WORKPALLET AND MACHINING SYSTEM

Description

[0001] The invention relates to a workpiece pallet for use in additive and subtractive workpiece machining. Furthermore, the invention relates to a machining system in which the workpiece pallet according to the invention is used.

[0002] From DE 10 2013 224 649 A1, a machine tool is known which comprises a machine control, a machine frame, a workpiece table, a tool holder, several translational and / or rotary axes for adjusting a relative position between the workpiece table and the tool holder, a tool magazine for one or more material-removing, in particular chip-removing, tools, a tool changing mechanism for automatically moving tools between the tool holder and the tool magazine, a welding head that can be inserted into the tool holder, and which has a workpiece temperature control device that is inserted between a workpiece table and a workpiece during workpiece production during welding and which includes a heater, wherein an insulating layer for thermal insulation of the heater from the workpiece table and optionally also a cooling device may be provided.the heating system is designed to heat the workpiece to temperatures exceeding 250 degrees Celsius.

[0003] DE 10 2017 114 812 A1 discloses a workpiece transport pallet with a storage surface on which a workpiece is placed and with a clamping mechanism that secures the workpiece. The clamping mechanism comprises a first and second claw that can be opened and closed, a pre-tensioning element that pre-tensions the first and second claws in the closing direction, and a movement-limiting element that releasably engages the first and second claws when they are open. FR 2 700 487 A1 discloses a pallet for transporting parts, with a carrier plate having an inner suction chamber and holes formed on an upper surface of the carrier plate that communicate with the inner chamber. The pallet includes interchangeable and removable parts that can be inserted into the holes.These parts include suction cups to ensure a grip on the top of the plate. Valves close the holes not occupied by the suction cups and positioning parts.

[0004] EP 0 087 719 A2 discloses a combined machine tool comprising a first machine tool with a rotary table and a vertically and horizontally movable cutting tool in the front part of the combined machine tool and a second machine tool in the rear part of the combined machine tool, as well as a pair of vertical columns between the first and the second machine tool, wherein the vertical columns are arranged at a predetermined distance from each other by means of a strut connected at their ends to the vertical columns, and wherein crossbeams supporting the supports of the first and second machine tools are slidably attached to opposite surfaces of the vertical columns, and a pallet transfer device for transporting a sequence of pallets with workpieces arranged on them between the first and second machine tools and between the vertical columns.wherein the pallet transfer device has an intermediate table fixedly connected to the strut, as well as actuating rods arranged horizontally between the intermediate table and the inner surfaces of the vertical uprights, movable along the axis of the combined machine tool, rotatable coupling hooks arranged at the front ends of the actuating rods, which can be engaged and disengaged with sleeve elements attached to both sides of the pallets, as well as drive means for advancing and retracting the actuating rods, wherein the engagement between the coupling hooks and the sleeve elements on the pallet and the subsequent retraction movement of the actuating rods effect the transport of the pallet with the workpiece from the rotary table of the first machine tool to the rotary indexing table of the second machine tool via the intermediate table, wherein the surfaces of the rotary table,The intermediate table and the rotary indexing table are essentially at the same height.

[0005] EP 0 614 725 A2 discloses a device for position-defined clamping of a workpiece at the workstation of a machine tool, comprising a base to be fixed at the workstation of the machine tool and a workpiece carrier that can be placed on the base and clamped to it, further comprising alignment elements on the base and on the workpiece carrier which cooperate in pairs and align the workpiece carrier in three mutually perpendicular coordinate axes and at right angles to the base, and a clamping device whose clamping force holds the tool carrier in the position on the base determined by the alignment elements, wherein the alignment element pairs for determining the position in a coordinate axis parallel to the line of action of the clamping force are opposing stop surfaces on the base and on the workpiece carrier.While for determining the position in the other two coordinate axes, two pairs of linear alignment elements are provided separately for each coordinate axis, each pair having a wedge-shaped centering ruler and a counterpart with a matching centering slot, and wherein the clamping device comprises several clamping elements, each having a clamping pin arranged on the workpiece carrier and a chuck arranged on the base, characterized in that the workpiece carrier has a continuously flat surface on the side facing the base in the clamped state, which forms the stop surfaces on this side in certain areas and on which the linear alignment elements on this side for determining the coordinate axes as well as the clamping pins of the clamping elements are attached.

[0006] The object of the invention is to provide a workpiece pallet and a machining system with which an improved workflow can be achieved when carrying out combined application processes (additive workpiece machining) and removal processes (subtractive workpiece machining).

[0007] The object of the invention is achieved for a workpiece pallet of the type mentioned at the outset with the features of claim 1. Here, the workpiece pallet comprises a clamping plate, which includes a first interface designed for positive locking on a machining table of a machine tool, and a receiving plate for securing a workpiece, which includes a second interface for securing a workpiece, wherein the clamping plate and the receiving plate are spaced apart from each other, and wherein a support web is arranged in a connecting gap between a top surface of the clamping plate and a bottom surface of the receiving plate, the support web being connected to the top surface of the clamping plate and to the bottom surface of the receiving plate, wherein the support web has a cross-sectional area in a cross-sectional plane oriented parallel to the bottom surface of the receiving plate, which is less than 15 percent, preferably less than 10 percent.particularly preferably less than 5 percent, in particular less than 1 percent, of the area of ​​the underside of the receiving plate, wherein the receiving plate is assigned at least one heating device designed for temperature control of the receiving plate.

