WO2020074568A1

WO2020074568A1 - Heating device with an infrared panel radiator

Info

Publication number: WO2020074568A1
Application number: PCT/EP2019/077326
Authority: WO
Inventors: Oliver Weiss; Holger Zissing; Lotta Gaab
Original assignee: Heraeus Noblelight Gmbh
Priority date: 2018-10-12
Filing date: 2019-10-09
Publication date: 2020-04-16
Also published as: DE102018125304A1

Abstract

The invention relates to a heating device with at least one infrared panel radiator for heating a powder for the production of a 3D moulded part in a construction space, comprising a construction platform for receiving the moulded part, a height-adjustable carrier plate and the infrared panel radiator arranged between the construction platform and the carrier plate. In order to provide a corresponding heating device with an infrared panel radiator for the production of a 3D moulded part in a construction space, which guarantees an optimised heat transfer to the sintering or melting powder with a homogeneous temperature distribution and which enables a simple retrofitting in an existing construction space as a high-temperature heating device, according to the invention, the infrared panel radiator has a conductor path which is formed by a resistive material that is electrically conductive and generates heat when current flows through, and which is covered by an electrically insulating cover layer, on a plate-type substrate element made of an electrically insulating material, and the infrared panel radiator is arranged on the carrier plate with its plate-type substrate element facing the construction platform. The invention also relates to a method for producing a 3D moulded part using the above-mentioned heating device.

Description

Heating device with an infrared area heater

description

TECHNICAL FIELD The present invention relates to a heating device with at least one infrared surface heater for heating a powder for producing a 3D molded part in a construction space, which has a construction platform for receiving the molded part, a height-adjustable support plate and the infrared surface heater arranged between Construction platform and carrier plate. The invention further relates to a method for producing a 3D molded part using the heating device.

Three-dimensional (3D) molded parts are usually produced using the layered structure technique and solidifying a loose powder by means of so-called selective laser beam sintering or laser melting. The term SLS is also used for selective laser sintering, for plastic powders, or SLM for selective laser melting, for metal powders. When heating the powder, be it a plastic powder or a metal powder, a homogeneous temperature distribution is required to avoid thermal stresses (cracks, warping) in the finished molded part. State of the art

The production of a 3D molded part from a plastic sinter powder is known from DE 10 2015 006 533 A1. To melt the plastic sinter powder, an infrared surface heater in the form of a silicone-based, flat heating foil with electrical resistance heating is used. A thermal insulation layer is provided at the bottom, opposite a height-adjustable support plate, and possibly on the side of the building platform. However, the silicone-based heating foil barely reaches temperatures higher than 200 ° C. These Heating power is sufficient for heating plastic sinter powders in the manufacture of 3D molded parts, but not in the manufacture of metallic 3D molded parts, which require significantly higher process temperatures overall. Instead of the silicone-based heating foil, DE 10 2015 006 533 A1 alternatively proposes to temper the building platform or the sintered powder on it by means of a heating coil through which heating oil flows and which are arranged below the mounting plate and on the side of the building platform. The temperature that can be achieved with the heating coils is not significantly higher than 200 ° C and the heat transfer to the sinter powder is inefficient (slow) due to this construction. A reservoir and, if necessary, a pump must also be provided for the tempering oil in order to convey the tempering oil through the heating coil. Overall, these additional devices result in a complex heating device, without an increase in efficiency in terms of rapid heat transfer or an extended temperature range being achievable.

DE 10 2015 211 538 A1 discloses a construction cylinder arrangement for a machine for the layer-by-layer production of three-dimensional objects by laser sintering or laser melting of powdery material. The powdery material is melted or sintered with a processing laser beam. In addition, a heating device in the form of a surface heater with infrared heating coils is provided. The arrangement is selected so that the main part of the heating power of the heating device heats the substrate.

DE 10 2012 012 344 B3 discloses a method and a device for the production of workpieces by beam melting of powdery material. In order to reduce the process-related temperature gradients, the powdery building material is preheated instead of with a platform heater by heating elements which are arranged on or in the side walls of the storage chamber and / or the process chamber.

