DE102005014483B4 - Device for the production of articles by layering of powdered material - Google Patents

Abstract

Apparatus for the production of articles by layering of powdery, in particular metallic or / and ceramic material, with a carrier arrangement (14) for providing a construction field (B) for the layer structure, an irradiation device (18) for irradiating the last on the carrier arrangement ( 14) prepared material powder layer in a layer associated with this cross-sectional area of the object or possibly the objects in question with laser radiation, which brings the material powder in this cross-sectional area by heating for fusing or possibly for sintering, wherein the irradiation device (18) a controllable target device (22 ) for the laser radiation for the location-selective irradiation of the construction field (B), characterized in that the irradiation device (18) has a plurality of controllable subsystems each having at least one laser radiation source (20) and one target device (22) f for the laser radiation source (20), so that the device has a plurality of laser radiation sources (20), and wherein the respective subsystems of the irradiation device (18) are assigned to respective sections (I-IV) of the construction field (B) on the carrier arrangement (14), so that several subsystems for simultaneous irradiation of the material powder in the construction field sections (I-IV) can be used.

Description

The invention relates to a device for the production of objects by layering of powdered, in particular metallic and / or ceramic material, with a support assembly for providing a construction field for the layer structure, an irradiation device for irradiating the last on the support assembly prepared material powder layer within the building field in one of these layer associated cross-sectional area of the object in question or possibly the objects in question with laser radiation, which brings the material powder in this cross-sectional area by heating for fusion or possibly sintering, wherein the irradiation device has a controllable target device for the laser radiation for the location-selective irradiation of the construction field.

The prior art of such devices can eg DE 199 05 067 A1 , the DE 102 36 907 A1 , the DE 102 08 150 A1 , the DE 101 12 591 A1 or the DE 196 49 865 A1 to get expelled.

The publication DE 299 07 262 U1 discloses a device having the features of the preamble of claim 1, wherein the carrier assembly comprises a position grid by means of which a plurality of building platforms, each adapted to carry an object to be manufactured, can be positioned at predetermined positions on the carrier assembly.

The publication WO 2004/014 636 A1 discloses a device in which a plurality of objects in different process chambers can be produced by means of a single laser beam source. For this purpose, the laser beam of the laser beam source is supplied by means of switchable or controllable optical elements the various process chambers in order to use the cost-intensive laser beam source can more effectively.

By the terms selective laser melting, selective powder melting, selective laser sintering, and the like. Like., More recently powerful methods for the production of objects of more complicated geometry have become known, these often being combined under the term "rapid prototyping" or "rapid tooling" or "rapid manufacturing" methods essentially based on the following principle:

The article to be produced is built up in layers from a fine-grained, powdery raw material in accordance with CAD data or geometric description data derived therefrom by solidifying or fusing the raw material according to a cross-sectional pattern of the article associated with the respective layer by location-selective irradiation. The irradiation takes place by means of laser radiation, wherein the control of a beam deflection device deflecting the laser beam takes place by means of a control device on the basis of geometric description data of the object to be produced. The control information is usually derived and provided by a microcomputer according to a corresponding program from CAD data.

The laser beam records on the last-prepared raw material layer the cross-sectional pattern of the article associated with that layer to selectively fuse the raw material to the cross-sectional pattern. After such an irradiation step, the preparation of the next material powder layer then usually takes place on the layer which has been finally fused selectively by irradiation and partially. After the formation of a sufficiently smooth powder layer on its surface, an irradiation step is then carried out in the manner explained above. The article thus arises layer by layer, wherein the cross-sectional layers of the article produced in succession are fused together so that they adhere to one another.

The respective adjustment of the layer level relative to the radiation source or to the beam deflection device normally takes place by corresponding lowering of a platform, which forms a carrier on which the object is built up in layers.

In selective laser melting, the irradiation of the material powder used is usually carried out under a protective gas atmosphere, e.g. Argon atmosphere, especially to suppress oxidation effects.

