Device for generating electron beam and 3D printing device

Abstract

The invention relates to a device for generating an electron beam (14), comprising: a wire-shaped hot cathode (11), which is significantly longer in the longitudinal direction than in the transverse direction perpendicular to the longitudinal direction, wherein, when the device is in operation, the electron beam (14) is emitted from the hot cathode (11), and due to the elongated shape of the hot cathode (11), the electron beam has an elongated linear cross section perpendicular to its propagation direction, and in the cross section, the extension in the longitudinal direction of the line is significantly greater than the extension in the transverse direction of the line; a cathode electrode (12); and an anode, wherein, when the device is in operation, a voltage for accelerating electrons emitted from the hot cathode (11) is applied between the cathode electrode (12) and the anode, and the hot cathode (11) is arranged spaced apart from the cathode electrode (12), so that when the device is in operation, electrons accelerated toward the anode are emitted from the hot cathode (11) in each transverse direction.

Description

Technical Field

[0001] The invention relates to a device for generating an electron beam, a 3D printing device for producing a spatially extended product, and a device for processing a workpiece by means of such a device. Background Art

[0002] Devices of the aforementioned type for generating electron beams are sufficiently known and can be designed, for example, as Pierce-type electron guns. An example of such a device designed as a Pierce-type electron gun is disclosed in WO 2014 / 009028 A1.

[0003] The Pierce-type electron gun has several disadvantages. To illustrate these disadvantages refer to Figures 12 to 18 The device shown in these figures comprises a wire-shaped hot cathode 1 which is significantly longer in the longitudinal direction than in a transverse direction perpendicular thereto. Furthermore, the device comprises a cathode electrode 2 which has a longitudinal groove 3 in which the hot cathode 1 is arranged. The longitudinal groove 3 has a rectangular cross section, wherein the extension of the longitudinal groove in the transverse direction is approximately three times greater than the diameter of the hot cathode 1 (see Fig.14 and Fig.18 ).

[0004] In addition, Figures 12 to 17 4. A voltage of up to 50 kV, for example, is applied between the electrode 2 and the anode electrode 4 for accelerating the electrons emitted from the hot cathode 1. In addition, a small voltage of, for example, about 10 V is applied to the hot cathode 1, so that a current flows through the hot cathode 1, which causes heating of the hot cathode 1. Due to this heating voltage, different voltage differences exist between the hot cathode 1 and the cathode electrode 2 at the beginning of the cathode electrode 2 and at the end of the cathode electrode.

[0005] exist Figures 16 to 18 In the figure, an electron beam 5 is drawn in, which is emitted from the hot cathode 1 toward the anode electrode 4, wherein the electron beam 5 has a slender linear cross-section (not shown) perpendicular to its propagation direction due to the shape of the hot cathode 1, wherein the extension in the longitudinal direction of the line is significantly greater than the extension in the transverse direction of the line.

[0006] From the basis Fig.18 It can be seen from the schematic diagram that only the electrons emitted from the side of the hot cathode 1 facing the anode electrode 4 contribute to the electron beam 5. However, in the actual application, the surface from which the electrons contributing to the electron beam 5 are emitted is further reduced to a narrow strip 6 extending in the longitudinal direction of the hot cathode 1. Fig.18 4 is shown in the middle region of the side of the hot cathode 1 facing the anode electrode 4 .

[0007] In such devices designed as Pierce-type electron guns, it has proven to be disadvantageous that the electron beam 5 is relatively inhomogeneous in the longitudinal direction of the line. The reason for this is that the tungsten wire used as the hot cathode 1 in most cases is usually polycrystalline, wherein the energy that the electrons moving in the polycrystalline body must have in order to be ejected from the crystal can be different for each polycrystalline body. Since a plurality of different polycrystalline bodies are arranged side by side in the longitudinal direction of the hot cathode 1 or in the longitudinal direction of the strip 6, a plurality of different energies of the electrons are generated in the longitudinal direction of the contour of the electron beam 5.

