METHOD FOR CLAMPING WORKPIECES AS WELL AS EMBOSSING DEVICE AND CLAMPING DEVICE

Description

[0001] The invention relates to a method for clamping workpieces, in particular workpieces made of ductile material, as well as an embossing device for use in this method and a clamping device also for use in this method.

[0002] For machining workpieces in machine tools, especially for cutting operations, the workpieces must be securely clamped and held in suitable clamping positions. The clamping must be designed to withstand even significant forces during machining operations without the workpiece moving or becoming detached from the clamping device. At the same time, the workpiece should be easily accessible to allow for multiple machining operations to be performed consecutively in a single clamping setup.

[0003] EP 1 071 542 B1 and WO 99 / 52678, which discloses the preamble of claim 1, as well as DE 10 2016 224517 A1, which discloses the preamble of claim 7, each propose a method for clamping workpieces in which, in a preparatory step, uniformly spaced recesses are made in the workpiece. These recesses serve only as coupling elements when clamping with a corresponding clamping device and are otherwise non-functional. After this preparatory step, the workpieces are held in clamping jigs that have contact surfaces for frictional holding on their clamping jaws and have form-locking elements complementary to the recesses in the workpiece for positive-locking positioning and securing. The workpiece is thus mixed and clamped by positive and frictional locking. This clamping method has generally proven successful.

[0004] Furthermore, DE 10 2009 052 334 A1 discloses a clamping method in which the workpiece is provided with a clamping structure near its base. This structure includes two grooves provided on the flanks of the workpiece, into which corresponding rib-like projections of two clamping jaws of a clamping vise engage. The grooves are machined, for example, in a milling operation and provide a positive-locking connection between the clamping jaws and the workpiece. The wall remaining on the workpiece and bounding the groove must be resistant to bending and fracture, which necessitates a certain minimum wall thickness of the groove. This determines the space required for the clamping structure on the workpiece.

[0005] When designing clamping systems, it must be taken into account that users will want to machine a range of different workpieces made from various materials without committing to a specific workpiece type or material. This must be considered during the design process. On the one hand, the clamping device must securely hold the workpieces, even when subjected to high machining forces, while on the other hand, it must not damage the workpieces, for example, by causing unacceptable deformation or chipping.

[0006] Starting from this, the object of the invention is to provide a clamping method with which a wide range of workpieces made of different materials can be securely clamped, whereby the space required by the clamping device on the workpiece should be as small as possible.

[0007] The clamping method according to the invention is based on the fact that, in a preparatory step, deformations are applied to the workpieces to be clamped in a defined grid, for example, in the form of a series of uniformly spaced recesses. These recesses (or other deformations) serve as positioning and coupling elements when clamping in a corresponding clamping device, but otherwise perform no function on the workpiece. For clamping the workpieces, the clamping jaws have contact surfaces for frictionally holding the workpiece. In addition, the clamping jaws are provided with positive locking elements, preferably arranged on the contact surfaces, which serve for positive locking positioning and securing the workpiece. The workpiece is thus clamped by a combination of frictional and positive locking.

[0008] According to the invention, the deformations applied to the workpiece are arranged in a grid with a center-to-center spacing of 2.5 mm to 3.5 mm. It has been shown that such a grid achieves an optimum with regard to the holding force and the area of ​​the workpiece subjected to holding pressure. Local stress peaks in the workpiece are reduced to a level tolerable for most materials, and a uniform transmission of the holding force between the clamping jaw and the workpiece is achieved. Chipping, cracking, or other workpiece damage is avoided. With a grid spacing of 3 mm, an optimum ratio of achievable holding force to contact area is obtained, which applies to the vast majority of ductile materials, such as plastics, especially plastically deformable plastics, aluminum, aluminum alloys, as well as other metal alloys and metals.

[0009] The recesses are preferably arranged in a row extending along the lower edge of the workpiece adjacent to its base. Preferably, the row is straight. However, the recesses can also be arranged in two or more rows, preferably parallel to each other. The recesses in the two rows can be arranged in pairs adjacent to each other or, alternatively, offset from each other. In at least one of the two (or more) rows, preferably in all rows, the grid spacing is set to a value between 2.5 mm and 3.5 mm, preferably 3 mm.

[0010] The deformations to be applied to the workpiece are depressions that are created by means of an embossing device through plastic deformation, whereby each depression is produced by material displacement using an embossing tooth. The depressions are preferably arranged in a straight line and at constant intervals. Between the depressions, there are areas that are either flat or slightly raised, separating the individual depressions.

[0011] The recesses preferably have a rectangular cross-section with rounded corners, decreasing in size towards the bottom of the recess. In the direction of their arrangement, the rectangular recesses preferably have a length that is at least as long as the length, measured in the same direction, of the area between any two adjacent recesses.