[0008] Preferably, the clamping plate, which is designed to secure the workpiece pallet to a machining table of a machine tool, is designed at least substantially as a plane-parallel plate. When the clamping plate is designed as a plane-parallel plate, it can be assumed that the two largest surfaces of the clamping plate lie in planes that are aligned parallel to each other, whereby the two largest surfaces do not necessarily have to be completely flat. With such a design of the clamping plate, an underside of the clamping plate facing away from the receiving plate rests flat on the typically flat surface of the machining table and can thus ensure advantageous force transmission between the workpiece pallet and the machining table.Furthermore, the upper surface of the clamping plate faces the mounting plate and is connected to the support web, in particular integrally. The first material thickness of the clamping plate corresponds to the distance between the two largest surfaces, i.e., the underside and the top, of the clamping plate.

[0009] Furthermore, the receiving plate, whose upper surface facing away from the clamping plate can be used to hold a workpiece, can be designed at least substantially as a plane-parallel plate, whereby the workpiece can, for example, be screwed directly to the upper surface or secured to the surface of the receiving plate using clamping elements such as manually operated clamping jaws. Furthermore, the underside of the receiving plate faces the clamping plate and is connected to the support web, in particular integrally. A second material thickness of the receiving plate corresponds to the distance between the two largest surfaces, i.e., the underside and the upper surface, of the receiving plate.

[0010] To achieve a favorable compromise between a robust mechanical coupling of the clamping plate and the receiving plate and thermal decoupling of the clamping plate from the receiving plate, the clamping plate and the receiving plate are spaced apart from each other and connected by a support web. The support web is located in a connecting gap between the clamping plate and the receiving plate and is mechanically connected to both a top surface of the clamping plate facing the receiving plate and a bottom surface of the receiving plate facing the clamping plate. Preferably, the largest surfaces of the support web are oriented transversely to the top surface of the clamping plate and transversely to the bottom surface of the receiving plate.Furthermore, it is preferably provided that a cross-sectional area of ​​the support web in a cross-sectional plane that is aligned parallel to the underside of the receiving plate is less than 15 percent, preferably less than 10 percent, particularly preferably less than 5 percent, and in particular less than 1 percent, of the area of ​​the underside of the receiving plate.

[0011] The surface area of ​​the underside of the mounting plate is, for example, the total surface area of ​​the mounting plate facing the clamping plate. Preferably, the surface area of ​​the underside of the mounting plate is the area that can be determined by projecting the underside of the mounting plate onto the cross-sectional plane in which the surface area of ​​the support web is also determined. Determining the surface area of ​​the underside of the mounting plate by projecting it onto the cross-sectional plane is particularly useful when the surface of the underside of the mounting plate is uneven, for example, comprising several surface sections arranged in different planes.

[0012] The design of the support rib described above ensures low thermal coupling between the clamping plate and the holding plate, so that heating of the holding plate and the workpiece mounted on it only leads to minimal heating of the clamping plate. This ensures that even when the holding plate is heated, the workpiece pallet has no positional tolerances relative to the machining table that would compromise the precise machining of the workpiece on the pallet.

[0013] Furthermore, it is preferably provided that a gap between the top of the clamping plate and the bottom of the receiving plate, which can also be referred to as the gap width of the connection gap between the clamping plate and the receiving plate, corresponds at least to the first material thickness of the clamping plate and / or the second material thickness of the receiving plate. Particularly preferably, the gap width of the connection gap is 1.5 to 3 times the first material thickness and / or the second material thickness.

[0014] It is advantageous if the clamping plate is made of a first metal material with a first coefficient of thermal expansion, and if the receiving plate is made of a second metal material with a second coefficient of thermal expansion, wherein the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion and wherein the second coefficient of thermal expansion is less than 16 / 1000000 [1 / K]. This measure is intended to minimize distortion of the workpiece pallet, which could lead to a shape deviation of the workpiece pallet and a positional deviation of the workpiece held on the workpiece pallet resulting from the shape deviation. It is provided that the receiving plate is heated to temperatures in the range of 300 degrees Celsius to 550 degrees Celsius, preferably to a temperature of 400 degrees Celsius, for machining the workpiece held on it.Due to the spacing of the clamping plate from the mounting plate, which is achieved through the mechanical connection and the extensive thermal decoupling by means of the support web, the clamping plate heats up significantly less, for example to temperatures in an interval of 50 degrees Celsius to 150 degrees Celsius.

[0015] If the same metal material is selected for the clamping plate and the receiving plate, significant differences in thermal expansion would occur within the workpiece pallet due to the large temperature differences between the clamping plate and the receiving plate. This would lead to significant internal stresses in the clamping plate and the receiving plate, and especially in the support web, to significant internal stresses and resulting elastic or possibly plastic deformations of the workpiece pallet.

[0016] If, however, different metal materials are chosen for the clamping plate and the mounting plate, with the first coefficient of thermal expansion of the clamping plate being greater than the second coefficient of thermal expansion of the mounting plate, then, with suitable material selection, only minor internal stresses will result in the clamping plate, the mounting plate, and the support web, despite the temperature difference of approximately 200°C to 400°C between the clamping plate and the mounting plate. This prevents undesirable elastic or, if applicable, plastic deformation of the workpiece pallet, especially of the support web.

[0017] It is preferably provided that the support web together with the clamping plate and the receiving plate defines at least one, in particular enclosed, cavity and / or that the support web is made of a metal material that has a specific thermal conductivity of less than 30 W / mK, in particular less than 20 W / mK, and / or a coefficient of thermal expansion of less than 16 / 1000000 [1 / K], in particular less than 14 / 1000000 [1 / K].

[0018] By way of example, it may be provided that the clamping plate has a coefficient of thermal expansion in an interval between 16 / 1000000 [1 / K] and 18 / 1000000 [1 / K].

