METHOD AND SYSTEM FOR MANUFACTURING OF THREE DIMENSIONAL OBJECTS

Abstract

Method and system for manufacturing of three dimensional objects comprising of base substrate (18) placed on the supporting plate (30), electron beam gun (2), feed means (17) for feeding of feedstock material to melting zone, positioning system (31, 36) for positioning of said supporting plate (30) with base substrate (18), vacuum tight operating chamber (29), wherein an energy source for generating of molten pool on the substrate and for melting of feedstock material in said system is gas-discharge electron beam gun (2) with cold circular cathode (8) placed between two circular anodic electrodes placed coaxially to said cathode (8) which generates electron beam (9) in the shape of hollow inverted cone, and feedstock guide (17) is placed along the axis of said of said electron beam gun (2), and said gas-discharge electron beam gun (2) and said feedstock guide (17) are combined in one functional assembly.

Claims

1. A system for manufacturing three-dimensional objects, said system comprising: a substrate placed on a supporting plate; an electron beam gun configured to generate an electron beam having a shape of a hollow inverted cone to form a molten pool on said substrate; a feedstock feeder configured to feed feedstock material through a feedstock guide and into a melting zone for layered manufacturing of the three-dimensional objects; a positioning system configured to move said melting zone relative to said substrate for forming the three-dimensional objects; a vacuum-tight operating chamber enclosing said substrate, said supporting plate, said electron beam gun, said feedstock guide, and said positioning system; a vacuum system configured to provide an operating vacuum in the vacuum-tight operating chamber; a control system configured to control and monitor operating conditions of said electron beam gun, said feedstock feeder, said positioning system, and said vacuum system for manufacturing the three-dimensional objects, wherein said electron beam gun is a gas-discharge electron beam gun with a circular cold cathode disposed annularly about an axis and between two circular anodic electrodes, with the circular anodic electrodes each extending coaxially to said circular cold cathode; wherein said feedstock guide extends along the axis of said electron beam gun, and wherein said gas-discharge electron beam gun and said feedstock guide are combined in one functional assembly.

2. The system of claim 1, wherein said functional assembly comprising said gas-discharge electron beam gun and said feedstock guide further comprises: a base flange defining a hole in the center thereof, with the feedstock guide fixed coaxially within said hole in said base flange; a circular high voltage insulator attached to said circular cold cathode and fixed to said base flange from below, with said circular high voltage insulator and said circular cold cathode each disposed coaxially with said feedstock guide; wherein said two circular anodic electrodes includes an internal circular anodic electrode, with said internal circular anodic electrode fixed within said hole in said base flange and adjacent and coaxially to said feedstock guide; and wherein said two circular anodic electrodes includes an external circular anodic electrode, a body of said gas-discharge electron beam gun functioning as said external circular anodic electrode.

3. The system of claim 1, wherein said circular cold cathode defines an emission surface having a shape of a segment of a sphere with its center on the axis of said electron beam gun; and wherein the center of the sphere determines a position of an apex of the hollow conical electron beam generated by said electron beam gun.

4. The system of claim 1, wherein said circular cold cathode is made of one of the following materials: aluminum, aluminum alloy, or stainless steel.

5. The system of claim 1, further comprising: a circular insert with a shape of a segment of a sphere, said circular insert inserted in an emission surface of said circular cold cathode, and wherein said circular insert is made of one of the following materials: aluminum, aluminum alloy, or hexaboride of lanthanum.

6. The system of claim 1, wherein said circular cold cathode defines a cavity configured for circulation of water for cooling.

7. The system of claim 1, wherein said circular cold cathode is attached to a high voltage insulator through a circular cold cathode holder, and wherein said circular cold cathode holder is made of a material that is stronger than the material of the circular cold cathode.

8. The system of claim 1, wherein said circular cold cathode holder defines a cavity configured for circulation of cooling water.

9. The system of claim 1, wherein cylindrical surface of said circular cold cathode is surrounded by a cylindrical by-cathode electrode.

10. The system of claim 1, wherein said circular cold cathode is attached to a high voltage insulator having ring shape with extended free surfaces.

11. The system of claim 1, wherein said electron beam gun further comprises: a base flange; and a body including top cylindrical part attached to said base flange, said body also including a bottom conical part having an inverted conoid shape.

12. The system of claim 1, wherein said feedstock guide defines a passage configured for circulation of cooling water.

13. The system of claim 1, wherein said electron beam gun is regulated to operate with an operating accelerating voltage of 5-45 kV.

14. The system of claim 13, wherein said electron beam gun is regulated to operate with an operating accelerating voltage of 5-15 kV.

15. The system of claim 1, further comprising a power supply configured to provide a regulated power of up to 45 kW to said electron beam gun, and wherein the power of the electron beam is regulated within a range of 0-45 kW.

16. The system of claim 15, wherein the power of the electron beam is regulated within a range of 0-15 kW.

17. The system of claim 1, wherein said vacuum system provides operating vacuum in said operating chamber within a range of 10-10.sup.2 Pa while manufacturing three-dimensional objects.

