SUPPORT SYSTEM FOR A MANUFACTURING PLANT AND CORRESPONDENT PROCESS

Description

[0001] The present invention relates to a support system for a manufacturing plant according to the preamble of claim 1, comprising a workpiece carrier. It further relates to a method for manufacturing a workpiece.

[0002] In additive manufacturing, also known as 3D printing, a workpiece is built up step by step from a material. In one variant, a powder of the material is applied layer by layer to a build platform ("stage"). The powder is melted in a controlled manner by the input of energy. After the molten areas have solidified, this process is repeated until the workpiece is complete. The energy input is achieved, for example, by targeted irradiation with electromagnetic radiation, particularly using a laser, or particle radiation. The layer-by-layer application of the powder is achieved, for example, by gradually lowering the build platform in a build cylinder. Such a device is known, for example, from EP-A-2 386 404.

[0003] For precise, high-quality manufacturing, the powder application must be uniform and dense. In particular, it is essential to prevent the material from settling locally during the manufacturing process. One possible cause of this is small cavities that collapse during the process. Irregularities in the uppermost powder layer lead to structural defects in the manufactured workpiece.

[0004] Another important aspect of the aforementioned manufacturing process is ensuring a flawless seal between the building platform and the building cylinder to prevent material loss through a leak in this seal into the space below the platform. Such material flow could also lead to undesirable unevenness in the applied layers of building material.

[0005] A wide range of building materials are used in additive manufacturing processes. Particularly well-known are meltable or partially meltable materials such as polymers, especially thermoplastic polymers, metallic powders, and ceramic powders.

[0006] After completion of the manufacturing process and removal of excess material, the workpiece is firmly attached to the build platform at the contact surfaces and often also connected via support structures. These support structures serve to stabilize the workpiece's position during manufacturing and to dissipate heat generated into the build platform.

[0007] Often, a workpiece produced using an additive manufacturing process is in a state where further processing steps are required, such as thermal treatments and subtractive manufacturing (i.e., material removal). This necessitates removing the workpiece from the build platform to perform these further processing steps. Since the build platform is an integral part of the additive manufacturing device and can only be removed with difficulty, the workpiece must be removed from the platform in place, which is time-consuming and usually requires manual intervention. Furthermore, multiple items are produced simultaneously (e.g., up to 100), which complicates access to individual workpieces during removal.

[0008] WO-A-2016 / 184994 discloses the preamble of claim 1 and relates to an additive manufacturing device in which an object is produced by selective crosslinking in a bath of crosslinkable liquid on a build platform that moves upwards against gravity. One embodiment specifies that the build platform is attached to moving parts, but neither the aforementioned requirements for easy transport are addressed, nor is it even mentioned that the attachment is detachable.

[0009] EP-A-1 614 501 relates to a tool holder on a machine tool that is released by heating. The heating is carried out inductively by an alternating magnetic field.

[0010] US patent application 2014 / 191439 relates to an additive manufacturing system in which the alternating phases of material deposition or stage feed and workpiece formation are avoided by machining along a spiral surface. One embodiment proposes integrating other machining devices, including subtractive ones, into the additive manufacturing system.

[0011] US-A-2015 / 335434 concerns a manufacturing process by combining additive and subtractive manufacturing to obtain flawless, layerless surfaces, and, if required, a structured, bioactive surface through additional additive manufacturing steps.

[0012] In machining processes (turning, milling, grinding, etc.), it is common practice to arrange interchangeable workpiece carriers, known as pallets, on a base plate. The pallets are equipped with suitable clamping devices for the workpieces, and more recently, with so-called zero-point clamping systems. These systems prevent displacement due to thermal expansion and mechanical stress on the pallet relative to its center during machining. The pallets are secured to the base plate with active clamping devices to withstand the loads encountered during machining.

[0013] However, this type of pallet is not suitable for additive manufacturing processes, especially those using layer-by-layer powder application. Specifically, they do not meet the necessary requirements: compatibility with the build material (allowing the workpiece to be built on the surface), void-free powder encapsulation while maximizing surface utilization (since additive manufacturing allows for the simultaneous production of multiple workpieces, and a high number of concurrently produced workpieces is crucial for profitability due to the significant time required), and dimensional stability under heat (deformation of the build surface in additive manufacturing is directly transferred to the workpiece due to the direct bond).

[0014] One object of the present invention is therefore to provide a solution in the form of a carrier system, a workpiece carrier and associated methods which allows a more rational transfer of the workpiece from the manufacturing device of additive manufacturing to a subsequent processing method, in particular subtractive post-processing (e.g. machining) or thermal post-treatment.

[0015] Such a support system is claimed 1 Claim 14 defines a corresponding method for manufacturing a workpiece. The further claims specify preferred embodiments and a manufacturing apparatus. Numerical data in the following description and in the claims are to be understood within the applicable tolerances.

[0016] According to a first aspect, a support system for a manufacturing plant and a workpiece carrier for such a support system are provided. The support system comprises a base carrier (or base plate), which is designed to be mounted in a process chamber of the manufacturing plant and which includes at least one positioning element, and a workpiece carrier on which a workpiece can be manufactured by a manufacturing process involving the layer-by-layer application of a powdered raw material. The workpiece carrier has a bottom surface and a top surface substantially opposite the bottom surface. The workpiece carrier has at least one first positioning device on its underside for precise, detachable attachment to the base carrier of the manufacturing device.The at least one positioning element and the at least one first positioning device are complementary and form a pin-hole pair. At least one section of the pin is made of a first material with a first coefficient of thermal expansion, and the hole, in a section critical for positional accuracy, is made of a second material with a second coefficient of thermal expansion. In a first alternative, the second coefficient of thermal expansion is lower than the first, so that if the temperature of the support system increases during the manufacturing process due to expansion of the pin section, a clamping effect occurs between the pin and the surrounding hole.In a second alternative, the first coefficient of thermal expansion is lower than the second coefficient of thermal expansion, so that if the temperature of the support system increases during the manufacturing process, a clamping effect occurs between the pin and the surrounding hole due to expansion of the retaining section of the hole.

