Method and apparatus for generatively manufacturing a three-dimensional object

Abstract

Disclosed is a method of generating a ceiling gas stream in the course of the generative manufacturing of a three-dimensional object in a process chamber by a layer-by-layer application and selective solidification of a building material within a build area arranged in the process chamber. The process chamber has a chamber wall having a process chamber ceiling lying above the build area. A ceiling gas stream of a process gas is passed through the process chamber which is streaming from the process chamber ceiling towards the build area in a controlled manner. In the course of this, the ceiling gas stream is supplied to the process chamber through ceiling inlets formed in the process chamber ceiling such that the ceiling gas stream is directed substantially perpendicularly to the build area downwards onto the build area as it exits the ceiling inlets.

Claims

1. A method of generating a ceiling gas stream in a generative manufacturing of a three-dimensional object in a process chamber by a layer-by-layer application and selective solidification of a building material within a build area located in a process chamber bottom, the method comprising: providing the process chamber having a chamber wall with a process chamber ceiling lying above and extending over the build area; passing a ceiling gas stream of a process gas through the process chamber by streaming the ceiling gas stream from the process chamber ceiling towards the build area in a controlled manner; and supplying the ceiling gas stream to the process chamber through multiple ceiling inlets formed in the process chamber ceiling which are spaced apart and distributed over a region of the ceiling of the process chamber directly above the build area, with the ceiling gas stream out of the ceiling inlets combining from multiple ceiling inlet gas streams flowing from the inlets and directed to flow in a manner perpendicularly to the build area and therefore downwards onto the build area as the ceiling gas stream exits the ceiling inlets, the process chamber ceiling including at least one window for passing radiation used for the solidification of the building material into the process chamber; and the process chamber ceiling further having at least one central inlet in a section bordering on the at least one coupling window, the central inlet providing a central partial ceiling gas stream out therefrom towards the build area, the central partial ceiling gas stream shaped so as to widen in such a manner that the central partial ceiling gas stream converges at margins of the central partial ceiling gas stream towards adjacent inlet ceiling gas streams or overlaps with adjacent inlet ceiling gas streams at least in a lowest part of the process chamber above the build area, the ceiling gas stream and the central partial ceiling gas stream combining in a controlled manner towards the build area to generate a combined gas stream at least across the whole build area.

2. The method according to claim 1, wherein the ceiling inlets are shaped and/or arranged and/or controlled such that the ceiling gas stream is homogeneously shaped in a lowest tenth of the process chamber height; and/or wherein the ceiling inlets are shaped and/or arranged and/or controlled such that the ceiling gas stream is homogeneously shaped in a plane of the build area and/or parallel above the build area, the plane extending at least across the area of the build area including a surrounding area of the build area or across a total area of the process chamber bottom.

3. The method according to claim 1, wherein the process chamber bottom lies below the process chamber ceiling, and the build area extends over a partial region of the process chamber bottom, a distribution of the ceiling inlets at the process chamber ceiling is about the same in areas relative to a total area of the process chamber bottom, wherein the ceiling inlets are designed and/or arranged and/or controlled such that inlet ceiling streams of the ceiling gas stream are respectively directed perpendicularly to the build area downwards onto the process chamber bottom when the inlet ceiling streams exit the ceiling inlets.

4. The method according to claim 1, wherein the ceiling gas stream is passed through the process chamber before and/or during and/or after the selective solidification of the building material.

5. The method according to claim 1, wherein the process chamber ceiling further comprises a hollow space having a wall that is closed in an outer wall region facing away from the process chamber and that possesses ceiling inlets in an inner wall region bordering the process chamber.

6. The method according to claim 5, wherein the inner wall region comprises a plate or the ceiling inlets are at least partly formed by holes of the plate so as to form a perforated plate; wherein the plate or the perforated plate has at least 10 holes; and/or wherein an average opening cross-section area of the holes does not exceed 10 cm.sup.2; and/or wherein a sum of the opening cross-section areas of the holes does not exceed 20% of a total area of the process chamber bottom.

7. The method according to claim 1, wherein at least one of the ceiling inlets and/or at least one additional gas inlet into the process chamber is designed and/or controlled such that, depending on a spatial configuration of the process chamber and/or on a position and/or size of a device arranged inside the process chamber, a velocity and/or an orientation and/or a jet cross-section of a partial ceiling gas stream streaming out of the ceiling inlet or the additional gas inlet are varied prior to and/or during and/or after the object manufacturing.

8. The method according to claim 1, wherein prior to and/or during and/or after the manufacturing of the object, a process gas is supplied to the process chamber in a closed process gas circuit and is discharged from the process chamber through an outlet; wherein the ceiling gas stream represents at least a part of the process gas circuit; and wherein supply and/or discharge pipes of the process gas circuit include a conveying unit that varies a velocity and/or velocity distribution and/or pressure distribution of a total process gas stream or of the ceiling gas stream in the process chamber prior to and/or during and/or after the manufacturing of the object.

9. The method of claim 8, wherein the process gas circuit further comprises at least one of the following gas streams that removes impurities generated during the solidification of the building material from the process chamber: a central gas stream that flows into the process chamber prior to and/or during and/or after the manufacturing of the object through a central inlet formed in the process chamber ceiling and flows out of the process chamber through at least one outlet, the central gas stream impinging within a central region of the build area at an angle of at least 45° to the build area; a lateral gas stream that flows into the process chamber prior to and/or during and/or after the manufacturing of the object through a side inlet arranged at a build area side and flows out of the process chamber through at least one outlet arranged at an opposite side of the build area.