[0008] Furthermore, it has been shown that the intensity distribution of the electron beam 5 depends very sensitively on the orientation of the wire-shaped hot cathode 1 in the slot 3 of the cathode electrode 2. Due to the different voltage differences between the hot cathode 1 and the cathode electrode 2 at the beginning of the cathode electrode 2 and at the end of the cathode electrode caused by the heating voltage, the hot cathode 1 must be arranged in the slot at a small angle relative to the longitudinal direction of the slot 3 in order to achieve an electron beam 5 with the same intensity at each end of the linear distribution. On the one hand, this slight tilting of the hot cathode 1 in the slot 3 is associated with a large calibration effort due to the sensitive dependence of the intensity distribution on the orientation mentioned. On the other hand, the achievable length of the linear intensity distribution is limited to about 100 mm, for example.

[0009] Furthermore, it has proven to be disadvantageous that such an apparatus designed as a Pierce-type electron gun is susceptible to particle vapors which can be emitted from the workpiece to be processed or the starting material to be loaded with the electron beam for 3D printing during operation of the apparatus. These particles can be deposited in particular at the edges of the slot 3 and form material deposits there which can affect the generation of the electron beam 5 or significantly deteriorate its quality. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a device of the type mentioned at the outset which is more efficient and / or by means of which a more uniform electron beam can be generated and / or by means of which a longer line length can be obtained and / or which is less sensitive to particle vapors. In addition, a 3D printing device of the type mentioned at the outset with such a device and a device for processing workpieces are to be specified.

[0011] In order to solve the above technical problems, the first aspect of the present invention relates to a device for generating an electron beam, comprising: - a wire-shaped hot cathode, which is significantly longer in the longitudinal direction than in the transverse direction perpendicular to the longitudinal direction, wherein when the device is in operation, the electron beam is emitted from the hot cathode, and the electron beam has an elongated linear cross-section perpendicular to its propagation direction due to the elongated shape of the hot cathode, in which the extension in the longitudinal direction of the line is significantly greater than the extension in the transverse direction of the line; a cathode electrode, the cathode electrode having a curved surface on the side facing the hot cathode, the surface having a vertex line and a parabolic cross-section; an anode, wherein when the device is in operation, a voltage for accelerating electrons emitted from the hot cathode is applied between the cathode electrode and the anode, characterized in that the hot cathode is arranged spaced apart from the cathode electrode so that when the device is in operation, electrons accelerated toward the anode are emitted from the hot cathode in each transverse direction.

[0012] By having electrons emitted from the hot cathode in all radial directions contribute to the electron beam, the efficiency of the device is improved because the current is increased for the same accelerating voltage.

[0013] In addition, the electrons emitted from the hot cathode in all radial directions contribute to the electron beam, and a larger number of hot cathode surface sections contribute to the electron beam. This results in: more polycrystals contribute to each region of the electron beam along the longitudinal direction of the intensity distribution, so that the energy of each region is averaged through a larger number of polycrystals. This results in greater uniformity of the electron beam along the longitudinal direction of the line.

[0014] There is a possibility that the cathode electrode has a smooth surface and / or an uninterrupted surface on the side facing the hot cathode, wherein the surface is not interrupted by grooves or the like in particular. Due to the smooth, uninterrupted surface of the cathode electrode, which in particular has no grooves, the device is less sensitive to particle vapors. In particular, there are no grooves at the edges of which particles could be deposited and material accumulation could form there. In addition, the device is significantly less sensitive to slight tilting of the hot cathode in the case of a smooth, uninterrupted surface of the cathode electrode, thereby reducing the calibration effort. In addition, a device that can generate electron beams with a greater line length can be provided thereby.

[0015] It can be provided that the cathode electrode has a curved surface on the side facing the hot cathode, in particular a hollow cylindrical concave curved surface. Here, the hollow cylindrical concave curved surface of the cathode electrode can have a vertex line, preferably a surface with a parabolic cross section. Here, preferably, the distance between the hot cathode and the surface of the cathode electrode in the vertex line area of ​​the concave curvature, in particular in the extreme value area of ​​the parabola, can be smaller than the distance between the hot cathode and other areas of the cathode electrode surface. By arranging the hot cathode in front of the electrode, in particular in front of the vertex line of the curved electrode surface, the device is even less sensitive to slight tilting of the hot cathode, thereby further reducing the calibration cost and being able to generate an electron beam with a greater line length. In addition, in the cathode electrode, part of the surface, in particular the vertex line and its surroundings, is shielded by the hot cathode, so that particle evaporation cannot occur in this area.