Technical task The object of the invention is to provide a method and a heating device for heating a powder for the production of a 3D molded part in an installation space, which ensure an optimized heat transfer to the sintered or melt powder with a homogeneous temperature distribution. The heating device should also function as a high-temperature heating device and enable simple retrofitting in an existing installation space

Brief description of the invention

This object is achieved by the subject matter of the independent claims.

According to an embodiment of a heating device with an infrared surface heater, the infrared surface heater comprises a conductor track covered with an electrically insulating cover layer and made of an electrically conductive resistance material on a plate-shaped substrate body made of an electrically insulating material and generating heat when current flows through. The infrared panel heater can be arranged on the carrier plate with its plate-shaped substrate body facing the building platform.

The heating device comprises at least one infrared area radiator for heating a powder for producing a 3D molded part in an installation space. The construction space is limited at the bottom by a construction platform for receiving the molded part or for receiving the powder to be sintered or melted.

In particular, the surface radiator can be designed as a floor surface radiator. An infrared surface radiator can be referred to as a bottom surface radiator, the main (surface) extension of which extends in two mutually perpendicular horizontal directions. The infrared area heater lies, for example, on the carrier plate and is arranged below the construction platform. For example, the infrared surface radiator can be installed with its substrate body facing the building platform. The substrate body in the form of a plate has a smooth surface, so that there is direct contact with the surface of the building Platform. This ensures good heat transfer to the construction platform.

The heating device can preferably be provided for heating a powder for producing an at least partially metallic 3D molded part. Alternatively or additionally, the heating device can be provided for heating a powder with a melting point greater than 200 ° C. or greater than 500 ° C. for the production of a 3D molded part. The heating device can preferably set ambient temperatures, in particular in the powder bed, preferably on the surface of the powder bed that is to be processed with the laser, of at least 300 ° C., at least 500 ° C. or more. In particular, the powder is a metal powder.

A metal powder comprises metallic components. The metal powder can consist of metallic components. The metal powder preferably comprises at least 50%, at least 75%, at least 90% or at least 95% of metallic constituents. Of particular interest are metal powders made of high-strength steels with a high carbon content and aluminum alloys of classes 5xxx, 6xxx and 7xxx according to the designation system according to EN 573-3 / 4, as well as titanium alloys.

The construction platform can be mounted on a mounting plate, in particular screwed on. In this case, the infrared surface radiator can be attached below the mounting plate and / or can be laterally surrounded by the mounting plate, preferably in such a way that there is direct contact with the surface of the substrate body of the infrared surface radiator. In this way, the IR surface heater heats the construction platform directly or indirectly via the mounting plate by means of heat conduction. Alternatively or additionally, an infrared surface heater can be arranged inside the mounting plate or embedded in it from above in order to ensure optimal heat transfer to the building platform. The mounting plate and / or the IR surface radiator are in turn located on a height-displaceable carrier plate which is lowered and / or raised in the course of the molded part's manufacturing process. According to one embodiment, the surface radiator can be arranged in an annular or tubular mounting plate. In particular, the surface radiator can be fully encapsulated in the mounting plate. A floor plate surface spotlight can be in direct contact with the mounting plate. It is conceivable that the surface radiator is formed in functional union as a mounting plate. According to one embodiment, the floor surface heater comprises several, for example 2, 4, 16 or more floor surface heater segments. Web, bridge and / or pillar-like sections of the mounting plate can be arranged between the bottom surface heater segments. In particular, the surface radiator can be spring-loaded or flexible in the vertical direction. In this way, damage when assembling the construction platform can be avoided.

The IR surface heater has a resistive conductor track, which is covered in particular with an electrically insulating cover layer and generates heat when current flows through it. The conductor track can be designed as a burned-in thick film layer. Thick film layers of this type are produced, for example, from resistance paste by means of screen printing or from metal-containing ink by means of inkjet printing and then baked at high temperature.

