DEVICE FOR THE ADDITIVE MANUFACTURING OF THREE-DIMENSIONAL OBJECTS

Description

[0001] The invention relates to a device for the additive manufacturing of three-dimensional objects by successive layer-by-layer selective exposure and the associated solidification of building material layers made of a building material that can be solidified by means of an energy beam.

[0002] Devices suitable for the additive manufacturing of three-dimensional objects are known per se. Using such devices, three-dimensional objects are additively built up from a material that can be solidified by means of an energy beam through successive, layer-by-layer selective exposure and the associated solidification of layers of building material formed in a build plane.

[0003] Occasionally, temperature control of individual building material layers can be advantageous, and in some cases even necessary. Temperature control serves, in particular, to reduce thermally induced stresses within the respective object (section), thus allowing targeted temperature control to influence the structural properties of the additively manufactured or produced object. Accordingly, devices of the type mentioned above are regularly equipped with temperature control units designed for at least partial temperature control of a building material layer formed in a single build plane.

[0004] Conventional temperature control systems typically only allow for static temperature control of individual building material layers. With such systems, it is possible, if at all, to achieve individually adjustable temperature control of different building material layers – for example, to account for the varying thermal properties of different materials – only with considerable effort.

[0005] US 2014 / 0263209 A1 discloses an additive manufacturing device with a plurality of diodes.

[0006] The invention is based on the objective of providing an improved device for the additive manufacturing of three-dimensional objects, particularly with regard to the possibility of individually adjustable temperature control of the respective building material layers.

[0007] The problem is solved by a device for the additive manufacturing of three-dimensional objects according to claim 1. The dependent claims relate to possible embodiments of the device.

[0008] The device described herein ("apparatus") is designed for the additive manufacturing of three-dimensional objects, i.e., for example, technical components or assemblies, by successively selectively exposing and thus solidifying layers of building material from a material that can be solidified by means of an energy beam, in particular a laser beam. The building material can be a particulate or powdered metal, plastic, and / or ceramic material. The selective solidification of the respective layers of building material to be selectively solidified is based on object-specific design data. This design data describes the geometric and structural shape of the object to be additively manufactured and can, for example, include sliced ​​CAD data of the respective object.

[0009] The device may be an SLM device, i.e. a device for carrying out selective laser melting processes (SLM process), in particular LaserCUSINGO process, or an SLS device, i.e. a device for carrying out selective laser sintering processes (SLS process).

[0010] The device comprises the functional components typically required for carrying out additive manufacturing processes, i.e., in particular, an energy beam generation device for generating an energy beam, i.e., in particular a laser beam, for the successive, layer-by-layer selective exposure and concomitant solidification of building material layers, and a coating device for forming building material layers to be selectively exposed or selectively solidified in a build plane. The actual selective exposure or selective solidification of the respective building material layers to be selectively solidified thus takes place in the build plane; generally, at least one building material layer to be selectively solidified or selectively solidified is formed in a build plane. Additive manufacturing processes carried out by means of the device take place in an inertable process chamber belonging to the device.The process chamber can form part of an (outer) housing structure of the device, on or in which device-side functional components are arranged or formed.

[0011] The device includes a temperature control unit as a further functional component. The temperature control unit is a separate functional component of the device from the energy beam generation unit. The temperature control unit is designed for at least partial temperature control of a layer of building material formed in a building plane, in particular one that is (still) to be selectively solidified or (already) selectively solidified. As will be explained below, the temperature control unit is designed for locally limited temperature control of one or more contiguous or non-contiguous areas of a layer of building material to be tempered. Temperature control of a layer of building material can mean (controlled) heating of at least one area of ​​the layer to a specific heating temperature or a specific heating temperature range and / or maintaining a heated area at a specific heating temperature or range.a heating temperature range as well as a (controlled) cooling of at least one area of ​​a building material layer to a specific cooling temperature or a specific cooling temperature range and / or a holding of a cooled area at a cooling temperature or a cooling temperature range.

[0012] The temperature control device comprises at least one temperature control element. The temperature control element is configured to generate a temperature control beam, in particular an electromagnetic one. The temperature control achievable by means of the temperature control device is thus carried out by means of at least one electromagnetic temperature control beam and therefore by a targeted introduction of electromagnetic radiation – as will be shown below, laser radiation – into at least one region of a building material layer to be temperature controlled, selectively hardened, or selectively hardened.