18. The system of claim 1, wherein said gas-discharge electron beam gun is configured to use an operating gas selected from one of the following gases: hydrogen, oxygen, a mixture of hydrogen and oxygen, nitrogen, helium, argon, air, or methane.

19. The system of claim 1, wherein control of electron beam power is fulfilled by control of electron beam current which is regulated by means of change of operating gas pressure inside the gas-discharge electron beam gun.

20. The system of claim 1, wherein said system is configured to use the feedstock material in the form of wire, cored wire, rod, wire bundle, powder, or a mixture of powders; and wherein said system is configured to use the feedstock material selected from the following materials: titanium, titanium alloys, intermetallic compounds of titanium, niobium, niobium alloys, intermetallic compounds of niobium, tantalum, tantalum alloys, aluminum, aluminum alloys, intermetallic compounds of aluminum, nickel based alloys, cobalt based alloys, tool steels, or a composite matrix.

21. The system of claim 1, wherein said feedstock guide is one of a plurality of different feedstock guides for feeding different kinds of feedstock materials; and wherein said plurality of different feedstock guides are changeable inside a same structure of said functional assembly comprising said gas-discharge electron beam gun and said feedstock guide.

22. The system of claim 1, wherein said functional assembly including said gas-discharge electron beam gun and said feedstock guide is rigidly fixed inside said operating chamber; and wherein said positioning system is configured to move said supporting plate and said substrate, thereby moving said melting zone relative to said substrate.

23. The system of claim 1, wherein said functional assembly comprising said gas-discharge electron beam gun and said feedstock guide further comprises a base flange defining a hole, with the feedstock guide extending through said hole in said base flange; wherein the base flange is rigidly fixed to a top plate of said operating chamber with parts of said gas-discharge electron beam gun disposed below said base flange and inside of said operating chamber; and wherein the feedstock material is fed into said operating chamber through said feedstock guide with one or more sealing inserts.

24. The system of claim 23 wherein said functional assembly is fixed rigidly on the top plate of said operating chamber through an intermediate spacer placed on an internal side of the top plate of said operating chamber.

25. The system of claim 1, wherein said positioning system is configured to move said functional assembly within said operating chamber, thereby moving said melting zone relative to said substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0062] FIG. 1 shows schematic design of functional assembly comprising gas-discharge electron beam gun and feedstock guide which is the key component part of the system for manufacturing of three dimensional objects according to the present invention.

[0063] Functional assembly 1 consists of gas-discharge electron beam gun 2 and feedstock guide 3 which are combined in one assembly unit by means of rigid fixing of feedstock guide body 5 in the central hole of base flange 4 of the said electron beam gun coaxially with said base flange. Cylindrical pan of gun's body 6 and circular high voltage insulator 7 are fixed to base flange 4 from below coaxially with it. Circular cathode 8 is attached to circular high voltage insulator 7 in such way that high voltage insulator provides reliable insulation of circular cathode which operates under high negative potential from other parts of the gun. Emission surface 8a of circular cathode 8 has a shape of segment of a sphere which center determines a position of apex 9a of hollow inverted cone formed by electron beam 9 generated by gas-discharge electron beam gun 2. Internal circular anodic electrode 10 is fixed coaxially in the central hole of base flange 4 along feedstock guide body 5, and gun's body consisted of cylindrical part 6 and conical part 11 has a function of external anodic electrode. Conical part 11 of gun's body and feedstock guide body 5 form a discharge space 12 of gas-discharge electron beam gun 2. Conical part 13 of feedstock guide and bottom end of conical part 11 of gun's body form circular gap for exit of hollow conical electron beam 9 outside of the gas- discharge electron beam gun 2. Operating gas is supplied to discharge space 12 of the gun through nipple embedded to cylindrical part 6 of gun's body or to the base flange 4 (it is not presented on the picture). High voltage is applied to the cathode through feedthrough 15 which is embedded in electrically insulated hole in the base flange 4. Feedstock material 16 (in the embodiment presented on FIG. 1 it is a wire) is fed to feedstock guide 3 from the top end by feed means 17.

[0064] Functional assembly 1 is placed relative to substrate 18 in such way that apex 9a of hollow inverted cone formed by electron beam 9 is located near the surface of substrate 18. Due to such location energy of concentrated electron beam 9 causes melting of substrate material with forming of molten pool 19 on the surface of substrate 18. Feedstock material 16 in the form of wire is fed to zone where molten pool 19 is forming (to melting zone), the end of wire is uniformly embraced by hollow conical electron beam 9 resulting in melting by influence of electron beam energy directly inside molten pool 19 or slightly above it in such way that molten feedstock material from the end of wire trickles down exactly to the center of molten pool 19.

