ADDITIVE MANUFACTURING SYSTEM FOR POWDERY STARTING MATERIAL AND METHOD FOR MANUFACTURING A COMPONENT

Abstract

The present invention relates to an additive manufacturing system for powdery starting material which comprises electron beam guns as irradiation units. The system comprises an improved shielding against ionizing radiation, in particular x-rays. By use of the additive manufacturing system according to the invention a compact an lightweight shielding of the construction area is achieved.

Claims

1. An additive manufacturing system for powdery starting material, including a vacuum chamber (1) comprising at least one construction area (2) with a construction platform (3); at least one powder reservoir (4) arranged to the side of the construction area (2); at least one powder application element (5), which is arranged horizontally movably between the at least one powder reservoir (4) and the at least one construction platform (3) for distributing powdery starting material from the at least one powder reservoir (4) on the at least one construction platform (3), wherein the powder application element (5) traverses the construction area (2) at least once for each powder distribution process; and at least one electron beam gun (6) associated to the at least one construction area (2); characterized in that the at least one construction area (2) is surrounded by a shielding (7) against ionizing radiation, which comprises four walls, two of which can be formed by walls of the vacuum chamber (1); and the walls of the shielding (7) at least on the two sides in the direction of movement of the at least one powder application element (5) consist of an upper part (8) and a lower part (9), wherein the upper part (8) is rigidly connected to the vacuum chamber (1), is formed from 2-11 horizontally spaced metal sheets (10) and has a clear height above the construction platform (3) that allows the powder application element (5) to move horizontally through the construction area (2), and the lower part (9) is connected to a vertically movable frame (12) and is formed from 2-11 horizontally spaced refractory metal sheets (11) which are arranged in a meshing manner with the metal sheets (10) of the upper part (8) and are attached to the movable frame (12) in a radiopaque manner; and the lower part (9) is movable relative to the upper part (8) in the vertical between a closed position and an open position, wherein the refractory metal sheets (11) of the lower part (9) in the closed position are arranged such that their lower edges mesh with a groove structure (13) on the surface of the construction area (2) while forming a labyrinth structure and are arranged such that their upper edges mesh with the metal sheets (10) of the upper part (8) while forming a labyrinth structure; and come to rest between the metal sheets (10) of the upper part in the open position at least to such an extent that they allow the horizontal movement of the powder application element (5) through the construction area (2).

2. The additive manufacturing system according to claim 1, characterized in that the refractory metal sheets (11) of the lower part (9) have a density of more than 10 g/cm.sup.3 at 20° C.

3. The additive manufacturing system according to claim 1, characterized in that the refractory metal sheets (11) of the lower part (9) consist of tungsten, molybdenum, rhenium, tantalum and/or mixtures or alloys thereof.

4. The additive manufacturing system according to claim 1, characterized in that the metal sheets (10) of the upper part (8) consist of stainless steel, copper, refractory metals and/or mixtures or alloys thereof.

5. The additive manufacturing system according to claim 1, characterized in that all four walls of the shielding (7) consist of an upper part (8) and a lower part (9).

6. The additive manufacturing system according to claim 1, characterized in that the radiopaque attachment of the refractory metal sheets (11) of the lower part (9) at the movable frame (12) comprises a spacer bolt fastening which has two different diameters, wherein the first diameter is dimensioned to match the bore in the refractory metal sheets (11) and the second diameter, which the spacer bolts have outside the bore, is larger in such a way that the radiation on the way through the bore is shielded by the spacer bolt in the same way as by the refractory metal sheet (11) in the non-perforated area.

7. The additive manufacturing system according to claim 1, characterized in that the refractory metal sheets (11) of the lower part (9) each have a thickness of 0.1 to 20 mm.

8. The additive manufacturing system according to claim 1, characterized in that the metal sheets (10) of the upper part (8) each have a thickness of 1 to 100 mm.

9. The additive manufacturing system according to claim 1, characterized in that the refractory metal sheets (11) of the lower part (9) and the metal sheets (10) of the upper part (8) each have a spacing of 1 to 50 mm relative to each other in meshing engagement.

