Three-dimensional additive manufacturing device

Abstract

This three-dimensional additive manufacturing device performs additive manufacturing by using an electron beam while ensuring manufacturing quality and protecting an electron gun, and comprises: an electron gun for emitting, in a direction that forms an angle larger than 0 degrees with respect to a normal of a manufacturing surface, an electron beam for melting a manufacturing material; a deflection part for deflecting the electron beam emitted from the electron gun toward the manufacturing surface; and a drift part for depositing vapor generated from the manufacturing surface at a position that is proximate to the electron beam emitted from the electron gun and that is located between the electron gun and the deflection part.

Description

3D additive manufacturing equipment

[0001] The present invention relates to a three-dimensional additive manufacturing apparatus.

[0002] In the above technical field, Patent Document 1 discloses an electron beam generating device having four polarizing units, a shielding plate, and an aperture.

[0003] Special Publication No. 57-37436

[0004] However, the technique described in the above document was not effective enough in reducing the influence of metal vapor.

[0005] An object of the present invention is to provide a technique for solving the above-mentioned problems.

[0006] To achieve the above object, the present invention provides a three-dimensional additive manufacturing (3D AM) device that performs additive manufacturing using an electron beam, comprising: an electron gun that emits an electron beam for melting a modeling material in a direction that forms an angle greater than 0 degrees with respect to a normal to a modeling surface; a deflection unit that deflects the electron beam emitted from the electron gun toward the modeling surface; and a drift unit that deposits vapor generated from the modeling surface at a position between the electron gun and the deflection unit and close to the electron beam emitted from the electron gun. The drift unit is preferably at least a portion of a cylindrical tube. The drift unit is preferably at least a portion of a conical tube. The drift unit is preferably at least a portion of a tube whose inner diameter expands in multiple stages away from the electron gun. The drift unit is preferably made of tungsten, molybdenum, tantalum, niobium, iridium, osmium, rhenium, hafnium, ruthenium, or technetium, at least downstream from the electron gun. The drift section preferably includes a curved plate-like member, and the drift section is preferably a cylindrical tube with a plate-like member disposed therein.

[0007] According to the present invention, it is possible to protect the electron gun while ensuring the quality of the object being manufactured.

[0008] FIG. 1 is a schematic diagram showing the configuration of a three-dimensional additive manufacturing device according to a first embodiment; FIG. 2 is a schematic diagram showing the configuration of a three-dimensional additive manufacturing device according to a second embodiment; FIG. 3 is a diagram showing the effect of the three-dimensional additive manufacturing device according to the second embodiment; FIG. 4 is a diagram showing the relationship between dimensions of the three-dimensional additive manufacturing device according to the second embodiment; FIG. 5 is a schematic diagram showing the configuration of a three-dimensional additive manufacturing device according to a third embodiment; FIG. 6 is a diagram showing the effect of the three-dimensional additive manufacturing device according to the third embodiment; FIG. 7 is a schematic diagram showing the configuration of a three-dimensional additive manufacturing device according to a fourth embodiment; FIG. 8 is a diagram showing the effect of the three-dimensional additive manufacturing device according to the fourth embodiment; FIG. 9 is a schematic diagram showing the configuration of a three-dimensional additive manufacturing device according to a fifth embodiment; FIG. 10 is a diagram showing the effect of the three-dimensional additive manufacturing device according to the fifth embodiment; FIG. 11 is a diagram showing the effect of the three-dimensional additive manufacturing device according to the fifth embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the components described in the following embodiments are merely examples and are not intended to limit the technical scope of the present invention.

[0010] First Embodiment A three-dimensional additive manufacturing apparatus 100 according to a first embodiment of the present invention will be described with reference to Fig. 1. The three-dimensional additive manufacturing apparatus 100 is an apparatus that performs additive manufacturing using an electron beam.

[0011] As shown in FIG. 1 , the three-dimensional additive manufacturing apparatus 100 includes an electron gun 101 , a deflection unit 102 , and a drift unit 103 .

[0012] The electron gun 101 emits an electron beam 111 for melting the modeling material in a direction that forms an angle greater than 0 degrees with respect to a normal 121 of the modeling surface 120 .

