Build cylinder arrangements for machines for layered production of three-dimensional objects having a fiber metal seal

Abstract

Build cylinder arrangements for machines for the layered production of three-dimensional objects by sintering or melting with a high-energy beam, of powdered material, are disclosed and have a base member and a piston that can be moved on an inner side of the base member along a central axis of the base member. The piston has at its upper side a substrate for building a three-dimensional object, and on the piston is a seal in abutment with the inner side of the base member for sealing the powdered material. The seal is a circumferential fiber metal seal of metal fibers that are pressed together and the pressed metal fibers are arranged with resilient compression stress between the piston and the inner side of the base member.

Claims

1. A build cylinder arrangement for a machine for the layered production of three-dimensional objects by sintering or melting with a high-energy beam a powdered material, the build cylinder arrangement comprising: a base member; a piston configured to be moveable on an inner side of the base member along a central axis of the base member, wherein the piston comprises a substrate at an upper side thereof; and a seal for sealing the powdered material in abutment with the inner side of the base member, wherein the seal for sealing the powdered material comprises a circumferential fiber metal seal comprising metal fibers that are pressed together, wherein the pressed metal fibers are arranged with resilient compression stress between the piston and the inner side of the base member, wherein the substrate and the seal for sealing the powdered material are constructed on an upper portion of the piston, which is releasably arranged on a remaining portion of the piston, and wherein the remaining portion of the piston includes a heating device arranged to heat the substrate to an operating temperature defined as 500° C.≤operating temperature ≤1000° C.

2. The build cylinder arrangement of claim 1, wherein the metal fibers that are pressed together form a knitted metal fabric.

3. The build cylinder arrangement of claim 2, wherein the knitted metal fabric comprises a circumferentially closed knitted stocking.

4. The build cylinder arrangement of claim 1, wherein the fiber metal seal is resiliently compressed with respect to its diameter by at least 0.4 mm or by at least 0.8%, or both by at least 0.4 mm and by at least 0.8%, as a result of the introduction into the base member at ambient temperature.

5. The build cylinder arrangement of claim 1, wherein a material or density, or both a material and a density, of the fiber metal seal is selected such that a thermal expansion of the inner diameter of the base member and a thermal expansion of the outer diameter of the fiber metal seal between ambient temperature and the operating temperature differ by a maximum factor of 2.

6. The build cylinder arrangement of claim 5, wherein the thermal expansion of the inner diameter of the base member and the thermal expansion of the outer diameter of the fiber metal seal between ambient temperature and the operating temperature differ by a maximum factor of 1.5.

7. The build cylinder arrangement of claim 1, wherein the fiber metal seal is inserted into a groove at an outer side of the piston, and the fiber metal seal radially overhangs the groove.

8. The build cylinder arrangement of claim 7, wherein the groove is constructed by a first seal carrier portion and a second seal carrier portion that is rotatable with a bayonet-type mechanism with respect to the first seal carrier portion.

9. The build cylinder arrangement of claim 1, wherein the fiber metal seal comprises a material that is resistant to corrosion in atmospheric oxygen at the operating temperature.

10. The build cylinder arrangement of claim 1, wherein the fiber metal seal comprises a material having a yield strength R.sub.p,0.2.sup.ET at the operating temperature that is at least 75% of yield strength R.sub.p,0.2.sup.ET at ambient temperature after the fiber metal seal has been kept for 100 hours at the operating temperature.

11. The build cylinder arrangement of claim 1, wherein the fiber metal seal comprises a high-grade steel.

12. The build cylinder arrangement of claim 11, wherein the fiber metal seal comprises Ni-containing high-grade steel, or a Ni alloy.

13. The build cylinder arrangement of claim 1, wherein the upper portion of the piston is releasably arranged on the remaining portion of the piston with a clamping mechanism or a torsion prevention means, or both a clamping mechanism and a torsion prevention means.

14. The build cylinder arrangement of claim 1, wherein the remaining portion of the piston includes a central portion having the heating device arranged to heat the substrate to the operating temperature.