[0019] Preferably, the support web is arranged in the connecting gap between the clamping plate and the receiving plate such that it runs close to the edge regions of both plates. Preferably, the clamping plate and the receiving plate have at least substantially the same cross-section, for example, circular, square, or rectangular, in a cross-sectional plane that is oriented transversely to a distance between the clamping plate and the receiving plate and parallel to the largest surfaces of the clamping plate and the receiving plate. Furthermore, it is preferably provided that the support web extends at least partially, and in particular completely, along a circumferential outer edge of the clamping plate or the receiving plate.The resulting cavity, formed by the top of the clamping plate, the bottom of the receiving plate, and the largest inward-facing surface of the support web, thus corresponds at least almost completely to the connection gap. It is particularly preferred that the cavity be sealed, as this allows for favorable control of heat transfer between the significantly warmer receiving plate and the comparatively cooler clamping plate.

[0020] This applies in particular if at least one insulating material from the group consisting of gas, liquid, and solid is contained in the cavity and / or if the cavity is evacuated. Preferably, the cavity is filled with a solid that has advantageous thermal insulation properties. Materials such as glass fiber mats or ceramic fiber mats can be used for this purpose, for example. Additionally or alternatively, the cavity can be evacuated to minimize the transfer of radiant heat from the receiving plate to the clamping plate via air or other gases contained in the cavity.

[0021] Furthermore, heat transfer between the mounting plate and the clamping plate is limited by a suitable material selection for the support web. Preferably, the specific thermal conductivity of the material from which the support web is made is less than 30 W / mK, and in particular less than 20 W / mK.

[0022] Additionally or alternatively, the support web may be made of a metal material with a coefficient of thermal expansion of less than 16 / 1,000,000 [1 / K], in particular less than 14 / 1,000,000 [1 / K]. This ensures low thermal expansion of the support web and low heat transfer through the support web from the mounting plate to the clamping plate.

[0023] In a further embodiment of the invention, a pressure relief valve is provided on the clamping plate, the receiving plate, or the support bracket. This valve is designed to create a predefined, fluidically communicating connection between the cavity and the surrounding environment of the workpiece pallet, thereby limiting any differential pressure between the cavity and the environment. A pressure relief valve is necessary to prevent pressure differences between the cavity and the surrounding environment of the workpiece pallet, as otherwise undesirable fluid expansion, particularly gas expansion, could occur during use of the workpiece pallet due to the intended heating of the receiving plate.Preferably, the compensating valve is designed such that it allows a fluid, in particular a gas, to flow out of the cavity or ambient air to flow into the cavity both when there is overpressure in the cavity, which has a predefinable pressure difference relative to the surroundings, and when there is underpressure, which has a predefinable pressure difference relative to the surroundings. In a simplified design, the compensating valve is configured as a pressure relief valve that allows a fluid, in particular a gas, to flow out of the cavity when there is overpressure in the cavity, which has a predefinable pressure difference relative to the surroundings. By way of example, the compensating valve in this case can be designed as a spring-loaded check valve.

[0024] It is advantageous if the support web is formed integrally with the mounting plate and projects from an underside of the mounting plate facing the clamping plate towards the clamping plate, and is fixed to an upper side of the clamping plate facing the clamping plate by fasteners. This ensures a reliable mechanical connection between the support web and the mounting plate. It should be taken into account that the mounting plate, when the workpiece pallet is used, is heated to a temperature between 300°C and 550°C, preferably to 400°C, and that considerable thermal expansion occurs as a result.The one-piece design of the support web and the mounting plate allows for a homogeneous force flow and temperature distribution between the support web and the underside of the mounting plate, which would be impossible or very difficult to achieve with screw fastening of the support web to the underside of the mounting plate. Furthermore, the one-piece design of the support web and the mounting plate avoids critical problems that could occur with screw fastening of the support web to the underside of the mounting plate, such as unintentional loosening of screw connections and / or overloading of the screw connections. Preferably, an end section of the support web facing away from the mounting plate is fastened to the mounting plate on its upper side, which faces the mounting plate.For example, this end section of the support rib can be attached laterally to a circumferential edge surface of the clamping plate, for example with screw fixings. In an alternative design of the workpiece pallet, the support rib is formed with both the receiving plate and the clamping plate.

[0025] Such a workpiece pallet can be produced, in particular, using a generative / additive machining process such as the cold gas spraying described in DE 10 2007 017 759 A1. This process also allows for the use of different materials for the clamping plate and the receiving plate. Additionally, the support web can be designed to have a material gradient between the clamping plate (made of a first material) and the receiving plate (made of a second material), thus incorporating a change in alloy composition between the two materials. This gradient facilitates a particularly advantageous adaptation to the coefficients of thermal expansion of the clamping plate and the receiving plate.

[0026] Preferably, the support web is designed as a circular ring extending along a distance axis between the clamping plate and the receiving plate, and has a fastening area that is designed as a ring collar extending radially, particularly outwards, and which is penetrated by the fastening elements arranged on the top of the clamping plate. This allows for a homogeneous stress distribution in the support web when using the workpiece pallet. Preferably, a large surface area of ​​the clamping plate and / or the receiving plate is circular. Furthermore, the annular support web can be arranged coaxially with the clamping plate and / or receiving plate, which is preferably cylindrical. The fastening area allows the support web, which is preferably integrally molded onto the receiving plate, to be fixed to the top of the clamping plate.For this purpose, the fastening area preferably extends radially outwards from a circular cylindrical outer surface of the support web. Preferably, the fastening area, designed as an annular collar, is provided with recesses that can be used to receive screws with which the fastening area can be fixed to the top of the clamping plate.

