current of 1A can be achieved. As a result, the acceleration voltage can be reduced to, for example, 10 kV to 15 kV. As a result, no high-energy X-ray radiation is generated when it hits the raw material for 3D printing, so that there is no need to shield the device expensively. Since the electron beam is beam-shaped into a relatively point-shaped or rotationally symmetrical beam in the working area, the raw material can still be effectively melted.

[0012] It can be provided that the deflection unit comprises at least one deflection electrode. In particular, the at least one deflection electrode can be designed and / or arranged in the device in such a way that an electron beam penetrating an opening of the anode electrode is reflected by the at least one deflection electrode. By deflecting the electron beam by means of electrodes as opposed to deflecting by means of a magnetic field, a significantly higher scanning speed of the electron beam can be achieved in the working area. In the geometric structure of the deflection electrodes used by way of example, deflection frequencies of up to 120 kHz can be achieved, since the deflection electrodes have a very low capacitance.

[0013] It can be provided that the at least one deflection electrode has a negative potential relative to the anode electrode, in particular the at least one deflection electrode is at the same potential as the cathode electrode, preferably connected to the same voltage source as the cathode electrode. Connection to the same voltage source ensures that the electrons are largely braked by the deflection electrode before they are accelerated in the direction of the working area.

[0014] There is the possibility that the deflection unit, in particular the at least one deflection electrode, is configured such that the electron beam penetrating the opening of the anode electrode is divided into a plurality of partial beams. In particular, the plurality of partial beams can overlap in the working area. By dividing into a plurality of partial beams and the subsequent overlapping in the working area, an electron beam having a linear cross section can be converted into an electron beam having a rotationally symmetrical cross section relatively efficiently.

[0015] It can be provided that the deflection unit comprises at least one further electrode which has a positive potential relative to the at least one deflection electrode and which can accelerate electrons as a result of the interaction with the at least one deflection electrode, wherein the further electrode in particular has an opening through which the electron beam starting from the at least one deflection electrode can pass. In this way, the braked electrons can be accelerated in the direction of the additional electrode. Therefore, the additional electrode should be positioned such that the acceleration takes place at the desired deflection angle.

[0016] There is the possibility that the deflection unit comprises at least two mutually opposed deflection electrodes, which are arranged in particular downstream of the further electrode in the propagation direction of the electron beam, wherein a voltage, in particular an alternating voltage, can be applied between the at least two mutually opposed deflection electrodes in order to deflect the electron beam. The deflection electrodes can be used to shape or homogenize the beam profile of the electron beam in the working area. In particular, the alternating voltage can have a relatively high frequency, for example up to 120 kHz, so that the electron beam or its beam parts can move back and forth in the working area or on the raw material at a high speed. In this case, the alternating voltage can be specifically influenced so that some areas of the surface of the raw material are exposed to the electron beam for a longer time than other areas.

[0017] It can be provided that the cathode electrode is divided into sections in the longitudinal direction of the wire forming the hot cathode. This makes it possible to facilitate the division into partial beams. In addition, this makes it possible to achieve a modular design of the device, since by arranging a plurality of sections of the cathode electrode in a row and by using a longer wire serving as a hot cathode, the source can be enlarged in the longitudinal direction of the linear electron beam.

[0018] According to the invention, the device for generating an electron beam is a device according to the invention.

[0019] It can be provided that the 3D printing device comprises a plurality of devices for generating electron beams, which are arranged in the 3D printing device in such a way that the electron beams of the devices impinge on the raw material from different directions during operation of the 3D printing device. For example, the devices can be arranged in a ring around the raw material, so that the raw material can be loaded with electron beams from all sides simultaneously. This leads to efficient and very uniform melting of the raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings.