[0016] There is a possibility that when the device is in operation, the electrons emitted from the hot cathode in the direction of the cathode electrode are reflected on the surface of the cathode electrode or in the region of the surface of the cathode electrode in the direction of the anode or are deflected in the direction of the anode. This ensures that substantially all of the electrons emitted from the hot cathode in the radial direction contribute to the electron beam.

[0017] It can be provided that the workpiece to be processed serves as an anode. This can be achieved in particular when the device for generating an electron beam is used in an apparatus for processing a workpiece. By using the workpiece as an anode, a separate anode electrode can be omitted. This can be achieved in particular in that the device is relatively insensitive to particle vapors. The size of the device can thereby be greatly reduced.

[0018] Alternatively, it can be provided that the anode is designed as an anode electrode, which in particular has an opening through which the electron beam emitted by the hot cathode can pass. This can be achieved in particular when the device for generating an electron beam is used in a 3D printing device for producing spatially extended products.

[0019] There is a possibility that the device comprises at least one deflection electrode, preferably a plurality of deflection electrodes, wherein the at least one deflection electrode is used in particular for compressing and / or focusing the electron beam. Here, the at least one deflection electrode can be arranged downstream of the anode electrode in the propagation direction of the electron beam.

[0020] A second aspect of the present invention relates to a 3D printing device for manufacturing a spatially extended product, comprising: at least one device for generating an electron beam, a working area, an initial material to be loaded with the electron beam is supplied or can be supplied to the working area for 3D printing, wherein the working area is arranged in the 3D printing device so that the electron beam hits the initial material, characterized in that the device for generating an electron beam is a device according to the present invention.

[0021] A third aspect of the present invention relates to an apparatus for machining a workpiece, comprising: at least one device for generating an electron beam, characterized in that the device for generating an electron beam is a device according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features and advantages of the present invention will be clearly described based on the following description of preferred embodiments with reference to the accompanying drawings, in which:

[0023] Figure 1 shows a schematic side view of a first embodiment of a device for generating an electron beam according to the invention;

[0024] Figure 2 Show according to Figure 1 A perspective view of the device;

[0025] Figure 3 shows a schematic side view of a second embodiment of the device for generating an electron beam according to the invention;

[0026] Figure 4 Show according to Figure 3 A perspective view of the device;

[0027] Figure 5 shows a schematic side view of a third embodiment of the device for generating an electron beam according to the invention;

[0028] Figure 6 Show according to Figure 5 A perspective view of the device;

[0029] Figure 7 shows a schematic side view of a fourth embodiment of a device for generating an electron beam according to the invention;

[0030] Figure 8 Show according to Figure 7 A perspective view of the device;

[0031] Fig. 9 A schematic side view of a fifth embodiment of the device for generating an electron beam according to the invention is shown, wherein the generated electron beam is shown;

[0032] Fig.10Show Fig. 9 Detailed enlargement of the image;

[0033] Fig.11 Show Fig.10 Detailed enlargement of the image;

[0034] Fig.12 A schematic side view of a first specific embodiment of a device for generating an electron beam in the form of a Pierce-type electron gun is shown;

[0035] Fig.13 Show according to Fig.12 A perspective view of the device;

[0036] Fig.14 A schematic side view of a second specific embodiment of a device for generating an electron beam in the form of a Pierce-type electron gun is shown;

[0037] Fig.15 Show according to Fig.14 A perspective view of the device;

[0038] Fig.16 A schematic side view of a third specific embodiment of a device for generating an electron beam in the form of a Pierce-type electron gun, wherein the generated electron beam is shown;

[0039] Fig.17 Show Fig.16 Detailed enlargement of the image;

[0040] Fig.18 Show Fig.17 Detail enlargement of . DETAILED DESCRIPTION

[0041] In the figures, identical or functionally identical parts or elements are provided with the same reference symbols.

[0042] The device shown includes a hot cathode 11, a cathode electrode 12 and an anode electrode 13. The device can generate an electron beam 14 (see Figures 9 to 11 ).

[0043] In all embodiments, the hot cathode 11 is constructed as a wire and extends into the Figure 1 , Figure 3 , Figure 5 , Figure 7 and Figures 9 to 11 The electron beam 14 extends in the plane of the drawing or in a longitudinal direction arranged perpendicular to the propagation direction of the electron beam 14. This design achieves a linear cross section of the electron beam 14, wherein the longitudinal direction of the linear cross section is oriented parallel to the longitudinal direction of the wire forming the hot cathode 11.