[0027] It is advantageous if a support ring is arranged coaxially to the support web in the connection gap, and is connected, particularly sealingly, to the top of the clamping plate and the underside of the receiving plate. The support ring has a smaller diameter than the annular support web and is arranged coaxially to the support web. Preferably, an inner surface of the support web and an outer surface of the support ring, together with the top of the clamping plate and the underside of the receiving plate, define the annular connection gap in this case.For example, the support ring can be used to accommodate a connector designed for electrically coupling the workpiece pallet to a suitably equipped machining table of a machine tool, in order to supply electrical power to the workpiece pallet and / or transmit electrical sensor signals from the workpiece pallet to the machine tool. In this case, the support ring can serve both as a support for the connector and as a protective bushing for electrical supply cables and / or sensor cables.Since the support ring has a smaller diameter than the annular support web, and the material thickness of the support web is at most equal to, but preferably less than, the material thickness of the support ring, the support ring ultimately exhibits a similar mechanical stiffness to the support web, thus largely preventing inhomogeneous deformation within the workpiece pallet. Preferably, the cross-sectional area of ​​the support ring in the plane perpendicular to the distance between the mounting plate and the clamping plate is less than 30 percent, preferably less than 10 percent, and particularly preferably less than 5 percent, of the cross-sectional area of ​​the support web.

[0028] According to the invention, at least one heating device is assigned to the receiving plate, which is designed for temperature control of the receiving plate. The heating device, which may in particular be an arrangement of several electric resistance heaters arranged in suitable recesses in the receiving plate, allows for targeted temperature control of the receiving plate. Preferably, in addition to the at least one heating device, at least one sensor device, in particular a temperature sensor, is assigned to the receiving plate, with the aid of which the temperature of the receiving plate can be determined and converted into an electrical sensor signal. It is particularly preferred that the workpiece pallet with the heating device and the optionally provided sensor device arranged thereon is electrically connected to a control device.The control unit can, for example, be assigned to the processing machine and enables the supply of electrical current to the heating device. For instance, the control unit is designed to regulate the temperature of the mounting plate via a temperature-dependent current supply based on the sensor signal from the sensor device.

[0029] In a further embodiment of the invention, the first interface comprises at least two locking pins projecting from the underside of the clamping plate, which forms a reference plane and faces away from the receiving plate. The longitudinal axes of these locking pins, aligned parallel to each other and perpendicular to the reference plane, define a mounting direction for the receiving plate. Each of the at least two locking pins has at least one undercut with respect to its longitudinal axes. The locking pins, which are designed to engage in suitable locking mechanisms in the machining table, enable rapid and precise reproducible clamping of the workpiece pallet to the machining table. The respective undercut serves to positively lock the locking pins to the machining table, which may be equipped with position-adjustable locking devices for this purpose.

[0030] In an advantageous embodiment of the invention, an electromechanical connector is arranged on the underside of the clamping plate, which is designed for a plug connection with a plugging movement aligned parallel to the mounting direction and for an electrical coupling between a plug receptacle arranged on a processing table of a machine tool and at least one electrical consumer assigned to the workpiece pallet and / or at least one sensor device assigned to the workpiece pallet.

[0031] It is advantageous if the connector is at least partially received in a recess of the clamping plate, with the recess being bordered by the support rib.

[0032] Preferably, the material thickness of the clamping plate differs from that of the second material thickness of the receiving plate by less than 30 percent, preferably less than 20 percent, and particularly less than 10 percent. This, in combination with the different coefficients of thermal expansion of the clamping plate and the receiving plate, allows for the lowest possible level of internal mechanical stresses in the workpiece pallet.

[0033] The object of the invention is achieved according to a second aspect of the invention with a machining system for workpiece machining, which comprises a workpiece pallet according to the invention and a machining machine with a machine bed, a machining table attached to the machine bed and an application head arranged on the machine bed, wherein the machine bed is assigned an adjusting device for a relative movement between the machining table and the application head, wherein the application head is designed for the discharge of a particle stream of metallic particles in the direction of the machining table, wherein the machining table has an interface receptacle for receiving and fixing locking pins and a plug-in receptacle for receiving the workpiece pallet which can be fixed on the machining table.

[0034] The machining center is designed for additive workpiece processing, for example using the MPA process (Metal Powder Deposition Process) developed by Hermle Maschinenbau GmbH or a laser-based deposition process such as laser sintering.

[0035] The machine tool comprises a machine bed, also referred to as a machine frame, and a worktable attached to the machine bed, which is in particular adjustable. Furthermore, a dispensing head is associated with the machine bed, designed to apply material to a workpiece. Finally, an actuating device for relative movement between the worktable and the dispensing head is provided, which may, for example, include one or more electromechanical or hydraulic linear actuators.

[0036] The machining table includes an interface mount for receiving and securing locking pins of a workpiece pallet. Furthermore, the machining table may include a plug mount for receiving a connector belonging to the workpiece pallet, enabling electrical coupling between the machining center and the workpiece pallet.

[0037] It is advantageous if a machining head for the machining of a workpiece that can be fixed on the workpiece pallet, in particular a milling head or a milling-turning head, is assigned to the machine bed and that the positioning device is designed for a relative movement between the machining table and the machining head and / or that, in addition to the machine tool, a heating chamber is provided which is designed for the temporary holding of the workpiece pallet during a heating process.