[0017] The manufacturing system can be, for example, an additive manufacturing device (e.g., for selective laser melting). It can also be a thermal post-processing system for a workpiece or a subtractive manufacturing system (e.g., machining). The process chamber can be a space within the manufacturing system where a specific manufacturing process (e.g., additive manufacturing) takes place. In particular, the base support can be part of a build platform for the manufacturing system. The base support can include fasteners suitable for attaching it to a base plate of the manufacturing system. These fasteners can be, for example, holes, pins, and / or screws. Specifically, the base support can be designed to be screwed to a base plate of the manufacturing system.

[0018] The manufacturing process can include, for example, selective laser melting or selective laser sintering. The powdered raw material can be a metal powder. The underside and top of the workpiece carrier can be provided as essentially flat surfaces and define opposite sides of the workpiece carrier. The build surface can be suitable for producing a workpiece on it by a process involving the layer-by-layer application of a powdered raw material. The first positioning device can have a circular cross-section or a cross-section other than a circle. Several first positioning devices (for example, in the form of an array of positioning devices) can be provided on the workpiece carrier. Furthermore, several positioning elements (for example, in the form of an array of positioning elements) can be provided on the base carrier.The number of positioning devices can differ from the number of positioning elements. The fact that the positioning element and the first positioning device are configured as a pin-hole pair can mean that either the positioning element is configured as a pin and the first positioning device as a hole, or that the positioning element is configured as a hole and the first positioning device as a pin. In other words, the pin-hole pair is configured such that either the base support includes the pin and the workpiece carrier the hole, or the base support includes the hole and the workpiece carrier the pin. In a case where multiple pin-hole pairs are provided, the base support can include both pins and holes, and the workpiece carrier can include associated holes and pins.The fact that the positioning element and the first positioning device are complementary can mean that a cross-section of the positioning element essentially corresponds to a cross-section of the first positioning device. In other words, the pin can be received by the hole with virtually no play.

[0019] The at least one section of the pin can be a positioning ring. The positioning ring can be essentially ring-shaped. For example, the positioning ring can be in the form of a disc-shaped ring. The thickness of the positioning ring can be constant. The at least one section of the pin can also be in the form of a cylinder. The coefficient of thermal expansion can be a coefficient of linear expansion or a coefficient of volumetric expansion. According to the first alternative, the clamping effect can be achieved, for example, by the pin section expanding radially, thus creating a frictional and positive fit between the pin and the hole.According to the second alternative, the clamping effect can be achieved, for example, by the retaining section of the hole extending in the (negative) radial direction of the hole, i.e. towards the pin, thus creating a force-fit and form-fit connection between the pin and the hole.

[0020] For example, a positive fit can be achieved in directions parallel to the top and bottom surfaces, and a frictional fit in a direction perpendicular to the top and bottom surfaces. The clamping effect can release again when the support system cools down.

[0021] The workpiece carrier can comprise a plate-shaped upper element and a plate-shaped lower element. The upper element can comprise the top surface, and the lower element can comprise the bottom surface. The upper element can be made of a different material than the lower element.

[0022] The lower element is hereinafter also referred to as the bottom part, and the upper element is hereinafter also referred to as the top part. An interface between the upper and lower elements can exist between the top and bottom of the workpiece carrier. The upper and lower elements can be in contact over a surface at this interface. However, a cavity or multiple cavities can also be provided between the upper and lower elements.

[0023] The upper and lower elements are each plate-shaped. The upper and lower elements can have an identical cross-sectional area at an interface (for example, a substantially rectangular cross-sectional area). The upper element is made of a different material than the lower element. For example, the upper element can be made of a material suitable for fabricating a workpiece using a manufacturing process, particularly selective laser melting. The upper element can be made of aluminum or an aluminum alloy. The lower element can be made of a heat-resistant material. The lower element can be made of tool steel, for example.

[0024] The lower and upper elements can be detachably connected. For example, the lower and upper elements can be screwed together. The two elements can also be connected using other detachable fastening devices, such as pins or pegs with corresponding holes, or clamps.

[0025] Starting from the top, the upper element can comprise at least 1 / 4 of the workpiece carrier's height, and the lower element can extend from the bottom to at most the height of the upper element, in which at least part of the first positioning device is formed, e.g., in the form of a hole. The upper element can, for example, comprise at most 3 / 4 of the workpiece carrier's height, e.g., approximately half the workpiece carrier's height.

[0026] The second material can have at least one of the following two properties: Heat resistant up to 550 °C, hardness in the range of 45 to 68 HRC (Rockwell C hardness).

[0027] The second material can also be heat-resistant up to 1000 °C. The hardness of the second material can, for example, be in the range of 50 to 55 HRC. This material can be tool steel. For example, the entire lower element can be made of the same material as the first positioning devices in the mounting section that is critical for positional accuracy.

[0028] The first positioning device can essentially be a hole, and the retaining section of the hole can essentially be an annular portion of the inner wall of the hole. The retaining section can include at least one ring pressed or screwed into each hole.

[0029] In the case that the mounting section includes a pressed-in or screwed-in ring, the ring can, for example, be made of one material and the rest of the workpiece carrier of another. This other material can, for example, be suitable for manufacturing a workpiece on using a specific manufacturing process.