10. The method according to claim 8, wherein a ratio of a total inlet opening area to a total outlet opening area of the process gas circuit is varied prior to and/or during and/or after the manufacturing of the object, whereby, a velocity and/or a pressure of the process gas is/are varied at least in a partial region of the process chamber.

11. A control unit for an apparatus for generatively manufacturing a three-dimensional object, wherein the control unit is designed for generating control commands for the automatic execution of a method according to claim 1.

12. An apparatus designed and/or controlled to automatically execute the method according to claim 1.

13. The method according to claim 1, wherein the ceiling inlets are uniformly distributed over a total region of the process chamber ceiling except for a coupling window region occupied by the at least one coupling window.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic cross-sectional side view of an embodiment of the manufacturing apparatus according to the invention having at least one solidification unit;

(2) FIG. 2 is a schematic cross-sectional side view of a further embodiment of the manufacturing apparatus according to the invention having at least two solidification units;

(3) FIG. 3 is a schematic view of a gas stream having a conventional circular impingement area within the build area flowing off towards the build area edge (in top view);

(4) FIG. 4 is a schematic view of a gas stream having a conventional elongate rectangular impingement area within the build area flowing off towards the build area edge (in top view);

(5) FIG. 5 is a schematic view of a gas stream flowing off towards the build area edge in the vicinity of a “long side” of an elongate oval impingement area according to the invention within the build area (in top view);

(6) FIG. 6 is a schematic view of a gas stream flowing off towards the build area edge in the vicinity of a “narrow side” of an elongate oval impingement area according to the invention within the build area (in top view);

(7) FIG. 7 is a schematic top view of an example of the arrangement of a build area in the process chamber of a manufacturing apparatus according to the invention with flow lines of the gas stream above the build area;

(8) FIG. 8 is a schematic cross-sectional side view of an arrangement of an inlet relatively to a build area with flow lines of the gas stream according to the invention in the process chamber;

(9) FIGS. 9a and 9b are schematic top views of examples of an inlet of a gas supply device according to the invention having an expanding effect;

(10) FIG. 9c shows two side views rotated by 90° with respect to each other of a further example of an inlet of the gas supply device according to the invention having an expanding effect;

(11) FIG. 9d schematically shows a process-chamber-sided top view on the left and a perspective view on the right of the inlet of FIG. 9c;

(12) FIG. 10a is a schematic cross-sectional side view of a process chamber of a manufacturing apparatus according to the invention having four solidification units (with a laser beam path);

(13) FIG. 10b is a schematic top view of working areas of the four solidification units within the build area of the process chamber of FIG. 10a;

(14) FIG. 11a is a schematic top view of an example of a build area extension in a manufacturing apparatus according to the invention by three impingement areas of the gas stream stringed together;

(15) FIG. 11b is a schematic top view of an example of a build area extension in a manufacturing apparatus according to the invention whose solidification device has six solidification units;

(16) FIG. 12a is a schematic cross-sectional side view of the process chamber of a manufacturing apparatus according to the invention having a ceiling gas stream;

(17) FIG. 12b is a schematic top view of the build area and of the ceiling inlets in the manufacturing apparatus of FIG. 12a;

(18) FIG. 13 is a schematic cross-sectional side view of a manufacturing apparatus according to the invention in which a central gas stream is combined with a ceiling gas stream in a process gas circuit;

(19) FIG. 14 is a schematic cross-sectional side view of a manufacturing apparatus according to the invention in which a lateral gas stream is combined with a ceiling gas stream in a process gas circuit;

(20) FIG. 15 is a schematic perspective view of a perforated metal plate for generating the ceiling gas stream according to the invention;

(21) FIG. 16 is a schematic perspective view inclined from below onto the perforated metal plate of FIG. 15 in a built-in state in the ceiling of a process chamber;

(22) FIG. 17 is a schematic perspective view inclined from above and partly in a vertical cross-section onto a process chamber having a perforated metal plate of FIGS. 15 and 16 built-in in its ceiling.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(23) Referring to FIG. 1, an embodiment of an apparatus 1 for generatively manufacturing a three-dimensional object is described, the apparatus being designed and/or controlled to preferably automatically execute a manufacturing method according to the invention. The layer manufacturing apparatus 1 schematically shown in FIG. 1 is a laser sintering of laser melting apparatus. For manufacturing a three-dimensional object 2 by a layer-by-layer application and selective solidification of a building material, it contains a process chamber 3 having a chamber wall 4 comprising a process chamber ceiling 4a.

(24) In the process chamber 3, an open-top container 5 having a container wall 6 is arranged. In the container 5, a support 7 movable in a vertical direction V is arranged at which a base plate 8 is mounted which closes the container 5 below and thereby forms its bottom. The base plate 8 may be a plate formed separately from the support 7, which is attached to the support 7, or it may be integrally formed with the support 7. Depending on a building material used (in particular, powder) and a process, a platform 9 may further be mounted on the base plate 8 as building support, on which the object 2 is built up. However, the object 2 may also be built up on the base plate 8 itself, which then serves as a building support. In FIG. 1, the object 2 to be built in the container 5 on the platform 9 is shown below a build area 10 defined by the upper edge of the container wall 6 in an intermediate state with several layers being already solidified, surrounded by building material 11 remaining non-solidified.