IR emitters are optionally equipped with an electrical resistance element made of a resistance material that generates heat when current flows through it. The electrical resistance element itself can form the actual heating element of the IR radiator. The resistance element, such as a wire, a conductor track or a layer of the resistance material, also heats the substrate by heat conduction, convection and / or heat radiation, so that this too - depending on the radiation characteristics of the specific substrate material - is the essential heating element of the IR radiator can form.

IR emitters show, in particular, a point-like or line-shaped radiation characteristic for the IR radiation, or - as an infrared area radiator - a two-dimensional or three-dimensional radiation characteristic that extends over the area, based on the geometry Adapted to the surface of the heating material to be heated, homogeneous radiation of two- or three-dimensional surfaces is possible.

The conductor track is applied to a preferably plate-shaped substrate body made of an electrically insulating material. The substrate body is preferably resistant to high temperatures. Preferred materials include glass and / or ceramic.

The conductor track can be at least partially separated from the surroundings by an electrical insulator. The conductor track can be covered by an electrically insulating cover layer. An insulator, in particular as an insulating cover layer for the conductor track, can comprise a porous, quartz glass. The insulator, in particular the quartz glass, can be arranged as a thermal and / or optical insulator on, in particular directly on, the surface radiator. The isolator can be opaque white.

The insulator, in particular the electrically insulating cover layer, advantageously has a thickness in the range from 5 pm to 20 pm or to 30 pm. The cover layer is also referred to as overglazing and is preferably made of

Executed quartz glass.

A thermally insulating cover layer can be applied to the insulator, in particular the electrically insulating cover layer, which has an insulating effect with respect to the carrier plate. The thermally insulating layer preferably has a thickness of 0.5 to 4.0 mm, particularly preferably 0.8 to 1.5 mm.

When producing a 3D molded part using the SLM process, a laser scans over the powder applied to the build platform and melts it locally in layers. Particularly with metallic materials with high melting points, high temperature gradients between the melting areas and the surrounding powder can result. Stress irregular cracks can often occur during the uneven heating and cooling of the workpiece. Many also have to After the assembly process, molded parts are temperature-treated in a further process step to ensure that the material is free of stress. In order to avoid stress cracks and additional process steps, mounting plates are used in known SLM systems, which are heated to about 200 ° C electrically by means of heating cartridges. The effective preheating or ambient temperature of the molded part is then reduced by heat conduction through the building platform and the already solidified part of the molded part and the powder bed itself. It is significantly lower than the nominal temperature of the building platform heating and increases with the progress of the construction and associated lowering of the construction platform towards the powder surface. For these reasons, some metal alloys cannot yet be processed using the SLM process.

The heating of the powder before the laser treatment for local melting or before the application of a new powder layer, temperature differences between the molded part, which has already solidified, and a new layer of powder are leveled or avoided entirely, so that no undesirable thermal effects such as that Bimetal effect occur.

The heating device thus enables a homogeneous heating of the resulting 3D molded part, so that subsequent, complex annealing of the molded part to reduce mechanical stresses can be dispensed with.

Another advantage of the heating device is that the infrared surface heater can be easily replaced in the event of a repair and that an existing installation space can also be retrofitted with the heating device.

It has proven to be advantageous if the substrate material contains or consists of quartz glass. Quartz glass is electrically insulating even at relatively high temperatures, has good resistance to corrosion, temperature and temperature changes and is available in high purity. For this reason, it is also suitable for high-temperature heating processes with high demands on purity and inertness as a substrate material for an IR surface heater. Special Another preferred substrate material is opaque quartz glass, which in particular has a porosity of less than 0.5%. The porosity is a dimensionless quantity and is measured using a porosimeter. A high density is achieved due to the low proportion of pores.