[0021] Figure 1A perspective view of a first embodiment of a 3D printing device according to the invention with a first embodiment of a device according to the invention for generating an electron beam, wherein the electron beam generated by the device is shown;

[0022] Figure 2 Shown in accordance with Figure 1 Another perspective view of the first embodiment of the 3D printing device according to the present invention;

[0023] Figure 3 A perspective view of a second embodiment of a 3D printing device according to the invention with a second embodiment of the device according to the invention for generating an electron beam, wherein the electron beam generated by the device is shown;

[0024] Figure 4 Shown in accordance with Figure 3 Another perspective view of a second embodiment of a 3D printing device according to the present invention;

[0025] Figure 5 Shown in accordance with Figure 3 Another perspective view of a second embodiment of a 3D printing device according to the present invention;

[0026] Figure 6 A schematic plan view of a third specific embodiment of a 3D printing device according to the invention having a plurality of devices according to the invention for generating electron beams is shown, wherein the electron beams generated by the devices are shown. DETAILED DESCRIPTION

[0027] In the various figures, identical or functionally identical components or elements are provided with the same reference numerals. In some of the figures, a Cartesian coordinate system is correspondingly shown.

[0028] In the described device, some or in particular all components can be arranged in a vacuum. The housing required for this is not shown in the figures.

[0029] exist Figure 1 and Figure 2 The first embodiment of the device 1 for generating an electron beam according to the invention shown in FIG. 1 comprises a hot cathode, a cathode electrode 2 and an anode electrode 3, not shown. In terms of these components, the device 1 essentially corresponds to an electron gun of the Pierce type. The device can generate an electron beam 4, which propagates from the hot cathode or from the cathode electrode 2 toward the anode electrode 3 in the Z direction of the coordinate system shown.

[0030] The hot cathode is designed as a wire and is arranged in a cavity in the cathode electrode 2, which is provided with the reference numeral 5. The hot cathode extends in a longitudinal direction, which corresponds to the Y direction of the coordinate system shown. Correspondingly, the longitudinal direction is arranged perpendicular to the propagation direction of the electron beam 4. This design results in a linear cross section of the electron beam 4, wherein the longitudinal direction of the linear cross section is oriented parallel to the longitudinal direction of the wire forming the hot cathode 1. The wire can have, for example, a diameter of 1 mm and a length in the Y direction of between 100 mm and 160 mm.

[0031] The hot cathode is charged with voltage by a voltage device (not shown) in such a way that a current flows through the hot cathode, which current causes the hot cathode to heat up. In this case, the hot cathode 1 can be at least partially at the same potential as the cathode electrode 2 .

[0032] The cathode electrode 2 can have, for example, a length in the Y direction of between 80 mm and 120 mm. The cathode electrode 2 comprises segments 6 which extend away from the hot cathode and which are at an angle of between 110° and 150°, for example, approximately 135°, to one another. In the exemplary embodiment shown, the two segments 6 are segmented, for example, into four segments 7.

[0033] It is entirely possible to provide for no segmentation or for segmentation into more or fewer sections.

[0034] The anode electrode 3 has an opening 8 through which the electron beam 4 emitted from the hot cathode can pass. The opening 8 is particularly rectangular and has a Figure 1 The longitudinal direction (extending in the Y direction) can have a significantly greater extension than in its transverse direction in order to enable an electron beam 4 having a linear cross section to pass through.

[0035] When the device 1 is in operation, a voltage for accelerating the electrons escaping from the hot cathode 1 is applied between the cathode electrode 2 and the anode electrode 3. The voltage can be, for example, between 10 kV and 15 kV. Here, the cathode electrode 2 is connected to the negative pole of a voltage source (not shown) and the anode electrode 3 is connected to the positive pole of the voltage source, wherein in particular the anode electrode 3 can also be connected to the ground.

[0036] The device 1 further comprises a plurality of deflection electrodes 9a, 9b, 9c, 9d serving as deflection means, which are arranged downstream of the anode electrode 3 in the beam path of the electron beam 4. In the illustrated embodiment, four deflection electrodes 9a, 9b, 9c, 9d are provided. However, there is the possibility of providing more or fewer deflection electrodes 9a, 9b, 9c, 9d.

[0037] In the exemplary embodiment shown, the individual deflection electrodes 9a, 9b, 9c, 9d are designed in the form of rods and have a cylindrical cross section. It is entirely possible for the individual deflection electrodes 9a, 9b, 9c, 9d to have other shapes.

