HK1155696B - Frame for a device for producing a three-dimensional object, and device having such a frame for producing a three-dimensional object - Google Patents

Description

Frame for an apparatus for producing three-dimensional objects and apparatus for producing three-dimensional objects having such a frame

Technical Field

The present invention relates to a frame for an apparatus for manufacturing three-dimensional objects.

Background

WO00/21736A discloses a frame for an apparatus of the same type for manufacturing three-dimensional objects. The device manufactures three-dimensional objects by consolidating a powdered build material layer by layer at locations corresponding to the cross-section of the object to be manufactured in each layer by means of the action of a laser or another energy source. The frame and the plate define a manufacturing space in which a three-dimensional object is manufactured. The frame and the plate modules are interconnected to form a replaceable housing, which can be inserted into and removed from the device.

A similar device for producing three-dimensional objects is known from DE19939616a 1. In the device according to the prior art, the production space is generally heated to a temperature of 100 to 150 ℃ during the laser sintering process.

One problem in conventional devices for producing three-dimensional objects is that it has hitherto not been possible to heat the frame to a significantly higher temperature externally, since the surroundings of the frame are subjected to a strong thermal load.

Disclosure of Invention

The object of the invention is to provide a frame for an apparatus for producing three-dimensional objects, which allows the production space to be heated to a significantly higher temperature.

This object is achieved by a frame for an apparatus for producing a three-dimensional object according to the invention and by an apparatus according to the invention.

By using a glass-ceramic plate and by selectively controlling the required heating zones, process temperatures up to 370 ℃ are possible. If the plate is completely above at the beginning of the production process, only the upper region of the frame is heated, and the other heating zones below are switched on depending on the production process. This avoids excessive thermal stress, in particular of the lower lifting mechanism. The glass-ceramic plate does not dissipate heat strongly in the vertical direction. This is advantageous in particular at the start of production, since the lifting mechanism is not subjected to an excessively high thermal load.

The device for producing three-dimensional objects is particularly suitable for use as a high-temperature laser sintering machine, by means of which sintering powders having a high melting point, such as Polyetheretherketone (PEEK), can be processed.

Drawings

Further features and advantages of the invention emerge from the description of the embodiments with the aid of the figures. The figures show:

FIG. 1 is a schematic view of an apparatus for fabricating a three-dimensional object according to the present invention;

FIG. 2 is a schematic horizontal cross-sectional view of a portion of a frame for an apparatus for fabricating three-dimensional objects according to the present invention;

fig. 3 is a schematic vertical sectional view of a planar heating element with two heating zones for a frame according to the invention; and

fig. 4 is a schematic vertical sectional view of a planar heating element with three heating zones for a frame according to the invention.

Detailed Description

Fig. 1 shows a schematic illustration of a device according to the invention for producing a three-dimensional object 3, which is designed in an exemplary embodiment as a laser sintering device.

The laser sintering device has an upwardly open frame 1 and a plate 2 which is movable in the frame in the vertical direction and which carries a three-dimensional object 3 to be produced. The frame 1 and the plate 2 define a manufacturing space inside. The plate 2 is connected to a lifting mechanism 12 which moves it in a vertical direction so that the layer of the object 3 to be consolidated is in a working plane 4. The frame 1 and the plate 2 are modularly interconnected to form a replaceable frame. After the manufacture of the three-dimensional object 3 has been completed, the exchangeable chassis and the object 3 produced therein can be removed from the device and replaced by a new exchangeable chassis.

Furthermore, an applicator 5 is provided for applying a layer of the powdery construction material 3 a. All laser-sinterable powders, such as polyamides, polystyrene, metals, ceramics, composite materials and, in particular, high-temperature plastics such as PEEK, can be used as construction material 3 a. The frame 1 is first fed with construction material 3a from a magazine 6. The applicator 5 is then moved into the working plane 4 at a predetermined height so that the layer of powdered construction material 3a is located at a defined height above the last consolidated layer. The device also has a laser 7 which generates a laser beam 7a which is focused by means of a deflection device 8 onto a predetermined point in the working plane 4. Whereby the laser beam 7a can selectively consolidate the powdered build material 3a at locations corresponding to the cross-section of the object 3 to be manufactured in each layer.