[0044] In the embodiment shown, the anode electrode 13 comprises two mutually spaced parts 13a, 13b, between which the electron beam 14 can pass. Instead of a multi-part anode electrode 13, a one-piece anode electrode 13 can also be provided. The one-piece anode electrode can then have an opening, through which the electron beam 14 emitted from the hot cathode can pass. The opening can be rectangular in particular and extend into the Figure 1 The longitudinal direction of the drawing plane has a significantly larger dimension than in its transverse direction in order to allow the linear electron beam 14 to pass through.

[0045] The hot cathode 11 is supplied with voltage from a voltage source (not shown), so that a current flows through the hot cathode 11 , which causes heating of the hot cathode 11 . In this case, the hot cathode 11 can be at least partially at the same potential as the cathode electrode 12 .

[0046] When the device is in operation, a voltage generated by a voltage source (not shown) for accelerating electrons emitted from the hot cathode 11 is applied between the cathode electrode 12 and the anode electrode 13. The voltage may be, for example, between 1 kV and 10 kV. Here, the cathode electrode 12 is connected to the negative pole of the voltage source, and the anode electrode 13 is connected to the positive pole of the voltage source, wherein in particular the anode electrode 13 may be additionally connected to a ground line.

[0047] There is the possibility of dispensing with the anode electrode in the device. In this case, for example, the metal workpiece to be processed can be used as the anode.

[0048] The cathode electrode 12 has a hollow space 15 which is open on one side, and the hot cathode 11 is arranged in the hollow space. The surface 16 of the cathode electrode 12 forming the hollow space 15 is smooth or uninterrupted. The surface 16 is configured as a hollow cylinder and is concavely curved, wherein the surface 16 has a parabolic cross section in particular. Thus, the concavely curved surface 16 of the cathode electrode 12 has a vertex line 17, which is at the Fig.11 The hot cathode 11 is arranged in front of the vertex line 17 or in front of the extreme value of the parabola (see Figure 1 ). Here, the hot cathode 11 and the surface 16 of the cathode electrode 12 have a distance that is smaller in the region of the vertex line 17 or the extreme value of the parabola than in other regions of the hot cathode 11 and the surface 16 of the cathode electrode 12 .

[0049] Fig.11 Indicates that in Fig.11The electrons emitted from the hot cathode 11 upward or in the direction of the vertex line 17 are also deflected downward in the direction of the anode electrode 13. Therefore, when the device is in operation, the electrons emitted from the hot cathode 11 in the direction of the cathode electrode 12 are reflected on the surface 16 of the cathode electrode 12 or in the region of the surface 16 of the cathode electrode 12 in the direction of the anode electrode 13 or are deflected in the direction of the anode electrode 13. This ensures that substantially all of the electrons emitted from the hot cathode 11 in the radial direction contribute to the electron beam 14.

[0050] In addition, according to Figure 1 and Figure 2 The embodiment of the invention comprises two deflection electrodes 18a, 18b downstream of the anode electrode 13 in the propagation direction of the electron beam 14. The two deflection electrodes 18a, 18b can also be omitted. The two deflection electrodes are only used for shaping the beam profile of the electron beam 14.

[0051] In addition, according to Figures 3 to 8 An embodiment of the invention comprises a further electrode 19 downstream of the deflection electrodes 18a, 18b in the propagation direction of the electron beam 14, the further electrode having an opening 20 for passing the electron beam 14. The further electrode 19 can have a positive potential relative to the deflection electrodes 18a, 18b, so that the electrons of the electron beam 14 are accelerated in the direction of the further electrode 19 and pass through the opening 20.

[0052] The various embodiments differ partly in the design of the anode electrode 13. Figures 1 to 4 In the embodiment of the present invention, the anode electrode 13 has two planar, plate-shaped and mutually spaced parts 13a, 13b. These parts are inclined relative to the horizontal line in the figure so that their ends facing each other extend upward into the hollow space 15 of the cathode electrode 12.

[0053] In accordance with Figure 5 and Figure 6 In the embodiment of , the components 13a, 13b are arranged similarly. However, the components are not designed to be planar but to be curved.