[0038] Preferably, in addition to the machine tool, a machining center is provided, comprising at least one machining head for machining a workpiece that can be fixed on the workpiece pallet, in particular a milling head, and a machining table of the machining center comprising an interface receptacle for receiving and fixing locking pins and a plug-in receptacle for receiving a workpiece pallet according to the invention. By way of example, it can be provided that one or more workpiece pallets are exchanged between the machine tool and the machining center by means of an automated handling device (workpiece changer), in particular an industrial robot, for an alternating sequence of machining steps and machining steps.It is advantageous that both the machining table of the machine tool and the machining table of the machining center, which may in particular be a milling-turning center, have the same interface fixtures, with which a quick fixing or release of the respective workpiece pallet on the respective machining table can be achieved with high repeatability.

[0039] An advantageous embodiment of the invention is shown in the drawing. Here, the drawing shows: Figure 1 is a purely schematic representation of a machining system for additive and subtractive workpiece machining with a machine bed, a machining table, a build-up head, a removal head, a workpiece pallet, and a workpiece. Figure 2 is a sectional view of the workpiece pallet according to the Figure 1 , and Figure 3, a sectional view of the machining table according to the Figure 1 .

[0040] One in the Figure 1 The purely schematically depicted machining system 1 is designed purely as an example for carrying out additive and subtractive workpiece machining. By way of example, the machining system is a machining center designed for performing milling operations (subtractive workpiece machining), turning operations (subtractive workpiece machining), and the MPA process developed by Hermle Maschinenbau GmbH (additive workpiece machining), whereby the present invention can also be used for other machining processes, in particular other additive manufacturing processes.

[0041] By way of example, the machining system 1 comprises a machine bed 2 upon which a machine housing 3 is mounted. The machine housing 3 defines a spatial volume, shown only schematically, within which the machining operations that can be performed with the machining system 1 are carried out. For example, a machining table 4, a coating head 5, and a removal head 6 are arranged on the machine bed 2. In a variant of the machining system, not shown in detail, the coating head is combined with the removal head, or the coating head and the removal head are arranged in separate machining units.

[0042] By way of example, it is provided that the processing table 4, the application head 5, and the removal head 6 are each assigned positioning devices, in particular electromechanical actuators, which are not shown in detail. Thus, the application head 5 and the removal head 6 can each be moved relative to the machine bed 2 in at least two mutually perpendicular spatial directions. Furthermore, it can be provided, for example, that the application head 5 and the removal head 6 can also be moved perpendicular to the plane of representation in a manner not shown in detail. Figure 1 The machining table 4 can be rotated relative to the machine bed 2 in two spatial directions. In particular, the machining table 4 can be rotated about the central axis 11 of the workpiece pallet 7 to enable turning operations.

[0043] On the purely exemplary plate-shaped processing table 4, a workpiece pallet 7 is arranged, which is shown in Figures 2 and 3 the fastening means (bolt pins 62, 63; bolt elements 71, 72) shown in more detail are fixed to the machining table 4 and which in turn carries a workpiece 8 which is to be machined with the aid of the application head 5 and the removal head 6.

[0044] Machining of the workpiece 8 with the removal head 6, which can be, for example, a milling head for carrying out milling operations on the workpiece 8, is possible at a workpiece temperature of 20 degrees Celsius, but can also be carried out at other, especially higher, workpiece temperatures.

[0045] In contrast, additive machining of workpieces involves a significantly higher workpiece temperature. This is because, for example, the MPA process requires heating the workpiece 8 to a temperature between approximately 350 and 450 degrees Celsius. This heating is achieved by partially heating the workpiece pallet 7. The heat radiated from both the partially heated workpiece pallet 7 and the heated workpiece 8 results in at least some heating of the volume enclosed by the machine housing 3.

[0046] To minimize the heating of the other components of the machining system 1, measures must be taken to limit, for example, heat transfer from the workpiece pallet 7. For this purpose, the workpiece pallet 7 is configured as described in more detail below. Furthermore, it can be provided that heat radiated from the workpiece pallet 7 and the workpiece 8 into the machine housing 3 is dissipated from the machine housing 3 in a suitable manner, for example, by means of air circulation with intermediate cooling.

[0047] As can already be seen from the purely schematic representation of the Figure 1The workpiece pallet 7 comprises a clamping plate 15 made of a first metal material, in particular steel, a receiving plate 16 made of a second metal material, in particular steel, arranged at a distance from the clamping plate 15, and a support web 17 extending between the clamping plate 15 and the receiving plate 16.

[0048] As an example, the clamping plate 15, with its underside 20 shown in more detail in Figure 2, rests on the substantially flat surface 9 of the machining table 4. The substantially flat underside 20 forms a first interface with the workpiece pallet 7.

[0049] Furthermore, the support web 17 can extend between a top surface 21 of the clamping plate 15 and a bottom surface 22 of the receiving plate 16. In addition, it is provided that the workpiece 8 is secured on a purely exemplary, flat top surface 23 of the receiving plate 16, serving as the second interface of the workpiece pallet 7, for example by clamping jaws 10.

[0050] As can be seen from the purely schematic and non-scale representation of Figure 2, the support rib 17 is formed integrally with the receiving plate 16 and extends from the underside 22 of the receiving plate 16 along a central axis 11 of the workpiece pallet 7 towards the top side 21 of the clamping plate 15. The support rib 17 is, purely by way of example, made of the same metal material as the receiving plate 16. Furthermore, it is shown, purely by way of example, that the clamping plate 15 and the receiving plate 16 are each formed as circular cylindrical plane plates parallel to each other, each arranged coaxially to the central axis 11.