Selective laser melting has hitherto been used predominantly for the production of filigree or intricately shaped small parts in single-part production. This is because the construction field on the carrier for the layer construction was limited to a relatively small construction field area, in particular because the beam deflection devices can selectively irradiate only a narrowly limited area with the required beam quality and, incidentally, the construction process often takes so long for larger parts, that other manufacturing processes are economically cheaper.

Furthermore, the production of larger objects by the method of selective laser melting would also require the handling of correspondingly large amounts of material powder, whereby the carrier platform would be charged with very heavy weight. The fine grading in the vertical movements of the support platform to set the correct working distance between the layer surface and the beam deflector becomes more difficult as the weight of the material powder on the support platform increases.

The invention has for its object to provide a device of the type mentioned above, which allows in comparison with the previous devices of this type, the production of larger items or possibly a larger number of items in a building process.

According to the invention, it is proposed that the irradiation device has a plurality of controllable subsystems, each with at least one laser radiation source and one target device for the laser radiation source, and that the respective subsystems of the irradiation device be assigned to respective sections of the construction field on the carrier device, so that several subsystems for simultaneous irradiation of the material powder in can be used the construction field sections.

The device thus detects a plurality of laser radiation sources whose beams can be steered in a controlled manner via the regions of the construction field assigned to them in order to remelt the layer-wise-prepared powder in a location-selective manner at the predetermined locations. The inventive device offers a variety of uses. Thus, e.g. all subsystems are used simultaneously to make a large object by layer-by-layer remelting of powder, each subsystem being used in the construction field section assigned to it. Preferably, the laser beams can be deflected beyond the edge regions of the construction field sections assigned to them by a small amount into adjacent construction field sections in order to ensure homogeneous fusion even at the construction field section boundaries. Another possible use of the device is the production of a large number of smaller parts by the simultaneous use of several subsystems for remelting or sintering of the powder. The control of the components of the device, in particular the irradiation subsystems is controlled by control computers in accordance with the geometric data of the objects to be produced and on the basis of a relevant control program.

The target devices for the radiation sources are preferably scanner devices. Conceivable within the scope of the invention, however, are also controllable micromirror arrays or the like for controlling the laser beam.

In a preferred embodiment of the invention in which the exploitable construction field has an area of about 0.25 m ² , four irradiation subsystems are used, each of which can be assigned to a respective quadrant of the construction field.

Also not excluded is a possible use, according to which at least two subsystems in a construction field section are used together, so that their Strahlauftreffpunkte overlap to achieve a greater energy density at least partially, or are closely spaced over the predetermined locations of the construction field led to a common wider Melting trace to produce.

Since a correspondingly larger amount of material powder accumulates on the carrier platform during the construction process of a larger object, it is important to provide for the vertical movement of the carrier platform a precisely adjustable, yet very strong lifting drive. According to a preferred embodiment of the invention, the carrier platform for the layer structure has a hydraulic lifting drive, which is preferably a hydraulic piston-cylinder unit, which is designed for correspondingly large lifting forces and precisely adjustable in different stroke positions.

The device according to the invention comprises a housing, which limits a process space for the layered production of one or more articles, and a device for producing and maintaining a protective gas atmosphere, in particular argon protective gas atmosphere in the process space. Preferably, the material powder can be introduced while maintaining the protective gas atmosphere as needed in the process space and be discharged from the process space. For powder handling, for example, mobile external powder storage silos of various sizes can be kept ready, which are completely closed and purged with inert gas, so that the powder stored therein is not exposed to air or atmospheric oxygen. During the building process, the material powder can be conducted from a storage silo into the process space by means of a vacuum feed pump, which can be arranged directly above the process space, and distributed there with a layer preparation device above the construction field. The powder can be pre-screened during transport into the process space to filter out particles of larger grain size or contiguous clusters of powder particles. The powder handling system can be completely closed and operated in the absence of oxygen. After completion of the building process, the powder can be sucked back from the process room into a powder reservoir. A Reuse of the powder, possibly after passing through a cleaning process or screening process included in the cycle, is basically possible.

