PRINT HEAD FOR 3D PRINTING OF METALS, DEVICE FOR ADDITIVELY MANUFACTURING THREE-DIMENSIONAL WORKPIECES, COMPRISING A PRINT HEAD AND METHOD FOR OPERATING A DEVICE

Abstract

The invention relates to a print head (1) for additively manufacturing three-dimensional workpieces, comprising a housing (3), a device (28) for feeding a metal (14), a piston (5), a reservoir (7) with an outlet opening (10) and an actuator device (12) for displacing the piston (5), wherein the reservoir (7, 27) has a melt region (20) and a displacement body chamber (21) for a liquid phase (8) of the metal (14), wherein the melt region (20) adjoins the inert atmosphere (22) and is connected to the displacement body chamber (21) such that, as a result of the displacement of the piston (5), the liquid phase (8) of the metal (14) can be stimulated to pass through the outlet opening (10), said outlet opening (10) being mounted on an insert (11) of the print head (1). The invention is characterised in that the print head (1) comprises a device (50) for feeding a protective gas (60) to the outlet opening (10) of the print head (1). The invention also relates to a device (100) for additively manufacturing three-dimensional workpieces and to a method for operating a print head (1).

Claims

1. A print head (1) for additively manufacturing three-dimensional workpieces, the print head (1) comprising a housing (3), a device (28) for delivering a metal (14), a piston (5), a reservoir (7, 27) with a discharge opening (10) and an actuator device (12) for displacing the piston (5), wherein the reservoir (7, 27) has a melting region (20) and a compression space (21) for a liquid phase (8) of the metal (14), wherein the melting region (20) is adjacent to an inert atmosphere (22) and is connected to the compression space (21) in such a way that the liquid phase (8) of the metal (14) can be induced to pass through the discharge opening (10) by movement of the displacement of the piston (5), wherein the discharge opening (10) is arranged on an insert (11) of the print head (1), characterized in that the print head (1) has a device (50) for delivering a protective gas (60) to the discharge opening (10) of the print head (1).

2. The print head (1) as claimed in claim 1, characterized in that the insert (11) has at least a nozzle plate (40) with the discharge opening (10), a guide sleeve (41) for guiding the piston (5), and a nozzle clamping nut (42) for fastening the nozzle plate (40) to the guide sleeve (41), and the device (50) for delivering the protective gas (60) is arranged on the nozzle clamping nut (42).

3. The print head (1) as claimed in claim 2, characterized in that , the device (50) for delivering a protective gas (60) forms, with the nozzle clamping nut (42), a gap (51) for delivering the protective gas (60) to the discharge opening (10).

4. The print head (1) as claimed in claim 3, characterized in that a choke (52) is formed inside the gap (51).

5. The print head (1) as claimed in claim 1, characterized in that the device (50) for delivering a protective gas (60) has a duct (53, 54) for delivering the protective gas (60) to the gap (51).

6. The print head (1) as claimed in claim 5, characterized in that the duct (53, 54) has a partial duct (54) which opens into an annular groove (55) of the device (50) for delivering a protective gas (60).

7. The print head (1) as claimed in claim 1, characterized in that the device (50) for delivering a protective gas (60) has a plane surface (56) which, with the nozzle clamping nut (42), forms the gap (51) and a peripheral protrusion (57) which, with the nozzle clamping nut (42), forms the choke (52) is formed on the plane surface (56).

8. A device (100) for additively manufacturing three-dimensional workpieces, the device (100) comprising a print head (1) as claimed in claim 1.

9. A method for operating a device (100) for additively manufacturing three-dimensional workpieces as claimed in claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the drawings:

[0028] FIG. 1 shows an example of a print head,

[0029] FIG. 2 shows an exemplary embodiment of the print head according to the invention,

[0030] FIG. 3 shows a detailed view of the print head according to the invention, and

[0031] FIG. 4 shows a view of a device for delivering a protective gas.

DETAILED DESCRIPTION

[0032] FIG. 1 shows a device 100 for additively manufacturing three-dimensional workpieces, in particular a 3D metal printer, and an example of a print head 1 for a 3D printer, in particular a metal printer. The print head 1 comprises a housing 3, a device 28 for delivering a metal 14 in solid phase, a piston 5, a reservoir 7, 27 with a discharge opening 10, and an actuator device 12 for displacing the piston. The reservoir 7, 27 has a melting region 20 and a compression space 21 for a liquid phase 8 of the metal 14, wherein the melting region 20 is adjacent to an inert atmosphere 22 and is connected to the compression space 21 in such a way that the liquid phase 8 of the metal 14 can be induced to pass through the discharge opening 10 by means of the displacement of the piston 5. The liquid phase 8 of the metal 14 is also referred to as the melt 8 and the inert atmosphere 22 is formed by introducing an inert gas 22 into the reservoir 7, 27. The introduction of the inert gas 22 into the reservoir 7, 27 preferably takes place via a cold region of the print head 1.

[0033] The housing 3 has a multi-part design, wherein it comprises at least a cooling flange 25, an insulating plate 26, and the reservoir 7, 27.