15. The build cylinder arrangement of claim 14, wherein the remaining portion further comprises a lower portion of the piston having a cooling device arranged to cool the piston, wherein a thermal insulation is provided between the central portion and the lower portion, and the lower portion of the piston has a circumferential seal in abutment with the inner side of the base member for sealing gas, wherein the circumferential seal is comprised at least partially of an elastomer material.

16. The build cylinder arrangement of claim 15, wherein the seal for sealing gas comprises a hydraulic or pneumatic seal whose outer diameter can be adjusted by a pressure of hydraulic fluid or gas in the seal.

17. The build cylinder arrangement of claim 1, wherein the base member comprises an insulation member that is substantially cylindrical and forms at least the inner side of the base member, wherein the insulation member is made of a material with a specific thermal conductivity ≤3 W/(m*K).

18. The build cylinder arrangement of claim 17, wherein the material of the insulation member is ceramic or glass.

19. The build cylinder arrangement of claim 18, wherein the glass is quartz glass.

20. The build cylinder arrangement of claim 19, wherein the quartz glass is opaque.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic cross-section of an embodiment of a build cylinder arrangement, mounted on a process chamber, during a laser melting processing operation of an object to be produced.

(2) FIG. 2 shows the build cylinder arrangement of FIG. 1 after completion of the object with locks retracted.

(3) FIG. 3 shows the build cylinder arrangement of FIG. 1 after the piston has been separated between the upper portion and remaining portion.

(4) FIG. 4 is a schematic cross-section of the replacement of a portion of the build cylinder arrangement of FIG. 1 with a new empty build chamber.

(5) FIG. 5 shows the new, empty build chamber of FIG. 4 when the remaining portion of the piston is coupled.

(6) FIG. 6 is a schematic oblique view of a fiber metal seal.

(7) FIG. 7A is a schematic cross-section of a pressing tool for producing a fiber metal seal in the still-uncompressed state.

(8) FIG. 7B shows the pressing tool of FIG. 7A in the compressed state.

(9) FIG. 8A is a schematic cross-section of a fiber metal seal in a two-part seal carrier with a bayonet-type mechanism in an open state.

(10) FIG. 8B shows the fiber metal seal and the seal carrier of FIG. 8A in a closed state.

(11) FIG. 9 is a schematic cross-section of a machine for the layered production of three-dimensional objects.

DETAILED DESCRIPTION

(12) FIG. 1 shows an embodiment of a build cylinder arrangement 1 that is fitted to an opening 2 in the base 3 of a process chamber. The build cylinder arrangement 1 is suspended via hooks 31 on the process chamber (illustrated only in FIG. 1); the hooks 31 are part of a replacement mechanism 30 for build chambers (see below).

(13) The build cylinder arrangement 1 includes a base member 5 that at least at the inner side is a quartz glass of low thermal conductivity and has a circular-cylindrical-jacket-like form. Furthermore, the build cylinder arrangement 1 includes a piston 6 that can be moved in an axial direction (in FIG. 1, from the top to the bottom) in the base member 5. The piston 6 has an upper portion 7 on which a substrate 8 is constructed.

(14) On the substrate 8, a three-dimensional object 11 is produced in a layered manner by upper-side powdered material 10 being scanned with a high-energy beam 12, e.g., a laser beam 13. The energy of the high-energy beam 12 is sufficient to melt an uppermost layer of the powdered material 10. The powdered material 10 is typically a metal powder with a mean particle size from 25 μm to 100 μm, e.g., with a D50 value of 40-60 μm.

(15) The upper portion 7 of the piston 6 has a powder seal 9 for sealing the powdered material 10 that is a fiber metal seal (see FIG. 6). The powder seal 9 abuts with radial compression stress against the inner side of the base member 5.

(16) The upper portion 7 of the piston 6 is positioned on a remaining portion 23 of the piston 6; both portions 7, 23 are clamped to each other in a reversible manner with a clamping device that is not illustrated in greater detail (and that is also a portion of the replacement mechanism 30) so that the two portions 7, 23 can be readily separated from each other and secured to each other.