[0030] Second positioning devices can be present on the upper and lower elements and be designed to be complementary to each other in order to precisely position and align the upper and lower elements. The second positioning devices can comprise a set of at least two holes, with a first hole and at least one second hole, the second hole being an elongated hole such that a positioning bolt of the second positioning device inserted therein is displaceable in at least one direction to compensate for thermal expansion of the upper element relative to the lower element. The elongated hole can extend in a direction that essentially corresponds to the connection direction between the first and second holes.

[0031] The first positioning device can be a hole with a circular cross-section, wherein a second, eccentrically arranged recess is present in the workpiece carrier, or a hole with an elliptical, oval, or polygonal cross-section, such that the workpiece carrier, when arranged on the base carrier with at least one complementarily shaped positioning element, is not rotatable. In particular, the workpiece carrier should not be able to rotate parallel to its top and bottom surfaces relative to the base carrier. For this purpose, a polygonal cross-section of the first positioning device may be advantageous, for example.

[0032] The edge surfaces of the workpiece carrier between the underside and the top surface can be inclined, so that the workpiece carrier tapers from the underside to the top surface. These inclined edge surfaces prevent clumping of powdered building material due to compression caused by thermal expansion of the workpiece carrier. Furthermore, they prevent the formation of voids in powdered building material applied to the workpiece carrier. The inclination of the edge surfaces can be, for example, 1° to 11°, particularly 3° to 9°, and further, particularly 5° to 7°, and, for example, 6°.

[0033] At least one edge surface of the workpiece carrier can have at least one gripping element in the form of a groove or a rib. The gripping element can run from top to bottom, i.e., from the top to the bottom. The gripping element can be configured so that a gripping device can engage with it and be secured to it, in particular by friction and / or positive locking, in order to move the workpiece carrier.

[0034] The gripping element can be designed in the form of a groove with a dovetail-shaped cross-section. The side walls of the gripping element can each have an undercut of 10° to 40° and, in particular, of 15° to 20°.

[0035] The at least one positioning element can include a pin, and the at least one positioning device can include a hole, with the lower element being formed from the second material. The second material of the lower element can be tool steel.

[0036] According to a second aspect, an additive manufacturing device is provided according to a manufacturing process comprising layer-by-layer application of a powdered raw material, with a build platform and a support system according to the first aspect, wherein the build platform of the manufacturing device comprises the base support of the support system. The base support can, for example, be screwed onto a base plate, so that the base support forms part of the build platform of the manufacturing device.

[0037] The base support can comprise an arrangement of positioning elements, wherein the arrangement of positioning elements includes pins with a circular cross-section and additional anti-rotation pins. Alternatively, the pins can have an elliptical, oval, or polygonal cross-section, such that the workpiece carrier is not rotatable when positioned on the base support. In particular, the workpiece carrier cannot be rotated in directions parallel to the top and bottom surfaces of the workpiece carrier.

[0038] According to a third aspect, a method for manufacturing a workpiece is provided. The method comprises arranging the workpiece carrier of the carrier system according to the first aspect on the base carrier of the carrier system in an additive manufacturing device, wherein the at least one positioning element comprises a pin and the at least one positioning device comprises a hole, and wherein the pin engages in the hole.The process further comprises performing additive manufacturing of a workpiece on the workpiece carrier by the manufacturing device, wherein the temperature of the carrier system increases during the manufacturing process and a clamping effect occurs between the pin and the surrounding hole due to expansion of the pin section or the mounting section of the hole; cooling of the carrier system, whereby the clamping effect is released; detaching the workpiece carrier together with the workpiece manufactured on it from the base carrier; and arranging the workpiece carrier on a carrier of a system for subtractive post-processing of the workpiece, wherein a pin of the carrier engages in the hole of the workpiece carrier, for example, in a heat-treatment process. The material of the lower element of the workpiece carrier can be heat-resistant with respect to the heat generated by the system.The clamping effect described above between the hole of the workpiece carrier and a pin of a base carrier of the system can also be used for thermal post-processing.

[0039] The release step can include: gripping the workpiece carrier with a gripper on a gripping element located on an edge surface of the workpiece carrier. The gripping element could, for example, be a dovetail-shaped groove.

[0040] Several workpiece carriers can be arranged side by side, possibly with a gap, on the base of the manufacturing device. The arrangement can be configured, for example, so that an entire surface of the base is covered by workpiece carriers. In a manufacturing process, a workpiece can be produced on each of the workpiece carriers.

[0041] Further preferred designs are as follows: As described above, workpiece carriers can be characterized, according to the first aspect, by the fact that at least on the surface where a workpiece is produced by additive manufacturing, they consist of a material on which this is possible. In the simplest case, the surface consists essentially of the material used for manufacturing.

[0042] For mounting on a suitably equipped base plate in the manufacturing device, the workpiece carriers, as described in the first aspect, can have corresponding positioning devices, preferably holes, on their underside. This allows the workpiece carrier to be positioned on the base plate, which has positioning devices, preferably pins, that complement the positioning device.

[0043] In a preferred embodiment, a functionally essential part of the positioning devices on the workpiece carrier consists of a material that is heat-resistant (e.g., up to 500 °C) and / or hardenable or hardened. This allows the workpiece carrier and workpiece to undergo heat treatment or withstand the stresses caused by clamping during machining or material removal processes. Tool steel is a suitable material.

[0044] High-temperature strength means that sufficient mechanical properties, particularly strength, are still present at a given higher temperature (e.g., 500 °C or 900 °C) for the respective application. The 0.2% proof stress can be used as a parameter for high-temperature strength; that is, the stress that causes a reversible strain of 0.2%. A 0.2% proof stress of at least 10 MPa, preferably 20 MPa, or even higher, such as 30 MPa or 40 MPa, can be considered a limit for high-temperature strength.

