Workpiece holder for a machine tool for clamping a workpiece by means of negative pressure, and machine tool

Abstract

The invention relates to a workpiece holder (18) for a machine tool (10) for clamping a workpiece (20) by means of negative pressure. The workpiece holder (18) has a workpiece contact surface (24) for contacting the workpiece (20), a suction chamber (26), to which the negative pressure can be applied for the purpose of clamping the workpiece (20) by suctioning the workpiece (20) against the workpiece contact surface (24), and a securing channel (38) for securing the negative pressure in the suction chamber (26). The securing channel (38) circumferentially surrounds the suction chamber (26) and can be subjected to a negative pressure in order to secure the negative pressure in the suction chamber (26).

Description

[0001] Title: Workpiece holder for a machine tool for clamping a

[0002] Workpiece using vacuum and machine tool

[0003] Description

[0004] The invention relates to a workpiece holder for a machine tool for clamping a workpiece by means of vacuum and to a machine tool.

[0005] Machine tools are typically designed to machine a workpiece. To prevent the workpiece's position from changing unintentionally during machining, the workpiece is often clamped using a workpiece holder to secure it for machining.

[0006] The workpiece can be clamped, for example, by placing the workpiece on a workpiece contact surface of the workpiece holder and applying negative pressure to a suction chamber of the workpiece holder. The negative pressure then sucks, or in particular presses, the workpiece against the workpiece contact surface, thereby clamping the workpiece.

[0007] The invention is based on the object of providing a workpiece holder for a machine tool for clamping a workpiece by means of vacuum, and a machine tool, each of which enables reliable and secure clamping of the workpiece. The invention achieves this object by providing a workpiece holder with the features of claim 1 and a machine tool with the features of claim 10. Advantageous further developments and / or refinements of the invention are described in the dependent claims.

[0008] A workpiece holder for a machine tool according to the invention is designed for clamping a workpiece by means of negative pressure. The workpiece holder has a workpiece contact surface, a suction chamber, and a securing channel. The workpiece contact surface is designed for contacting the workpiece. The suction chamber can be subjected to negative pressure for the purpose of clamping the workpiece by suctioning the workpiece against the workpiece contact surface. The securing channel is designed to secure the negative pressure in the suction chamber. The securing channel circumferentially surrounds the suction chamber and can be subjected to negative pressure to secure the negative pressure in the suction chamber.

[0009] Advantageously, the safety channel prevents an unwanted reduction in the negative pressure in the suction chamber. If an ambient medium enters the suction chamber between the workpiece holder and a workpiece clamped with the workpiece holder, the ambient medium can be removed via the safety channel before it enters the suction chamber. The safety channel thus prevents the ambient medium from accidentally reaching the suction chamber and reduces the negative pressure in the suction chamber. Therefore, the workpiece holder enables reliable and secure clamping of the workpiece.

[0010] The machine tool can be designed as a welding machine, in particular a laser welding machine.

[0011] The workpiece can be formed as a sheet metal, a material panel, and / or a stamped and bent part. In particular, the width and / or length of the workpiece can be more than five times, in particular ten times, the thickness of the workpiece.

[0012] The workpiece may be a flat component. The workpiece may not have any inherent rigidity. The workpiece may have a width and / or length of at least 1 m (meter), in particular 2 m.

[0013] The workpiece holder can be surrounded by an ambient medium. The ambient medium can be gaseous. The ambient medium can be air. Each negative pressure can be a pressure that is lower than the pressure of the ambient medium. Preferably, each negative pressure can be a pressure that is lower than the atmospheric ambient pressure surrounding the workpiece and / or the workpiece holder. In particular, a value of the negative pressure in the suction chamber and / or a value of the negative pressure in the securing channel can be at least 500 mbar (millibars) lower than the atmospheric ambient pressure.

[0014] The workpiece contact surface can be a flat surface.

[0015] The suction chamber can be designed as a recess in the workpiece holder.

[0016] The suction chamber can be open to the workpiece contact surface. The suction chamber can have a suction opening. The suction opening can be limited by the workpiece contact surface.

[0017] The workpiece can cover the suction space, in particular the suction opening, for the purpose of clamping the workpiece.

[0018] The suction of the workpiece against the workpiece contact surface can be achieved by the ambient medium pressing the workpiece against the workpiece contact surface due to a pressure difference between a pressure in the suction chamber and a pressure of the ambient medium.

[0019] If the workpiece is sucked against the workpiece contact surface by means of the negative pressure in the suction chamber, a technical zero gap can form between the workpiece and the workpiece contact surface.

[0020] For every 100 mbar pressure difference between the pressure in the suction chamber and the pressure of the ambient medium, a contact pressure of the workpiece against the workpiece contact surface of 10 kN / m 2 (kilonewtons / square meter).

[0021] The workpiece holder can have a clamped state and a released state. In the clamped state, the workpiece can be sucked against the workpiece contact surface by means of the negative pressure in the suction chamber. In the released state, the workpiece cannot be sucked against the workpiece contact surface.