(25) The laser sintering apparatus 1 further contains a storage container 12 for a building material 13 which can be solidified by an electromagnetic radiation and is, in this example, in powder form and a recoater 14 movable in a horizontal direction H for applying the building material 13 layer-by-layer onto the building support or onto a previously applied layer within the build area 10. Optionally, a radiation heater 15 is arranged in the process chamber 3 for heating the applied building material 13. As radiation heater 15, e.g. an infrared radiator may serve.

(26) In order to selectively solidify the applied building material 13, the laser sintering apparatus 1 contains a solidification device 30 (also referred to as irradiation device in the following) having a laser 31 generating a laser beam 32. The laser beam 32 is deflected via a deflecting device 33 and is focused by a focusing device 34 via a coupling window 35, which is mounted in the process chamber ceiling 4a, onto the building support or a previously applied layer of the building material 13. The solidification device 30 may basically also comprise further solidification units, which are not seen in the cross-sectional side view of FIG. 1, having further lasers and/or deflecting and focusing devices and/or coupling windows.

(27) The laser sintering apparatus 1 further contains a control unit 39 via which the individual components of the apparatus are controlled (indicated by arrows in FIG. 1) in a coordinated manner for executing the building process, in particular, a method according to the invention. Alternatively or additionally, a control unit may also be partially or completely be arranged outside the apparatus 1. The control unit may contain a CPU whose operation is controlled by a computer program (software). The computer program may be stored separately from the apparatus on a storage medium, from which it can be loaded into the apparatus, in particular, into the control unit 39. The control unit is preferably a control unit according to the invention.

(28) During operation, the building support, which is a surface of the platform 9 in this example, is located at the beginning of the manufacturing process at the height of the build area 10 and is respectively lowered for applying a building material layer by a height corresponding to the desired layer thickness.

(29) By moving the recoater 14 within the build area 10, a layer of the building material 13 in powder form (pulverulent) is respectively applied to the building support or a pre-existing upper powder layer. The application takes place at least over the total respective cross-section of the object 2 to be manufactured. Optionally, the pulverulent building material 13 is heated up by means of the radiation heater 15 to an operating temperature. Subsequently, the cross-section of the object 2 to be manufactured is scanned by the laser beam 32, so that the pulverulent building material 13 is solidified at the points corresponding to the cross-section of the object 2. These steps are repeated as long as until the object 2 is completed.

(30) According to the invention, a gas stream 40 of a process gas is supplied to the process chamber 3 through a gas supply device (not shown) arranged in the process chamber ceiling 4a while the object 2 is being manufactured in order to remove impurities generated in the course of the selective solidification from the process chamber 3. A process-chamber-sided inlet of the gas supply device (not shown in FIG. 1) may have an arbitrary suitable arrangement in the process chamber ceiling 4a and form. The gas stream 40 exits the process chamber 3 through outlets 42a and 42b arranged at opposed build area sides approximately at the height of the build area. The outlets 42a and 42b are merely schematically indicated in FIG. 1. They may have any suitable arrangement and geometry, in particular according to the further-above-described advantageous configurations of the invention. In particular, the outlets 42a and 42b may be arranged in or at the chamber wall 4, directly at the build area edge or at a distance therefrom, as well as not necessarily at the height of the build area.

(31) After exiting the gas supply device, the gas stream 40 streams through the process chamber 3 in a non-guided manner and substantially vertically, this means except for a possible billowing of the gas stream 40 and a minor deviation of margin regions of the gas stream 40 by up to approximately 20° from a vertical with respect to the build area 10, towards the build area 10. There, the gas stream 40 impinges in an impingement area A3 according to the invention, which lies centrally within the build area 10, onto the upper building material layer and is laterally deflected partly by the upper building material layer, partly, as the case may be, by a suction effect of the outlets 42a and 42b. Subsequently, the gas stream flows off, preferably substantially parallel to the build area 10, towards the outlets 42a and 42b and thereby removes impurities from the process chamber 3.

(32) FIG. 2 shows a further embodiment of the manufacturing apparatus 1 according to the invention. In differs from the apparatus of FIG. 1 in the configuration of the solidification device 30 and in a specific configuration of a process-chamber-sided inlet of the gas supply device.

(33) The manufacturing apparatus 1 in FIG. 2 is a so-called multi-scanner-machine since the solidification device 30 comprises several solidification units. In the cross-sectional side view of FIG. 2, two of them can be seen. Components of the one solidification unit 30a on the left in the figure are denoted by an additional index “a”, those of the other one solidification unit 30b on the right in the figure by an additional index “b”.

(34) By way of example only, each solidification unit comprises a laser 31a/31b generating a laser beam 32a/32b, as well as a deflecting device 33a/33b, a focusing device 34a/34b, and a coupling window 35a/35b. Alternatively, a solidification unit may also comprise only one or a part of the above-mentioned elements.

(35) To each solidification unit, a working area (in FIG. 2 on the left and on the right) within the build area 10 is assigned which can be scanned by the respective laser beam 32a or 32b. In this example, the working areas are arranged axially symmetrically with respect to a central plane which goes through a central point Z0 of the build area and is perpendicular to the build area 10 and to the drawing plane.