[0045] The positioning devices can be inserts that are screwed or pressed into holes in the body of the workpiece carrier.

[0046] In a particularly preferred embodiment, an upper part (upper element) of a workpiece carrier consists of a material that is compatible with additive manufacturing, and a lower part (lower element) consists of a material chosen to be suitable for positioning purposes, preferably a tool steel.

[0047] For a uniform, dense, and void-free coating with powder used in additive manufacturing, the edges of the workpiece carriers are chamfered in a preferred embodiment, giving them the overall shape of a truncated pyramid. The upward taper, away from the base plate, results in a dense powder coating. With appropriately selected angles of the side surfaces, the further advantage arises that, in the event of dimensional changes due to temperature fluctuations, particularly expansion, the powder can shift upwards between adjacent workpiece carriers or between the workpiece carrier and the build cylinder.

[0048] One problem with the upwardly tapered shape of the workpiece carriers is that they can no longer be gripped by conventional grippers, as these cannot find purchase on the side walls or engage underneath the workpiece carriers. A preferred solution to this problem is to provide a gripping groove in the side wall with vertical or, better yet, slightly undercut side walls (dovetail groove). A gripper finds sufficient purchase in such a groove, especially in the version with undercut side walls, where a positive fit is possible.

[0049] The invention according to the aspects mentioned above will be further explained with reference to preferred embodiments and the figures.

[0050] They show: Figure 1: Isometric view of a build cylinder of an additive manufacturing system with workpiece carriers; Figure 2: Isometric view of a base carrier for the manufacturing system according to Figure 1Figure 3 Isometric view from below of three embodiments (3a, 3b, 3c) of workpiece carriers of the Figure 1 Figure 4: Top view of a workpiece carrier of a first embodiment of a carrier system; Figure 53: D-view of an "unfolded" workpiece carrier according to Figure 4 Figure 6: Section through an arrangement of the workpiece carrier according to Figure 5 on a base plate; Figure 7 Section through a workpiece carrier according to Figure 3c with a second embodiment of the positioning device; Figure 8 Isometric view from below of a workpiece carrier according to Figure 3c with a third embodiment of a positioning device; Figure 9 Enlarged view of workpiece carriers on a base plate with partial section through a positioning device according to Figure 8 Figure 10: Section through an arrangement of a workpiece carrier according to Figure 4 Cut and uncut on a base carrier with positioning pins.

[0051] Figure 1 Figure 1 schematically shows a view of a build cylinder 2 of an additive manufacturing machine with the build platform 4 that can be moved vertically within it. In particular, a laser melting process is to be considered here, in which the build platform is coated layer by layer with powder of the build material and in each newly applied layer the structures of the workpiece are created by melting the powder using a laser.

[0052] The building platform 4 includes a base support or base plate 6 (not visible here, see Figure 2The workpiece carrier 8 or pallets 8 are arranged on the workpiece carrier 8, ideally, as shown, such that the entire surface of the base carrier 6 is covered. To accommodate the size of the workpieces being produced, pallets 8 of various sizes are used, as one workpiece is typically produced per pallet. However, this does not preclude the presence of an unused pallet or the production of multiple workpieces on a single pallet. The base carrier 6, together with the pallets 8, forms a support system.

[0053] For positioning the pallets 8, the base carrier 6 has pins 10. On their underside 12, the pallets 8 have recesses 14 which, in cross-section, are complementary to the pins 10 at least along one circumferential line, so that the pins 10 slide into the recesses 14 with minimal resistance, but in any case with minimal to practically no play, thus holding the pallets 8 precisely in one position. The terms "recess" and "indentation" are used synonymously herein and have the same meaning within the scope of this disclosure. For the smallest pallets 16, which have only one recess 14, it is advantageous, not to say necessary, for automatic loading of the base carrier 6 to provide an anti-rotation device. In this case, it consists of a smaller anti-rotation recess 18 and corresponding anti-rotation pins 20 in the base carrier 6.

[0054] The anti-rotation measures can also generally be designed as eccentric projections and corresponding recesses in the underside of the pallets 8, as will be explained later. Alternatives include forming the pins 10 in a shape other than circular symmetry, e.g., with an oval, elliptical, or polygonal cross-section, or another measure that disrupts the circular symmetry, such as a radially projecting nose, or combinations of the aforementioned shapes.

[0055] The pallets 8 according to the present embodiment show, at least on their upper surface 11, a material on which a workpiece can be produced using additive manufacturing. This is therefore a material that is compatible with the respective building material. In the context of the production of workpieces from metallic powders, such a material is, for example, an aluminum alloy.

[0056] Another difficulty arises from the elevated temperatures that occur during the production process. For example, the base carrier 6 is heated to a temperature of, say, 200 °C. Furthermore, the melting of the building material, particularly in the initial phase near the surface 11, results in additional energy input, leading to a local temperature increase. These elevated temperatures cause thermal expansion effects. Nevertheless, at least the surface of the pallet must meet high dimensional accuracy requirements. Apart from dimensional changes in the xy-plane, i.e., parallel to the top surface 11 (see Figure 1 ), also warping, i.e. deviations from a perfectly flat surface with changing temperature, and displacements in the xy-plane due to play around the pins 10 are to be avoided or at least reduced to an acceptable level.

[0057] XY displacements are reduced by making the recesses 14, at least in the area crucial for positioning, from a material with a correspondingly low coefficient of thermal expansion. Tool steel is preferred, particularly heat-resistant tool steel, with a view to the subsequent transfer of the pallets 8 to a machining tool or to thermal post-treatment at high temperatures, such as hot isostatic pressing.