[0013] The temperature control element is designed as a temperature control diode or incorporates one. A temperature control diode is a semiconductor element designed to generate a temperature control beam, which is a laser beam. The optical properties, i.e., the wavelength, of the temperature control beam generated by a temperature control diode depend, among other things, on the semiconductor material(s) used. Depending on the specific design, temperature control diodes can generate wavelengths between 650 and 2000 nm, particularly between 800 and 1000 nm, and laser powers in the range of 0.1 to 10 watts; naturally, exceptions at the higher and / or lower end of this range are conceivable.

[0014] A temperature control diode is typically a surface emitter diode, or simply surface emitter, configured to emit a laser beam perpendicularly from a plane of the semiconductor element that forms the actual temperature control diode. In the assembled state of the temperature control device, the emitting surface of such a semiconductor element is typically oriented towards the respective layer of the component material to be temperature controlled. These surface emitter diodes are also known as VCSELs (vertical cavity surface emitting lasers) and are distinguished from other diode designs, particularly edge emitter diodes, by their variable beam characteristics, specifically the beam profiles and intensities of the laser beams they can generate. Thus, different temperature control beams with varying beam characteristics can be generated using these surface emitter diodes.This allows for individual or individually adaptable, yet homogeneous temperature control of building material layers.

[0015] Particular advantages of the device lie in the fact that, through the described design of the temperature control unit, i.e., especially through the use of temperature control diodes, thermal stresses in the layers of the building material being tempered, and thus in the additively manufactured or produced objects, can be reduced. This has a positive effect on the structural properties, i.e., the mechanical stability and dimensional accuracy of the objects. Furthermore, the temperature-dependent absorption properties of the building material can be specifically influenced.

[0016] Overall, the device is improved, particularly with regard to the possibility of individually adjustable temperature control of the respective building material layers.

[0017] From the foregoing, it follows that the temperature control diodes are typically variable in at least one parameter relating to the properties of the temperature control beam generated by them, in particular their output power, intensity, wavelength, etc. Advantageously, the device includes a control unit, implemented in hardware and / or software, which can be assigned to or associated with the temperature control unit. The control unit is designed to control the operation, i.e., in particular to control at least one parameter relating to the properties of the temperature control beam generated by a respective temperature control diode, of one or more temperature control diodes. The control unit enables individual control of each temperature control diode and thus individually adjustable temperature control of each layer of the building material to be cooled.For example, the geometry of corresponding temperature control radiation profiles can be adapted (almost) arbitrarily by appropriately controlling one or more temperature control diodes. Such temperature control radiation profiles can, for example, be strip-shaped, allowing a locally limited, strip-shaped area of ​​a building material layer to be temperature controlled. The same applies, of course, to other temperature control radiation profile geometries.

[0018] Furthermore, by appropriately controlling one or more temperature control diodes, it is possible to generate (virtually) any spatially and / or temporally variable temperature control radiation profile, particularly with regard to a building material layer being tempered, which is locally limited. These profiles are composed of the temperature control radiation generated by the respective diodes. In this way, any spatially and / or temporally variable temperature ramps to a specific heating temperature can be achieved when heating building material layers. Similarly, any spatially and / or temporally variable temperature ramps to a specific cooling temperature can be achieved when cooling building material layers.

[0019] The device may include a sensing device configured to detect the temperature of a building material layer to be tempered. The sensing device may be designed as a temperature sensor, e.g., in the form of a pyrometer, or may include such a sensor. The device, or a further control device if present, may be configured to individually control the operation of one or more tempering diodes based on sensing information generated by the sensing device describing the detected temperature of a building material layer to be selectively hardened or selectively hardened, with regard to a specific heating or cooling temperature. The control of the operation of the tempering diodes, i.e., generally the tempering of a building material layer to be tempered, can thus be accompanied by temperature monitoring of the building material layer to be tempered.