[0012] The material displacement that occurs during the creation of the depressions causes the workpiece material to flow, thereby creating a zone of hardened material under and around the depression. Particularly in metals and metal alloys, this zone can exhibit increased strength, making it especially suitable for absorbing and distributing forces within the workpiece.

[0013] Preferably, during embossing, a gap is left between the embossing tool and the workpiece between adjacent embossing teeth, into which displaced material can penetrate. The workpiece surface, which is smooth before the embossing process (e.g., cylindrical or flat), thus acquires the desired deformations, such as indentations, during the preparatory operation. Material displacement between these indentations can also create wavy or raised deformations of the workpiece surface. This results in a workpiece surface that not only has indentations for receiving the clamping jaw's positive locking elements but is also curved in multiple ways. In other words, the formerly smooth workpiece surface can exhibit a certain regular deformation after the formation of the indentations, particularly in the areas between or around them.

[0014] In the method according to the invention, the clamping surfaces of the clamping jaws are preferably brought into full contact with the workpiece surface when the workpiece is clamped. In other words, the clamping surface of the clamping jaw is pressed firmly against the workpiece surface, which may have been slightly deformed in the preparatory step. The workpiece surface can be smoothed by re-deforming (elastically or plastically) any material that was forced out of the workpiece surface until, ideally, the flat clamping surface rests completely against the workpiece. This can be accompanied by less further plastic deformation of the workpiece, which ensures that the workpiece is held particularly securely in the clamping device between the clamping jaws.

[0015] The embossing device according to the invention serves to carry out the method according to the invention. The embossing device includes at least one embossing die having a grid-defining embossing structure, the grid spacing being between 2.5 mm and 3.5 mm. The embossing die can be a linearly movable die, a roller die, or the like. The embossing device includes a support for receiving the workpiece, the support being arranged opposite the embossing die. The support can itself be designed as an embossing die, so that the desired positioning and coupling elements are applied to the workpiece on two opposing, diverging sides in a single operation.

[0016] For embossing, the embossing die(s) are preferably pressed against the workpiece by means of a force generation device. The force generation device is preferably configured to apply a predetermined force to the embossing die(s) against the workpiece. This ensures that the embossing depth is determined by the ductility of the workpiece material. In any case, damage to the workpiece due to excessive force is prevented.

[0017] The indentations are preferably created using the embossing device while measuring the penetration depth of the embossing teeth. This ensures that the indentations reach a target depth during the embossing process, but that a maximum depth is not exceeded. Mechanical means for limiting the penetration depth, such as stop teeth on the embossing jaws (between the embossing teeth), are not present. Instead, a clearance is formed between each pair of embossing teeth, the boundary of which does not come into contact with the workpiece. The penetration depth of the embossing teeth is preferably set to a value greater than the tooth height of the retaining teeth. This prevents both uncontrolled workpiece deformation during clamping and excessive wear of the retaining teeth.

[0018] The embossing device has several embossing teeth whose center-to-center spacing corresponds to the grid dimension. Preferably, each embossing tooth is provided with at least one, and preferably two or more, concavely rounded flanks, so that the flank angle decreases continuously at the point of entry into the workpiece as the embossing tooth penetrates the workpiece. In this way, similar penetration depths are achieved even with materials of varying ductility, ensuring that the embossed workpieces always fit the clamping device. Even with a large variability in the ductility of different workpiece materials, a low variability in the penetration depths of the embossing teeth is achieved. This ensures that the positive locking elements of the clamping device fit into the recesses regardless of the workpiece material. This applies at least to a wide range of workpiece materials.

[0019] As mentioned, materials with different ductility result in at least slightly different penetration depths of the embossing teeth and thus slightly different cross-sectional areas of the depressions. However, by controlling or regulating the embossing force, it can be ensured that the embossed depressions always have a depth greater than the tooth height of the retaining teeth.

[0020] The retaining teeth of the clamping jaws are so small that they fit into even the smallest anticipated recesses. Therefore, if the workpiece is made of a very ductile material and the recesses are rather large, they may engage with some lateral play. However, the pressure exerted by the clamping surfaces of the jaws on the workpiece surface, and thus on the area surrounding each recess, can narrow the recesses slightly, so that the retaining teeth ultimately engage without any play.

[0021] The embossing teeth of the die define a gap between them, into which some workpiece material can flow during the embossing process. This gap preferably has a cylindrical contour. Furthermore, the embossing teeth are preferably formed on a projection of the die. This ensures that no flat surface outside the embossing teeth comes into contact with the workpiece surface during the embossing process. As a result, the individual depressions can be surrounded by a more or less large ring-shaped protrusion, depending on the workpiece ductility. The workpiece surface can deform freely outside the depressions. This is achieved because the embossing force acts only and exclusively between the embossing teeth and the workpiece.