With regard to good emissivity, it is particularly preferred if the quartz glass contains an additional component, preferably elemental silicon, which absorbs in the spectral range of the infrared radiation. The preferably used elementary silicon as an additional component forms its own Si phase dispersed in the quartz glass matrix and causes the glassy matrix material to turn black, specifically at room temperature, but also at an elevated temperature above, for example, 600 ° C. This achieves a good radiation characteristic in the sense of a broadband, high emission at high temperatures for wavelengths between 2 and 8 pm. It is thus possible to provide a higher radiation output per unit area than with a substrate material made of pure quartz glass. In addition, a homogeneous radiation and a uniform temperature field can be generated even with thin substrate wall thicknesses and / or with a comparatively low conductor occupancy density.

In order to minimize heat losses and to avoid overheating of the support plate or the stamp underneath, it has proven useful to provide a thermal insulation layer between the support plate and the infrared surface radiator. Alternatively or in addition, a liquid-cooled plate can be used.

It is also advantageous if the heating device comprises a further infrared surface radiator, which in particular has a conductor track covered with an electrically insulating cover layer and made of an electrically conductive resistance material that generates heat when current flows, preferably on an electrically insulating substrate material.

The installation space can be delimited by at least one side wall, at least two side walls, at least three side walls or more side walls, Of which or of which at least a part is formed by at least one further infrared surface radiator, which can be referred to as a side surface radiator, the substrate element of the surface radiator itself forming the side wall of the installation space - or a part thereof - and this or is turned away. An infrared surface radiator can be referred to as a side surface radiator, the flutter extension of which extends in the surface in a horizontal direction and a vertical direction perpendicular thereto.

In this embodiment, which is also referred to as jacket heating, the number of components that limit the installation space is minimized. In particular, at least one side wall, or parts thereof, is formed by at least one side surface radiator. In this way, the installation space is also heated from the side. Another infrared area heater forms at least part of one or more side walls. The lateral heating of the powder and the at least partially solidified molded part when the support platform is passed under the animal helps to optimize the temperature distribution when the molded part is placed under the oil, so that the temperature gradient between the building platform and the powder surface is minimized.

In the case of a circular cylindrical side wall, the infrared surface radiator can also have a circular cylindrical shape, so that even with this geometry there is no loss of space due to the surface radiator. A circular-cylindrical side wall can comprise a plurality of infrared surface emitters in the form of a cylinder barrel.

In order to minimize heat dissipation to the outside, the side wall on its side facing away from the molded part can be completely or partially covered by a thermal insulation layer. In the event that the side wall is formed by an infrared surface radiator, this is covered on the outside by the thermal insulation layer. As an alternative or in addition, an at least partially liquid-cooled jacket can be used.

The infrared area heater can be electrically controlled in zones. It has proven to be particularly advantageous if the conductor track of the infrared Flat radiator comprises a printed heating meander, which can be electrically controlled in particular zones. With this embodiment, the temperature profile of the installation space and in particular the construction platform can be set in a targeted manner. Furthermore, the zones of the jacket heating can be switched on step by step, for example if the building platform lowers in the course of the molding process. The different activation of the zones of the jacket heating means that a temperature gradient in the vertical direction upward in the direction of the powder surface, as would occur with a pure construction platform heating, can be minimized. This makes it possible to work with heating of the resulting 3D molded part, which optimizes the manufacturing process of the 3D molded part. A subsequent, expensive annealing of the molded part to reduce mechanical stresses can be omitted.

With regard to the method for producing an at least partially metallic 3D molded part, the powder being melted and / or sintered by means of a laser, the aforementioned object is achieved in that the powder and / or the 3D molded part is provided with at least one infrared Surface heater is heated.

The powder and / or the 3D molded part are heated continuously or at least temporarily, for example intermittently, by the infrared area heater. In particular, the at least one infrared area heater heats the powder and / or the 3D molded part at least before or while the powder is melted and / or sintered by the laser.

The laser treatment causes a local melting or sintering of the powder and the application of a new layer from the powder on the 3D molded part that has already been partially manufactured. By heating the powder before or during the laser treatment using an infrared radiator, temperature differences between the molded part that has already solidified in parts and the new layer of powder are leveled or avoided entirely, so that no undesirable thermal effects such as the bimetal effect occur.

In one embodiment, the at least one infrared area heater heats the Powder and / or the 3D molded part continuously while the powder is melted and / or sintered by the laser.