[0022] The safety channel and the suction chamber can be designed separately from each other.

[0023] This allows the vacuum value in the suction chamber and the vacuum value in the safety channel to differ from each other. Alternatively, the workpiece holder can have a connection between the safety channel and the suction chamber. This allows the vacuum value in the suction chamber and the vacuum value in the safety channel to be the same.

[0024] The safety channel can have a safety channel depth and a safety channel width. The ratio of the safety channel depth to the safety channel width can be at least 1:3. With such a ratio, the safety channel can have a particularly advantageous, particularly low, flow resistance.

[0025] The vacuum in the securing channel may be insufficient or unsuitable for clamping the workpiece.

[0026] The workpiece contact surface can define the securing channel. At least a portion of the workpiece contact surface can be arranged between the securing channel and the suction chamber.

[0027] The securing channel can be designed as a recess in the workpiece holder. The securing channel can be designed as a groove.

[0028] The locking channel can be open toward the workpiece contact surface. The locking channel can have a locking channel opening. The locking channel opening can be limited by the workpiece contact surface.

[0029] The workpiece can cover the safety channel, in particular the safety channel opening, for the purpose of securing the negative pressure in the suction chamber.

[0030] In the clamped state, the securing channel can run in an edge area of ​​the workpiece.

[0031] One aspect of the workpiece holder can be that the negative pressure in the suction chamber makes it possible to clamp large components using the workpiece holder. In particular, the negative pressure in the suction chamber can be used to clamp the workpiece across a large area. This avoids point-like or linear contact pressures.

[0032] Another aspect of the workpiece holder can be that the negative pressure in the suction chamber allows the workpiece to be clamped at a defined distance from a machining device of the machine tool. This advantageously eliminates the need to measure and adjust the distance between the workpiece and the machining device while machining the clamped workpiece.

[0033] A further aspect of the workpiece holder can be that a workpiece which has an undesired curvature is aligned by clamping it using the negative pressure in the suction chamber in such a way that the undesired curvature is reduced.

[0034] A further aspect of the workpiece holder can be that the negative pressure in the suction chamber reduces or completely prevents any curvature of the workpiece and / or any distortion of the workpiece, for example due to heat input, during machining of the workpiece with the machine tool.

[0035] A further aspect of the workpiece holder can be that by clamping by means of the negative pressure in the suction chamber, one side of the workpiece facing away from the workpiece contact surface is free of mechanical clamping elements, so that the workpiece is freely accessible for the machine tool and, in particular, no interfering contour hinders the machining of the workpiece.

[0036] In a further development of the workpiece holder, the suction chamber is formed by a number, for example 1, 2, 3 or 4, of channels and / or by a number, for example 1, 2, 3 or 4, of recesses. The recesses can be referred to as pocket recesses. The channels and / or the recesses can be formed separately from one another. This means that in the event of a leak in one of the channels and / or in one of the recesses, the workpiece can continue to be clamped reliably and securely by the remaining channels and / or remaining recesses. Each channel of the suction chamber can be designed as a groove.

[0037] In a further development of the workpiece holder, each channel of the suction chamber has a channel depth and a channel width. The ratio of the channel depth to the channel width is at least 1:3. This advantageously allows high contact pressures to be achieved while simultaneously maintaining low flow resistance in the channels.

[0038] In a further development of the workpiece holder, the channels have a channel that is circumferentially enclosed by each of the other channels. In particular, the other channels can be arranged concentrically with respect to the channel. In a further development of the workpiece holder, the workpiece holder has a suction chamber connection point for connecting a vacuum generation device and a safety channel connection point for connecting the vacuum generation device. Advantageously, the suction chamber and the safety channel can thus be connected independently of one another to the vacuum generation device. This prevents mutual influence of the vacuum in the suction chamber and the vacuum in the safety channel. The vacuum generation device can have at least one vacuum pump for generating the vacuum.

[0039] In a further development of the workpiece holder, the workpiece holder has a suction chamber valve, via which the suction chamber can be subjected to negative pressure, and a safety channel valve, via which the safety channel can be subjected to negative pressure. The suction chamber valve and the safety channel valve can each have a closed and an open position. The suction chamber valve and the safety channel valve can be moved to the closed or open position independently of one another.

[0040] In a further development of the workpiece holder, the workpiece holder has a suction chamber pressure gauge for measuring the negative pressure in the suction chamber and a safety channel pressure gauge for measuring the negative pressure in the safety channel. This allows the pressure in the suction chamber and the pressure in the safety channel to be measured.

[0041] In a further development of the workpiece holder, the workpiece holder has a number of support bodies that can be placed within the suction chamber. The number of support bodies form a surface section of the workpiece contact surface. This advantageously prevents the workpiece from warping when the suction chamber is subjected to negative pressure.

[0042] In a further development of the workpiece holder, a web is arranged between the suction chamber and the securing channel. The web forms a surface section of the workpiece contact surface. The flow resistance between a workpiece clamped with the workpiece holder and the surface section of the workpiece contact surface formed by the web can be greater than the flow resistance of the securing channel. This allows the ambient medium to be discharged particularly reliably via the securing channel if it gets between the workpiece and the workpiece contact surface.