[0022] The clamping device according to the invention has at least one, preferably several, clamping jaws whose workpiece clamping surface is provided with positive locking elements arranged in the predetermined grid of the recesses, i.e., having a uniform center-to-center distance of 2.5 mm to 3.5 mm, preferably 3 mm. The positive locking elements are preferably teeth whose shape is similar to that of the embossing teeth, with the retaining teeth preferably being smaller than the embossing teeth. Therefore, with materials of low ductility, the size and shape of a recess can correspond to the shape and size of a retaining tooth. With materials of high ductility, the recesses produced by the embossing teeth can also be larger and deeper, so that the retaining teeth initially engage in the recesses with some play.To accommodate potentially varying embossing depths, the retaining teeth (or other positive locking elements) are preferably less high than the depth of the indentations embossed into the workpiece. When the workpiece is clamped, however, some of the material displaced by the embossing teeth can flow back and ultimately completely and preferably without gaps enclose the retaining teeth of the clamping device. Furthermore, a surface contact between the workpiece clamping surface and the workpiece can be achieved. This maximizes both the positive locking and the frictional locking.

[0023] Different embossing dies with differently sized embossing teeth can be provided for various workpiece materials. Additionally or alternatively, different embossing forces can be used for different workpiece materials. For this purpose, the embossing device can be designed so that the embossing force is adjustable accordingly. Additionally or alternatively, a measuring or monitoring device can be provided for measuring or monitoring the penetration depth of the embossing teeth into the workpiece. The embossing device can be designed to terminate the embossing process when the desired depth of the indentations is reached. In all presented embodiments, the depth of the indentations is between 0.2 mm and 2 mm. Preferably, the depth of the embossed indentation is 0.02 mm to 0.05 mm greater than the height of the retaining tooth.

[0024] Further details and advantages of the clamping system according to the invention will become apparent from the drawing and the claims. These show: Figure 1 a prepared workpiece during clamping in a clamping device according to the invention, Figure 2 a stamp belonging to a stamping device, in a perspective overview view, Figure 3 the embossing die in its relation to the workpiece during the embossing process, in a schematic representation, Figure 4 an embossing tooth during the embossing process as it penetrates the workpiece, Figure 5 the workpiece after the preparatory embossing process, in a schematic perspective view, Figure 6 the workpiece and an embossing die in a slightly different embodiment after the embossing process, in a schematic representation, Figure 7 the workpiece and a clamping jaw during clamping of the workpiece, in a cutaway schematic representation, Figure 8a diagram showing the relationship between grid dimension and normalized holding force, Figure 9 a embossing device in a schematic top view, Figure 10 a modified embodiment of an embossing die and an associated workpiece after the embossing process, in a schematic side view, Figures 11 and 12 Further embodiments of the clamping system according to the invention and associated workpieces.

[0025] Figure 1Figure 1 illustrates a method for clamping workpieces 10. In a preparatory step, deformations 11, for example in the form of a series of recesses 12, have been applied to the workpiece 10, which is illustrated schematically as an example. These serve as positioning and coupling elements when clamping in a corresponding clamping device 13. The clamping device 13 comprises at least one movable clamping jaw 14 and an associated abutment 15, which can also be designed as a clamping jaw and be mirror-symmetrical to the clamping jaw 14. Other abutments, such as clamping jaws with smooth clamping surfaces, are also possible.

[0026] The following description of the clamping jaw 14 applies to the present and all further embodiments, to the abutment 15 designed as a clamping jaw or to further clamping jaws and abutments accordingly.

[0027] The clamping jaw 14 has a series of positive locking elements 16, which can be in the form of retaining teeth 17 that fit the recesses 12 in shape, position, and size. The retaining teeth 17 are, for example, arranged in a straight row at a distance from a bearing surface 18 formed on the clamping jaw 14. However, the retaining teeth can also be arranged in a different pattern, for example, in a zigzag pattern or in two or more rows. The preferably flat bearing surface 18 is arranged perpendicular to a clamping surface 19, from which the retaining teeth 17 project. The clamping surface 19 is preferably a flat surface. Preferably, the retaining teeth 17 are all uniformly formed.

[0028] The recesses 12 and the retaining teeth 17 are arranged in a matching grid R, which is in Figure 1The workpiece 10 is symbolically marked. The grid R defines the center-to-center distances of the recesses 11 and the center-to-center distances of the retaining teeth 17 to a uniform value between 2.5 mm and 3.5 mm. Preferably, the center-to-center distance of the retaining teeth 17 and the recesses 12 is set to 3 mm in the grid R.