A treatment chamber, in which the frame 1, the plate 2, the lifting mechanism 12 and the applicator 5 can be arranged, is designated by the reference numeral 10. Reference numeral 9 denotes an opening in the processing chamber 10 for introducing the laser beam 7 a. Furthermore, a control unit 11 is provided, via which the device is controlled in a coordinated manner for carrying out the production process.

During operation of the device, the plate 2 is moved in a first step by the lifting device 12 so far that a layer thickness is present above it below the work plane 4. A first layer of material 3a is then applied to the plate 2 and leveled by means of the magazine 6 and the applicator 5. The control unit 11 thus controls the deflection device 8 such that the deflected laser beam 7a hits the layer of material 3a selectively at the location to be consolidated. Whereby the material 3a is consolidated or sintered at these locations.

In the next step, the plate is lowered by the thickness of the next layer by the lifting mechanism 12. The second layer of material is applied, smoothed and selectively cured by means of a laser beam 7a by means of a magazine 6 and an applicator 5. These steps are carried out so often until the desired object 3 is made.

Fig. 2 shows a schematic horizontal cross-section of a part of a frame 1 of an apparatus for manufacturing a three-dimensional object according to the invention.

The frame 1 has a glass-ceramic plate 13 on its inner side facing the manufacturing space. For example, a glass ceramic plate 13 of the name Robax (registered trademark) of Schott corporation may be used. In the embodiment shown, the glass-ceramic plate 13 has a wall thickness of about 5 mm. The special properties of the glass-ceramic plate 13 are high heat resistance and a small coefficient of thermal expansion, whereby little distortion occurs along the plate at large temperature differences. The glass-ceramic plate 13 therefore does not show defects such as cracks (as in the case of ordinary glass) or warping (as in the case of metal). The glass-ceramic plate 13 also has a low thermal conductivity, so that no significant heat transfer takes place, in particular in the direction of the plate plane. The temperature gradient in the plane of the plate substantially persists. Furthermore, the glass ceramic plate 13 has a good flatness, so that, in particular in the case of a single piece of glass ceramic plate 13, a good seal is achieved between the frame 1 and the plate 2 or the sealing lip mounted thereon. Furthermore, the cleaning of the glass-ceramic plate 13 is simple and it does not form an expansion gap, which may be filled with powder.

The frame 1 also has a planar heating element 14 on the outside of the glass-ceramic plate 13 remote from the manufacturing space. For example, a flat heating element 14 of the company Freek under the name Mikanit (trademark) can be used. In the illustrated embodiment, the planar heating element 14 is formed by an artificial mica sheet, which is wound from flat heating wires into a resistance heater. The artificial mica sheet is typically connected on both sides with an insulating plate and a support plate. The direct mounting of the artificial mica plates on the electrically insulating glass-ceramic plate 13 allows to dispense with internal insulating plates and support plates. This enables a good thermal connection of the heating wire to the glass-ceramic plate 13.

Fig. 3 shows a schematic vertical sectional view of a planar heating element 14 with two heating zones 14a, 14b for a frame 1 according to the invention. In the embodiment shown, the planar heating element 14 defines two vertically superposed heating zones 14a, 14b, which are individually controllable. The control unit 11 controls only the heating zone or zones above the plate 2 according to the manufacturing process. Such a planar heating element 14 allows for a simple use, since only a compact planar heating element 14 has to be mounted on each side of the frame 1. Furthermore, these planar heating elements 14 allow a simple configuration with respect to the number and position of the heating zones 14a, 14b, which are separately controllable. The production process can thus subsequently enlarge the heating area downwards, so that only the currently required regions are heated, which are actually filled with powder. As a result, on the one hand, as little heat as possible is emitted to the outside, and on the other hand, the components of the three-dimensional object are prevented from being distorted.