Preferably, at least one lock chamber is provided on the process space, which is flushable by means of protective gas and, if necessary, to open or close to the process room or outwards. Such a lock allows e.g. the removal of small or medium-sized objects from the process space without abandoning the protective gas atmosphere in the process space.

As is known per se, a device for preparing a respective material powder layer on the last irradiated material powder layer may be provided which has a distance of the desired powder layer thickness over the last irradiated layer away movable smoothing slide for leveling a respective amount of powder material over the last irradiated layer. The smoothing slider may be adapted to carry a supply of material powders and to deliver thereon material powder for layer preparation.

In particular, when using the device according to the invention for the production of large objects, it is expedient that the process chamber can be opened at its top, so that a crane load can lift the heavy objects from the process room. According to another variant, the process space may be provided with a side door which allows lateral access by means of a forklift or the like to the process space in order to transport a heavy object out of the process space.

• 1 zeigt eine grob schematische Darstellung einer Vorrichtung der eingangs genannten Art und dient zur Erläuterung des Verfahrens des selektiven Laserschmelzens.
• 2 zeigt ein Ausführungsbeispiel einer Vorrichtung nach der Erfindung in einer perspektivischen Darstellung.
• 3 zeigt eine Draufsicht auf die Vorrichtung gemäß 2.
• 4 ist eine schematische Darstellung des Baufeldes auf einer Trägerplattform der Vorrichtung aus den 2 und 3.
• 5 zeigt in einer teils gebrochenen Darstellung einen Teil der Vorrichtung aus den 2 und 3 in einer perspektivischen Darstellung, wobei der untere Bereiche des geöffneten Prozessraums erkennbar ist.
• 6 zeigt für eine Vorrichtung nach der Erfindung ein Schutzgas- und Pulverkreisla ufsystem.

An embodiment of the invention will be explained below with reference to the figures.

• 1 shows a rough schematic representation of a device of the type mentioned above and serves to explain the method of selective laser melting.
• 2 shows an embodiment of a device according to the invention in a perspective view.
• 3 shows a plan view of the device according to 2 ,
• 4 is a schematic representation of the construction field on a support platform of the device of the 2 and 3 ,
• 5 shows in a partially broken representation of a part of the device from the 2 and 3 in a perspective view, wherein the lower portions of the opened process space is recognizable.
• 6 shows for a device according to the invention, a protective gas and Pulverkreisla ufsystem.

The explanatory sketch according to 1 shows a snapshot in the manufacture of an object 2 by building up in layers from a powder 4 , For example, steel powder with a grain size of, for example 10 microns - 60 microns. The construction of the object 2 takes place in a process room 6 which of the process space housing 8th is limited. In the process room 6 prevails inert gas atmosphere, preferably argon atmosphere, wherein the arrow 10 in 1 the protective gas supply - and the arrow 12 the protective gas discharge implies. The layered building of the object 2 takes place on a carrier platform 14 which is vertically movable by means of a vertical drive unit and can be positioned in different vertical settings. A smoothing slider 16 serves for the preparation and leveling of a new powder layer on the respectively last irradiated powder layer, wherein the smoothing slide 16 at a vertical distance corresponding to the desired powder layer thickness to the last irradiated layer horizontally across the support platform 14 is moved away. After the preparation of such a powder layer then comes the irradiation device 18 from laser 20 and beam deflection unit 22 used to remelt the powder at the predetermined locations corresponding to the powder layer associated with the cross-section of the article to be manufactured by irradiation. In the example, the laser beam 24 through an f-theta lens 26 into the process space 6 introduced, the lens 26 also as a window of the housing 8th serves.

After completion of the current irradiation process, the carrier platform 14 lowered by the measure of the desired powder layer thickness, whereupon then the smoothing slide 16 a new amount of powder over the build platform 14 distributed to produce the next layer to be irradiated. The above-described processes of irradiation and layer preparation are alternately continued until the article 2 is completed.

1 shows a conventional variant of a generic device with only a system of laser 20 and beam deflection unit 22 , With such a single system, normally only a relatively small construction field B can be placed on the carrier platform 14 to make an object. Here, the invention provides a remedy.