[0043] A machine tool according to the invention comprises a workpiece holder as described above and a vacuum generating device. The vacuum generating device is configured to apply the vacuum to the suction chamber for clamping the workpiece and to apply the vacuum to the securing channel for securing the vacuum in the suction chamber. The vacuum generating device can comprise at least one vacuum pump for generating the vacuum.

[0044] In a further development of the machine tool, the machine tool is designed to produce an assembly with a channel structure. The assembly comprises the workpiece and another workpiece. The channel structure is formed by the workpiece and the another workpiece. The machine tool has a processing device for producing a material-to-material connection between the workpiece and the another workpiece. The vacuum generation device is designed to apply a vacuum to the channel structure for the purpose of pressing the workpiece and the another workpiece together. The machine tool has a measuring device for measuring the vacuum in the channel structure. The measuring device is designed to detect a tightness of the channel structure or a leakage of the channel structure based on the measured vacuum in the channel structure.

[0045] Advantageously, the negative pressure in the channel structure can be used to press the two workpieces together and to detect a leak or a leak. This allows the negative pressure in the channel structure to fulfill a dual function. Due to the dual function of the negative pressure, a number of manufacturing steps for the assembly can be reduced, thereby shortening the assembly's production time. In particular, a subsequent separate leak test of the manufactured assembly can be eliminated.

[0046] The assembly can be a heat exchanger, in particular for cooling batteries, preferably vehicle batteries. The workpiece and the additional workpiece can each be made of aluminum or stainless steel. The workpiece and / or the additional workpiece can be a stamped or bent part or a stamped part.

[0047] The further workpiece can have a width and / or a length of at least 1 m (meter), in particular 2 m.

[0048] The channel structure can be configured to conduct a cooling fluid. The channel structure can be configured to be closed along its perimeter. The channel structure can extend from an inlet of the assembly for introducing the cooling fluid to an outlet of the assembly for discharging the cooling fluid. The cooling fluid can be gaseous or liquid; in particular, the cooling fluid can be air or water.

[0049] For example, the inlet can be connected to the vacuum generating device for applying the negative pressure to the channel structure, and the outlet can be connected to the measuring device for measuring the negative pressure in the channel structure. Alternatively, the outlet can be connected to the vacuum generating device for applying the negative pressure to the channel structure, and the inlet can be connected to the measuring device for measuring the negative pressure in the channel structure.

[0050] The assembly may be surrounded by the ambient medium.

[0051] The negative pressure in the channel structure can be a pressure that is lower than the pressure of the ambient medium. Preferably, the negative pressure can be a pressure that is lower than the atmospheric ambient pressure surrounding the assembly. In particular, the negative pressure applied to the channel structure can be at least 500 mbar lower than the atmospheric ambient pressure of the assembly.

[0052] The processing device can have a laser beam source for generating laser radiation for welding the two workpieces together.

[0053] The measuring device may include a pressure sensor for measuring the negative pressure in the channel structure. The measuring device may include a microcontroller or computer for detecting leaks in the channel structure based on the measured negative pressure in the channel structure.

[0054] The measuring device can be configured to determine a position of a leak in the channel structure based on the measured negative pressure in the channel structure. The measuring device can be configured to determine a size of a leak in the channel structure based on the measured negative pressure in the channel structure.

[0055] The measuring device can be designed to release the assembly for repairing the leak if the determined size of the leak is smaller than a predetermined size.

[0056] The machine tool can be configured to carry out a method for producing the assembly with the channel structure. The method can comprise the steps of: arranging the workpiece on the further workpiece to form the channel structure; pressing the workpiece and the further workpiece together by applying negative pressure to the channel structure; establishing the integral connection between the workpiece and the further workpiece; and detecting the tightness of the channel structure or the leakage of the channel structure by measuring the negative pressure in the channel structure.

[0057] The workpiece can be arranged on the other workpiece in such a way that the workpiece rests against the other workpiece. In particular, the arrangement of the workpiece on the other workpiece can result in contact between the workpiece and the other workpiece.

[0058] The material connection can be established if the negative pressure value in the channel structure is at least 500 mbar lower than the atmospheric ambient pressure value of the assembly.

[0059] The workpiece and the other workpiece can be pressed together by suctioning the workpiece against the other workpiece using the negative pressure in the channel structure. The workpiece and the other workpiece can be pressed together in such a way that a technically zero gap is formed between the workpiece and the other workpiece.

[0060] The method may comprise the step of specifying a target pressure, wherein the negative pressure is applied to the channel structure in such a way that a value of the negative pressure in the channel structure is less than or equal to a value of the target pressure.

[0061] The integral connection can be a welded joint. The integral connection can be created by laser welding. Leakage in the channel structure can occur, for example, as a result of a welding defect, such as end-crater cracks, and / or thermal distortion of the workpieces.