[0065] Arrow 20 on the FIG. 1 symbolically indicates movement of functional assembly 1 relative to the substrate 18 which means accordingly movement of molten pool 19. Molten pool which was formed during preliminary position of functional assembly 1 quickly solidifies as soon as it leaves zone of electron beam heating (melting zone) due to heat transfer to the substrate body and due to heat radiation from molten pool surface with formation of solid deposited layer (molten puddle) 21 and resulting in growing of substrate thickness on some value. It should be noted that movement of functional assembly 1 relative to the substrate 18 can be fulfilled by means of movement of functional assembly 1 or substrate 18 or by movement of both these parts in the same time.

[0066] FIG. 2 shows an alternative embodiment of functional assembly comprising gas-discharge electron beam gun and feedstock guide with a few possible design solutions. In this variant circular cathode 8 is attached to high voltage insulator 7 through circular cathode holder 22 which is made from more strong material than cathode is made. Circular cathode holder 22 at this variant is designed with circular cavity 23 for cooling water, inlet nipple 24 and outlet nipple 25 for supply and drain of cooling water to circular cathode holder 22 accordingly are embedded in electrically insulated holes in the base flange 4. Also FIG. 2 shows a variant of functional assembly design wherein conical part 11 of gas-discharge electron beam gun and feedstock guide structure are made with water cooling. Also FIG. 2 shows a variant of design of high voltage insulator 7 wherein it is made in shape of a ring with extended free surfaces, at the same time showed configuration of extended free surfaces is only an example which not excludes application of other surface configurations depending on applied current-voltage characteristics of gas-discharge electron beam gun.

[0067] FIG. 3 shows schematic design of circular cathode 8 in variant wherein circular insert 26 with the shape of segment of a sphere which is made of the materials with higher emission ability is inserted in the emission surface 8a of the circular cathode.

[0068] FIG. 4 shows schematic design of an embodiment of functional assembly 1 comprising gas-discharge electron beam gun and feedstock guide wherein powder 25 is used as feedstock material. In showed configuration feedstock powder 25 is fed to the melting zone by gas flow 26 through nozzle 27 on the end of feedstock guide 3. One of the numerous industrial methods of powder supply and configurations of nozzle can be applied for feeding of powder depending on powder material, fraction composition, carrier gas and other physical and chemical characteristics of powder. FIG. 4 also shows a design of feedstock guide 3 with water cooling 28.

[0069] FIG. 5 shows schematic design of the complete system for manufacturing of three dimensional objects according to the present invention in embodiment where functional assembly 1 comprising gas-discharge electron beam gun 2 and feedstock guide 3 together with feed means 17 are placed completely inside operating chamber. Said complete system consists of vacuum tight operating chamber 29, said functional assembly 1 comprising gas-discharge electron beam gun 2 and feedstock guide 3, said feed means 17, base substrate 18 for forming of three dimensional objects placed on the supporting plate 30, accurate positioning systems 31 and 36 for providing of movement of melting zone relative to the substrate along trajectory specified by operator or program, vacuum system 32, high voltage power supply 33 for gas-discharge electron beam gun, gas supply system 34 for gas-discharge electron beam gun, control system 35 for control of all equipment, mechanisms and instruments which are parts of said complete manufacturing system, for monitoring of operating conditions of all systems and for control by technological process of manufacturing of three dimensional objects. There are two variants to provide movement of melting zone relative to the substrate in embodiment with complete placement of said functional assembly inside operating chamberfirst one is with placement of supporting plate with attached base substrate on the moving platform of positioning system 31 and with rigidly fixed functional assembly, second one is with placement of functional assembly on the moving platform of positioning system 36 and with rigidly fixed supporting plate with attached base substrate.

[0070] FIG. 6 shows schematic design of the complete system for manufacturing of three dimensional objects according to the present invention in embodiment where functional assembly comprising gas-discharge electron beam gun 2 and feedstock guide 3 is fixed rigidly on the top plate 37 of operating chamber 28 through intermediate tubular spacer 38 in such way that only that parts of said gas-discharge electron beam gun 2 which are attached to the base flange 4 of said functional assembly from below are placed inside vacuum space of operating chamber 29, and feedstock material 16 in this case is fed to operating chamber from outside through feedstock guide by means of feed means equipped by sealing inserts 39. In this case movement of melting zone relative to the substrate along trajectory specified by operator or program is provided by means of placement of supporting plate with attached base substrate on the moving platform of positioning system.

INDUSTRIAL APPLICABILITY

[0071] The method and system for manufacturing of three dimensional objects presented by this invention can be used for effective manufacturing of high quality parts of complex configuration especially made of reactive materials which melting processes require usage of protective atmosphere and of energy sources with high power concentration for example such as titanium, titanium alloys, intermetallic compounds of titanium, niobium, niobium alloys, intermetallic compounds of niobium, tantalum, tantalum alloys, aluminum, aluminum alloys, intermetallic compounds of aluminum, nickel based alloys, cobalt based alloys, tool steels, composite matrix. Also presented method and system can be effectively applied under conditions where weight and dimensions of complete manufacturing system for manufacturing of three dimensional objects are critical parameters for example on the board of spacecraft.

[0072] Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the following claims.