[0058] The Figure 4-6Figure 1 shows a first embodiment of the workpiece carrier 8 (pallet 8), which is provided in the form of a sandwich-like structure, wherein the pallet 8 is composed of an upper part 57 (hereinafter also referred to as "upper element 57") and a lower part 59 (hereinafter also referred to as "lower element 59"). The upper part 57 consists of the material required for additive manufacturing, i.e., a material on which a workpiece can be built up from the build material using the respective additive manufacturing process. The lower part 59, on the other hand, consists of a material of high strength and a different, in particular lower, coefficient of thermal expansion, as is also described below for the sockets 28 and 42 of the second and third embodiments. The upper part 57 and the lower part 59 are connected to each other in a suitable manner. Preferably, this is done in a detachable manner, e.g., as shown, by screws 61, which are preferably arranged symmetrically around the positioning recess 14.The screws 61 are screwed into corresponding blind holes 63 in the upper part 57.

[0059] In this design, it was observed that a lower temperature gradient occurs within the upper part 57, and consequently, there is a lower tendency for the formation of a convex upper surface. Another factor that counteracts convexity can be the lower part 59, which, as a rigid and temperature-stable element, prevents the formation of a concave bulge on the underside of the upper part 57. For precise relative positioning of the lower part 59 and upper part 57 during assembly, a first positioning bolt 65 is proposed in the lower part 59, which can be inserted into a precisely matching first positioning hole 67 in the upper part 57. Spaced apart from the positioning bolt 65, the lower part 59 has a second positioning bolt 69, which is designed for insertion into a second positioning hole 71.The positioning hole 71 has the special feature of being extended in the direction of the connecting line to the first positioning hole 67, i.e., it has an oval cross-section or is provided in the form of an elongated hole. This compensates for the different thermal expansion of the upper part 57 and lower part 59 when the pallet 8 is heated, without stressing the second positioning bolt 69. For larger pallets 8, it may be necessary to provide additional positioning bolts and holes, which are laterally offset from the connecting line between the first positioning bolt 65 and the second positioning bolt 69. For these, third positioning holes (not shown) are provided, which have a larger cross-section than the respective positioning bolts to allow displacement in any direction in the xy-plane.Likewise, the holes 63 for the screws 61 in the lower part 59 are designed with an interference fit compared to the shaft of the screws 61, so that the screw heads of the screws 61 and their shaft in the lower part 59 can shift according to the relative thermal expansion of the upper part 57.

[0060] A workpiece carrier 8 (pallet 8) of a second embodiment of a carrier system is shown. Figure 7The body 9 of the pallet 8 is made entirely of a material suitable as a substrate for additive manufacturing. The upper surface of the body 9 defines the surface of the pallet 8 on which the workpiece can be mounted. A cylindrical recess 32 is machined into the underside of the body 9, which internally carries a thread 26. A socket 28 made of tool steel, essentially in the form of a ring, is screwed into the thread 26. The socket 28 has an anti-rotation recess 30. In this case, there are two diametrically opposed anti-rotation recesses 30 in the socket 28, which serve to engage a screwdriver for screwing the socket 28 in and out.

[0061] The recess 32, which receives the socket 28, is bounded by a relatively thin cylindrical wall 36 surrounded by an expansion joint 38. The cylindrical wall 36, which also carries the thread 26 on its inner surface, is, if necessary, designed with a smaller diameter than the circumference of the socket 28 to compensate for any potentially greater thermal expansion of the material of the body 9 of the lower element compared to the material of the socket 28 under manufacturing conditions. In particular, the smaller diameter is chosen such that, at the highest temperature expected during additive manufacturing, the socket 28 is held securely and without play in the thread 26.

[0062] It should be noted that with this solution the socket 28 and the corresponding threads 26 in the pallet 8 for the socket must be manufactured with high precision, since the socket 28 and the anti-rotation recess 30 must be positioned precisely.

[0063] During machining operations, where higher forces act on the pallet 8, the socket 28 serves as an attachment point for the anchoring devices typically used there, e.g., pins with extendable balls or claws. It is also possible to remove the socket 28 for machining operations where it is an obstruction or cannot withstand the forces, e.g., hot isotactic pressing.

[0064] In the third embodiment according to Figure 8A socket 42 is pressed into the recess 44 in the pallet 8. The socket 42 has a lug 46 in which the anti-rotation recess 48 is located. Here, too, an expansion joint 50 is provided to reduce stresses that may arise due to differing coefficients of thermal expansion between the body of the pallet 8 and the socket 42. The wall 52 into which the socket 42 is pressed is designed such that it holds the socket 42 securely without play, even at the highest temperatures encountered, and even in the case of a greater thermal expansion of the pallet 8 body than of the socket 42.

[0065] As described in the second embodiment above, the socket 42 is made of heat-resistant tool steel and the body of the pallet 8 is made of a material suitable as a substrate for additive manufacturing (for example, aluminum or an aluminum alloy).

[0066] In this design, the position of the anti-rotation opening 48 is predetermined; however, precise vertical positioning (z-direction) must be ensured when pressing in the socket 42. To prevent this positioning from being lost even at the highest temperatures, a higher preload, i.e., a smaller dimension of the wall 52 compared to the socket 42, must be provided, which subjects the material to a higher stress.

[0067] Furthermore, regarding fastening during machining and removal, the explanations given above for version 28 apply.