In addition, it is provided in another procedure that the at least one infrared area heater also heats the powder and the 3D molded part after the powder has been melted and / or sintered by the laser, in particular after completion of the production of the 3D molded part.

It is advantageous to continue controlled heating after the sintering is completed in order to be able to control a temperature ramp. Additional thermal energy is introduced into the powder and / or the 3D molded part by the laser, the heating of the powder and / or 3D molded part preferably taking place below the melting temperature by means of the at least one infrared surface radiator, whereas the additional is carried out by the laser The thermal energy provided raises the temperature of the powder and / or 3D molded part locally, particularly in a punctiform manner, to a temperature above the melting temperature. In the sense of the application, “heating” is to be understood to mean that the temperature is raised to a temperature below the melting temperature. In the sense of the application, “melting” or “sintering” is to be understood to mean that an at least local temperature increase to a temperature corresponding to or above the melting temperature takes place. In the various embodiments of the heating device, it may be useful to arrange several smaller area radiators under the construction platform. Corresponding webs should be arranged between the emitters to absorb the forces acting on the construction platform and to transmit them to the carrier plate. The powder and / or the 3D molded part is advantageously heated to a temperature of at least 250 ° C. or at least 500 ° C.

In any case, it has proven useful to heat the powder and / or the 3D molded part to a temperature below the melting temperature of the powder. Depending on the specific melting temperature of the preferably metallic powder, it is heated to a temperature of not more than 500 ° C., not more than 200 ° C., not more than 100 ° C. or not more than 50 ° C. below the melting temperature of the powder. The optimized setting of the temperature of the powder and / or the 3D molded part during the sintering process by means of the laser avoids stress cracks and other errors during melting due to excessive temperature differences.

The heat on the powder and / or the 3D molded part during sintering is preferably carried out vertically from below and / or horizontally from at least one side.

According to one embodiment, at least one infrared surface radiator, in particular a side surface radiator, comprises different heating zones which are controlled separately from one another, in particular depending on a position of the powder and / or the 3D molded part. The heating zones can, for example, be arranged adjacent to one another in the vertical direction. The heating zones can overlap in the vertical direction. The heating zones can be designed without overlaps in the vertical direction. At least 2, at least 3, at least 5 or at least 10 heating zones can be provided in the vertical direction.

According to one embodiment, the heating zone height can be at least 3 cm and / or a maximum of 6 cm. According to another embodiment, the heating zone height can be at least 8 cm and / or a maximum of 12 cm. Depending on the height of the machine room, the heating zone height can be at least 1/10 and / or at most 1 of the height of the machine room. The machine room height can be at least 20 cm or at least 30 cm. Further preferred embodiments are described in the claims.

Execution example

The invention is explained in more detail below on the basis of an exemplary embodiment and a patent drawing. The drawing shows in detail: Figure 1 shows an embodiment of the heating device in a schematic representation and in a side view, and Figures 2 to 4 further embodiments of the heating device;

FIG. 1 schematically shows an embodiment of the heating device with several infrared surface radiators 4, 4 ', 4 ”in a construction space 1 for the production of 3D molded parts 5. Above the construction space 1 there is the process chamber 2, in which units, not shown here to control the assembly process of the molded parts 5 are housed. A laser unit 3 is schematically arranged at the upper end of the process chamber 2, which is suitable for heating the powder P for producing the 3D molded part 5 with a high-energy laser beam emanating therefrom and selectively sintering and / or melting it .