(36) The apparatus 1 may have further pairs of solidification units which are not to see in the cross-sectional side view of the FIG. 2 and which are preferably arranged and/or designed similarly to FIG. 2. An example of a four-scanner-machine having four solidification units on the whole is described further below referring to FIGS. 10a and 10b. Furthermore, referring to FIGS. 11a and 11b, an example of a six-scanner-machine having six solidification units on the whole is described.

(37) Further, the gas supply device (not shown) ends in FIG. 2 in a process-chamber-sided inlet 43, which may, for instance, be a nozzle. The nozzle 43 protrudes from the process chamber ceiling 4a not substantially, here, by way of example only, by approximately 4 cm downwards into the process chamber 3 with a process chamber height measured vertically from the build area 10 up to a coupling window 35a/35b being approximately 49 cm. Alternatively, the inlet 43 may also protrude deeper or, alternatively, not protrude at all into the process chamber 3.

(38) In FIG. 2, the nozzle 43 is arranged approximately centrally between the coupling windows 35a and 35b of the two solidification units 30a and 30b shown. Since the gas stream 40 streams substantially vertically downwards towards the build area 10, the impingement area A3 of the gas stream 40 also lies centrally in the build area and, thus, in both working areas which can be scanned by the two laser beams 32a or 32b within the build area 10. That way, each working area is flown over/through by its own gas stream portion flowing in FIG. 2 either to the left or to the right from the centre Z0 of the build area. Therefore, impurities generated in the respective working areas are removed by the respective gas stream portions on the shortest route towards the build area edge. Consequently, the two lasers 31a and 31b do not mutually disturb one another with regard to the impurities which they cause in the manufacturing process by irradiating the powder.

(39) Subsequently, the advantageous effects of an elongate oval impingement area according to the first aspect of the invention as compared to the conventional circular or elongate rectangular impingement areas, which advantageous effects have been set forth above with reference to FIGS. 3 to 6, will be further described and supplemented referring to FIGS. 7 to 11.

(40) FIG. 7 shows in a schematic top view an example of the arrangement of the build area in the process chamber of a manufacturing apparatus according to the invention with flow lines of the gas stream above the build area. In particular, it may be the apparatus 1 of FIG. 1 or 2.

(41) In this example, the build area 10 has a rectangular build area edge BR, which may preferably be quadratic and may, for instance, be 400 mm×400 mm. Here, also the chamber wall 4 of the process chamber 3 is rectangular in a horizontal cross-section at a height of the build area. By way of example only, symmetry axes of both rectangles coincide. Around the build area 10, a process chamber bottom 4b is shown, lying, for example, approximately at the height of the build area.

(42) Symmetrically arranged with respect to a centre Z0 of the build area 10, there is the elongate oval impingement area A3 of the gas stream according to the invention. In this example it is elliptical, having a long axis of the ellipse parallel to a narrow side of the build area. A dashed line shows an orthogonal projection of the process-chamber-sided opening of an inlet of the gas supply device (for example, the nozzle 43 in FIG. 1 or 2). In particular by an expanding effect of the inlet, i.e. an effect of widening a cross-section of the gas stream towards the build area, the impingement area A3 is larger than the projection of the opening of the inlet onto the build area 10.

(43) After impinging within the impingement area and the deflection, the gas stream flows along the build area 10 and the process chamber bottom 4b towards the outlets 42a and 42b, which, by way of example only, extend over the whole respective narrow side of the chamber wall 4 parallel to the narrow sides of the build area. In particular, the outlets 42a and 42b extend here on their both ends beyond the respective build area side.

(44) Due to a distance D, which may, for instance, be 10 to 20 cm or larger, between an outlet 42a/42b and the nearest narrow side of the build area 10, a suction effect exerted, as the case may be, by the outlet on the gas stream volume is relatively small above the build area 10. Therefore, the deflection of the gas stream after the impingement mainly takes place due to the rebound of the gas stream at the upper building material layer within the impingement area A3 and due to a subsequent flowing off of the gas stream portions into respective nearby regions which are not charged by the gas stream afterflow, the latter being continuous at least during the solidification. The flow lines of the gas stream portions flowing off towards the outlets 42a, 42b after the deflection are indicated by continuous curved lines.

(45) Additional outlets may be provided at the long sides of the chamber wall 4, in particular centrally, in order to support the discharging of the gas stream portions flowing off at the “narrow sides” of the ellipse A3 from the process chamber.

(46) FIG. 8 is a schematic cross-sectional side view of an example of flow lines of a gas stream according to the invention in the process chamber, which may be part of the manufacturing apparatus 1 of FIG. 1 or 2. The gas stream 40 streams into the process chamber 3 through the inlet 43, which may e.g. be designed as a nozzle. With regard to the construction of the nozzle 43, for instance, the descriptions referring to FIG. 7 or 9a may apply here.

(47) The nozzle 43 has an inner cross-section length Li (which lies in the drawing plane of FIG. 8) growing in a vertical direction towards the build area 10. Due to this, the gas stream 40 passing through the nozzle 43 gets wider in the direction of this inner cross-section length or, respectively, it gets expanded.

(48) In the course of this, however, an inner cross-section area of the nozzle 43 preferably remains substantially constant over the extension of the nozzle 43 in the direction towards the build area 10, so that the velocity of the gas stream 40 also remains substantially unchanged as it passes through the nozzle 43.