[0068] Figure 10 shows a preferred embodiment of the pin 10. More precisely, shows Figure 10One embodiment, wherein a tool carrier 8 is mounted on a base carrier 6 by means of pins 10 and associated recesses 14. The workpiece carrier 8 can be one of the aforementioned embodiments, in particular a workpiece carrier of the first embodiment according to the Figure 4-6A pin cap 85 is attached to a pin base 81 by means of a screw 83. A ring 87 made of a material with a higher coefficient of thermal expansion than the lower element 59 of the workpiece carrier 8 of the first embodiment (as shown here) or the sockets 28 or 42 of the other embodiments is clamped between the pin base 81 and the pin cap 85. An aluminum alloy is preferred for this purpose. The ring 87 is arranged, in particular, such that it abuts precisely the sockets 28 or 42 or, as shown here, an annular collar 91 of the lower element 59. When a pallet 8 is placed on a base support 6, the pins 10 slide into the recesses 14 of the pallets with as little play as possible, but still with ease. When temperatures increase, the ring 87 expands more than the surrounding material, which holds the pallets (workpiece carriers) 8 to the base carrier 6 with increasing force.

[0069] As an alternative to the embodiment of the pin 10 described above, a material with a higher coefficient of thermal expansion can also be provided at the edges of the hole. In particular, a retaining section 28, 42, 91 of the hole (14) can be made of a material with a higher coefficient of thermal expansion than the material of a section of the pin 10. In the case of the first embodiment, this means that the collar 91 of the hole and, optionally, the entire lower element 59 are formed of the material with the higher coefficient of thermal expansion. In the case of the second and third embodiments, this means that the socket 28 and the socket 42, respectively, are formed of the material with the higher coefficient of thermal expansion. According to this alternative, when the support system is heated, the surrounding hole 14 expands in a negative radial direction towards the pin 10, thus achieving the desired clamping effect.

[0070] The collar 91 also serves to engage a holding device during subsequent machining steps, analogous to the sockets 28 and 42. If machining is unfavorable for the material of the lower part, such as excessively high temperatures, the lower part can be removed.

[0071] Especially in additive manufacturing processes, where powder is applied layer by layer over a surface, it is crucial to prevent the formation of voids or other irregularities in the layers. Therefore, the spaces between the pallets 8 and the wall of the build cylinder 2 must be filled uniformly with the build material powder. Another factor to consider is thermal expansion and contraction during the manufacturing process. As the pallets 8 expand, it must be ensured that the build material powder can escape from the spaces that shrink as a result of this expansion.On the other hand, even in the case of a reduction in the dimensions of the pallets, it must be ensured that the powder can fill the enlarging gaps in a manner more corresponding to the flow of a liquid, so that, at least after the application of a layer of powder and its smoothing, it is certain that no further displacements or movements in the powder occur, i.e., the system is stable.

[0072] To meet these requirements, a truncated pyramid shape for the pallets has proven suitable. The side walls of the pallets 8 in the exemplary embodiments are inclined, so that the pallets taper from the bottom 12 to the top 11. This creates a kind of funnel effect, which on the one hand allows the powder to escape when the gaps between the pallets or between the pallets and the cylinder wall decrease, and on the other hand ensures safe, resistance-free sliding in the event of an increase in these gaps.

[0073] From another perspective, undercuts or cavities should be avoided for the aforementioned reason. In particular, this eliminates gaps between the underside 12 of the pallets and the surface of the base support 6, which would allow a gripper to reach under a pallet. The beveled side walls 95 further complicate pallet handling. Therefore, a gripping groove 97 is provided on at least one side wall 95 to ensure a secure grip. Its side walls 98 are vertical, but preferably slightly undercut, so that the gripping groove 97 is dovetail-shaped and provides a hold for a suitable gripper. Due to the relatively small dimensions of the gripping grooves 97, their nearly vertical orientation, and the limited undercut required to achieve the dovetail shape, they do not pose a risk of uneven powder coating.

[0074] A particular feature of the processes involving the targeted melting of powdered material is that material is also removed from the surface of the substrate when the workpiece is removed. In the first embodiment, a further advantage in this respect is that the upper part 57 can be easily replaced. It is even conceivable that the upper part 57 could be made smaller, so that the gripping groove 97 is only present in the lower part 59 made of tool steel. This significantly simplifies the shape of the upper part 57, namely a truncated pyramid with straight, uninterrupted side walls.

[0075] In this respect, it is also conceivable to replace the loss of material from pallet 8 on the upper part 57 in another way, e.g. by an intermediate additive manufacturing step, with which the material loss is compensated for by growing new material.

[0076] In the embodiments described above, the base support 6 comprises at least one pin 10 and the workpiece carrier 8 comprises at least one hole 14. In alternative embodiments, however, the pin-hole pairs can also be arranged in reverse, so that the base support 6 has at least one hole and the workpiece carrier 8 has at least one corresponding pin. The clamping effect described above is also achieved in these embodiments in the manner described above. In all other aspects, these embodiments are identical to those described above. Furthermore, several pin-hole pairs can also be provided such that the base support 6 has both pins and holes, and that the workpiece carrier 8 has corresponding holes and pins.

[0077] In summary, the specified pallets (workpiece carriers) 8, together with the base carrier 6, form a carrier system that allows for the easy transport of a workpiece and its pallet between an additive manufacturing system and systems for other workpiece processing (machining, heat treatment, cleaning, measuring), particularly by means of a robot. This results in significant potential for streamlining processes. Through suitable pallet design, negative effects, such as those caused by thermal expansion or the risk of uneven powder coating, have been avoided. For example, in a process, a workpiece carrier 8 can be automatically transported from an additive manufacturing system (more precisely, from a base carrier 6 of the system) (e.g., a selective laser melting system) to a subtractive machining system for the manufactured workpiece.Optionally, in an intermediate step, the workpiece carrier 8 together with the workpiece can be positioned in a system for thermal post-processing.