10. The additive manufacturing system according to claim 1, characterized in that at least two joints are provided in each layer of refractory metal sheets (11) of the upper part (8) and/or the lower part (9) which have a gap of up to 50 mm.

11. The additive manufacturing system according to claim 10, characterized in that the joints of two successive layers of refractory metal sheets (11) within the upper part (8) and/or the lower part (9) are each arranged out of alignment.

12. The additive manufacturing system according to claim 1, characterized in that the powder application element (5) is a doctor blade or a roller.

13. A method for manufacturing a component by use of an additive manufacturing system including the steps a) providing an additive manufacturing system according to claim 1; b) providing powdery starting material in the at least one powder reservoir (4) and evacuating the vacuum chamber (1); c) moving the lower part (9) of the shielding (7) into the open position; d) distributing powdery starting material from the at least one powder reservoir (4) on the at least one construction platform (3) by horizontally moving the powder application element (5) between the at least one powder reservoir (4) and the at least one construction platform (3) with at least one complete traversing of the construction area (2); e) moving the lower part (9) of the shielding (7) into the closed position; f) generating a layer of the component by irradiating the powdery starting material by means of the at least one electron beam gun (6); and g) repeating steps c) to f) until the component is finished.

14. The additive manufacturing system according to claim 11, characterized in that the powder application element (5) is a doctor blade or a roller.

15. The additive manufacturing system according to claim 5, characterized in that the radiopaque attachment of the refractory metal sheets (11) of the lower part (9) at the movable frame (12) comprises a spacer bolt fastening which has two different diameters, wherein the first diameter is dimensioned to match the bore in the refractory metal sheets (11) and the second diameter, which the spacer bolts have outside the bore, is larger in such a way that the radiation on the way through the bore is shielded by the spacer bolt in the same way as by the refractory metal sheet (11) in the non-perforated area.

16. The additive manufacturing system according to claim 5, characterized in that the refractory metal sheets (11) of the lower part (9) each have a thickness of 0.1 to 20 mm.

17. The additive manufacturing system according to claim 5, characterized in that the metal sheets (10) of the upper part (8) each have a thickness of 1 to 100 mm.

18. The additive manufacturing system according to claim 5, characterized in that the refractory metal sheets (11) of the lower part (9) and the metal sheets (10) of the upper part (8) each have a spacing of 1 to 50 mm relative to each other in meshing engagement.

19. The additive manufacturing system according to claim 5, characterized in that at least two joints are provided in each layer of refractory metal sheets (11) of the upper part (8) and/or the lower part (9) which have a gap of up to 50 mm.

20. The additive manufacturing system according to claim 5, characterized in that the joints of two successive layers of refractory metal sheets (11) within the upper part (8) and/or the lower part (9) are each arranged out of alignment.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0054] FIG. 1 is a perspective sectional view of an additive manufacturing system according to the invention in the closed state in the starting position;

[0055] FIG. 2 is a perspective sectional view of the construction area surrounded by the shielding;

[0056] FIG. 3 is a perspective sectional view of the system of FIG. 1 in the open state with the powder application element before entering the construction area;

[0057] FIG. 4 is a perspective sectional view of the system of FIG. 1 in the open state with the powder application element within the construction area; and

[0058] FIG. 5 is a perspective sectional view of the system from FIG. 1 in the closed state after the powder application element has left the construction area again.

DESCRIPTION OF THE FIGURES

[0059] The figures only show a preferred embodiment variant as an example of the invention. They are therefore not to be understood as restrictive.

[0060] FIG. 1 shows a perspective sectional view of an additive manufacturing system according to the invention. In the vacuum chamber (1) a construction area (2) is disposed in which a single construction platform (3) is disposed. This is shown in the upper starting position at the start of construction. To the left and right of the construction area (2) there is a respective powder reservoir (4) with an adjoining slot for receiving excess powder. The powder application element (5), in this example a doctor blade that is suspended from a movable traverse, conveys an amount of powder from the powder reservoir (4) onto the construction platform (3) in the construction area (2), which is slightly larger than is required for one layer of the component, so that it can be ensured that the entire surface of the construction platform (3) is coated evenly. Excess powder is conveyed beyond the opposite powder reservoir (4) into the slot and from there it reaches a collecting container. In FIG. 1, the powder application element (5) is in the left starting position.