(49) Due to the expanding effect of the nozzle 43, in the drawing plane of FIG. 8, an outer gas flow line of the gas stream 40—it is indicated by a continuous line—deviates e.g. by approximately 20° from a vertical)(90° with respect to the build area 10. The vertical approximately corresponds to the direction of a central gas stream flow line streaming towards the centre Z0 of the build area 10, which is also indicated by a continuous line. Depending on a gas stream density and/or suction effect of the outlet, the course of the gas flow lines in margin regions of the gas stream 40 may get flatter (indicated by a dashed line in FIG. 8).

(50) With a constant inner cross-section area of the nozzle 43 over its extension, the gas stream 40 is simultaneously concentrated in the nozzle 43 in a direction perpendicular to the drawing plane (in FIG. 8 not visible). This will be subsequently visualized in further examples with the aid of FIGS. 9a-9d.

(51) Referring to FIGS. 9a-9d, in the following, several examples of an inlet of the gas supply device in form of a nozzle having an expanding effect on the gas stream according to the invention are described. In the course of this, the gas supply line (not shown) ending in the nozzle has, by way of example only, always a circular inner cross-section. Further, also here the nozzle preferably has, similarly to FIG. 8, a substantially constant inner cross-section area for the gas stream flowing through the nozzle. The nozzles shown in FIGS. 9a-9d may, in particular, be employed in the manufacturing apparatus 1 described with reference to FIGS. 1-8.

(52) FIG. 9a schematically shows in a top view a first embodiment of such a nozzle, which may, for example, be the nozzle 43 of FIG. 2 or 8. A circular pipe-sided inner cross-section 50 of the nozzle is shown by a dashed line. In this embodiment, a process-chamber-sided inner cross-section 60 (here, at the same time an opening area) of the nozzle has the shape of an ellipse which is concentric with the gas supply pipe. The opening area 60 does not necessarily need to be elliptical, it rather may be an arbitrary elongate oval having two perpendicular symmetry axes 61 and 62 as shown.

(53) FIG. 9b shows a schematic top view of a second embodiment of the nozzle which differs from the one of FIG. 9a only in that the short axis of the ellipse is parallel shifted to the left by a distance dl from a vertically drawn symmetry axis of the circular inner cross-section 50. The long axis a of the ellipse still coincides in the top view of FIG. 9b with a horizontally drawn symmetry axis of the circular inner cross-section 50.

(54) Such an offset dl may be used for a preferably minor deflection of the gas stream as it passes through the nozzle, in order to effect a corresponding shifting of its impingement area within the build area. The offset dl may, for instance, be approximately 3 mm with a long axis a of the ellipse being approximately 75 mm. In the course of this, deviations from a concentric arrangement of the two inner cross-sections 50 and 60 are preferably small, in order to avoid undesired turbulences of the gas stream streaming out of the nozzle at any rate.

(55) FIGS. 9c and 9d show a third embodiment of an inlet of the gas supply device in form of a nozzle 43 having a partially expanding effect on the gas stream according to the invention. This nozzle differs from the one of FIG. 9b in that its process-chamber-sided opening area 60 extends in a direction of its longitudinal axis 61 considerably farther to one side than to the opposite side with respect to a central axis 55 of the circular gas supply pipe. In this manner, the shaping of the gas stream according to the invention may be adapted to specific, for instance, asymmetric spatial conditions in the process chamber. In the course of this, in particular, the process-chamber-sided opening area 60 of the nozzle may also be designed arbitrarily strongly asymmetric along its longitudinal axis 61, whereas FIGS. 9c-9d show by way of example only an elliptical opening area 60. As for the rest, the above description with regard to FIGS. 9a and 9b may correspondingly apply here.

(56) FIG. 9c schematically shows two side views of the nozzle 43 rotated relatively to one another by 90° around the central axis 55 of the supply pipe. The left side view is, as in FIG. 8, aligned with respect to an inner cross-section length Li of the nozzle 43 which grows in a direction vertically towards the build area 10 (not shown). As in FIG. 8, the gas stream 40 according to the invention (not shown) is expanded in a direction of the growing inner cross-section length Li as it passes through the nozzle 43. The right side view shows a taper of the nozzle 43 in a direction perpendicular hereto with a constant inner cross-section area, whereby the gas stream 40 is concentrated. Altogether, this results in a process-chamber-sided elongate oval opening area 60 of the nozzle 43, which leads to an elongate oval impingement area of the gas stream 40 within the build area 10 according to the invention (as, for instance, illustrated in FIG. 7).

(57) Further, FIG. 9d shows on the left a schematic process-chamber-sided top view (i.e. a view from below) of the nozzle of FIG. 9c and on the right its schematic perspective view. For being detachably fastened at the process chamber ceiling 4a, the nozzle 43 in FIGS. 9c and 9d has at its end with the circular inner cross-section 50 an external thread 56 representing the fastening device according to the invention. In this example, the process chamber ceiling 4a (not shown) has a complementary inner thread.

(58) In a not shown fourth embodiment of an inlet of the gas supply device in form of a nozzle having an expanding effect on the gas stream according to the invention, the process-chamber-sided opening area is not elliptical but rather only axially symmetrical with respect to its longitudinal extension, being, however, irregularly oval-shaped apart from that. Thus, such a nozzle possesses only one axis of symmetry (its longitudinal axis) and is, beyond that, not concentric with the gas supply pipe ending in the nozzle. As for the rest, the above description with regard to FIGS. 9a-9d correspondingly applies here.