[0062] Measuring the negative pressure in the channel structure can comprise measuring a value of the negative pressure in the channel structure before the material connection is established and measuring a value of the negative pressure in the channel structure after the material connection is established. Detecting the tightness or leakage can comprise determining a deviation between the measured value of the negative pressure before the material connection is established and the measured value of the negative pressure after the material connection is established. Detecting the tightness or leakage can comprise comparing the deviation with a predetermined deviation. The leakage can be detected if the deviation is greater than the predetermined deviation. The tightness can be detected if the deviation is less than or equal to the predetermined deviation.

[0063] The amount of the specified deviation can, for example, be less than or equal to 100 mbar, in particular 50 mbar.

[0064] A further aspect of the method may be that a leak may occur during the production of the material-to-material connection due to a manufacturing error, which draws the ambient medium into the channel structure and reduces the negative pressure in the channel structure. The reduction in the negative pressure in the channel structure can be measured. Based on the measured reduction in the negative pressure in the channel structure, the leak in the channel structure can be detected. The tightness of the channel structure can be detected if no reduction in the negative pressure in the channel structure is measured.

[0065] The negative pressure in the channel structure can be measured while the material connection is being established. In particular, the negative pressure in the channel structure can only be measured while the material connection is being established. The leakage of the channel structure can be detected if an increase in the negative pressure in the channel structure, in particular of more than 50 mbar, is measured while the material connection is being established. The tightness of the channel structure can be detected if no increase in the negative pressure in the channel structure, in particular of more than 50 mbar, is measured while the material connection is being established. The leakage of the channel structure can comprise determining a position of a leak in the channel structure based on the measured negative pressure in the channel structure.This can advantageously facilitate repair of the leak, since the location of the leak is known. Determining the location of the leak in the channel structure can be achieved by determining the position of the material connection at a time of a pressure increase in the negative pressure in the channel structure. In other words, the position of the material connection, determined at the time of the pressure increase, can be the position of the leak.

[0066] Detecting a leak in the duct structure may include determining the size of a leak in the duct structure based on the measured negative pressure in the duct structure. This can advantageously be used to decide whether a repair is cost-effective or not. Determining the size of the leak may be performed by determining the magnitude and / or rate of a negative pressure increase in the duct structure. For example, a larger leak may exhibit a higher and / or faster negative pressure increase in the duct structure than a smaller leak.

[0067] The method may comprise the step of: releasing the assembly for repair of the leak if the determined size of the leak is smaller than a predetermined maximum size.

[0068] The method may comprise the step of repairing the leak by creating another material bond at the location of the leak. Repairing the leak may be performed immediately after creating the material bond. Alternatively, the creation of the material bond may be interrupted to repair the leak and continued after the leak has been repaired.

[0069] Further advantages and advantageous embodiments of the invention can be gathered from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention both individually and in any combination. They show: Fig. 1 is a schematic representation of a machine tool with a workpiece holder for clamping a workpiece.

[0070] Fig. 2 is a schematic oblique view of the workpiece holder of Fig. 1,

[0071] Fig. 3 is a schematic sectional view of the workpiece holder of Fig. 1,

[0072] Fig. 4 is a schematic oblique view corresponding to Fig. 2 for a variant of the

[0073] Workpiece holder,

[0074] Fig. 5 is a schematic sectional view of the workpiece holder of Fig. 4,

[0075] Fig. 6 is a schematic oblique view corresponding to Fig. 2 for a further variant of the

[0076] Workpiece holder,

[0077] Fig. 7 is a schematic sectional view of an assembly before machining with the machine tool of Fig. 1, which is clamped with the workpiece holder,

[0078] Fig. 8 is a schematic sectional view of the assembly of Fig. 7 after machining with the machine tool,

[0079] Fig. 9 is a schematic sectional view of a further assembly during machining with the machine tool of Fig. 1, wherein the further assembly has a leak, and

[0080] Fig. 10 is a schematic flow chart of a method for manufacturing an assembly using the machine tool of Fig. 1.

[0081] Fig. 1 shows a machine tool 10 in the form of a laser welding machine. The machine tool 10 has a processing device 12 for producing a material-to-material connection in the form of a welded joint.

[0082] The processing device 12 has a laser beam source for generating laser radiation 14 for creating the weld. The laser beam source has a processing head 16 from which the laser radiation 14 emerges. For reasons of clarity, only the processing head 16 is shown in Fig. 1.

[0083] The machine tool 10 has a workpiece holder 18. The workpiece holder 18 is designed to clamp a workpiece 20 using vacuum. The workpiece 20 is a flat workpiece. The workpiece 20 is a sheet metal. The width and length of the workpiece 20 are more than five times the thickness of the workpiece 20. The workpiece 20 has no inherent rigidity. The workpiece 20 has a width and a length of at least 1 m each.

[0084] To generate the negative pressure for clamping the workpiece 20, the machine tool 10 has a negative pressure generating device 22. The negative pressure generating device 22 has a vacuum pump for generating the negative pressure.

[0085] Fig. 2 shows the workpiece holder 18 of the machine tool 10 without the workpiece 20 and Fig. 3 shows a cross-section of the workpiece holder 18 with the workpiece 20.