Powder P is typically a metal powder, but plastic powders can also be used. The powder P is located on the construction platform 6, which is arranged on a height-displaceable support plate 7 indicated by the double directional arrow 8 with a stamp 7.1. The construction platform 6 is mounted on a mounting plate 9, which simplifies the exchange of the construction platform 6. The construction platform 6 - supported by the mounting plate 9 - is heated by one of the infrared surface radiators 4, which is arranged on the carrier plate 7. The infrared surface heater 4 is insulated from the carrier plate 7 by a thermal insulation layer 4i, which is applied directly to the infrared surface heater 4, and additionally by a cooling plate 10. The cooling plate 10 consists, at least on the side facing the infrared area radiator, preferably of a material which reflects the infrared radiation well, or is coated with such a material. This can be aluminum, gold, silver, copper or polished steel, for example. On the one hand, it has the effect that only a small part of the heat radiation is absorbed by the cooling plate and the necessary cooling capacity can thus be reduced. On the other hand, the reflected heat radiation is again partially absorbed by the IR surface heater and contributes to its further heating. This allows the necessary electrical power, which is necessary to keep the IR surface heater at a constant Operating temperature, reduced and thus the energy efficiency of the heating process can be increased.

The reflective cooling plate can be positioned at a small distance on the back of the IR surface radiator. This distance is preferably in the range from 5 to 50 mm. The smaller the distance between the surface radiator and the reflecting cooling plate, the more effective the reflecting effect of the cooling plate. In the case of a metal cooling plate, which can be electrically at ground or another electrical potential, a short circuit must be avoided. The distance is usually less than 10 mm, preferably at most 5 mm, in particular at most 2.5 mm. The distance can be greater than 0.5 mm, preferably at least 1 mm, in particular at least 1.5 mm. For example, the distance is 2.0 mm ± 0.15 mm.

The interplay of insulation layer 4i and reflective cooling plate 10 can be described as follows. Due to its low emissivity, the thermal insulation layer ensures that only a small part of the total radiation power of the panel radiator is emitted backwards towards the cooling plate. The cooling plate can in turn reflect a large part (up to 99%) of the incoming loss radiation, so that a large part of the lost radiation hits the infrared radiator again. Theoretically, the infrared heater would be hotter, but this is prevented by the individual temperature control, so that the infrared heater only consumes less electricity (less voltage). It has been shown that the combination of thermal insulation layer and reflecting cooling plate in thermal equilibrium can achieve an energy consumption of the infrared radiator that is up to 80% lower than when the infrared radiators are heated. Since the lost radiation contributes to the self-heating of the infrared radiators, higher heating rates can also be achieved.

The construction space 1 is further heated laterally by two infrared surface radiators 4 ', 4 “, which simultaneously form the side walls of the construction space. On the outside, these infrared surface radiators 4 ', 4 ”or the side walls are covered by a thermal insulator, which is in the form of a further, thermal insulation layer 4ii, 4iii on the infrared surface radiator 4 ', 4 "is present. In addition, a cooling plate 10 ', 10 "is provided on both sides of the jacket heating.

A seal 12 is provided between the height-adjustable support plate 7 and the side walls in order to maintain a suitable atmosphere in the installation space 1 permanently and to minimize heat losses at this point.

The infrared surface radiators 4, 4 ″, 4 ″ shown in side view in the heating device are each arranged with their plate-shaped substrate body 4s facing the building platform 6 in the building space 1. The substrate body 4s in the form of a plate has a smooth surface which, in the case of the surface emitter 4 on the carrier plate 7, lies directly against the surface of the mounting plate 9 and the construction platform 6 connected to it. Because of the particularly good radiation characteristics of the material of the substrate body 4s, good heat transfer to the construction platform 6 is guaranteed. In principle, it is also possible to install the infrared surface radiators with the electrically insulating cover layer facing the installation space, but the advantage of a possibly special radiation characteristic of the substrate body material is not used.

The plate-shaped substrate body 4s has a rectangular shape with a plate thickness of 2.5 mm. It consists of a composite material with a quartz glass matrix. The matrix is visually translucent to transparent. When viewed microscopically, it shows no open pores and at most closed pores with maximum dimensions of less than 10 pm on average. A phase of elemental silicon in the form of non-spherical areas is homogeneously distributed in the matrix. Their weight percentage is 5%. The maximum dimensions of the Si phase areas are on average (median) in the range from about 1 to 10 pm. The composite material is gas-tight, it has a density of 2.19 g / cm ³ and it is stable in air up to a temperature of around 1200 ° C.