[0051] Furthermore, it is provided, purely by way of example, that a first material thickness 25 of the clamping plate and a second material thickness 26 of the receiving plate are essentially identical. In contrast, a third material thickness 27 of the support web 17 is considerably smaller than the first and second material thicknesses 25 and 26. For example, the first material thickness 25 and the second material thickness 26 are each approximately 30 mm, while the third material thickness is approximately 1 mm.

[0052] The underside 22 of the receiving plate 16, the top side 21 of the clamping plate 15, and an inner surface 24 of the support web 17 define a cavity 30. By way of example, the cavity 30 is further defined by an outer surface 32 of a support ring 31, which is arranged coaxially to the central axis 11. Both the support ring 31 and the support web 17 are designed as circular cylindrical sleeves extending along the central axis 11 and are arranged coaxially with each other. Furthermore, a fourth material thickness 28 of the support ring 31 is shown to be 0.5 mm; the corresponding representation in Figure 2 is not to scale.

[0053] By selecting the third material thickness 27 and the fourth material thickness 28, which are considerably thinner than the first material thickness 25 and the second material thickness 26, a high thermal resistance can be achieved between the receiving plate 16 and the clamping plate 15, thus limiting heat transfer between the receiving plate 16 and the clamping plate 15.

[0054] The representations of Figure 1 and 2 shows that a gap width of a connecting gap 18 extending between the underside 20 of the clamping plate 15 and the top side 23 of the receiving plate 16 is chosen to be greater than the first material thickness 25 and the second material thickness 26, for example 1.6 times the first material thickness 25.

[0055] By way of example, the support ring 31, which extends as a circular cylindrical sleeve along the central axis 11, has at each end an annular collar 42, 43 serving as a fastening area. By way of example, the annular collar 42 is provided with an axially oriented end face against the underside 22 of the mounting plate 16 and is sealed to the mounting plate 16 by means of fasteners not shown, for example, screws. In the same way, the annular collar 43 is provided with an axially oriented end face against the upper side 21 of the clamping plate 15 and is sealed to it by means of fasteners, in particular screws, which are also not shown.

[0056] The support web 17, which is integrally formed on the mounting plate 16, is provided with an annular collar 44 at one end region facing away from the mounting plate 16. This annular collar 44 rests with an axially oriented end face on the upper surface 21 of the clamping plate 15 and is sealed to the clamping plate 15 by fasteners, in particular screws, which are not shown in detail.

[0057] By way of example, a transition between the respective ring collar 42, 43, 44 and the support ring 31 or the support web 17 is designed with a curvature 45, 46, 47. The curvatures 45, 46, 47 are dimensioned, taking into account the respective material thickness 27, 28 and the properties of the metal material from which the support ring 31 or the support web 17 are made, such that these areas of the support ring 31 or the support web 17 can be elastically deformed within certain limits as a solid-state hinge. This allows for relative movement between the clamping plate 15 and the receiving plate 16, such as can occur with thermal expansion of the workpiece pallet 7.

[0058] By way of example, it is provided that the receiving plate 16, which is designed as a circular cylindrical plane-parallel plate, has several axial bores extending radially outwards from the central axis 11. These bores are arranged at equal angular intervals in a cross-sectional plane (not shown) oriented transversely to the central axis 11, relative to the central axis 11. The axial bores 33 are each circular cylindrical with a first diameter 34 and each has a diameter change at its end to a second diameter 35. They open onto an annular outer surface 36 of the receiving plate 16. Circular cylindrical heating cartridges 37 (not shown) are accommodated in each of the axial bores 33 and are secured in the respective axial bore 33 by a plug 38 screwed into the bore 33 (not shown).Each of the heating cartridges 37 is connected via an electrical supply line 39 to a printed circuit 40 which is associated with a connector 54 which is arranged in the clamping plate 15.

[0059] By way of example, two temperature sensors 50, 51 are arranged on the underside 22 of the mounting plate 16 and are electrically connected to the printed circuit 40 via sensor lines 52, 53. The printed circuit 40, in turn, is connected, in a manner not shown in detail, to contact pins 55 of an electromechanical connector 54 associated with the mounting plate 15. The connector 54 has, by way of example, a plug housing 56 that is rotationally symmetrical about the central axis 11 and is received in a recess 58 in the mounting plate 15 by means of a radially projecting annular collar 57, which is designed, for example, as a stepped bore. To ensure that the connector 54 is secured to the mounting plate 15, a centering bushing 60 is received in the recess 58, which positively locks the annular collar 57 of the connector to the mounting plate 15.An inner surface 61 of the centering bushing 60 is partially conically shaped and thus serves to center the workpiece pallet 7 relative to the machining table 4.

[0060] The processing table 4 is as shown in the illustration. Figure 3 provided with a centrally arranged centering pin 65, the outer surface 66 of which is at least partially conical in shape, is adapted to the inner surface 61 of the centering bushing 60 in order to ensure a positive centering between the workpiece pallet 7 and the machining table 4.

[0061] For locking the workpiece pallet 7 to the machining table 4, the machining table 4 comprises, by way of example, at least two through-bores 67, 68, each circularly cylindrical and oriented perpendicular to the flat surface 9 of the machining table 4. Each of the through-bores 67, 68 is associated with an actuator 69, 70, which may, for example, be a hydraulic cylinder and is designed for the linear movement of an associated locking element 71, 72. The locking element 71, 72 enables a positive locking connection of a locking pin 62, 63, which is located on the underside 20 of the clamping plate 15 and is inserted into the respective through-bore 67, 68.For this purpose, each of the locking pins 62, 63 is provided with a recess 64 designed as an annular groove, which forms an undercut in the axial direction along the central axis 11 and prevents the workpiece pallet 7 from being removed from the machining table 4 when the locking elements 71, 72 of the actuating members 69, 70 engage in the respective recess 64.