[0061] An electron beam gun (6) is embedded in the ceiling of the vacuum chamber (1) above the construction area (2). The entire construction area (2) is surrounded on all four sides by a shielding (7) which consists of an upper part (8) and a lower part (9). The shielding (7) is in the closed state because the powder application element (5) is still in the starting position. FIG. 2 again shows an enlarged view of the construction area (2) surrounded by the shielding (7). In the example shown here, the upper part (8) consists of four metal sheets (10) made of stainless steel with a thickness of 30 mm at the outside and 20 mm at the inside in a distance of 13 mm. The lower part (9) consists of three refractory metal sheets (11) made of pure tungsten with a thickness of 3 mm in a distance of 30 mm. The density of the refractory metal sheets (11) is therefore 19.25 g/cm.sup.3. The refractory metal sheets (11) of the lower part (9) are arranged in a meshing manner in the metal sheets (10) of the upper part (8) and overlap with them by 45 mm.

[0062] The metal sheets (10) of the upper part (8) are each dimensioned somewhat shorter from the outside towards the construction area (2). This makes it easier to attach them by means of the bolts to the stepped mounting at the ceiling of the vacuum chamber (1). The refractory metal sheets (11) are attached to the movable frame (12) and can be raised above it. In the closed position shown here, their lower edges engage into a groove structure (13) which forms the edge area of the construction area (2). The groove structure (13) is dimensioned similarly to the structure of the upper part, i.e. in the present example, grooves of 13 mm width are milled at a distance of 20 mm around the construction platform (3) in the surface of the vacuum chamber (1), since the grooves correspond to the distances between the sheets and the webs remaining in between correspond to the thickness of the sheets.

[0063] To produce a component, the powder reservoirs (4) are filled with a powdery starting material, for example with titanium powder, the system is moved to the starting position shown in FIG. 1 and the vacuum chamber (1) is evacuated. To produce the first layer of the component, titanium powder is then conveyed by use of the powder application element (5) from the powder reservoir (4) towards the construction area (2). Either immediately before the powder application element (5) starts moving or when it has almost reached the closed shielding (7), its lower part (9) is raised by means of the movable frame (12) and pushed into the upper part (8), so that the range of movement of the powder application element (5) is enabled. The electron beam gun (6) is deactivated during this time. This situation is shown in FIG. 3. There, with the shielding (7) in the open state, the groove structure (13) can now also be clearly seen.

[0064] FIG. 4 shows the powder application element (5) as it traverses the construction area (2) and distributes the titanium powder on the construction platform (3). FIG. 5 shows the powder application element (5) immediately after traversing the construction area (2). As soon as the powder application element (5) has left the construction area (2) again, the lower part (9) is lowered again into the closed position. The lower edges of the refractory metal sheets (11) again engage into the groove structure (13). The powder application element (5) then moves on to the end position behind the right powder reservoir (4) and thus discharges excess titanium powder into the collecting slot. As soon as the shielding (7) is closed again, the electron gun (6) can be activated and start writing the layer data for the first layer.

[0065] After the first layer has been written, the process begins again in the other direction. In systems in which only one powder reservoir (4) is installed, the powder application element (5) can either remain in the position beyond the construction area (2) until the layer is written and the lower part (9) of the shielding (7) is raised again and only then move back to the starting position to take new powder, or immediately after traversing the construction area (2) move back to the starting position in a reciprocating movement before the shielding (7) is closed.

LIST OF REFERENCE SYMBOLS

[0066] 1 Vacuum chamber [0067] 2 Construction area [0068] 3 Construction platform [0069] 4 Powder reservoir [0070] 5 Powder application element [0071] 6 Electron beam gun [0072] 7 Shielding [0073] 8 Upper part [0074] 9 Lower part [0075] 10 Metal sheet [0076] 11 Refractory metal sheet [0077] 12 Frame [0078] 13 Groove structure