The embedded Si phase contributes to the overall opacity of the composite material and has an impact on the optical and thermal egg properties of the composite material. At high temperature, this shows a high absorption of heat radiation and a high emissivity.

On the substrate body 4s there is a conductor track 4c made of an electrically conductive resistance material which generates heat when current flows through, in this case a platinum conductor track which is applied from a platinum resistor paste to the surface of the substrate body 4s by screen printing or by means of ink-jet printing and then at a higher level Temperature was baked. The conductor track 4c of the infrared panel heater 4, 4 ″, 4 ″ comprises a printed heating meander which can be electrically controlled in zones. The zones which can be controlled individually are designated z1 and z2 by way of example in the figure. The zone-by-zone heating of the heating meander can have a targeted effect on the temperature distribution in the process of building the 3D molded part 5. The opposite side of the substrate body 4s serves - as explained above - when using the infrared area radiator as a radiation surface for heat radiation. The conductor track 4c is covered by an electrically insulating cover layer 4d made of white opaque quartz glass (overglazing), which additionally serves as a thermal and optical insulator directly on the surface radiator. The electrically insulating cover layer 4d has a thickness of approximately 5 pm to 20 pm or up to 30 pm.

The thermally insulating covering layer 4i, which has an insulating effect with respect to the carrier plate 7, is applied to the electrically insulating covering layer 4d. This thermally insulating layer has a thickness of approximately one millimeter (1 mm).

The heating device is characterized by a high emissivity for thermal radiation and effective use of the power fed in with a simple geometric design of the infrared panel heaters. When used in the area of 3D printing, a homogeneous temperature distribution and an optimized heat transfer to the sintered or melt powder are guaranteed.

The heating device shown in FIG. 2 shows an IR surface heater 4, which is designed as a floor surface heater and is completely surrounded by the mounting plate 9. is encapsulated. The bottom surface radiator 4 is inserted into the mounting plate 9 through a lateral slot (not shown here). This results in good contact with the building platform 6 and thus with the powder P or with the molded part 5. FIGS. 3 and 4 show further variants with regard to the position of the floor surface radiator 4 between the building platform 6 and the carrier plate 7.

According to FIG. 3, the bottom surface radiator 4 is inserted from above into a corresponding recess in the mounting plate 9, so that there is direct contact with the building platform 6. The heat transfer to the powder P and the molded part 5 is thereby optimized. It is important that the surface radiator 4 is spring-mounted so that the construction platform 6 is not damaged during assembly.

In this as well as in the other embodiments of the heating device, it can be helpful to arrange several smaller area radiators under the construction platform. Corresponding webs should be arranged between the emitters, which absorb the forces that act on the construction platform and transmit them to the carrier plate.

Figure 4 finally shows the bottom surface radiator 4 in a position in which it is used in the lower region of the mounting plate 9. In relation to the heat transfer to the powder or to the molded part, this position results in a particularly uniform heating pattern.

Reference list

1 installation space

2 process chamber

3 laser unit

4, 4 ″, 4 “IR surface radiators

4c conductor track

4d electrically insulating cover layer 4i thermally insulating top layer

4s substrate body

5 3D molded part

6 construction platform

7 carrier plate

7.1 stamp

8 directional arrow

9 mounting plate

10, 10 'cooling plate, thermal insulation layer

12 seal

P powder

z1, z2, z3 heating zones

Claims

1. Heating device with at least one infrared area radiator (4; 4 ″; 4 “) for heating a powder (P) for producing an at least partially metallic 3D molded part (5) and a laser for melting the powder (P).

2. Heating device in particular according to claim 1 with at least one infrared area radiator (4; 4 '; 4 ") for heating a powder (P) for the production of a 3D molded part (5) in a construction space (1) which is a construction platform (6) for receiving the molded part (5), encompasses a carrier plate (7) and the infrared surface radiator (4) designed as a bottom surface radiator, arranged between the building platform (6) and carrier plate (7).