[0086] The workpiece holder 18 has a workpiece contact surface 24 for contacting the workpiece 20. The workpiece contact surface 24 is designed as a flat surface.

[0087] The workpiece holder 18 has a suction chamber 26. The suction chamber 26 is formed as a recess in the workpiece holder 18. The suction chamber 26 is cuboid-shaped. The suction chamber 26 is open toward the workpiece contact surface 24. The suction chamber 26 has a suction opening 28. The suction opening 28 is bounded by the workpiece contact surface 24.

[0088] The workpiece holder 18 has a plurality of support bodies 30 that can be placed within the suction chamber 26. Each support body 30 can be cube-shaped. The support bodies 30 form a surface section of the workpiece contact surface 24. The support bodies 30 can prevent warping of the workpiece 20. The support bodies 30 can be placed within the suction chamber 26 without being fastened. In other words, the support bodies 30 can be loosely inserted within the suction chamber 26.

[0089] The suction chamber 26 can be subjected to negative pressure for the purpose of clamping the workpiece 20 by suctioning the workpiece 20 against the workpiece contact surface 24. For this purpose, the workpiece 20 covers the suction opening 28 for the purpose of clamping the workpiece 20. The suction of the workpiece 20 against the workpiece contact surface 24 is achieved by an ambient medium 32, which surrounds the workpiece 20 and the workpiece holder 18, pressing the workpiece 20 against the workpiece contact surface 24 due to a pressure difference between a pressure in the suction chamber 26 and a pressure of the ambient medium. In the illustrated embodiment, the ambient medium 32 is air. In order to clamp the workpiece 20 safely and reliably during the machining of the workpiece 20 with the machine tool 10, the suction chamber 26 is subjected to negative pressure in such a way that the pressure in the suction chamber 26 is 500 mbar lower than a pressure of the ambient medium 32.As a result, a technical zero gap is formed between the workpiece 20 and the workpiece contact surface 24.

[0090] By clamping the workpiece 20 using the negative pressure in the suction chamber 26, if the workpiece 20 exhibits an undesired curvature, the workpiece can be aligned using the negative pressure in the suction chamber 26, thus reducing the undesired curvature. The negative pressure in the suction chamber 26 enables the workpiece 20 to be clamped flat.

[0091] Furthermore, by clamping the workpiece 20 using the negative pressure in the suction chamber 26, it can be achieved that the workpiece 20 is clamped at a defined distance from the machining head 16. The distance between the workpiece 20 and the machining head 16 can be constant across the entire workpiece 20, thereby eliminating the need to regulate the distance between the workpiece 20 and the machining head 16 during machining of the workpiece, thus simplifying the machining of the workpiece 20.

[0092] By clamping the workpiece 20 by means of the negative pressure in the suction chamber 26, a warpage, which can occur, for example, due to heat input during machining of the workpiece 20 with the machine tool 10, can be reduced or completely avoided.

[0093] Furthermore, clamping the workpiece 20 using the negative pressure in the suction chamber 26 eliminates the need for mechanical clamping elements, so that the workpiece 20 is freely accessible to the machining head 16. In particular, the machining head 16 can be guided unhindered over the workpiece 20 for the purpose of machining the workpiece 20.

[0094] The workpiece holder 18 has a suction chamber connection point 36 for connecting the vacuum generating device 22. The suction chamber connection point 36 can be designed as a threaded hole.

[0095] The vacuum generating device 22 can be connected to the suction chamber connection point 36 by means of a suction chamber valve (not shown in Fig. 2) of the workpiece holder 18. The suction chamber valve can assume a closed or an open position. In the open position, the suction chamber 26 can be subjected to the negative pressure via the suction chamber valve by means of the vacuum generating device 22, and in the closed position, the negative pressure in the suction chamber 26 cannot leave the suction chamber 26. The suction chamber valve ensures that the vacuum generating device 22 no longer has to provide the negative pressure for the suction chamber 26 after the suction chamber 26 has been subjected to the negative pressure and the suction chamber valve has subsequently been moved into the closed position.

[0096] The workpiece holder 18 has a securing channel 38. The securing channel 38 is formed as a recess in the workpiece holder 18. The securing channel 38 is a groove. The securing channel 38 has a rectangular shape. The securing channel 38 has a securing channel depth 40 and a securing channel width 42. The ratio of the securing channel depth 40 to the securing channel width 42 can be at least 1:3. The securing channel depth 40 and the depth 44 of the suction chamber 26 can be equal.

[0097] The securing channel 38 is open toward the workpiece contact surface 24. The securing channel 38 has a securing channel opening 46. The securing channel opening 46 is delimited by the workpiece contact surface 24.

[0098] The securing channel 38 circumferentially surrounds the suction chamber 26. A web 48 is arranged between the suction chamber 26 and the securing channel 38. The web 48 forms a surface section of the workpiece contact surface 24. As a result, a surface section of the workpiece contact surface 24 is arranged between the securing channel 38 and the suction chamber 26.