[0013] The deflection unit 102 deflects the electron beam 111 emitted from the electron gun 101 toward the modeling surface 120 .

[0014] The drift unit 103 deposits vapor 121 generated from the modeling surface 120 at a position between the electron gun 101 and the deflection unit 102 and close to the electron beam 111 emitted from the electron gun 101 .

[0015] According to the above configuration, it is possible to protect the electron gun while ensuring the quality of the object being manufactured.

[0016] Second Embodiment Next, a 3D additive manufacturing apparatus according to a second embodiment of the present invention will be described with reference to FIG. 2 and subsequent figures. FIG. 2 is a diagram illustrating the configuration of a 3D additive manufacturing apparatus 200 according to this embodiment. The 3D additive manufacturing apparatus 200 is an electron beam 3D metal additive manufacturing apparatus that operates in a vacuum. 3D additive manufacturing apparatuses 200 include powder and wire-based directed energy deposition (DED) and powder bed fusion (PBF) methods.

[0017] A cathode 201 made of tungsten, LaB6 crystal, or the like is provided as a light source (electron gun) at the most upstream of the 3D additive manufacturing device 200. The cathode 201 is heated to approximately 1500 to 2000°C and generates an electron beam.

[0018] A grid 202 is disposed near the cathode 201, and is applied with a lower potential than the cathode 201. An anode 203, which is at a higher potential than the cathode 201, is provided below the grid 202.

[0019] The electron beam from the cathode 201 is extracted downward by the potential of the anode 203. At this time, the grid potential suppresses the electron beam emission area, thereby reducing the apparent electron generation area (light source).

[0020] For example, if the anode 203 is at GND potential and the cathode 201 is at minus several tens of kV, the electron beam 222 accelerated by the voltage between the cathode 201 and the anode 203 passes through the anode 203 and is irradiated in the direction of the modeling surface 204 .

[0021] Furthermore, a cylindrical drift tube 205 is provided below the anode 203. The drift tube 205 is provided between the cathode 201 and the deflection lens 206 to allow the metal vapor 121 generated from the modeling surface 120 to adhere thereto. The drift tube 205 may be at least a portion of a cylindrical tube, and it is sufficient that the drift tube 205 is functionally intact even if a portion of the cylindrical tube is missing. For example, the drift tube may be a curved plate-like member, or may be a cylindrical tube with such a plate-like member disposed inside.

[0022] The diameter of drift tube 205 is larger than that of electron beam 222 emitted from cathode 201, and the closer the diameter is to that of electron beam 222, the greater the effect of removing metal vapor 121. However, if there is any misalignment on the optical axis due to mechanical installation error of cathode 201, there is a possibility that electron beam 222 may come into contact with the lower end of drift tube 205. Therefore, a gun alignment coil 208 is provided around drift tube 205 to adjust the position to prevent such interference.

[0023] This configuration eliminates the need for two or more stages of deflection, which can cause problems with optical axis alignment, and prevents the metal vapor 241 from the modeling surface 204 from adversely affecting the light source (reducing electron emission efficiency and increasing electron beam spread). Furthermore, using the drift tube 205 also makes it possible to keep the angle of one stage of deflection to 3.5° or less, thereby solving the problem of increased electron beam aberration. This makes it possible to improve modeling accuracy and modeling quality. The drift tube 205 may also be configured to be replaceable.

[0024] The electron beam 222 is irradiated onto the shaping surface 204 through a drift tube 205 for blocking the directionality of the metal vapor 241, a deflection lens 206 with a deflection center at the lower end of the drift tube 205, and an objective lens 207. An astigmatism correction coil (not shown) is attached near the objective lens 207, and a scanning deflection coil (not shown) is attached below it.

[0025] These components are surrounded by an electron gun chamber 209, liner tubes 210 and 211, and a modeling chamber 212, and are maintained at a vacuum. The upper liner tube 210 is connected to the lower liner tube 211 downstream of the deflection lens 206 using a liner tube joint 213. The liner tube joint 213 connects the liner tubes 210 and 211 while maintaining the vacuum using an O-ring or the like.