(59) FIG. 10a shows a schematic cross-sectional side view of a process chamber of a manufacturing apparatus according to the invention having four solidification units, only two of which are to see in the cross-sectional side view. In particular, it may be an apparatus 1 of FIG. 2. In this example, each solidification unit 30a and 30b comprises a laser and a focusing optics, which generate a laser beam 32a/32b which can scan an assigned working area 10a/10b of a build area 10.

(60) FIG. 10b shows a (by way of example only) quadratic build area of FIG. 10a in a schematic top view. In this example, four working areas 10a, 10b, 10c, and 10d of the four solidification units are identical quadrants completely covering the build area 10. They respectively overlap each other at sides facing each other. The overlapping regions are shown as hatched. For the sake of better illustration, a side of the working area 10c is shown. An elongate oval impingement area according to the invention may be arranged here, for instance, as in FIG. 11b with respect to working areas 10a-10d.

(61) FIG. 11a schematically shows in a top view an example of a build area extension in a manufacturing apparatus according to the invention by stringing together three elongate oval impingement areas of the gas stream according to the invention.

(62) As for the rest, the above description with regard to FIGS. 1-10 may apply in this example.

(63) By way of example only, here, three impingement areas A3 are similarly formed (elliptically, for instance, as in FIG. 7) and similarly oriented. They also share a common axis of symmetry (not shown), which is, respectively, the long axis of the ellipse. Furthermore, this common axis of symmetry also coincides with the long axis of symmetry of the rectangular build area 10. The impingement areas A3 overlap each other at narrow sides of the ellipses facing each other. Altogether, this results in a nearly uniform stream course of the impinging gas stream according to the invention along the build area 10, wherein, after impinging, the gas stream predominantly flows off on a short, nearly straight route from the impingement area to the respective outlet 42a or 42b. As for the rest, the above description with regard to FIG. 7 correspondingly applies here.

(64) FIG. 11b schematically shows in a top view a further example of a build area extension in a manufacturing apparatus according to the invention. Here, in contrast to FIG. 11a, only two elongate oval impingement areas of the gas stream are stringed together. As for the rest, the above description with regard to FIG. 11a correspondingly applies also in this example.

(65) In FIG. 11b, the build area 10 is subdivided in six partially overlapping working areas 10a-10f of six solidification units of the solidification device. As for the rest, the above description with regard to a four-scanner-machine with reference to FIGS. 10a/10b correspondingly applies here. Also here, by way of example only, the working areas 10a-10f are equal, they are preferably respectively quadratic in shape. For a better illustration, the working area 10a is highlighted by hatching.

(66) In FIG. 11b, the common axis of symmetry of the two impingement areas A3 passes substantially centrally through the build area 10. This common axis of symmetry passes centrally and symmetrically with respect to the row of the working areas 10a, 10d, and 10e arranged on the left in the figure and the row of the working areas 10b, 10c, and 10f arranged on the right in the figure. As already mentioned further above, such a central symmetrical arrangement of the impingement areas with respect to the working areas 10a-10f has, inter alia, the advantage of short, nearly straight routs for the gas stream flowing off to the outlets 42a/42b after its impingement. Moreover, that way, the individual working areas are streamed over by respective different, their own gas stream portions, so that impurities above one of the working areas do not or scarcely get to the other working areas, so that the increased number of solidification units does not negatively affect the removal of impurities above the build area.

(67) With the build area allocation as in FIG. 11b in a six scanner laser sintering system, in the above-mentioned preferably closed process gas circuit of a central gas stream according to the invention and a ceiling gas stream according to the invention, the volume ratio of the ceiling gas stream to the central gas stream may, for instance, be 5:1. The resulting six volume parts of the process gas can then be, for instance, discharged from the process chamber through respectively three outlets arranged at both long sides of the build area (in particular, respectively one at a working area).

(68) FIG. 12a is a schematic cross-sectional side view of the process chamber of a manufacturing apparatus according to the invention having a ceiling gas stream. The manufacturing apparatus may, in particular, be the laser sintering apparatus 1 described with reference to FIGS. 1-11. Through ceiling inlets 45 (indicated by continuous arrows) arranged in a process chamber ceiling 4a, a ceiling gas stream 44 (indicated by dashed arrows) is supplied to the process chamber 3. This one descends vertically in form of a substantially homogeneous process gas carpet from the process chamber ceiling 4a onto the process chamber bottom 4b lying below it and being formed by the build area 10 and its surrounding, which corresponds to the remaining region of the process chamber bottom 4b here. A beam path of a solidification device, which may comprise one or more, e.g. four, solidification units having respectively one laser, is schematically indicated by two sides of a triangle 32 passing the process chamber 3.

(69) FIG. 12b is a schematic top view on the build area 10 and on the ceiling inlets 45 in the manufacturing apparatus of FIG. 12a. In this example, the ceiling inlets 45 are substantially uniformly distributed over a total region of the process chamber ceiling 4a, with the exception of a region occupied by a coupling optics (for instance, coupling window, not shown) for the solidification radiation, for generating a substantially homogeneous ceiling gas stream 44.