Fig. 4 shows a schematic vertical sectional view of a planar heating element 14' of a further embodiment. The planar heating element 14 'is similar to the planar heating element 14, except that the planar heating element 14' has three heating zones 14a, 14b, 14 c. The control unit 11 controls only the heating zone or zones above the plate 2 in accordance with the manufacturing process, i.e. in temporal sequence 14a, 14b, 14 c.

Temperature detectors (not shown) are integrated in the planar heating elements 14, 14'. They are in planar contact with the respective glass-ceramic plate 13 approximately in the center of the respective heating zone 14a, 14b, 14 c. This enables a temperature measurement close to the process, wherein the temperature of the powder bed can be tapped very close to the process temperature.

Each planar heating element 14, 14' also has a laminar graphite sheet 15 on its outer side remote from the production space. These laminar graphite sheets 15 are not necessarily required but have the advantage of uniform heat distribution. They have the dimensions of the heating zones 14a, 14b, 14c of the respective planar heating elements 14, 14'. For example, a laminated graphite sheet 15 of SGL Carbon corporation under the name Sigraflex (registered trademark) may be used. The layered graphite sheets 15 have a strong anisotropic thermal conductivity characteristic, i.e., the thermal conductivity is significantly greater in the planar direction of the layered graphite sheets 15 than in the direction perpendicular to the planar direction.

The frame 1 also has a glass fibre mat 16 on the outside of the laminar graphite sheets 15 remote from the manufacturing space. For example, a glass fiber mat 16 of Promat corporation under the name Promaglaf HTI1200 (registered trademark) may be used. The function of each glass fibre mat 16 is to bias the glass-ceramic plate 13 and the other plate parts of the frame 1 over a large area towards a support element 18 described below.

The glass fiber mat 16 ensures good insulation both outwards and downwards. Another advantage of the glass fiber mat 16 is its elasticity during temperature cycling.

The frame 1 also has an outer plate 17, which is preferably made of glass ceramic, on the outer side of the glass fibre mats 16 facing away from the production space. The outer panel 17 assists the support element 18 described below in pressing the glass fibre mat 16 inwardly.

The frame 1 also has a plurality of supporting elements 18, preferably made of high-grade steel, which support the frame 1, in particular on the respective edges of the frame. In particular, the function of the support element 18 is to press the glass-ceramic plate 13 and the outer plate 17 against each other. Thereby compressing and biasing the glass fiber mat 16 in the middle. In addition, the support elements 18 are each arranged on an edge of the frame 1 and connect the walls of the frame 1 there. In the exemplary embodiment shown, the support elements 18 are made of high-grade steel, so that they have a lower thermal conductivity and a lower coefficient of thermal expansion than aluminum. In addition, high-quality steel has better corrosion resistance than aluminum.

The supporting element 18 has a polygonal bar 18a made of a quadrangular hollow profile which is as thin-walled as possible. The thermal conductivity is limited by the thin wall thickness, and the support member 18 also has a plurality of holding metal plates 18c that support the respective glass-ceramic plates 13 from the inside. The support element 18 also has outer pressure plates 18b which are screwed to the hollow profiles 18a and which, in cooperation with the clamping plates 18c, clamp the individual layer parts of the frame 1 against one another. The four walls of the frame 1 are connected together by such a structure. The support element 18 also has a plurality of spacers 18d, preferably made of a thermally insulating material, which fixedly predetermine the spacing between the glass-ceramic plate 13 and the outer plate 17. The support element 18 also has a plurality of sheet metal strips 18e which round the frame 1 on its respective inner edge. The metal strips 18e prevent powder from entering the joints between the different parts of the frame 1 and facilitate cleaning of the frame 1. The support elements 18 ensure a complete support of the frame 1, so that the brittle glass-ceramic plate 13 does not have to have a function for supporting the frame 1.

The frame 1 also has a housing 19 on the outer side of the outer panel 17 remote from the manufacturing space. The casing 19 constitutes the shell of the frame 1 and also ensures another insulation towards the outside.