[0062] In a central recess 73 of the centering pin 65, a socket 74 is arranged, which is provided for electromechanical coupling with the connector 54 and which comprises plug sleeves adapted to the contact pins 55 (not shown in detail), which in turn are connected in a manner not shown in detail to an electrical conductor arrangement that passes through the recess 73 and which can be connected in a manner not shown in detail to a machine control of the machining system 1.

[0063] As can be further seen in Figure 2, the cavity 30 contains an exemplary insulating material 48 made of glass fiber mats, which largely prevents heat transfer between the receiving plate 16 and the clamping plate 15 by means of radiant heat. Thus, heat transfer between the receiving plate 16 and the clamping plate 15 is largely limited to the thermal coupling of these two components by means of the support web 17 and the support ring 31.

[0064] Since, according to the preceding description, both the support ring 31 and the support web 17 are sealed to both the clamping plate 15 and the receiving plate 16, the cavity 30 is sealed, in particular gas-tight. To limit gas expansion in the cavity 30 during heating of the receiving plate 16 and the associated pressure increase in the cavity 30 to a level that would prevent damage to the workpiece pallet 7, a fluid channel 12 is formed in the clamping plate 15. The fluid channel 12 extends between the cavity 30 and the area surrounding the workpiece pallet 7 and, by way of example, opens onto an outer circumferential surface 49 of the clamping plate 15.In the fluid channel 12, a spring-loaded check valve 14 is arranged as a purely exemplary example, which is configured in such a way that it opens when there is a predefinable pressure difference between a pressure in the cavity 30 and an ambient pressure and thus allows gas to escape from the cavity 30.

[0065] The operation of the machining system 1 can be described as follows: First, the workpiece pallet 7 is placed away from the machining system 1 at a suitable workstation and is fitted with a workpiece 8, which is precisely aligned to the centering bushing 60 serving as a centering means and is fixed in this position by means of clamping jaws 10 on the top 23 of the mounting plate 16.

[0066] The workpiece pallet 7, bearing the workpiece 8, is then placed in a heating cabinet (not shown) where the temperature is maintained at a temperature comparable to that which occurs during subsequent machining in the machining system 1 due to the heating of the mounting plate 16 and the workpiece 8 attached to it. Electrical contact is made with the connector 54 in this heating cabinet, allowing the heating cartridges 37 in the mounting plate 16 to be supplied with electrical energy and enabling the mounting plate 16 and the workpiece 8 attached to it to be heated to a predefined target temperature, in particular 400 degrees Celsius.

[0067] Once the target temperature for the workpiece 8 is reached, the workpiece pallet 7 can be transferred to the machining system 1 and placed on the machining table 4. This placement process occurs during a downward lowering movement of the workpiece pallet 7 along the central axis 11, causing the locking pins 62, 63 to engage in the through-holes 67, 68. Furthermore, the mechanical interaction between the centering bushing 60 and the centering pin 65 ensures precise mechanical alignment of the workpiece pallet 7 with respect to the machining table 4. Subsequently, the actuators 69, 70 are actuated, causing the locking elements 71, 72 to engage in the recesses 64 of the locking pins 62, 63, thus ensuring a positive locking of the workpiece pallet 7 to the machining table 4 in all spatial directions.

[0068] The geometric center point of the workpiece pallet 7 is determined without play with respect to the machining table 4 by the centering action between the centering bushing 60 and the outer surface 66 of the centering pin 65. Preferably, only these two components are responsible for centering the workpiece pallet 7 with respect to the machining table 4, while all other components, such as the locking pins 62, 63, serve only to secure the workpiece pallet 7 to the machining table 4, but not to center it with respect to the central axis 11.

[0069] Since the electrical connection between the connector 54 and the socket 74 is also established when the workpiece pallet 7 is attached to the machining table 4, further electrical energy can be supplied to the heating cartridges 37 in the mounting plate 16 from this point onward, so that the temperature of the mounting plate 16 and the workpiece 8 attached to it can be maintained. A machine control system (not shown) can monitor the temperature of the mounting plate 16 using temperature sensors 50 and 51 and supply the heating cartridges 37 with the necessary energy according to the target temperature for the workpiece 8.

[0070] Subsequently, a relative movement of the machining table 4 and suitable relative movements of the application head 5 or the removal head 6 can be performed to carry out additive or subtractive machining of the workpiece 8. After completion of the machining steps on the workpiece 8, the workpiece pallet 7 is unlocked by suitable control of the actuators 69, 70, so that the workpiece pallet 7 with the workpiece 8 held on it can be removed from the machining system.

Claims

1. Workpiece pallet (7) for additive and subtractive workpiece machining, comprising a clamping plate (15) which comprises a first interface (20) for a form-fitting fixation to a machining table (4) of a processing machine (1), the workpiece pallet (7) further comprising a receiving plate (16), which comprises a second interface for fixing a workpiece, wherein the clamping plate (15) and the receiving plate (16) are arranged spaced apart from one another and wherein a supporting web (17) is arranged in a connecting gap (18) between an upper surface (21) of the clamping plate (15) and a lower surface (22) of the receiving plate (16), which supporting web (17) is connected to the upper surface (21) of the clamping plate (15) and to the lower surface (22) of the receiving plate (16), the supporting web (17) having in a cross-sectional plane aligned parallel to the lower surface of the receiving plate (16) a cross-sectional area which is less than 15 percent, preferably less than 10 percent, particularly preferably less than 5 percent, and especially less than 1 percent, of an area of the lower surface of the receiving plate, characterized in that at least one heating device (37) is assigned to the receiving plate (16), which is designed for temperature control of the receiving plate (16).