[0026] (Operation) When the cathode 201 is heated to 1500°C or higher by passing a current through a tungsten wire or the like, an electron beam from the cathode 201, to which a negative voltage of several tens of kV is applied, is accelerated relative to the anode 203, which is at ground potential (GND). The grid 202 suppresses extraction of the electron beam from the cathode 201. For example, if the voltage of the grid 202 is set significantly lower than that of the cathode 201, the electron beam accelerated toward the anode 203 can be reduced to almost zero, and if the voltage of the grid 202 is brought closer to the voltage of the cathode 201, the accelerated electron beam increases.

[0027] The electron beam 222 that passes through the opening of the anode 203 enters the deflection lens 206 with a divergence angle that is small enough not to touch the bottom end of the drift tube 205, is deflected in the normal direction of the modeling surface 204, and is focused on the modeling surface 204 by the objective lens 207. Even if there is a deviation on the optical axis due to a mechanical installation error of the cathode 201, the gun alignment coil 208 adjusts it so that the beam does not touch the bottom end of the drift tube 205.

[0028] 3 is an enlarged view showing the configuration near the light source. During the melting process during modeling, a large amount of metal vapor 241 is emitted from the molten pool on the modeling surface 204. Some of this vapor enters the liner tube 210 and rises. The metal vapor 241 in the liner tube 210 is blocked by the drift tube 205 so that it does not reach the cathode 201.

[0029] 3, the deflection angle of the deflection lens is set to 3.5°, and the drift tube 205 blocks the metal vapor 241, and the cathode 201 is in its shadow. The drift tube 205 is a non-magnetic metal pipe, and is formed in a cylindrical shape with an inner diameter that matches the outer shape of the electron beam 222 emitted from the cathode 201 with a certain opening angle.

[0030] By providing the drift tube 205 with a deflection angle of 3.5°, deposition of metal vapor onto the cathode 201 can be prevented. In reality, metal deposition due to metal vapor 241 from the modeling surface 204 can be observed on the right wall surface of the drift tube 205 in the drawing, but metal deposition is only observed near the bottom end of the left wall surface in the drawing, and not on the upper end. The deflection angle is not limited to 3.5°, and can be up to 4° as long as deflection aberration does not pose a problem.

[0031] The conditions under which steam does not reach the openings of the grid 202 are as follows (see FIG. 4).

[0032] Θ > tan -1 ((R G +R D ) / L G-D ) where Θ is the deflection angle, R G is the opening radius of the grid 202, R D is the inner radius of the bottom end of the drift tube 205, L G-D is the distance between the grid 202 and the bottom end of the drift tube 205. For example, R G =1.5mm, R D =5mm, L G-D = 110 mm, Θ > 3.38°. In other words, the deflection angle can be reduced to 3.5° while preventing deposition, and the deflection aberration can be kept small. In other words, the effect on the electron beam shape can be reduced.

[0033] As described above, by providing the drift tube 205 between the anode 203 and the deflection lens 206, metal deposition on the cathode can be prevented with a single stage deflection at a low deflection angle.

[0034] Third Embodiment Next, a three-dimensional additive manufacturing apparatus according to a third embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram illustrating the configuration of a three-dimensional additive manufacturing apparatus 500 according to this embodiment. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second embodiment in that it is provided with a tapered drift tube 505. The other configurations and operations are the same as those of the second embodiment, and therefore the same configurations and operations are denoted by the same reference numerals and detailed description thereof will be omitted.

[0035] The drift tube 505 is tapered so that its inner diameter gradually decreases toward the top. This allows a larger amount of metal vapor to be deposited on the inner surface of the drift tube 505, effectively preventing metal deposition on the cathode with a single-stage deflection at a low deflection angle, as shown in Figure 6. The drift tube 505 may be at least a portion of a conical tube.

[0036] Fourth Embodiment Next, a three-dimensional additive manufacturing apparatus according to a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram for explaining the configuration of a three-dimensional additive manufacturing apparatus 700 according to this embodiment. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second embodiment in that it includes a drift tube 705 whose diameter changes in a stepped manner. The other configurations and operations are the same as those of the second embodiment, and therefore the same configurations and operations are denoted by the same reference numerals and detailed description thereof will be omitted.

[0037] The drift tube 705 is formed so that its inner diameter gradually decreases toward the top. This allows a highly productive shape to be realized, as shown in Figure 8, while allowing a greater amount of metal vapor to be deposited on the drift tube 705. In other words, the drift tube 705 may be at least a part of a tube whose inner diameter gradually increases in multiple steps as it moves away from the electron gun.