(70) FIG. 13 is a schematic cross-sectional side view of a manufacturing apparatus according to the invention in which a central gas stream is combined with a ceiling gas stream in a closed process gas circuit. The manufacturing apparatus may, for instance, possess properties described with regard to FIGS. 1-12, the process chamber 3 may, in particular, be designed similarly to that of FIG. 12a/12b.

(71) Supply pipes 46a and discharge pipes 46b of the process gas circuit comprise a conveying unit 47, which, in this example, combines a turbine and additionally a filter in a recirculation-filter-device. The filter serves for removing impurities from the process gas discharged from the process chamber 3.

(72) In a regulated or unregulated splitting unit 48, a process gas supplied to the process chamber 3 via ceiling inlets 45 is split into a ceiling gas stream 44 according to the invention and a central gas stream 40 (for instance, according to the first aspect of the invention). This splitting is monitored and/or regulated depending on requirements of the concrete application by using metering points 51 arranged in various supply pipe branches. The metering points may, for instance, measure the respective process gas stream. The regulation may, for example, be carried out depending on the constructional design of the process chamber 3 and/or on a concrete fabrication process.

(73) FIG. 14 is a schematic cross-sectional side view of a manufacturing apparatus according to the invention in which a lateral gas stream is combined with a ceiling gas stream in a closed process gas circuit. The apparatus in FIG. 14 differs from the one of FIG. 13 only in that a lateral gas stream 49 is supplied to the process chamber 3 instead of the central gas stream 40.

(74) The lateral gas stream 49 flows substantially parallel and preferably in a laminar manner above the build area 10. It is supplied to the process chamber 3 via a side inlet of the supply pipe 46a arranged at one build area side and discharged from the process chamber via an outlet of the discharge pipe 46b arranged at an opposite build area side.

(75) FIG. 15 is a schematic perspective view of a perforated metal plate for generating a ceiling gas stream according to the invention in a process chamber, whose ceiling has a hollow space for this (not shown). In other words, the perforated metal plate 52 in FIG. 15 is an example for an inner wall region of such a hollow space according to the invention. In this example, the perforated metal plate 52 has a plurality of holes 53 representing ceiling inlets according to the invention.

(76) The perforated metal plate 52 further has a larger inner opening 54 in its central region which, in a built-in state of the perforated metal plate 52 in the process chamber ceiling 4a surrounds inter alia coupling windows 35a, 35b for coupling the solidification radiation into the process chamber 3. In the advantageous configuration as shown, the perforated metal plate 52 has a number of approximately 2000 holes 53 on the whole, which are distributed over the perforated metal plate 52 substantially —in particular, with the exception of the inner opening 54 as well as two approximately hexagonal areas 71 which serve as baffles for deflecting gas streams, which guide into the hollow space (not shown) of the process chamber ceiling 4a and thus provide for an equal or approximately equal velocity of the partial streams of the ceiling gas stream—uniformly since they are equally sized and arranged at regular distances from each other on average. In the course of this, here, the holes 53 have a diameter of approximately 2.5 mm. In the course of this, the ratio of an area perforated by holes 53 to a total process chamber ceiling area is approximately 3,8%.

(77) FIG. 16 shows the perforated metal plate 52 of FIG. 15 in a built-in state in the ceiling 4a of a process chamber 3 in a schematic perspective view inclined from below. In this example, four coupling windows 35a, 35b, 35c, and 35d of a four-scanner-machine, which may, in particular, be an apparatus as in FIG. 2, are arranged in the process chamber ceiling 4a within the inner opening 54. Centrally between the coupling windows 35a, 35b, 35c, and 35d, a nozzle 43 is arranged, through which the central gas stream 40 (not shown) according to the invention can stream into the process chamber 3.

(78) FIG. 17 shows a process chamber 3 having a perforated metal plate 52 as in FIGS. 15 and 16 built-in in its ceiling 4a, partly in a vertical cross-section, in a schematic perspective view inclined from above. In the course of this, in particular, it may be a process chamber 3 of the four-scanner-machine 1 shown in FIG. 2. A gas supply pipe or, respectively, supply pipe 46a ends in a central gas inlet, here in form of a nozzle 43, representing the gas supply device according to the first aspect of the invention. The process chamber ceiling 4a lies above a build area 10 and comprises a hollow space 73 having a wall. This hollow space wall comprises an outer wall region 74 turned away from the process chamber 3 and an inner wall region bordering the process chamber 3, which is formed by the perforated metal plate or, respectively, the perforated plate 52. In a vertical wall section of the process chamber wall, an outlet 42a or 42b starts directly above the process chamber bottom 4b or, respectively, a plane of the build area 10, the outlet having two opening slits extending horizontally. The outlet 42a or 42b extends at a distance from an edge of the build area 10 and parallel to a side of the build area 10 and extends in this exemplary embodiment in its length beyond the side length of the build area 10 being parallel thereto, so that a removal of impurities in regions above the process chamber bottom 4b which do not lie above the build area 10 is improved.

(79) FIGS. 15 to 17 show that a process chamber ceiling 4a does not necessarily need to be plane-shaped and/or lie parallel to the build area 10 across the whole of its area. Vertically above the build area 10, the process chamber ceiling 4a shown here is substantially plane and lies parallel thereto, it, however, has a section 72 rising up away from the process chamber bottom in a slant manner above a region of the build area edge.