[0034] The piston 5 has a multi-part design, wherein it comprises at least a piston rod 17 made from a metal material and a ceramic plunger 18. Starting from the actuator device 12, the piston rod 17 projects through the cooling flange 25 and the insulating plate 26 into the reservoir 7, 27, where it merges into the plunger 18.

[0035] The cooling flange 25 has a recess 30 for accommodating the actuator device 12 which takes the form of a piezoelectric actuator 12. The piezoelectric actuator 12 is fixed in the recess 30 during operation in such a way that, when voltage is applied, it exerts a working stroke on the piston 5, specifically on the piston rod 17 of the piston. The piston rod 17 transmits the working stroke to the plunger 18 such that the latter induces the liquid phase 8 of the metal 14 to pass through the discharge opening 10. The piston 5 can be returned to a starting position without actuating the actuator 12 by a spring 13, wherein the spring 13 is arranged in the recess 30 of the cooling flange 25 between a shoulder 24 and the actuator 12. The spring takes the form of a disk spring. The cooling flange 25 moreover has cooling ducts 31 for cooling purposes. The cooling ducts 31 are arranged between the cooling flange 25 and the insulating plate 26 and a cooling medium is flushed through them. This serves to create a cooling effect with respect to the heating due to the melt 8 and to cool the actuator 12 during operation. The cooling flange 25 is formed from a metal material. The insulating plate 26 bearing on sides of the cooling ducts 31 is formed from a heat-insulating material and in such a way that it reduces heat transfer from the reservoir 7, 27 to the cooling flange 25.

[0036] The device 28 for delivering the metal 14 opens into the reservoir 7, 27 and is arranged in the cooling flange 25 and the insulating plate 26. The device 28 projects through the cooling flange 25 and the insulating plate 26 and the metal 14 or the material 14 to be printed can be delivered from outside by the device 28. Pre-metered pieces of material or pellets can preferably be used. An opening 29 through which the material 14 passes into the reservoir 7, 27 is situated at the transition from the insulating plate 26 to the reservoir 7, 27. The opening 29 can be closed by a device 32 such that it is preferably open only when the material 14 is being delivered, as a result of which the escape of energy or gas from the inert atmosphere 22 is reduced.

[0037] The reservoir 7, 27 is designed as a crucible 27, wherein an inductor 35 is arranged outside the crucible 27 and a sensor 36, in particular a temperature sensor, is arranged inside the crucible. Another insulator (not shown) can optionally be situated between the crucible 27 and the inductor 35 or the inductor coil 35.

[0038] The metal 14 passes in a solid phase 14 into the melting region 20 of the crucible and is heated by the inductor 35 until it changes to a liquid phase 8. When the melt 8 has reached a desired process temperature, which is determined by the temperature sensor 36, the print head 1 can start operating. The liquid phase 8 or the melt 8 moves, under the gravitational pressure of the melt 8 or owing to a combination of gravitational pressure and the atmospheric pressure of the inert gas 22, past the plunger 18 and into the compression space 21. The plunger 18 of the piston 5 is surrounded at a pressure side 19 in the melt 8 or by melt 8 and at the side connected to the piston rod 17 in the inert atmosphere 22 or by the inert atmosphere 22. The piston rod 17 does not come into contact with the melt 8 as a result of the process. The ceramic of the plunger 18 is advantageously a very good conductor of heat in order to be able to effectively transmit the heat generated by the inductor 35 into the compression space 21.

[0039] When the piezoelectric actuator 12 is activated, the pressure side 19 of the plunger 18 exerts a pressure on the melt 8 in the compression space 21 in the direction of the discharge opening 10 and ensures that a drop 15 is emitted through the discharge opening 10 of the reservoir 7, 27 or the compression space 21. The discharge opening 10 is designed to emit drops 15 of the liquid phase 8 of the metal 14, wherein the discharge opening 10 has the form of a nozzle 10 and can be rigidly connected to the crucible 27 or, as shown in the exemplary embodiment, has a replaceable insert 11 which allows different nozzle geometries to be used.

[0040] FIG. 2 shows part of an exemplary embodiment of the print head 1 according to the invention, wherein the insert 11 has at least a nozzle plate 40 with the discharge opening 10, a guide sleeve 41 for guiding the piston 5, and a nozzle clamping nut 42 for fastening the nozzle plate 40 to the guide sleeve 41, and the device 50 for delivering the protective gas 60 is arranged on the nozzle clamping nut 42.

[0041] FIG. 3 shows a detailed view of the print head 1, wherein the device 50 for delivering the protective gas 60 forms, with the nozzle clamping nut 42, a gap 51 for delivering the protective gas 60 to the discharge opening 10. A choke 52 is moreover formed inside the gap 51. The device 50 for delivering a protective gas 60 has a duct 53, 54 for delivering the protective gas 60 to the gap 51.

[0042] FIG. 4 shows a view of the device for delivering the protective gas, wherein the duct 53, 54 has a partial duct 54 which opens into an annular groove 55 of the device 50 for delivering the protective gas 60.

[0043] The device 50 for delivering a protective gas 60 moreover has a plane surface 56 which, with the nozzle clamping nut 42, forms the gap 51 and a peripheral protrusion 57 which, with the nozzle clamping nut 42, forms the choke 52 is formed on the plane surface 56.