[0038] That is, according to this embodiment, a drift tube with higher productivity can be used, and metal deposition on the cathode can be prevented by single-stage deflection with a low deflection angle.

[0039] Fifth Embodiment Next, a three-dimensional additive manufacturing apparatus according to a fifth embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 is a diagram for explaining the configuration of a three-dimensional additive manufacturing apparatus 900 according to this embodiment. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the fourth embodiment in that it includes a drift tube 905 whose diameter changes stepwise and whose material changes. The other configurations and operations are the same as those of the fourth embodiment, and therefore the same configurations and operations are denoted by the same reference numerals and detailed description thereof will be omitted.

[0040] The drift tube 905 is configured by combining a drift tube 951, a drift tube 952, and a drift tube 953, each having a different inner diameter.

[0041] The possibility that the divergent electron beam 222 will hit the downstream side of the drift tube 905 due to mechanical vibration or during alignment adjustment, etc., and melt the drift tube 905, cannot be eliminated. Therefore, as shown in Figure 9, only the downstream portion 953 of the drift tube 905 is made of tungsten, which has a high melting point. The tungsten lower portion 953 of the drift tube is fixed to the SUS upper portions 951 and 952 by a screw-type fastener. Thus, at least the downstream portion of the drift tube 905, far from the electron gun, is made of tungsten, molybdenum, tantalum, niobium, iridium, osmium, rhenium, hafnium, ruthenium, or technetium.

[0042] To confirm the effect of shielding vapor from the modeling surface using such a drift tube 905, EDS analysis was performed at three locations inside the drift tube: the side on which vapor deposition was performed and the top, middle, and bottom of the shaded side on which vapor deposition was not performed.

[0043] This is a model created using Ti64 powder material, with Ti as the analysis target. The analysis results are as follows, confirming a sufficient effect. Ti intensity on the vapor deposition side of the lower part 953 (right side in the figure) > Ti intensity on the vapor deposition side of the middle part 952 (right side in the figure) > Ti intensity on the vapor deposition side of the upper part 951 (right side in the figure) >> Ti intensity on the shadow side of the lower part 953 (left side in the figure). Ti was not detected in the middle part 952 or the shadow side of the upper part 951 (left side in the figure) (Figures 10 and 11).

[0044] As described above, according to this embodiment, a drift tube with higher productivity can be used, and metal deposition on the cathode can be prevented by single-stage deflection with a low deflection angle.

[0045] [Other Embodiments] The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the technical scope of the present invention. Furthermore, systems or devices that combine separate features included in each embodiment in any way are also included in the technical scope of the present invention.

[0046] Furthermore, the present invention may be applied to a system made up of multiple devices, or may be applied to a single device.

Claims

1. A three-dimensional additive manufacturing device that performs additive manufacturing using an electron beam, comprising: an electron gun that emits an electron beam for melting the modeling material in a direction that forms an angle greater than 0 degrees with respect to the normal to the modeling surface; a deflection unit that deflects the electron beam emitted from the electron gun toward the modeling surface; and a drift unit that deposits vapor generated from the modeling surface at a position close to the electron beam emitted from the electron gun, between the electron gun and the deflection unit.

2. The three-dimensional additive manufacturing device according to claim 1, wherein the drift portion is at least a part of a cylindrical tube.

3. The three-dimensional additive manufacturing device according to claim 1, wherein the drift portion is at least a part of a conical tube.

4. The three-dimensional additive manufacturing device according to claim 1, wherein the drift section is at least a part of a tube whose inner diameter expands in multiple stages as it moves away from the electron gun.

5. A three-dimensional additive manufacturing device according to any one of claims 1 to 4, wherein the drift section, at least downstream from the electron gun, is made of tungsten, molybdenum, tantalum, niobium, iridium, osmium, rhenium, hafnium, ruthenium, or technetium.

6. The three-dimensional additive manufacturing device according to claim 1, wherein the drift portion includes a curved plate-like member.

7. The three-dimensional additive manufacturing device according to claim 6, wherein the drift section is a cylindrical tube with the plate-like member disposed inside.

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