[0099] The safety channel 38 is designed to secure the negative pressure in the suction chamber 26. The safety channel 38 can be subjected to a negative pressure to secure the negative pressure in the suction chamber 26. The workpiece 20 covers the safety channel opening 46 to secure the negative pressure in the suction chamber 26.

[0100] Securing the negative pressure in the suction chamber 26 is achieved by ensuring that, if the ambient medium 32 accidentally enters between the workpiece contact surface 24 and the clamped workpiece 20, the ambient medium 32 is removed by means of the negative pressure in the securing channel 38 before the ambient medium 32 enters the suction chamber 26. As a result, the negative pressure in the suction chamber 26 is not reduced, and the workpiece 20 remains securely and reliably clamped during machining with the machine tool 10.

[0101] The negative pressure in the securing channel 38 is insufficient for clamping the workpiece 20. In other words, if the securing channel 38 is subjected to negative pressure and the suction chamber 26 is not subjected to negative pressure, the workpiece 20 cannot be sucked against the workpiece contact surface 24 by the negative pressure in the suction chamber 26 in such a way that the workpiece is securely and reliably clamped during machining with the machine tool 10.

[0102] The safety channel 38 and the suction chamber 26 are formed separately from each other. The negative pressure value in the suction chamber 26 and the negative pressure value in the safety channel 38 can differ from each other.

[0103] The workpiece holder 18 has a safety channel connection point 52 for connecting the vacuum generating device 22. The safety channel connection point 36 can be designed as a threaded hole.

[0104] The vacuum generating device 22 can be connected to the suction chamber connection point 36 by means of a safety channel valve (not shown in Fig. 2) of the workpiece holder 18. The safety channel valve can assume a closed or an open position. In the open position, the safety channel 38 can be subjected to negative pressure via the safety channel valve by means of the vacuum generating device 22, and in the closed position, the negative pressure in the safety channel 38 cannot leave the safety channel 38 via the safety channel valve. The safety channel valve ensures that the vacuum generating device 22 no longer has to provide negative pressure for the safety channel 38 after the safety channel 38 has been subjected to negative pressure and the safety channel valve has subsequently been moved into the closed position.

[0105] In Figs. 4 and 5, a further embodiment of the workpiece holder 18 of Figs. 1 to 3 is shown, wherein the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the above explanations regarding the embodiment of Figs. 1 to 3, so that essentially only the existing differences are discussed.

[0106] Fig. 4 shows that the suction chamber 26 can be formed by a plurality of channels. The suction chamber 26 is formed by two separate channels. Each channel of the suction chamber 26 is designed as a groove. Each channel of the suction chamber 26 is open toward the workpiece contact surface 24. Each channel of the suction chamber 26 has a rectangular shape. Each channel of the suction chamber 26 has a channel depth 54 and a channel width 56, see Fig. 5. The ratio of the channel depth 54 to the channel width 56 can be at least 1:3.

[0107] The channels of the suction chamber 26 have a channel that is circumferentially enclosed by the other channels. The other channels of the suction chamber 26 are arranged concentrically with respect to the channel.

[0108] A web 58 is arranged between each two adjacent channels of the suction chamber 26. Each web 58 forms a surface section of the workpiece contact surface 24. As a result, a surface section of the workpiece contact surface 24 is arranged between each two adjacent channels of the suction chamber 26.

[0109] The suction opening 28 is formed by the plurality of channels of the suction chamber 26. The size of the suction opening 28 can be at least five times, in particular three times, the size of the safety channel opening 46.

[0110] The workpiece holder 18 has a plurality of suction chamber connection points 36. Each channel of the suction chamber 26 can be connected to the vacuum generation device 22 via a suction chamber connection point 36. This allows the channels of the suction chamber 26 to be individually subjected to the vacuum.

[0111] The securing channel 38 is arranged concentrically with the channels of the suction chamber 26. The channels of the suction chamber 26 and the securing channel 38 can be designed identically or differently. For example, a securing channel depth or width can be at least 30% less than a channel depth of the channels of the suction chamber 26 or a channel width of the channels of the suction chamber 26.

[0112] Fig. 6 shows a further embodiment of the workpiece holders 18 of Figs. 1 to 5, wherein the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the above explanations regarding the embodiments of Figs. 1 to 5, so that essentially only the existing differences are discussed.

[0113] Fig. 6 shows that the channels of the suction chamber 26 are connected to one another by means of a connection 60. The connection 60 is designed as a groove. The suction chamber 26 is connected to the securing channel 38 by means of the connection 60. The workpiece holder 18 shown in Fig. 6 has a single suction chamber connection point 36. All channels of the suction chamber 26 are subjected to negative pressure via the single suction chamber connection point 36. Through the connection 60, when the suction chamber 26 is subjected to negative pressure, the securing channel 38 is simultaneously subjected to negative pressure.

[0114] Fig. 1 shows that the workpiece 20 is clamped by means of the workpiece holder 18. Another workpiece 62 is arranged on the workpiece 20, forming a channel structure 64.