(17) In the remaining portion 23 of the piston 6 is a heating device 14 (e.g., with electric heating loops, only schematically illustrated in FIG. 1), by which the substrate 8 can be heated from below. Typically, an operating temperature of the substrate 8 and the powdered material 10 is between 500° C. and 1000° C. is adjusted, e.g., between 500° C. and 650° C.

(18) In the embodiment shown, the remaining portion 23 of the piston 6 has a central portion 15 in which the heating device 14 is constructed and a lower portion 16 on which a gas seal 17 for sealing gas is arranged. The gas seal 17 is produced from an elastomer material, for example, from silicone, and can be inflated with gas pressure of an operating gas to increase its radius and thus to enable a tighter abutment on the base member 5 (“pneumatic seal”). In the lower portion 16 is a cooling device 18 (e.g., cooling coils for cooling water schematically illustrated in FIG. 1), by which the lower portion 16 and the gas seal 17 can be kept at a moderate temperature (e.g., around 100° C. or less). Thermal insulation 22 (e.g., a ceramic plate) is arranged between the central portion 15 and the lower portion 16. Secured to the lower portion 16 the arm 19 is a lifting device, by which the piston 6 can be axially moved.

(19) During the production of the object 11, a protective gas atmosphere (for instance, N.sub.2 or a noble gas such as argon) is in the process chamber and in the base member 5 around the object 11. The gas seal 17 prevents penetration of atmospheric oxygen from the environment.

(20) On the base member 5 there is formed a lock mechanism 20 by which locks 21 can be radially extended and retracted. The lock mechanism 20 is also part of the replacement mechanism 30.

(21) Referring to FIG. 2, after completion of the three-dimensional object 11, the piston 6 is moved downwards until the lower side of the substrate 8 or of the upper portion 7 is axially just above the locks 21. Subsequently, the locks 21 are extended radially inwards.

(22) The gas seal 17 has moved past the base member 5. The inner space of the build cylinder arrangement 1 is then still protected by the powder seal 9, and small quantities of atmospheric oxygen can reach the object 11. However, since no further melting processes take place, this small oxygen introduction is generally non-critical. If desired, a cover can be placed on the upper opening 2 to protect the process chamber located above from the introduction of oxygen.

(23) Referring to FIG. 3, after the upper portion 7 and remaining portion 23 have been decoupled and the piston 6 has been lowered further, the piston 6 is separated. The upper portion 7 remains resting on the locks 21, and the remaining portion 23 of the piston 6 is retracted further.

(24) Referring to FIG. 4, the build chamber 25 (the base member 5 together with the substrate 8 including the finished object 11 that is arranged thereon) and the powder seal 9 (closed with a cover 24), can be removed from the process chamber (see the base 3 thereof). The build chamber 25 and the object 11 are still hot at this time, e.g., at more than 500° C. As a result of the powder seal 9 and the cover 24, the protective gas atmosphere present inside is substantially maintained. The powder seal 9 may as a result of the metal material of its fibers withstand the atmospheric oxygen that acts from below. The cooling of the build chamber 25 and of the finished object 11 can then be carried out in a location remote from the process chamber in a cooling store, typically over a period of several hours.

(25) At the same time, a new build chamber 26, with a new base member 5 and new upper portion 7 of the piston 6, is arranged at the opening 2 of the process chamber.

(26) Subsequently, the piston 6 or the remaining portion 23 thereof approaches from below the upper portion 7 of the piston 6 of the new build chamber 26, see FIG. 5. As soon as contact is established, the locks 21 can be retracted radially outwardly. When the piston 6 is lifted further, the lower portion 23 is introduced into the new base member 5. The gas seal 17 can be briefly relaxed to facilitate the introduction of the gas seal 17.

(27) Subsequently, it is possible to begin the layered production of a new three-dimensional object on the substrate 8 of the new build chamber 26. It is not necessary to wait for the previously produced three-dimensional object 11 to be cooled (see FIG. 4).