[0078] With the carrier systems of the first to third embodiments described herein, a method for manufacturing a workpiece can be carried out, for example, as follows. First, the workpiece carrier 8 of the carrier system is arranged on the base carrier 6 of the carrier system in an additive manufacturing device according to one of the embodiments. Here, the pin 10 of the base carrier 6 engages in the hole 14 of the workpiece carrier 8, as shown in Figure 10The process is illustrated. Subsequently, an additive manufacturing process is carried out on the workpiece carrier 8 using the manufacturing device. Due to the process heat generated, the temperature of the carrier system increases during the manufacturing process. A clamping effect occurs between the pin 10 and the surrounding hole 14 due to the thermal expansion of section 87 of the pin 10, since the material of section 87 has a higher coefficient of thermal expansion than the material of the hole 14 of the workpiece carrier 8 surrounding section 87. Alternatively, a clamping effect occurs between the pin 10 and the surrounding hole 14 due to the expansion of the support section 28, 42, 91 of the hole 14, since, according to the alternative, the material of the support section 28, 42, 91 has a higher coefficient of thermal expansion than the material of at least section 87 of the pin 10.

[0079] After additive manufacturing, the carrier system cools down, releasing the clamping force. The workpiece carrier 8, along with the workpiece manufactured on it, is then detached from the base carrier 6 and transported to a subtractive post-processing system. The workpiece carrier 8 is positioned on a carrier within the subtractive post-processing system, with a pin 10 of the carrier engaging in the hole 14 of the workpiece carrier 8. Alternatively, the workpiece on the workpiece carrier 8 can undergo one or more intermediate processing steps between additive and subtractive manufacturing, such as thermal post-processing in a corresponding system, which—similar to the additive and subtractive manufacturing systems—also includes a base carrier with corresponding pins.

[0080] Examples of heat treatments suitable for additive manufacturing and corresponding pallet surfaces are given below: Aluminum alloy: Heat treatment in the range of approximately 200 °C to approximately 500 °C, preferably approximately 400 °C to approximately 540 °C. Titanium alloys: Heat treatment in the range of approximately 400 °C to approximately 995 °C (depending on the alloy type), preferably approximately 480 °C to approximately 730 °C.

[0081] The pallets 8 and the base carrier 6 are preferably characterized by the following numerical values: The angle of the side walls 95 is 1°–11°, preferably 3° to 9°, 5° to 7°, or approximately 6°. Larger angles, in particular, lead to a noticeable reduction in the area available for production. Smaller angles cause the powder to become blocked and generally render the process ineffective. Especially with an angle that is too small, the powder is trapped in gaps and no longer moves upwards when these gaps shrink due to thermal expansion. The height of the upper part 57 is ¼ to ¾ of the total height of a pallet. However, a height of at most half the height of the pallet is preferred. The side walls 98 of the gripping groove 97 are each inclined at 10° to 40°, preferably 10° to 20°, and more preferably 15° to 20°, relative to the bottom of the gripping groove 97; a preferred value is approximately 15°. The depth of the gripping grooves can range between 3 mm and 6 mm, with 4 mm being a preferred value. A minimum depth of 1 mm can be considered the absolute lower limit.Pallet height: 25 mm to 35 mm. Hardness of positioning parts (sockets 28, 42; base 59; possibly also base support 6): approx. 45 to approx. 68 HRC (Rockwell C hardness), preferably approx. 50 to approx. 55 HRC.

[0082] From the preceding description of exemplary embodiments, variations and additions are accessible to those skilled in the art without leaving the scope of protection of the invention as defined by the claims. These include, among others: The base carrier 6 can be provided with a circumferential rim, which in particular compensates for the gap between the build cylinder wall, which has rounded corners, and the sharp corners of the pallets, thus saving build material that would otherwise have to be used to fill the resulting relatively large gap between the side walls of the pallets and the build cylinder wall. The base carrier 6 is an integral part of the additive manufacturing system or is designed as an adapter plate and is attached to an existing build platform of the additive manufacturing system in a suitable manner. Both detachable and permanent connections are conceivable in this context. The anti-rotation measures can be omitted for pallets that have at least two positioning features (recesses 14). The pallet 8 has more than one gripping groove 97, e.g., on more than one side, preferably on opposite sides, or more than one groove 97 on one side.The latter can be advantageous for larger pallets. It is also conceivable to arrange gripping grooves at the corners of the pallets, that is, to equip at least one corner with a gripping groove. Instead of a gripping groove, the inverse measure is present, namely a rib that has a constant or decreasing width relative to the pallet body. In the second positioning devices, an elongated hole 71 has a length that is at most 0.4 mm greater than its width, and a hole with a larger diameter ("third positioning hole," in addition to or as an alternative to elongated hole 71) has a diameter that is at most 0.4 mm larger than the first (positioning) hole 67.

Claims

1. Support system for a manufacturing system, comprising: a base support (6) that is arranged to be secured in a process chamber of the manufacturing system and which comprises at least one positioning element; and a workpiece holder (8) on which a workpiece can be produced according to a manufacturing process including the layered application of a raw material in powder form, wherein the workpiece holder (8) has a lower side (12) and a building side as its upper side (11) which is located substantially opposite the lower side (12), on its lower side (12), the workpiece holder (8) has at least one first positioning device for its releasable, positionally accurate attachment to the base support (6) of the support system, the at least one positioning element (10) and the at least one first positioning device (14) are designed in a complementary manner and form a pin / hole pair comprising a pin and a hole, at least one section (87) of the pin is made of a first material having a first thermal expansion coefficient, characterized in that the hole is made of a second material having a second thermal expansion coefficient in a retaining section (28, 42, 91) that is decisive for the positioning accuracy, and wherein the second thermal expansion coefficient is lower than the first thermal expansion coefficient such that a clamping effect results between the pin and the surrounding hole in the event of a temperature increase of the support system during the manufacturing process due to the expansion of the section (87) of the pin, or wherein the first thermal expansion coefficient is lower than the second thermal expansion coefficient such that a clamping effect results between the pin and the surrounding hole in the event of a temperature increase of the support system during the manufacturing process due to the expansion of the retaining section (28, 42, 91) of the hole.