[0038] The deflection electrodes 9a, 9b, 9c, 9d are likewise at a negative potential or at a plurality of different negative potentials. In particular, it can be provided that one, a plurality or all of the deflection electrodes 9a, 9b, 9c, 9d are at the same negative potential as the cathode electrode 2. Preferably, one, a plurality or all of the deflection electrodes 9a, 9b, 9c, 9d are connected to the negative pole of the same voltage source as the cathode electrode 2. This makes it possible for the electrons of the electron beam 4 to essentially reach a state of rest next to the deflection electrodes 9a, 9b, 9c, 9d.

[0039] The electron beam 4 is deflected by, for example, approximately 50° to 60° by the deflection electrodes 9a, 9b, 9c, 9d. It is entirely possible to provide for a different deflection angle.

[0040] The deflection electrodes 9a, 9b, 9c, 9d are spatially offset relative to one another, in particular in the propagation direction of the electron beam 4 emitted from the anode electrode 3, or in the Z direction. Due to the spatial offset of the individual deflection electrodes 9a, 9b, 9c, 9d relative to one another, a portion of the electron beam 4 is deflected closer to the anode electrode 3 than another portion of the electron beam 4. In this way, the electron beam 4 is split into a plurality of partial beams 10a, 10b, 10c, 10d during the deflection.

[0041] Depend on Figure 1 It can be seen that in Figure 1 From left to right or in the negative Y direction, the first deflection electrode 9a and the third deflection electrode 9c are arranged below the second deflection electrode 9b and the fourth deflection electrode 9d, respectively. Figure 1 The electron beam 4 that hits the second and fourth deflection electrodes 9b, 9d is deflected to the right earlier than the electron beam 4 that hits the first and third deflection electrodes 9a, 9c. Figure 1 The partial beams 10b, 10d of the center electron beam 4 deflected by the second deflection electrode 9b and the fourth deflection electrode 9d extend above or in the negative Z direction at a distance from the partial beams 10a, 10c deflected by the first deflection electrode 9a and the third deflection electrode 9c.

[0042] The device 1 also includes another electrode 11 downstream of the deflection electrodes 9a, 9b, 9c, 9d in the propagation direction of the electron beam 4 or the partial beam 10a, 10b, 10c, 10d, which has an opening 12 for allowing the electron beam 4 or the partial beam 10a, 10b, 10c, 10d to pass through. In particular, the opening 12 is also rectangular and can have a larger extension along its longitudinal direction than along its transverse direction. The other electrode 11 is connected to the ground, for example, and therefore has a positive potential relative to the deflection electrodes 9a, 9b, 9c, 9d. Therefore, the electrons of the electron beam 4 or the partial beam 10a, 10b, 10c, 10d braked next to the deflection electrode are accelerated from the deflection electrodes 9a, 9b, 9c, 9d in the direction of the other electrode 11 and pass through the opening 12.

[0043] Since the maximum value of the positive potential of the electrode 11 is arranged substantially in the center of the opening 12, the individual partial beams 10a, 10b, 10c, 10d are slightly deflected in the direction of the center of the opening 12 of the electrode 11, so that they approach one another in the further course of the beam. This ultimately leads to the partial beams 10a, 10b, 10c, 10d overlapping in the working region 13, so that the electron beam 4 that recombine in the working region preferably has an approximately rotationally symmetrical cross section.

[0044] In the working area 13 , for example, a rod-shaped starting material 20 made of metal for 3D printing can be arranged, which starting material can be melted by the recombined electron beam 4 .

[0045] In accordance with Figure 1 and Figure 2 In an embodiment of the invention, two groups 14, 15 of additional multi-part deflection electrodes 16b, 16d; 17a, 17c are arranged downstream of the electrode 11, and a further electrode 18 with an opening 19 is additionally arranged downstream of each of the deflection electrodes. In this case, the partial beams 10b, 10d extend through between the individual parts of the deflection electrodes 16b, 16d, and the partial beams 10a, 10c extend through between the individual parts of the deflection electrodes 17a, 17c. Thus, the deflection electrodes 16b, 16d of the first group 14 act on the partial beams 10b, 10d, and the deflection electrodes 17a, 17c of the second group 15 act on the partial beams 10a, 10c.