(28) FIG. 6 is a schematic oblique view of a fiber metal seal 60, as used in a build cylinder arrangement. The fiber metal seal 60 is constructed in a closed annular manner and includes metal fibers 61 that are pressed together. Typically, the metal fibers are already intertwined before compression, typically woven or knitted, and/or twisted and/or rolled up (not illustrated in greater detail).

(29) To produce a fiber metal seal 60, the procedure is typically as follows: in step 1, circular knitting of a metal wire hose (also called knitted stocking) is first carried out, typically with a diameter of approximately 80 mm. In step 2, the hose is cut to a required axial length, if necessary. In step 3, the hose piece obtained is tapped to remove loose wire pieces caused by the cut, if required. In step 4, the hose piece is twisted to form a knitted cord. Subsequently, in step 5, the cord is placed in a pressure die (pressing tool) in a helical manner. Finally, in step 6 it is pressed into an annular shape.

(30) Alternatively to steps 4 and 5, it is also possible to place the metal wire hose or hose piece directly or after axial rolling-up into a pressure die, where the hose piece is placed like a stocking over a core of the pressure die.

(31) FIG. 7A is a schematic cross-section of a pressure die 70 by which a fiber metal seal can be produced. The rotationally symmetrical pressure die 70 includes an inner portion 71, which has a shoulder 72, and a substantially tubular outer portion 73. In the example shown, a metal wire hose 74 is placed over the core 75 of the pressure die 70. If desired, the core 75 can also be constructed in a conical manner towards the top (not illustrated) to facilitate placement of the metal wire hose 74. By lowering a pressing stamp 76, the metal wire hose 74 is pressed. In doing so, the metal wire hose is plastically and also resiliently deformed.

(32) As a result of the compression, the fiber metal seal 60 is obtained, FIG. 7B. After removing the pressing tool, there is a rebound (resilient expansion) of the fiber metal seal 60, see the contour lines 81 illustrated with broken lines, whereby the outer radius, the inner radius and the axial height of the seal 60 increase again.

(33) This resilient deformation region (“resilient play”) can be used to apply a resilient pressure in a radial direction to the fiber metal seal 60 in the mounted state in a build cylinder arrangement. On the one hand, the fiber metal seal is thereby in close abutment with the inner side of the base member and the outer side of the piston, on the other hand, different thermal expansions of the piston and base member can be compensated for to a given degree.

(34) FIG. 8A shows a first seal carrier portion 82 with a shoulder 83 and a second cover-like seal carrier portion 84 for the assembly of a fiber metal seal 60 on the piston 6, e.g., on the substrate 8. On the first seal carrier portion 82 is a guiding groove 85 for a guiding projection 86 on the second seal carrier portion 84; the guiding groove 85 and guiding projection 86 form a bayonet-type mechanism. It should be noted that typically at least two such guiding grooves 85 and guiding projections 86 are provided, where for reasons of simplicity, only one set is illustrated in FIG. 8A.

(35) When the second seal carrier portion 84 is removed, the fiber metal seal can be placed without (or at most with only a little) deformation on the shoulder 83 of the first seal carrier portion 82.

(36) Subsequently, the second seal carrier portion 84 can be clamped (twisted) on the first seal carrier portion 82 by the bayonet-type mechanism, to form a groove 87 in which the fiber metal seal 60 is retained or axially clamped, see FIG. 8B. It should be noted that the fiber metal seal 60 protrudes radially beyond the groove 87.

(37) The wire material (material of the metal fibers) of the fiber metal seal preferably has a comparatively low thermal expansion, typically in accordance with the material of the base member (or the inner side thereof) of the build cylinder arrangement. The pretensioning can thereby be kept substantially constant even at the operating temperature. Generally, the thermal expansion of the wire material deviates by less than 20% from the thermal expansion of the material of the base member. The wire material should further be resistant to oxidation in atmospheric oxygen above 500° C., e.g., up to at least 600° C., so that when the build chamber is removed in the hot state the fiber metal seal does not burn off or otherwise become damaged. The wire material should further be selected in such a manner that the elastic modulus thereof when heated to the operating temperature drops only slightly, e.g., by less than 20% with respect to ambient temperature over (at least) 100 hours. Similarly, the yield strength (R.sub.p,0.2) when heated should only decrease slightly, e.g., by less than 30% with respect to ambient temperature over (at least) 100 hours. Nickel-based alloys such as Inconel® 718 or Inconel® X750 or Nimonic® 90 are wire materials that can also comply with the above properties. FIG. 9 is a schematic side view of an embodiment of a machine 90 for the layered production of a three-dimensional object 11 (or of several three-dimensional objects). The machine 90 includes a gas-tight process chamber 92 that can be filled and/or purged in a manner not illustrated in greater detail with an inert gas (protection gas), such as nitrogen, or a noble gas, such as argon.