The frame 1 thus constructed has the following features:

the frame 1 and the apparatus belonging to this class are suitable for the manufacture of three-dimensional objects 3 from a construction material 3a having a melting point higher than 150 ℃ and in particular higher than 180 ℃. Process temperatures of up to about 370 ℃ are possible by the materials used and by the selective control of the required heating zones 14a, 14b, 14 c. If the plate 2 is completely above at the beginning of the manufacture, only the upper region of the frame 1 is heated, which is actually filled with powder. The production process then switches on the other, lower heating zones. This avoids excessive thermal stress, in particular of the lifting mechanism 12. The material of the glass-ceramic plate 13 also dissipates heat hardly in the vertical direction. This is advantageous in particular at the start of production, since the lifting mechanism 12 is not subjected to an excessively high thermal load. The result is as little heat as possible being sent down and out.

In the illustrated embodiment, the frame is described as a multi-part laminated composite in which adjacent parts are in contact with each other. Such contact is not important for the invention, so that further layers may be provided between the described layer parts, without departing from the scope of protection defined in the claims. The term "outside the manufacturing space" used in particular in the claims does not necessarily mean a specific outer surface of the respective layer part. The term "outside the production space" rather describes the orientation of the layer structure from the production space to the outside.

The scope of protection is not limited to the embodiments shown, but it includes other variants and modifications as long as they fall within the scope defined by the following claims.

For example, the frame and the device for producing three-dimensional objects according to the invention are not limited to laser sintering devices. The frame is also suitable for use in a stereolithography apparatus in which a photocurable resin is used as a construction material instead of a powder, or for an electron beam sintering or melting apparatus in which an electron beam is used instead of a laser. Applications in three-dimensional printing or FDM (fused deposition modeling) are also contemplated.

Claims (11)

1. A replaceable frame for a device for producing three-dimensional objects (3), wherein the replaceable frame has a frame (1) and a vertically movable plate (2) in the frame (1), wherein the frame (1) and the plate (2) define a production space in the interior thereof, and the replaceable frame can be inserted into and removed from the device, wherein the device produces the three-dimensional object (3) in the production space by consolidating a powdery or liquid construction material (3 a) layer by layer at a location corresponding to the cross section of the object (3) to be produced in each layer; wherein the frame (1) has a glass-ceramic plate (13) on its inner side facing the manufacturing space;

the replaceable rack further comprises planar heating elements (14, 14 ') on the outer side of the glass ceramic plate (13) remote from the manufacturing space, wherein the planar heating elements (14, 14') define a plurality of vertically superposed heating zones (14 a, 14b, 14 c) which can be individually controlled.

2. A replaceable housing according to claim 1, characterised in that the planar heating element (14, 14') has a laminar graphite sheet (15) on its outer side remote from the manufacturing space.

3. A replaceable housing according to claim 1 or 2, further comprising a glass fibre mat (16) arranged on the outside of the planar heating element (14, 14') remote from the manufacturing space.

4. A replaceable housing according to claim 3, further comprising an outer panel (17) on the outside of the glass fibre mat (16) remote from the manufacturing space.

5. A replaceable housing according to claim 4, wherein the outer plates are made of glass ceramic.

6. A replaceable housing according to claim 1 or 2, further comprising a support element (18) supporting a component of the frame (1).

7. A replaceable housing according to claim 6, characterised in that the supporting elements are made of high-grade steel and support the frame (1) components on its edges.

8. Device for producing a three-dimensional object (3), comprising an interchangeable housing according to claim 1, wherein the device produces the three-dimensional object (3) by consolidating a powdery or liquid construction material (3 a) layer by layer in a production space, which is delimited by the frame (1) and the plate (2), at a position corresponding to the cross section of the object (3) to be produced in the layers.

9. The device according to claim 8, characterized in that the device has a consolidation means in the form of a laser (7) or another energy source.

10. The device according to claim 8 or 9, characterized in that the device is adapted to manufacture a three-dimensional object (3) from a construction material (3 a) having a melting point above 180 ℃.

11. The device according to claim 8 or 9, further comprising a control unit (11) which controls only the heating zone or zones above the plate (2) according to the manufacturing process.