[0020] The temperature control unit comprises several temperature control diodes. These diodes can be arranged in any spatial configuration relative to a build plane in which the respective layers of the building material to be temperature-controlled are formed or are formed. One exemplary arrangement involves the temperature control diodes, or several temperature control diodes, as a subset of the total number of temperature control diodes present in the unit, arranged in rows and / or columns in at least one common plane, particularly one parallel to the build plane. An arrangement of temperature control diodes in connected rows and columns can be referred to as a matrix-like arrangement, or simply a matrix.A corresponding matrix therefore comprises at least one row, typically several parallel rows, of at least two temperature control diodes each, and at least one column, typically several parallel columns, of at least two temperature control diodes each. A corresponding row of temperature control diodes extends at an angle, in particular perpendicularly, to a corresponding column of temperature control diodes, and vice versa.

[0021] In addition to the described arrangement of corresponding temperature control diodes in a common plane, the temperature control diodes, or several temperature control diodes, can be arranged one above the other in several planes, particularly parallel to the mounting plane, as a subset of the total number of temperature control diodes present in the temperature control system. An arrangement of temperature control diodes in several planes can result in a particularly compact, possibly nested, arrangement of corresponding temperature control diodes. The temperature control diodes arranged in the respective superimposed planes can be positioned with a specific spatial offset relative to each other. The temperature control jet generated by a temperature control diode arranged in an upper plane thus does not strike a temperature control diode arranged in a lower plane, but rather passes through a free space, e.g.,in the form of a gap, a bore, or other opening, between temperature control diodes arranged immediately adjacent to one another in a lower plane. The arrangement of the temperature control diodes in several planes above one another is chosen such that the temperature control beams can be directed onto a specific layer of the building material to be tempered.

[0022] The temperature control diodes are arranged – regardless of their specific arrangement relative to one another – on or in a holding device, in particular a housing-like structure. According to claim 1, the holding device is arranged or configured outside the process chamber of the device. In an embodiment not belonging to the invention, the holding device can be arranged in a wall of the process chamber. An arrangement of the temperature control device outside the process chamber of the device requires a suitable means of directing the temperature control beams generated by the temperature control diodes, which can be realized, for example, by a passage window arranged or configured in a process chamber wall that allows the respective temperature control beams to pass into the process chamber.

[0023] Regardless of whether they are located outside or inside the process chamber, the holding device comprises a support structure, in particular a frame-like or frame-shaped structure, on or in which the temperature control diodes are arranged. The support structure typically includes a number of predeterminable or predetermined mounting positions on or in which at least one temperature control diode can be or is arranged. The arrangement of the temperature control diodes on or in the support structure can be detachable (without damage or destruction), which simplifies, for example, replacement when necessary for service and / or repair.

[0024] The holding device can be mounted to allow movement in at least one degree of freedom relative to the process chamber or build plane. Movements of the holding device are effected by a drive and / or guide device, in particular an (electric) motor, which can be coupled to or is coupled to it. Movements of the holding device make it possible to move the temperature control diodes relative to a layer of build material to be temperature-controlled, e.g., with regard to a specific temperature control situation. Movements of the holding device can include translational degrees of freedom along at least one translational axis and / or rotational degrees of freedom about at least one rotational axis. These movements can be, for example, linear, rotary, tilting, or pivoting movements. Naturally, combined movements in several different degrees of freedom are possible.

[0025] For an arrangement of the holding device within the process chamber (and not according to the invention), it is particularly important that a corresponding drive and / or guide device can be provided by a device-side functional component that is movably mounted within the device-side process chamber in at least one degree of freedom. The holding device can therefore be motionally coupled to a device-side functional component that is movably mounted within the device-side process chamber in at least one degree of freedom. The device-side functional component can, for example, be the coating unit, which is set up in the build plane for the formation of building material layers to be selectively exposed or selectively solidified. The coating unit is typically movably mounted in one translational degree of freedom relative to the build plane.The holding device can therefore be motion-coupled with the coating device, which can be realized, for example, by the holding device being arranged directly or indirectly, i.e., with the interposition of at least one component or group of components, on the coating device.

[0026] As mentioned, the holding device can comprise a support structure, particularly a frame-like or frame-shaped one, on or in which the temperature control diodes are arranged. Movements of the temperature control diodes, e.g., with regard to a specific temperature control situation, relative to a layer of the building material to be cooled, can also be implemented such that at least one temperature control diode is mounted on or in the support structure, movable in at least one degree of freedom relative to the support structure and thus also relative to a layer of the building material to be cooled. For this purpose, the support structure provides a suitable drive and / or guide device by means of which movements of the temperature control diodes can be realized. The above statements regarding the movement of the holding device relative to the build plane apply analogously to the movement of a temperature control diode relative to the support structure.