(80) This section 72 does not impair the functioning of the ceiling gas stream according to the invention, but is rather designed as the whole inlet region of the process chamber ceiling 4a such that, during operation, a homogeneous ceiling gas stream pours out from the openings 53 into the process chamber 3 substantially vertically to the build area 10. This is made possible by a defined control of a process gas volume which is pumped into the hollow space 73 of the process chamber ceiling 4a from the in this example two supply pipes (not to see in FIG. 17, arranged above the hexagonal areas 71 in FIG. 16) relatively to a process gas volume exiting the hollow space 73 through the holes 53 of the perforated plate 52 towards the process chamber 3. By a suitable setting of parameters, such as e.g. a volume flow rate of the gas stream into the hollow space 73 and/or a ratio of the areas of the opening cross-sections at in- and outlets of the hollow space 73, an overpressure relatively to the ambient pressure in the process chamber 3 can be generated during operation, preferably, in the whole region of the hollow space 73, which overpressure provides for a to a large extent equal velocity of the partial streams of the gas stream which stream through the holes 53 into the process chamber 3. In other words, a gas volume introduced into the hollow space 73 does not stream further into the process chamber on the shortest route through holes 53 of the perforated plate 52 lying close to the supply pipes, but rather firstly continuously floods the hollow space 73, so that after a short starting period, substantially in the whole hollow space 73 or, respectively, substantially at all openings 53 of the inner wall region 52 towards the process chamber 3, a substantially equal pressure, i.e. an overpressure relatively to the process chamber pressure, prevails. Such an overpressure can effect a homogeneous ceiling gas stream through the openings 53 of the inner wall region or, respectively, perforated plate 52 of the process chamber ceiling 4a, e.g. in the present exemplary embodiment of a process chamber ceiling 4a having a big number of openings 53 of equal shape and equal opening area. In this case, the partial streams of the ceiling gas stream have substantially equal velocities and a substantially equal volume stream.

(81) An influencing factor with regard to a target homogenisation of the ceiling gas stream a hole size may be, i.e. an area and/or shape of an opening cross-section of the holes 53 in the inner wall region 52. At a constant volume flow rate of a process gas which is introduced into the hollow space 73, a characteristic of the ceiling gas stream can be purposefully changed by constructively simple means, e.g. by exchanging the inner wall region 52 of the process chamber ceiling 4a, for instance, by a perforated plate having an irregular arrangement of the holes. Partial streams of the ceiling gas stream exiting the above-described section 72 of the process chamber ceiling 4a which is slant to the build area 10, firstly traversing the holes 53 at a correspondingly acute angle to the build area 10, may be gradually guided, again, into an approximately vertical direction to the build area 10 as they pass to the build area 10, as caused by further effects, e.g. suction effects of other regions of the ceiling gas stream or a deflection by a bordering vertical region of the process chamber wall, whereby in a lower region, e.g. a lower half, of the process chamber 3, again, a ceiling gas stream is produced which is substantially vertically directed to the build area 10.

(82) Even though the present invention has been described on the basis of a laser sintering or laser melting apparatus, it is not limited to the laser sintering or laser melting. It may be applied to arbitrary methods for generatively manufacturing a three-dimensional object by a layer-by-layer application and selective solidification of a building material (preferably in powder form), independently of the manner in which the building material is being solidified. The selective solidification of the applied building material may be performed by an energy supply of any suitable kind. Alternatively or additionally, it may, for example, also be performed by 3D-printing, for instance by applying an adhesive.

(83) In the course of the selective solidification by an energy supply, energy may in general be supplied to the building material, for instance, by electromagnetic radiation or particle radiation. In the course of this, the radiation has such an effect on the building material in the respective region of a layer to be solidified that it changes its aggregation state, undergoes a phase transition or another structural change and, after a subsequent cooling down, is available in a solidified form. Preferably, the building material is a powder, wherein the radiation may, in particular, be a laser radiation. In this case, the radiation has such an effect on a region of the respective layer to be solidified that powder grains of the building material are partially or completely melted in this region by the energy supplied by the radiation and, after a cooling down, are interconnected forming a solid body.

(84) A solidification device for the selective solidification by energy supply may, for instance, comprise one or more gas or solid state lasers or any other type of lasers, such as e.g. laser diodes, in particular VCSEL (Vertical Cavity Surface Emitting Laser) or VECSEL (Vertical External Cavity Surface Emitting Laser) or a row of these lasers. Generally, any device using which energy can be selectively applied to a layer of the build material as radiation may be used for the selective solidification. Instead of a laser, for instance, another light source, an electron beam, or any other energy or, respectively, radiation source may be used which is suitable for solidifying the building material. Instead of deflecting a beam, also the selective solidification using a movable line irradiation device may be applied. The invention may also be applied to the selective mask sintering, where an extended light source and a mask are used, or to the High-Speed-Sintering (HSS), where a material is selectively applied onto the building material which material enhances (absorption sintering) or reduces (inhibition sintering) the absorption of radiation at the corresponding points and then an irradiation is performed non-selectively in a large-area manner or using a movable line irradiation device.

(85) In the context of the present invention, basically all kinds of building material suitable for the generative manufacturing may be used, in particular, plastics, metals, ceramics, respectively preferably in powder form, sand, filled or mixed powders.