[0115] The workpiece 20 and the additional workpiece 62 are each made of aluminum. The additional workpiece 62 is a stamped part. The additional workpiece 62 has a width and a length of at least 1 m.

[0116] The channel structure 64 is arranged between the workpiece 20 and the further workpiece 62. The channel structure 64 can consist of one, in particular a single, channel that extends in a meandering fashion from an inlet to an outlet. The channel structure 64 is designed to conduct a cooling fluid. The cooling fluid can be water, for example.

[0117] The machine tool 10 is designed to produce an assembly 66 from the two workpieces 20, 62 by welding the two workpieces 20, 62 together. The produced assembly 66 is a heat exchanger for cooling batteries.

[0118] Fig. 7 shows the assembly 66 before the two workpieces 20, 62 are welded together. The additional workpiece 62 is arranged on the workpiece 20. The workpiece 20 has the inlet 68 for introducing the cooling fluid and the outlet 70 for discharging the cooling fluid.

[0119] The inlet 68 is connected to the vacuum generating device 22 for applying a vacuum to the channel structure 64. The outlet 70 is connected to a measuring device 72 of the machine tool 10 for measuring the vacuum in the channel structure 64. The measuring device has a pressure sensor for measuring the vacuum in the channel structure 64.

[0120] By applying the negative pressure to the channel structure 64, the workpiece 20 and the additional workpiece 62 are pressed together. The negative pressure applied to the channel structure 64 is at least 500 mbar lower than the pressure of the ambient medium 32. As a result, the workpiece 20 is sucked against the additional workpiece 62 by means of the negative pressure in the channel structure 64. The workpiece 20 and the additional workpiece 62 are pressed together in such a way that a technical zero gap forms between the workpiece 20 and the additional workpiece 62.

[0121] If the negative pressure in the channel structure 64 measured by the measuring device 72 is at least 500 mbar lower than the value of the pressure of the ambient medium 32, the measuring device 72 can initiate the production of the assembly 66.

[0122] The production of the assembly 66 comprises creating a material-to-material connection in the form of a weld seam between the workpiece 20 and the further workpiece 62. For this purpose, the processing head 16 is guided over the further workpiece 62 while the laser radiation 14 emerges from the processing head 16. The laser radiation 14 strikes the further workpiece 62 and welds the workpiece 20 to the further workpiece 62. In other words, the workpiece 20 and the further workpiece 62 are joined together by laser welding.

[0123] The workpiece 20 and the further workpiece 62 are pressed against each other and against the workpiece holder 18 with negative pressures in such a way that a distance 74 between the machining head 16 and the further workpiece 62 is constant while the machining head 16 is guided over the further workpiece 62.

[0124] During the establishment of the integral connection, the negative pressure in the channel structure 64 is measured by the measuring device 72. In the illustrated initial example in Fig. 7, during the establishment of the integral connection, no pressure increase in the channel structure 64 that exceeds a predetermined limit is detected by the measuring device 72. The predetermined limit can, for example, be less than or equal to 100 mbar, in particular less than or equal to 50 mbar. In the illustrated embodiment, the predetermined limit is 50 mbar. Due to the lack of a pressure increase greater than 50 mbar during the establishment of the integral connection, the measuring device 72 detects that the channel structure 64 is leak-tight.

[0125] Fig. 8 shows the manufactured assembly 66. The workpiece 20 is connected to the other workpiece 62 by means of the integral connection 76 in the form of a welded joint. During the production of the integral connection 76, the measuring device 72 detected the tightness of the channel structure 64.

[0126] In Fig. 9, a further assembly 66 is shown during manufacture by means of the machine tool 10, wherein the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the above explanations regarding the assembly 66 of Figs. 1 to 8, so that essentially only the existing differences are discussed.

[0127] Fig. 9 shows that a leak 78 occurs during the production of the material-to-material connection 76 due to a welding defect. The leak 78 is a breakthrough in the additional workpiece 62, causing the channel structure 64 to leak.

[0128] Due to the occurrence of the leak 78, the ambient medium 32 enters the channel structure 64, thereby reducing the negative pressure in the channel structure 64. The reduction in the negative pressure in the channel structure 64 is detected by the measuring device 72 as a pressure increase greater than 50 mbar. Due to the pressure increase during the establishment of the material connection 76, which is greater than 50 mbar, the measuring device 72 detects the leak.

[0129] The measuring device 72 is configured to determine a position of the machining head 16 at the time of detecting the pressure increase. The position of the machining head 16 at the time of the pressure increase corresponds to a position of the leak 78. In other words, detecting the leak comprises determining the position of the leak 78 based on the measured negative pressure in the channel structure 64.

[0130] Additionally, the measuring device 72 can be configured to determine the size of the leak 78 based on the rate of pressure increase. For this purpose, an assignment table can be stored in the measuring device 72, by means of which the measured rate of pressure increase can be assigned to the size of the leak 78. In other words, detecting the leak involves determining the size of the leak 78 based on the measured negative pressure in the channel structure 64.