[0027] The invention is explained in more detail with reference to exemplary embodiments shown in the drawings. These show: Figs. 1 and 2 each show a schematic representation of a device according to an exemplary embodiment; and Fig. 3 shows a schematic representation of a temperature control device according to an exemplary embodiment.

[0028] Fig. 1 Figure 1 shows a schematic representation of a device 1 according to an embodiment of the invention. The device 1 serves for the additive manufacturing of three-dimensional objects 2, i.e., in particular technical components or technical component groups, by successively selectively exposing and thereby solidifying layers of a build material made of a solidifiable powdered material 3, i.e., a metal powder, by means of a laser beam 5 generated by a laser beam generator 4. The selective exposure and the associated selective solidification of the respective layers of build material to be solidified are based on object-specific build data. Such build data describe the geometric or geometric-constructive shape of the object 2 to be additively manufactured. For example, such build data can include sliced ​​CAD data of the object 2 to be manufactured.

[0029] The device 1 comprises an inertizable process chamber 6 in which the actual additive manufacturing of the respective objects 2 takes place. The process chamber 6 can form part of a housing structure (not shown) of the device 1. At least some of the functional components of the device 1 required for carrying out additive manufacturing processes are arranged or formed in the process chamber 6, i.e., in particular, a coating unit 7, which is movably mounted as indicated by the horizontally oriented double arrow P1 and is configured for forming layers of building material to be solidified in a build plane. Functional modules, i.e., specifically a powder module 8 for providing powdered building material 3, a build module 9 in which the actual additive construction of the object 2 takes place, and an overflow module 10 for receiving unsolidified building material 3, are arranged on or in the process chamber 6.The functional modules can be detachably connected or linked to process chamber 6 in the sense of interchangeable containers.

[0030] The device 1 comprises a temperature control unit 11 as a further functional component. The temperature control unit 11 is a separate functional component of the device 1 from the laser beam generation unit 4. The temperature control unit 11 is designed for at least partial temperature control of a layer of building material formed in a build plane, in particular a layer that is (still) to be selectively solidified or is (already) selectively solidified. Temperature control of a layer of building material means the (controlled) heating of at least a region of the layer of building material to a specific heating temperature or a specific heating temperature range and / or maintaining a heated region at a heating temperature or a heating temperature range, as well as the (controlled) cooling of at least a region of the layer of building material to a specific cooling temperature or a specific cooling temperature range.to understand a specific cooling temperature range and / or maintaining a cooled area at a cooling temperature or cooling temperature range.

[0031] The temperature control device 11 comprises several temperature control elements 12 (see Fig. 3 The temperature control elements 12 are each configured to generate a temperature control beam, in particular an electromagnetic beam. The temperature control beams generated by the respective temperature control elements 12 combine to form a temperature control radiation profile 13. The temperature control achievable by means of the temperature control device 11 is therefore carried out by means of electromagnetic temperature control radiation and thus by a targeted introduction of electromagnetic radiation into at least one area of ​​a building material layer to be temperature controlled.

[0032] The temperature control elements 12 are each designed as a temperature control diode, specifically as a surface emitter diode. A temperature control diode is a semiconductor element designed to generate a temperature control beam, which is a laser beam. The optical properties, i.e., the intensity and wavelength, of the temperature control beam generated by a temperature control diode depend, among other things, on the semiconductor material(s) used. Depending on the specific design, the temperature control diodes can, for example, generate wavelengths between 800 and 1000 nm and laser powers in the range of 0.1 to 10 watts. The surface emitter diodes used as temperature control diodes are characterized by variable beam properties of the laser beams they generate. Thus, different temperature control beams with different beam properties can be generated using the surface emitter diodes. This allows for individual or...Individually adjustable, yet homogeneous temperature control of building material layers is possible.

[0033] The temperature control diodes are therefore typically variable in at least one parameter relating to the properties of the temperature control beam generated by them, in particular in their output power, intensity, wavelength, etc. The device 1 comprises a control unit 14, implemented in hardware and / or software, associated with the temperature control unit 11. The control unit 14 is configured to control the operation, i.e., in particular to control at least one parameter relating to the properties of the temperature control beam generated by a respective temperature control diode, of one or more temperature control diodes. The control unit 14 enables individual control of each temperature control diode and thus individually adjustable temperature control of each layer of the building material to be tempered.For example, the geometry of corresponding temperature control radiation profiles 13 can be adapted (almost) arbitrarily by appropriately controlling one or more temperature control diodes. Such temperature control radiation profiles 13 can, for example, be strip-shaped, so that a locally limited strip-shaped area of ​​a building material layer to be temperature-controlled can be controlled. The same applies, of course, to other temperature control radiation profile geometries.