2 shows a device according to the invention with a process space housing 8th one Carrier platform cased 28 , a hydraulic lifting device 30 for the carrier platform and an irradiation device 18 with several subsystems of laser radiation sources 20 and scanner facilities 22 , The irradiation device 18 is located on the upper wall 30 of the process chamber housing 8th , How out 3 can be better seen, includes the irradiation device 18 four subsystems each with a laser radiation source 20 and a scanner device 22 , The laser radiation sources are in the 2 and 3 through coupling interfaces 20 for externally supplied optical fiber fiber laser represents. For example, fiber lasers with an output power of 100 watts each can be used. The irradiation device 18 is built on a common optical bench and can be moved in total by means of a high-precision linear unit within the machine to create the necessary space for the removal of a component from the process room.

In 3 For example, four f-theta lenses 26 are window and focus units in the top wall 30 of the process chamber housing 8th intended. Each f-theta lens 26 is a respective laser irradiation source irradiation subsystem 20 and target device 22 assigned. Preferably, the lenses 26 changeable on the wall 30 assembled.

4 shows a sketch of a possible construction site division on the support platform 14 , The construction field B is in four quadrants I - IV divided, each with an irradiation subsystem with laser radiation source 20 and target device 22 ( 3 ) can be assigned to a quadrant of the construction field to the last in this quadrant on the build platform 14 to irradiate the prepared powder layer. By simultaneous use of all four irradiation subsystems can thus be a across all four construction field sections I - IV extending object are produced. In order to be able to generate continuous transitions during irradiation at the construction field section boundaries, the area of the construction field which can be reached by the individual irradiation subsystems is in each case slightly larger than the respective quadrant I - IV according to 4 ,

5 shows the top of the carrier platform 14 , with the carrier platform in its shaft 29 is raised relatively far, so that the preparation of a first powder layer can be started. For this purpose, in the example, a combined powder dispenser / smoothing slide 16 over the carrier platform 14 moved away, with the smoothing slider 16 while it gives off powder on its underside, which it on the carrier platform 14 smooth strokes. Thereafter, the irradiation device can then be used to fuse powder of this last-prepared layer.

Also in the device according to the invention, the layer preparation and the layer irradiation are preferably carried out in alternating steps.

Lowering and positioning of the carrier platform 14 takes place by means of the hydraulic lifting device 30 , whose positioning accuracy is in the example case at +/- 2 microns. In the construction platform 14 For example, a heating system can be integrated, which serves to preheat the powder.

Not shown is a powder feed system comprising a storage silo, which may contain, for example, 1000 kg of steel powder and, for example, is adjacent to the machine housing of the device. A vacuum conveying system serves to transfer the powder from the storage silo into the coating unit 16 to promote in the process room. The storage silo is installed in a trolley and also serves as a general powder transport container.

6 shows for a particular variant of the invention, a protective gas system with integrated powder extraction. In the process room 6 protrudes a suction hose 50 into it, at a pump 52 connected. Between the pump 52 and the process room 6 are in the suction line 50 a powder trap 54 and a powder filter 56 intended. At the pressure side of the pump 52 is a protective gas hose 58 for the inert gas supply to the process room 6 connected. at 60 is the protective gas supply hose 58 at the process room 6 connected. During the normal construction process, the recirculation cycle is used 50 . 52 . 54 . 56 . 58 for flushing the process room 6 with the protective gas (preferably argon). at 62 a valve for venting the protective gas circulation is indicated. at 64 a source of inert gas is shown passing through the valve 66 to the inert gas line 58 connected.

The branch 68 on the line 58 with the valves 70 . 72 serves to rinse a lock 74 with inert gas. The lock 74 can be used for introducing and dispensing objects in the process chamber housing 6 or from the housing 6 while maintaining the inert gas atmosphere in the process room 6 be used.

The opening 76 in the front door of the process chamber housing 8th FIG. 12 illustrates a glove opening that is normally sealed by a glove that can be used by an operator to access the process space 6 and possibly from the process room 6 on the lock 74 access.