[0054] exist Figures 7 to 11 In the embodiment of Figures 1 to 4 However, the components are not inclined relative to the horizontal in the drawing, so that their ends facing each other do not extend upward into the hollow space 15 of the cathode electrode 12.

[0055] The device for generating an electron beam can be integrated into a 3D printing device for producing spatially extended products. For this purpose, for example, in the working area 21 (see Fig. 9) may be arranged with a rod-shaped starting material made of metal for 3D printing, which can be melted by the electron beam 14. Alternatively, a powdered starting material may also be provided.

[0056] In the described devices and apparatuses, some or in particular all of the components may be arranged in a vacuum. The housing required for this is not shown or not shown completely in the figures. Fig. 9 The housing 22 is schematically shown in FIG.

Claims

1. A device for generating an electron beam (14), comprising: - a wire-shaped hot cathode (11) which is significantly longer in a longitudinal direction than in a transverse direction perpendicular to the longitudinal direction, wherein, when the device is in operation, an electron beam (14) is emitted from the hot cathode (11), and, due to the elongated shape of the hot cathode (11), the electron beam 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; - a cathode electrode (12) having, on the side facing the hot cathode (11), a curved surface (16) with an apex line (17) and a parabolic cross section; - an anode, wherein, when the device is in operation, a voltage for accelerating electrons emitted from the hot cathode (11) is applied between the cathode electrode (12) and the anode, The invention is characterized in that the hot cathode (11) is arranged at a distance from the cathode electrode (12) so that when the device is operated, electrons accelerated toward the anode are emitted from the hot cathode (11) in each lateral direction.

2. The device according to claim 1, characterized in that The cathode electrode (12) has a smooth surface (16) and / or an uninterrupted surface (16) on the side facing the hot cathode (11).

3. The device according to claim 1 or 2, characterized in that: The surface is a hollow cylindrical concavely curved surface (16).

4. The device according to claim 3, characterized in that The distance between the hot cathode (11) and the surface (16) of the cathode electrode (12) in the vertex line (17) region of the concave curved portion is smaller than the distance between the hot cathode (11) and the surface (16) of the cathode electrode (12) in other regions.

5. The device according to claim 1 or 2, characterized in that: When the device is in operation, electrons emitted from the hot cathode (11) in the direction of the cathode electrode (12) are reflected on the surface (16) of the cathode electrode (12) or in the region of the surface (16) of the cathode electrode in the direction of the anode or are deflected in the direction of the anode.

6. The device according to claim 1 or 2, characterized in that: The workpiece to be machined serves as the anode.

7. The device according to claim 1 or 2, characterized in that: The anode is configured as an anode electrode (13).

8. The device according to claim 1, characterized in that The device comprises at least one deflection electrode (18a, 18b).

9. The device according to claim 7, characterized in that The device comprises at least one deflection electrode (18a, 18b).

10. The device according to claim 9, characterized in that The at least one deflection electrode (18a, 18b) is arranged downstream of the anode electrode (13) along the propagation direction of the electron beam (14).

11. The device according to claim 2, characterized in that The surface (16) is not interrupted by grooves.

12. The device according to claim 4, characterized in that The distance between the hot cathode (11) and the surface (16) of the cathode electrode (12) in the extreme value region of the parabola is smaller than the distance between the hot cathode (11) and the surface (16) of the cathode electrode (12) in other regions.

13. The device according to claim 7, characterized in that The anode electrode has an opening through which an electron beam (14) emitted from the hot cathode (11) can pass.

14. The device according to claim 8 or 9, characterized in that The device comprises a plurality of deflection electrodes (18a, 18b).

15. The device according to claim 8 or 9, characterized in that The at least one deflection electrode (18a, 18b) is used to compress and / or focus the electron beam.

16. A 3D printing device for manufacturing a spatially extended product, comprising: - at least one device for generating an electron beam, - a working area, to which a starting material to be loaded with an electron beam is supplied or can be supplied for 3D printing, wherein the working area is arranged in the 3D printing device such that the electron beam impinges on the starting material, Characterized in that the device for generating an electron beam is a device according to any one of claims 1 to 15.

17. An apparatus for processing a workpiece, comprising: At least one device for generating an electron beam, characterized in that the device for generating an electron beam is a device according to any one of claims 1 to 15.

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