[0034] Furthermore, by appropriately controlling one or more temperature control diodes, it is possible to generate (almost) any spatially and / or temporally variable temperature radiation profiles. In this way, in connection with heating building material layers to be tempered, any spatially and / or temporally variable temperature ramps to a specific heating temperature can be realized. Similarly, in connection with cooling building material layers to be tempered, any spatially and / or temporally variable temperature ramps to a specific cooling temperature can also be realized.

[0035] The device 1 can include a detection device (not shown, as it is optional) configured to detect the temperature of a building material layer to be tempered. The detection device can be designed as a temperature sensor, e.g., in the form of a pyrometer. The control device 14 can be configured to individually control the operation of one or more tempering diodes based on detection information generated by the detection device, describing the detected temperature of a building material layer to be selectively hardened or selectively hardened, with regard to a specific heating or cooling temperature. The control of the operation of the tempering diodes, i.e., generally the tempering of a building material layer to be tempered, can thus be accompanied by temperature monitoring of the building material layer to be tempered.

[0036] Based on Fig. 3 Figure 11, which shows a schematic representation of a temperature control device 11 according to an exemplary embodiment, clearly shows that the temperature control device 11 comprises several temperature control elements 12 or several temperature control diodes. According to the figure in Fig. 3 In the illustrated embodiment, the temperature control diodes are arranged in rows and columns in a common plane, which is particularly parallel to the mounting plane. This arrangement of temperature control diodes can be described as a matrix-like arrangement, or simply matrix.

[0037] Besides the in Fig. 3 In addition to the arrangement of corresponding temperature control diodes shown in a common plane, the temperature control diodes can also be arranged one above the other in several planes, particularly those parallel to the plane of assembly. The temperature control diodes arranged in the respective superimposed planes can be positioned with a specific spatial offset relative to each other. The temperature control beam generated by a temperature control diode arranged in an upper plane thus does not strike a temperature control diode arranged in a lower plane, but rather passes through a gap, e.g., in the form of a slit, a bore, or other opening, between temperature control diodes arranged immediately adjacent to each other in a lower plane.

[0038] Based on Fig. 3 It is further evident that the temperature control diodes are arranged on or in a housing-like holding device 15. The holding device 15 comprises a frame-like or frame-shaped holding structure 16 on or in which the temperature control diodes are arranged. The holding structure 16 comprises a number of predeterminable or predetermined arrangement positions (not further specified) on or in which at least one temperature control diode can be arranged or is arranged. The arrangement of the temperature control diodes on or in the holding structure 16 can be detached (without damage or destruction). Returning to Fig. 1 It is evident that the holding device 15, and thus the temperature control device 11, is arranged or configured outside the process chamber 6. Specifically, the holding device 15 is arranged or configured in the area of ​​a process chamber wall forming a ceiling region of the process chamber 6. An alternative arrangement of the holding device 15, or a further holding device 15, is shown in dashed lines. This alternative arrangement is located in the area of ​​a process chamber wall forming a side region of the process chamber, for example, an inclined wall. The aforementioned arrangement options for the temperature control device 11 outside the device-side process chamber require a suitable beam path for the temperature control beams generated by the temperature control diodes, which, for example,This can be achieved by a passage window arranged or formed in a process chamber wall, enabling the passage of respective temperature control jets into the process chamber 6.

[0039] The holding device 15 could also be integrated into a process chamber wall of the process chamber 6 (not according to the invention).

[0040] Although in Fig. 1 Although not shown, it is possible that the holding device 15 or the temperature control device 11 is mounted to be movable in one degree of freedom relative to the process chamber 6 or the build plane, respectively. Movements of the holding device 15 can be effected by a drive and / or guide device, in particular an (electric) motor, which can be coupled to or is coupled to it. Movements of the holding device 15 make it possible to move the temperature control diodes relative to a layer of build material to be tempered, e.g., with regard to a specific temperature control situation. Movements of the holding device 15 can include translational degrees of freedom along at least one translational axis and / or rotational degrees of freedom about at least one rotational axis. Movements of the holding device 15 can be, for example, linear, rotary, tilting, or pivoting movements.