[0131] Additionally, the measuring device 72 can be configured to release the assembly 66 for repair of the leak 78 if the determined size of the leak 78 is smaller than a predetermined maximum size. If the determined size is larger than the predetermined maximum size, the measuring device 72 can initiate disposal of the assembly 66.

[0132] If the assembly 66 is released by the measuring device 72 for repair of the leak 78, the machining head 16 is positioned at the position of the leak 78 for the purpose of establishing another material-to-material connection at the position of the leak 78. The leak 78 is sealed by means of the additional material-to-material connection.

[0133] Fig. 10 shows an exemplary sequence of a method for producing an assembly with the machine tool of Fig. 1.

[0134] The method comprises the steps of: a) arranging the workpiece 20 on the further workpiece 62 to form the channel structure 64; b) pressing the workpiece 20 and the further workpiece 62 together by applying the negative pressure to the channel structure 64; c) establishing the material-to-material connection 76 between the workpiece 20 and the further workpiece 62; and d) detecting the tightness of the channel structure 64 or the leakiness of the channel structure 64 by measuring the negative pressure in the channel structure 64 during the establishment of the material-to-material connection 76. Detecting the leakiness of the channel structure 64 can comprise determining the position of the leaky point 78 of the channel structure 64 based on the measured negative pressure in the channel structure 64. Detecting the leakage of the channel structure 64 may include determining the size of the leak 78 of the channel structure 64 based on the measured negative pressure in the channel structure 64.The method may include the step: e) releasing the assembly 66 for repairing the leak 78 if the determined size of the leak 78 is smaller than the predetermined maximum size. The method may include the step: f) repairing the leak 78 by establishing the further material connection at the position of the leak 78.

Claims

Patent claims 1. Workpiece holder (18) for a machine tool (10) for clamping a workpiece (20) by means of negative pressure, comprising: a workpiece contact surface (24) for contacting the workpiece (20), a suction chamber (26) which can be subjected to the negative pressure for the purpose of clamping the workpiece (20) by suction of the workpiece (20) against the workpiece contact surface (24), and a securing channel (38) for securing the negative pressure in the suction chamber (26), wherein the securing channel (38) circumferentially surrounds the suction chamber (26) and can be subjected to a negative pressure for securing the negative pressure in the suction chamber (26).

2. Workpiece holder (18) according to claim 1, wherein the suction space (26) is formed by a number of channels and / or by a number of recesses.

3. Workpiece holder (18) according to claim 2, wherein each channel of the suction chamber (26) has a channel depth (54) and a channel width (56), wherein a ratio of the channel depth (54) to the channel width (56) is at least 1:

3.

4. Workpiece holder (18) according to claim 2 or 3, wherein the channels have a channel which is circumferentially enclosed by each of the remaining channels.

5. Workpiece holder (18) according to one of the preceding claims, wherein the workpiece holder (18) has a suction chamber connection point (36) for connecting a vacuum generating device (22) and a safety channel connection point (52) for connecting the vacuum generating device (22).

6. Workpiece holder (18) according to one of the preceding claims, wherein the workpiece holder (18) has a suction chamber valve, via which the suction chamber (26) can be subjected to the negative pressure, and a safety channel valve, via which the safety channel (38) can be subjected to the negative pressure.

7. Workpiece holder (18) according to one of the preceding claims, wherein the workpiece holder (18) has a suction chamber pressure measuring device for measuring the negative pressure in the suction chamber (26) and a safety channel pressure measuring device for measuring the negative pressure in the safety channel (38).

8. Workpiece holder (18) according to one of the preceding claims, wherein the workpiece holder (18) has a number of support bodies (30) which can be placed within the suction space (26), wherein the number of support bodies (30) form a surface section of the workpiece contact surface (24).

9. Workpiece holder (18) according to one of the preceding claims, wherein a web (48) is arranged between the suction chamber (26) and the securing channel (38), wherein the web (48) forms a surface section of the workpiece contact surface (24).

10. Machine tool (10), comprising: a workpiece holder (18) according to one of the preceding claims, a vacuum generating device (22) for applying the vacuum to the suction chamber (26) for clamping the workpiece (20) and for applying the vacuum to the securing channel (38) for securing the vacuum in the suction chamber (26).

11. Machine tool (10) according to claim 10, wherein the machine tool (10) is designed to produce an assembly (66) with a channel structure (64), wherein the assembly (66) comprises the workpiece (20) and a further workpiece (62), wherein the channel structure (64) is formed by the workpiece (20) and the further workpiece (62), wherein the machine tool (10) has a machining device (12) for producing a material-to-material connection (76) between the workpiece (20) and the further workpiece (62), wherein the vacuum generating device (22) is designed to apply a vacuum to the channel structure (64) for the purpose of pressing the workpiece (20) and the further workpiece (62) against one another, wherein the machine tool (10) has a measuring device (72) for measuring the vacuum in the channel structure (64), wherein the measuring device (72) is designed to detect a tightness of the channel structure (64) or a leakage of the channel structure (64) based on the measured vacuum in the channel structure (64).

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