(38) Connected to the process chamber 92 is a storage cylinder arrangement 93 for a powdered material 10 (illustrated with dots) from which the three-dimensional object 11 is produced by laser sintering or laser melting. The powdered material 10 may, for example, include metal particles with a mean particle size (D50) of 25-100 μm. By stepwise raising a powder piston 95 with a powder lifting device 96, a small quantity of the powdered material 10 is raised over the level of the base 3 of the process chamber 92 so that, with a sliding member 97 that can be actuated in a motorized manner, this small quantity can be moved to a build cylinder arrangement 1 (for instance, constructed as illustrated in FIG. 1).

(39) The build cylinder arrangement 1 that is also connected to the process chamber 92 has the piston 6, on which at the upper side (on the substrate) the three-dimensional object 11 is built up. Before the production of a new layer of the three-dimensional object 11, the piston 6 is lowered by a step with a lifting device 91 and a small quantity of the powdered material 10 is scraped with the sliding member 97 in the build cylinder arrangement 1.

(40) Subsequently, the newly applied powder layer is locally illuminated from above with a processing laser beam 100 (e.g., from a local processing laser 101 and introducing through a window 103 into the process chamber 92) at locations that are designated for a local solidification (melting, sintering) of the powdered material 10, and thereby powerfully locally heated. The processing laser beam 100 is guided (scanned) over the substrate by an optical scanner unit 102 (containing one or more mirrors that on the whole can be pivoted about at least two axes).

(41) Subsequently, additional layers are produced until the three-dimensional object 11 is complete. Excess powdered material 10 can be spread with the sliding member 97 into a collection container 94.

(42) For a rapid sequence of the production of three-dimensional objects, the build cylinder arrangement 1 (or the base member thereof including the upper portion of the piston 6) can be replaced, as described in FIGS. 1 to 5.

LIST OF REFERENCE NUMERALS

(43) 1 Build cylinder arrangement 2 Opening (process chamber) 3 Base (process chamber) 5 Base member 6 Piston 7 Upper portion (piston) 8 Substrate 9 Seal for sealing the powdered material (powder seal) 10 Powdered material 11 Three-dimensional object 12 High-energy beam 13 Laser beam 14 Heating device 15 Central portion (piston) 16 Lower portion (piston) 17 Seal for sealing gas (gas seal) 18 Cooling device 19 Arm 20 Locking device 21 Lock 22 Thermal insulation 23 Remaining portion (piston) 24 Cover 25 Build chamber 26 New build chamber 30 Replacement mechanism 31 Hook 60 Fiber metal seal 61 Metal fiber 70 Pressure die (pressing tool) 72 Inner portion 72 Shoulder (inner portion) 73 Outer portion 74 Metal wire hose (knitted stocking) 75 Core 76 Pressing stamp 81 Contour lines (fiber metal seal after rebound) 82 First seal carrier portion 83 Shoulder (first seal carrier portion) 84 Second seal carrier portion 85 Guiding groove (bayonet type mechanism) 86 Guiding projection (bayonet type mechanism) 87 Groove 90 Machine 91 Lifting device 92 Process chamber 93 Storage cylinder arrangement 94 Collection container 95 Powder piston 96 Powder lifting device 97 Sliding member 100 Processing laser beam 101 Processing laser 102 Optical scanner unit (laser scanner) 103 Window

OTHER EMBODIMENTS

(44) A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.