The suction hose 50 can also be used, for example, after completion of the construction process, the excess powder from the process room 6 suck. The powder is then attached to the powder trap 54 separated and via a filter and sieve device 55 a collection container 57 fed. This also takes place under a protective gas atmosphere. The powder recovery can thus be carried out with substantial exclusion of oxygen.

With 80 is in 6 a powder reservoir, which powder for the ongoing construction process in the process room 6 can provide.

The construction field B according to 4 can have a size of 500 mm x 500 mm. Also, the stroke range of the carrier platform 14 eg 500 mm. This results in a construction space volume, which allows the production of comparatively large items.

On the other hand, it is also possible to produce a multiplicity of smaller objects simultaneously with the device according to the invention, so that in this respect one can speak of a high-throughput SLM device, where SLM stands for Selective Laser Melting.

In 2 is the control computer system 82 the device according to the invention recognizable. The control computer system 82 serves to control the hydraulic control system of the hydraulic cylinder 30 , for controlling the irradiation device 18 , for controlling coating devices and possibly further components of the device.

Claims (12)

Apparatus for the production of articles by layering of powdery, in particular metallic or / and ceramic material, with a carrier arrangement (14) for providing a construction field (B) for the layer structure, an irradiation device (18) for irradiating the last on the carrier arrangement ( 14) prepared material powder layer in a layer associated with this cross-sectional area of the object or possibly the objects in question with laser radiation, which brings the material powder in this cross-sectional area by heating for fusing or possibly for sintering, wherein the irradiation device (18) a controllable target device (22 ) for the laser radiation for the location-selective irradiation of the construction field (B), characterized in that the irradiation device (18) comprises a plurality of controllable subsystems each having at least one laser radiation source (20) and one target device (22) for the laser radiation source (20), so that the device has a plurality of laser radiation sources (20), and wherein the respective subsystems of the irradiation device (18) are assigned to respective sections (I-IV) of the construction field (B) on the carrier arrangement (14), so that several subsystems for simultaneous irradiation of the material powder in the construction field sections (I-IV) can be used. Apparatus for producing objects according to Claim 1 , characterized in that each target device (22) comprises a scanner device for the controlled deflection of the laser beam supplied to it. Apparatus for producing objects according to Claim 1 or 2 , characterized in that four irradiation subsystems are provided, each of which is assigned to a respective quadrant (I-IV) of the construction field (B). Device according to one of the preceding claims, characterized in that the exploitable construction field (B) has an area of at least 0.09 square meters, preferably of at least 0.20 square meters. Device for producing objects according to one of the preceding claims, characterized in that the carrier arrangement has a vertically movable carrier platform (14) and a hydraulic actuator (30) for the lifting positioning of the carrier platform (14). Device for producing articles according to one of the preceding claims, characterized by a housing (8) which delimits a process space (6) for the layer-by-layer production of one or more articles, and a device (52, 54, 56, 58, 60) for Production and maintenance of a protective gas atmosphere, in particular argon protective gas atmosphere in the process space (6). Apparatus for producing objects according to Claim 6 , characterized in that material powder while maintaining the inert gas atmosphere, if necessary, in the process chamber (6) can be introduced. Apparatus for producing objects according to Claim 6 or 7 , characterized in that at the process space (6) at least one lock chamber (74) is provided which is flushable by means of shielding gas and, if necessary, to the process chamber (6) towards or to open and close. Device for producing objects according to one of Claims 6 to 8th , characterized in that it comprises a device (16) for preparing a respective material powder layer on the last irradiated material powder layer, said layer preparation device has a distance of the desired powder layer thickness over the last irradiated layer away movable smoothing slider for leveling a respective amount of material powder over the last irradiated layer. Apparatus for producing objects according to Claim 9 , characterized in that the smoothing slide (16) is adapted to carry a supply of material powder and deliver thereon material powder for layer preparation. Device for producing objects according to one of Claims 6 to 10 , characterized in that the smoothing slide (16) is formed in its lower edge region of Teflon or / and silicone. Device for producing objects according to one of Claims 6 to 11 , characterized in that a heating device is provided for heating the material powder in the process space.

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