2. Workpiece pallet (7) according to claim 1, characterized in that the clamping plate (15) is made of a first metal material with a first coefficient of thermal expansion and that the receiving plate (16) is made of a second metal material with a second coefficient of thermal expansion, wherein the first coefficient of thermal expansion is greater than the second coefficient of thermal expansion and wherein the second coefficient of thermal expansion is less than 16 / 1000000 [1 / K].

3. Workpiece pallet (7) according to claim 1 or 2, characterized in that the support web (17) together with the clamping plate (15) and the receiving plate (16) defines at least one, in particular closed, cavity (30) and / or that the support web (17) is made of a metal material which has a specific thermal conductivity of less than 30 W / mK, in particular less than 20 W / mK, and / or a coefficient of thermal expansion of less than 16 / 1000000 [1 / K], in particular less than 14 / 1000000 [1 / K].

4. Workpiece pallet (7) according to claim 3, characterized in that at least one insulating material (48) from the group: gas, liquid, solid, is accommodated in the cavity (30) and / or that the cavity (30) is evacuated.

5. Workpiece pallet (7) according to claim 3 or 4, characterized in that a compensating valve (14) is attached to the clamping plate (15) or to the receiving plate (16) or to the supporting web (17), which compensating valve (14) is designed for a predeterminable, fluidically communicating connection between the cavity (30) and an environment of the workpiece pallet (7) for limiting a differential pressure between the cavity (30) and the environment.

6. Workpiece pallet (7) according to one of the preceding claims, characterized in that the supporting web (17) is formed in one piece with the receiving plate (16) and projects from a lower surface (22) of the receiving plate (16) facing the clamping plate (15) in the direction of the clamping plate (15) and is fixed with fasteners to an upper surface (21) of the clamping plate (15) facing the receiving plate (16).

7. Workpiece pallet (7) according to claim 6, characterized in that the supporting web (17) is designed as a circular ring which extends along a spacing axis (11) between the clamping plate (15) and the receiving plate (16) and has a fastening region which is designed as an annular collar (44) extending in the radial direction and which is penetrated by the fasteners which are arranged on the upper surface (21) of the clamping plate (15).

8. Workpiece pallet (7) according to claim 6 or 7, characterized in that a support ring (31) is arranged in the connecting gap (18) coaxially to the support web (17), which support ring (31) is connected to the upper surface (21) of the clamping plate (15) and to the lower surface (22) of the receiving plate (16), in particular in a sealing manner.

9. Workpiece pallet (7) according to one of the preceding claims, characterized in that the first interface comprises at least two locking pins (62, 63) which project from an lower surface (20) of the clamping plate (15), which forms a reference plane, the at least two locking pins (62, 63) facing away from the receiving plate (16), wherein longitudinal axes of the at least two locking pins (62, 63) are aligned parallel to one another and transversely to the reference plane and determine a mounting direction for the receiving plate (16), the at least two locking pins (62, 63) each having at least one undercut (64) relative to the longitudinal axes.

10. Workpiece pallet (7) according to claim 9, characterized in that an electromechanical plug connector (54) is arranged on the lower surface (20) of the clamping plate (15), which is designed for a plug connection with a plug-in movement aligned parallel to the assembly direction and for an electrical coupling between a plug-in receptacle (74) arranged on a machining table of a processing machine (1) and at least one electrical consumer (37) associated with the workpiece pallet (7) and / or at least one sensor (50) associated with the workpiece pallet (7).

11. Workpiece pallet (7) according to claim 10, characterized in that the plug connector (54) is received at least partially in a recess (58) of the clamping plate (15), the recess (58) being bordered at least partially by the supporting web (17).

12. Workpiece pallet (7) according to one of the preceding claims, characterized in that a first material thickness (25) of the clamping plate (15) differs from a second material thickness (26) of the receiving plate (16) by an amount of less than 30 percent, preferably by an amount of less than 20 percent, in particular by an amount of less than 10 percent.

13. Machining system (1) for machining workpieces, with a workpiece pallet (7) according to one of the preceding claims and with a processing machine comprising a machine bed (2), a machining table (4) mounted on the machine bed (2) and an application head (5) arranged on the machine bed (2), wherein an adjusting system for a relative movement between the machining table (4) and the application head (5) is associated with the machine bed (2), wherein the application head (5) is designed for delivering a particle stream of metallic particles in the direction of the machining table (4), wherein the machining (4) table has an interface receptacle (67, 68) for receiving and fixing locking pins (62, 63) and a plug-in receptacle (74) for receiving the workpiece pallet (7).

14. Machining system (1) according to claim 13, characterized in that a removal head (6), in particular a milling head, for machining a workpiece (8) which can be fixed on the workpiece pallet (7), is associated with the machine bed (2), and wherein the adjusting system is constructed for a relative movement between the machining table (4) and the removal head (6) and / or wherein a heat chamber is provided in addition to the processing machine, which heat chamber is constructed for temporarily receiving the workpiece pallet (7) during a heating process.

15. Machining system according to claim 13 or 14, characterized in that in addition to the processing machine, a machining centre is provided which has at least one removal head (6), in particular a milling head, for machining a workpiece (8) which can be fixed on the workpiece pallet (7) and wherein a machining table (7) of the machining centre comprises an interface receptacle (67, 68) for receiving and fixing locking pins (62, 63) and a plug-in receptacle for receiving the workpiece pallet (7) according to one of the claims 1 to 12.