[0046] The components of the deflection electrodes 16b, 16d; 17a, 17c are arranged in accordance with Figure 1 and Figure 2 In an embodiment of the present invention, it is formed by two or four plates lying opposite one another, between which the assigned partial beams 10a, 10b, 10c, 10d pass.

[0047] A voltage, in particular an AC voltage, can be applied between the individual components of the deflection electrodes 16b, 16d; 17a, 17c respectively associated with one of the partial beams 10a, 10b, 10c, 10d. A corresponding voltage source is not shown. The AC voltage can have a frequency of 10 kHz and above, for example, up to 120 kHz.

[0048] The deflection electrodes 16b, 16d; 17a, 17c are used to shape or homogenize the beam profile of the electron beam 4 in the working area 13. In particular, due to the relatively high frequency of the AC voltage, the deflection electrodes 16b, 16d; 17a, 17c can move the partial beams 10a, 10b, 10c, 10d back and forth at a relatively high speed in the working area 13 or on the raw material 20. In this case, in particular, the AC voltage can be influenced in a targeted manner so that some areas of the surface of the raw material 20 are exposed to the electron beam 4 for a longer time than other areas.

[0049] exist Figures 3 to 5 The second embodiment shown in FIG. 1 differs from the first embodiment in that the openings 12 and 19 of the electrodes 11 , 18 correspond essentially to the openings 8 in the anode electrode 3 in terms of their shape and size.

[0050] On the other hand, the cathode 2 of the second embodiment is shaped differently from the cathode 2 of the first embodiment.

[0051] Furthermore, the deflection electrodes 9 a , 9 b , 9 c , 9 d of the second embodiment are shaped differently from the deflection electrodes 9 a , 9 b , 9 c , 9 d of the first embodiment.

[0052] Furthermore, instead of providing a separate deflection electrode 16b, 16d; 17a, 17c for each partial beam 10a, 10b, 10c, 10d, exactly two deflection electrodes 16, 17 are provided in each group 14, 15, between which two partial beams of the partial beams 10a, 10b, 10c, 10d extend.

[0053] In particular, the partial beams 10b, 10d extend between the two deflection electrodes 16 of the first group 14, while the partial beams 10a, 10c extend between the two deflection electrodes 17 of the second group 15. Thus, the deflection electrodes 16 of the first group 14 act on the partial beams 10b, 10d, while the deflection electrodes 17 of the second group 15 act on the partial beams 10a, 10c.

[0054] exist Figure 6, an embodiment of a 3D printing device is shown, which includes a plurality of devices 1 for generating electron beams 4. Here, the devices 1 are arranged in a ring around a rod-shaped raw material 20, so that the electron beams 4 of the devices 1 hit the raw material 20 from different directions when the 3D printing device is running.

Claims

1. A device (1) for generating an electron beam (4), comprising: - an elongated wire-shaped hot cathode from which an electron beam (4) is emitted when the device (1) is in operation, and which, due to the elongated shape of the hot cathode, has an elongated, wire-shaped cross section perpendicular to its propagation direction, in which the extension in the longitudinal direction of the wire is significantly greater than the extension in the transverse direction of the wire, - cathode electrode (2), - an anode electrode (3) having an opening (8) through which the electron beam (4) emitted from the hot cathode can pass, wherein when the device is in operation, a voltage is applied between the cathode electrode (2) and the anode electrode (3) for accelerating the electrons escaping from the hot cathode, - a deflection unit, which can deflect the electron beam (4) that penetrates the opening of the anode electrode (3), wherein, when the device is in operation, the cross section of the electron beam (4) is changed by the deflection unit so that the extension along the longitudinal direction of the line is reduced and the extension along the transverse direction of the line is increased, and the deflection unit is configured so that the electron beam (4) that penetrates the opening (8) of the anode electrode (3) is divided into a plurality of partial beams (10a, 10b, 10c, 10d), and the plurality of partial beams (10a, 10b, 10c, 10d) overlap in the working area (13).