2. Workpiece holder (8) in a support system according to claim 1, wherein a workpiece can be produced on the workpiece holder according to an additive manufacturing process including the layered application of a raw material in powder form, the workpiece holder (8) has a lower side (12) and a building side as its upper side (11) which is located substantially opposite the lower side (12), on its lower side (12), the workpiece holder (8) has at least one of the first positioning devices (14) for its releasable, positionally accurate attachment to the base support (6) of the manufacturing device, and the workpiece holder (8) comprises a plate-shaped upper element (57) and a plate-shaped lower element (59), the upper element comprises the upper side (11) and the lower element (59) comprises the lower side (12), and the upper element (57) is made of a different material than the lower element (59).

3. Workpiece holder according to claim 2, wherein the lower element (59) and the upper element (57) are detachably connected to each other and optionally screwed to each other.

4. Workpiece holder (8) according to one of claims 2 to 3, wherein starting from the upper side (11), at least 1 / 4 of the height of the workpiece holder (8) forms the upper element (57), and starting from the lower side (12) up to the upper element (57) at most, the lower element (59) extends, in which at least part of the first positioning device (14) is provided in the form of a hole.

5. Workpiece holder (8) according to one of claims 2 to 4, wherein the second material exhibits at least one of the following two properties: - heat resistant up to 550 °C, - hardness in the range of 45 to 68 HRC (Rockwell hardness C).

6. Workpiece holder (8) according to one of claims 2 to 5, wherein second positioning devices (67, 71, 65, 69) are provided on the upper element (57) and on the lower element (59) and have a mutually complementary configuration in order to be able to fasten the upper element (57) and the lower element (59) to each other in a positionally accurate manner, and the second positioning devices (67, 71, 65, 69) comprise a set of at least two holes (67, 71) including a first hole (67) and at least one second hole (71), the second hole being shaped as an oblong hole so that a positioning bolt (71) of the second positioning devices inserted therein is displaceable in at least one direction in order to compensate for a thermal dimensional change of the upper element (57) relative to the lower element (59).

7. Workpiece holder (8) according to one of claims 2 to 6, wherein the first positioning device is substantially a hole (14), the retaining section (28, 42, 91) of the hole substantially represents an annular portion of the inner wall of the hole and optionally comprises at least one ring (28, 42) per hole that is pressed in or screwed in.

8. Workpiece holder (8) according to claim 7, wherein the first positioning device is substantially a hole (14) and has a circular cross-section, and a second recess (18) that is arranged eccentrically to the hole (14) is provided in the workpiece holder (8), or the hole (14) has an elliptical, oval, or polygonal cross-section so that the workpiece holder (8), when placed on the base support (6) with at least one positioning element (10) of a complementary configuration, is rotationally locked.

9. Workpiece holder according to claim 8, wherein the lower element (59) is made of the second material.

10. Workpiece holder (8) according to one of claims 2 to 9, wherein lateral surfaces (95) of the workpiece holder (8) between the lower side (12) and the upper side (11) are inclined so that the workpiece holder (8) tapers from the lower side (12) to the upper side (11).

11. Workpiece holder (8) according to one of claims 2 to 10, wherein at least one lateral surface of the workpiece holder (8) has at least one gripping means in the form of a groove or a ridge, preferably in the form of a groove having a dovetail cross-section.

12. Manufacturing device of the additive kind using a manufacturing process including the layered application of a raw material in powder form comprising a building stage and a support system according to one of claims 1 to 11, wherein the building stage of the manufacturing device comprises the base support (6) of the support system.

13. Manufacturing device according to claim 12, wherein the base support (6) comprises an arrangement of positioning elements, wherein the arrangement of positioning elements includes the pins (10) and wherein at least one, preferably all of the pins (10) have either a circular cross-section and additionally each at least one rotational locking pin (20) or an elliptical, oval, or polygonal cross-section so that the workpiece holder (8), when placed on the base support (6), is rotationally locked.

14. Method for producing a workpiece, comprising: placing the workpiece holder (8) of the support system according to one of claims 1 to 11 on the base support (6) of the support system in a manufacturing device of the additive kind, wherein the at least one positioning element (10) and the at least one positioning device (14) are designed in a complementary manner and form a pin / hole pair comprising a pin and a hole and wherein the pin engages in the hole; carrying out an additive manufacture of a workpiece on the workpiece holder (8) by means of the manufacturing device, the temperature of the support system increasing during the manufacturing process and a clamping effect resulting between the pin and the surrounding hole due to the expansion of the section (87) of the pin or due to the expansion of the retaining section (28, 42, 91) of the hole; cooling the support system, whereby the clamping effect is released again; disengaging the workpiece holder (8) together with the workpiece produced thereon from the base support (6), preferably by means of a gripper, by gripping the workpiece holder (8) at a gripping means (97) arranged on a lateral surface of the workpiece holder (8); optionally arranging the workpiece holder (8) on a support of an installation for thermal post-processing of the workpiece; and arranging the workpiece holder (8) on a support of an installation for the subtractive post-processing of the workpiece wherein a positioning element (10) of the support and the positioning device (14) of the workpiece holder (8) engage in each other.

15. Method according to claim 14, wherein a plurality of workpiece holders (8) is arranged side by side on the base support (6) of the manufacturing device.