3. Heating device according to claim 1 or 2, characterized in that the infrared surface radiator (4; 4 '; 4 ") with an electrically insulating cover layer (4d) covered conductor track (4c) from an electrically conductive and heat when current flows generating resistance material on a plate-shaped substrate body (4s) made of an electrically insulating material.

4. Heating device according to one of the preceding claims, characterized in that the bottom surface radiator (4) with its plate-shaped substrate body (4s) facing the building platform (6) is arranged on the carrier plate (7).

5. Heating device according to claim 3 or 4, characterized in that the electrically insulating material of the substrate body (4s) contains quartz glass.

6. Heating device according to claim 5, characterized in that the quartz glass is opaque and has a porosity of less than 0.5%.

7. Heating device according to claim 5 or 6, characterized in that the quartz glass contains an additional component, preferably elemental silicon, which absorbs in the spectral range of the infrared radiation.

8. Heating device according to one of the preceding claims, characterized in that a thermal insulation layer (10; 10 ″) is provided between the carrier plate (7) and bottom surface radiator (4).

9. Heating device according to one of the preceding claims, characterized in that the building platform (6) is connected to a mounting plate (9), the mounting plate (9) being arranged between the floor surface heater (4) and the building platform (6) and / or wherein the mounting plate (9) is arranged on the side of the floor surface radiator (4).

10. Heating device according to one of the preceding claims, characterized in that the heating device comprises at least one infrared area heater (4 '; 4 ") designed as a side area heater and that the installation space (1) is delimited by at least one side wall of at least part of which is formed by the side surface radiator (4 '; 4 “).

11. Heating device according to claim 10, characterized in that the side surface heater has a conductor track (4c) covered with an electrically insulating cover layer (4d) and made of an electrically conductive resistance material on a plate-shaped substrate body (4s ) made of an electrically insulating material, and the plate-shaped substrate body (4s) of the side surface radiator (4 '; 4 ") faces the construction space (1).

12. Heating device according to claim 10 or 11, characterized in that the side wall on its side facing away from the molded part (5) is covered by a thermal insulation layer (4i) and a cooling plate (10 ').

13. Heating device according to one of the preceding claims, characterized in that the conductor track (4c) of the infrared surface radiator, in particular the bottom surface radiator and / or the side surface radiator (4; 4 '; 4 ") can be electrically controlled in zones, whereby in particular the infrared area heater each comprises at least one printed heating meander.

14. Heating device according to one of claims 3 to 13, characterized in that the electrically insulating cover layer (4d) has a thickness in the range from 5 pm to 30 pm.

15. A method for producing an at least partially metallic 3D molded part (5) from a powder (P), the powder being melted and / or sintered by means of a laser (3), characterized in that the powder (P) and / or the 3D molded part (5) is heated with at least one infrared area radiator (4; 4 '; 4 “).

16. The method according to claim 15, characterized in that the powder (P) and / or the 3D molded part (5) is heated to a temperature of at least 250 ° C or at least 500 ° C.

17. The method according to claim 15 or 16, characterized in that the powder (P) and / or the 3D molded part (5) is heated to a temperature below the melting temperature of the powder.

18. The method according to any one of claims 15 to 17, characterized in that the powder (P) and / or the 3D molded part (5) to a temperature of not more than 500 ° C, not more than 200 ° C, no more is heated as 100 ° C or not more than 50 ° C below the melting temperature of the powder (P).

19. The method according to any one of claims 15 to 18, characterized in that the powder (P) and / or the 3D molded part (5) is heated vertically from below and / or horizontally from at least one side.

20. The method according to any one of claims 15 to 19, characterized in that a vertical relative movement of the powder (P) and / or the 3D molded part (5) during heating relative to at least one infrared surface radiator (4; 4 '; 4th "), In particular a side surface radiator (4 ', 4").

21. The method according to any one of claims 15 to 20, characterized in that at least one infrared radiator (4; 4 '; 4 "), in particular a side surface heater, different heating zones (z 1, z 2, z 3), which are controlled separately from one another, in particular depending on a position of the powder (P) and / or the 3D molded part (5).