2. The device (1) according to claim 1, characterized in that When the device is in operation, the cross section of the electron beam (4) is changed by the deflection unit so that the extension in the longitudinal direction of the line is the same as the extension in the transverse direction of the line.

3. The device (1) according to claim 1, characterized in that The electron beam (4) has a rotationally symmetric cross section.

4. The device (1) according to claim 1, characterized in that The deflection unit comprises at least one deflection electrode.

5. The device (1) according to claim 4, characterized in that The at least one deflection electrode is designed and / or arranged in the device (1) such that the electron beam (4) penetrating the opening (8) of the anode electrode (3) is reflected by the at least one deflection electrode.

6. The device (1) according to claim 4 or 5, characterized in that The at least one deflection electrode has a negative potential relative to the anode electrode (3).

7. The device (1) according to claim 6, characterized in that The at least one deflection electrode is at the same potential as the cathode electrode (2).

8. The device (1) according to claim 7, characterized in that The at least one deflection electrode is connected to the same voltage source as the cathode electrode (2).

9. The device (1) according to claim 4 or 5, characterized in that The at least one deflection electrode is configured such that an electron beam (4) penetrating an opening (8) of an anode electrode (3) is divided into a plurality of partial beams (10a, 10b, 10c, 10d).

10. The device (1) according to claim 4 or 5, characterized in that The deflection unit comprises at least one further electrode (11) which has a positive potential relative to the at least one deflection electrode and which enables electrons to be accelerated as a result of an interaction with the at least one deflection electrode.

11. The device (1) according to claim 10, characterized in that The further electrode (11) has an opening (12) through which the electron beam (4) originating from the at least one deflection electrode can pass.

12. The device (1) according to claim 4 or 5, characterized in that The deflection unit comprises at least two mutually opposite deflection electrodes, wherein a voltage can be applied between the at least two mutually opposite deflection electrodes in order to deflect the electron beam (4).

13. The device (1) according to claim 12, characterized in that The deflection unit comprises at least one further electrode (11) which has a positive potential relative to the at least one deflection electrode and which is capable of accelerating electrons as a result of interaction with the at least one deflection electrode, the deflection electrode being arranged downstream of the further electrode (11) in the propagation direction of the electron beam (4).

14. The device (1) according to claim 12, characterized in that An alternating voltage can be applied between the at least two mutually opposite deflection electrodes.

15. The device (1) according to claim 12, characterized in that The deflection unit comprises at least one further electrode (18), which is arranged downstream of the at least two mutually opposite deflection electrodes in the propagation direction of the electron beam (4).

16. The device (1) according to claim 15, characterized in that The further electrode has an opening (19) through which the electron beam (4) can penetrate.

17. The device (1) according to any one of claims 1 to 5, characterized in that The design and / or control of the hot cathode, the cathode electrode (2) and the anode electrode (3) correspond to the design and / or control of a Pierce-type electron gun.

18. The device (1) according to any one of claims 1 to 5, characterized in that The cathode electrode (2) is divided into sections (7) along the longitudinal direction of the metal wire forming the hot cathode.

19. A 3D printing device for manufacturing a product extending in space, the 3D printing device comprising: - at least one device (1) for generating an electron beam (4), - a working area (13) to which a raw material (20) for 3D printing to be subjected to the electron beam (4) is supplied or can be supplied, wherein the working area (13) is arranged in the 3D printing device so that the electron beam (4) impinges on the raw material (20), Characterized in that the device (1) for generating an electron beam (4) is a device (1) according to one of claims 1 to 18.

20. The 3D printing device according to claim 19, characterized in that: The starting material (20) is designed in the form of a rod and consists of metal or includes metal.

21. The 3D printing device according to claim 19 or 20, characterized in that: The 3D printing device comprises a plurality of devices (1) for generating electron beams (4), wherein each device is arranged in the 3D printing device so that the electron beams (4) of each device impinge on the raw material (20) from different directions when the 3D printing device is in operation.

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