[0041] Fig. 2 Figure 1 shows a schematic representation of a device 1 according to a further embodiment (not according to the invention). In contrast to the one in Fig. 1 In the illustrated embodiment, the holding device 15 or the temperature control unit 11 is arranged within the process chamber 6. The holding device 15 is mounted so as to be movable in one degree of freedom relative to the process chamber 6 or the build plane. This is achieved by mounting the holding device 15 on a functional component of the device 1, which is itself mounted so as to be movable in at least one degree of freedom within the process chamber 6. The functional component is the coating unit 7, which, as indicated by arrow P1, is mounted so as to be movable in one translational degree of freedom relative to the build plane. Of course, a stationary arrangement of the holding device 15 or the temperature control unit 11 within the process chamber 6 is also conceivable.

[0042] For all embodiments, the movements of the temperature control diodes relative to a component layer to be temperature controlled can alternatively or additionally be realized such that one or more temperature control diodes are movably mounted on or in the mounting structure 16 in at least one degree of freedom relative to the mounting structure 16 and thus also relative to a component layer to be temperature controlled. For this purpose, the mounting structure 16 would be provided with a suitable drive and / or guide device (not shown) by means of which movement of the temperature control diodes can be realized.

[0043] With the in the Fig. 1 , 2The devices shown 1 enable the implementation of a method for the additive manufacturing of three-dimensional objects 2 by successive layer-by-layer selective exposure and the associated solidification of building material layers formed in a building plane from a building material 3 that can be solidified by means of an energy beam 5.

Claims

1. Device (1) for additive manufacturing of three-dimensional objects (2), comprising: an energy beam generating device for successive layer-by-layer selective exposure and associated solidification of building material layers from a building material; a process chamber (6) in which the successive layer-by-layer selective exposure and the associated solidification of building material layers can be carried out; A temperature control device which is provided for a locally limited temperature control of one or more contiguous or non-contiguous areas of a building material layer to be tempered, comprising: a holding device (15) comprising a holding structure which is arranged or formed outside the process chamber (6), and a plurality of tempering diodes arranged on or in the holding device (15), each of which is designed to produce a tempering beam, so that the plurality of tempering diodes can produce a plurality of corresponding tempering beams for the tempering of respective building material layers.

2. Device according to claim 1, characterized in that the tempering diodes in series and / or column-like arrangement in at least one plane.

3. Device according to claim 1 or 2, characterized in that the holding device (15) comprises a frame-like or -shaped holding structure (16), on or in which the tempering diodesarearranged.

4. Device according to one of the preceding claims,characterized in that the tempering diodes are formed as surface emitter diodes, VCSEL diodes, or comprise such.

5. Device according to one of the preceding claims, characterized in that the tempering diodes are typically variable in at least one of the beam properties of the tempering beam parameter, in particular in its output power, intensity, wavelength, etc., which can be generated via this tempering beam.

6. Device according to one of the preceding claims, characterized by a control device, which allows an individual control of respective tempering diodes and thus an individually adjustable tempering of respective building material layers to be tempered.

7. Device according to claim 6,characterized in that the beam profile and / or the output power and / or the intensity and / or the wavelength are variable as corresponding beam properties.

8. Device according to claim 6, characterized in that the control device (14) is equipped to drive single or more temperature control diodes, whereby locally and / or temporally variable, in particular with regard to a to be tempered building material layer locally limited, temperature control radiation profiles,which are composed of the temperature control beams produced by the respective temperature control diodes, can be generated.

9. Device according to claim 8, characterized by a detection device for detecting the temperature of a building material layer to be tempered, wherein the or another device-side control device is arranged to control the operation of single or more temperature control diodes on the basis of a generated by the detection device, the detected temperature of a selectively solidified or selectively solidified building material layer descriptive detection information individually with regard to a certain heating or cooling temperature.

10. Device according to claim 9, characterized in that the detection device is formed as a temperature sensor in the form of a pyrometer or comprises one.

11. Device according to one of the preceding claims, characterized in that the arrangement of the tempering diodes on or in the holding device (15) is detachable.