[0029] When the workpiece 10 is clamped between the clamping jaws 14, 15, the retaining teeth 17 engage in the recesses 12, and the clamping surface 19 comes into contact with the workpiece surface 20 surrounding the recesses 12. The clamping surface 19 exerts a compressive force on the workpiece surface 20. Simultaneously, the retaining teeth 17 rest in the recesses 12 without play. The workpiece 10 is thus clamped by friction and form-fit. Due to the small grid spacing of preferably 3 mm, this results in a virtually continuous, form-fit clamping of the workpiece 10 with low local force peaks. At the same time, the engagement of the retaining teeth 17 in the recesses 12 fixes the workpiece position parallel to the clamping jaws 14, 15.

[0030] Figure 2Figure 1 illustrates part of a tool for forming the recesses 12 on the workpiece 10. The recesses 12 are not part of the desired workpiece geometry, but merely serve to clamp the workpiece 10. They are placed in an area of ​​the workpiece 10 where no machining operations are required in the selected clamping setup.

[0031] Figure 9 Figure 31 illustrates an embossing device 31 for producing the indentations 12 on the workpiece 10. The embossing device 31 preferably has two embossing dies 21, 21' which can be moved and clamped towards each other by means of a force-generating device 30. The force-generating device is connected to the two embossing dies 21, 21' and is configured to exert a controlled force on a workpiece 10 held between the two embossing dies 21, 21'. The two embossing dies 21, 21' are preferably identical and arranged as mirror images of each other.

[0032] The in Figure 2 The illustrated embossing die 21 has a support surface 22 onto which the workpiece 10 can be placed before an embossing process is carried out. The support surface 22 can be a flat surface or a surface with multiple interruptions. It is also possible to omit such a support surface 22.

[0033] Parallel to the support surface 22, a rib 23 is formed on the embossing die 21, which is provided with preferably rounded recesses 24. These recesses 24 preferably each follow a cylindrical surface and define the embossing teeth 25 between them, which are arranged in the grid R. In other words, their center-to-center distances are fixed in the preferred grid from 2.5 mm to 3.5 mm and are, for example, uniformly 3 mm.

[0034] The ridge 23 can otherwise be parallel-flanked or wedge-shaped, i.e., tapering towards the tips of the embossing teeth 25. Furthermore, the embossing teeth can also be rounded on these flanks.

[0035] Figure 3 To further illustrate understanding, the relationship between the size of the embossing teeth 25 and the depressions 12 produced in the workpiece 10 is shown. As can be seen, the embossing teeth 25 are only partially pressed into the material of the workpiece 10 during the embossing process, i.e., their respective height H (see Figure 3 ) is greater than the depth T of the produced depressions 12. The height H of the embossing teeth 25 can be determined starting from a in Figure 3 The distance between the deepest points of the depressions 24 and the tooth tip is measured along the imaginary line shown with a dashed line and is, for example, 3 mm. The depth T of the depressions 12 then corresponds to the penetration depth of the teeth.

[0036] In an embossing process, the embossing dies 21 are preferably moved towards each other by force, the embossing process preferably being force-controlled, or at least force-limited. This means that the depth T results from an interaction between the material ductility of the workpiece 10 and the applied embossing force. In contrast to displacement-controlled embossing processes, which have a defined penetration depth, this prevents damage to the workpiece 10. Additionally or alternatively, the penetration depth of the embossing teeth can be measured during the embossing process. The penetration depth is the distance the embossing jaws travel after the workpiece first contacts the end faces of the embossing teeth. The embossing device can be configured to terminate the embossing process when the desired penetration depth, and thus the desired depth of the indentation, is reached.The depth T of the recess 12 is preferably at least slightly greater than the height of a retaining tooth 17. The difference can be, for example, 0.02 to 0.05 mm, or possibly less or more.

[0037] Figure 4 This illustrates the embossing process on a highly flowable and therefore ductile material, such as ductile aluminum. The embossing tooth 25 penetrates the workpiece surface 20 locally, whereby the material of the workpiece 10 yields to the embossing tooth 25 and deforms. An affected zone 26 is formed in which the material of the workpiece 10 is compacted and may also be hardened by deformation. In addition, a non-planar deformation of the workpiece surface 20 can form around the created depression 12, for example in the form of a ridge-like bulge or elevation 27 or in another slight lifting of the workpiece surface 20 against the penetration direction of the embossing tooth 25. This is Figure 5 and 6illustrated again in an exaggeratedly heightened manner.

[0038] How Figure 4 As can also be seen, the cross-section of the embossing tooth increases from its front surface 25a towards its root. Due to the preferably present curvature of its flanks 24a, 24b, the penetration resistance of the embossing tooth increases disproportionately with increasing penetration depth.

[0039] How Figure 6 As shown, the workpiece surface 20 is curved multiple times after the penetration of the depressions 12, even if it was previously flat, especially between the depressions 12, i.e., it curves around different centers of curvature and thus deviates from the flat shape as well as from other simple geometric shapes, such as the cylindrical shape.

[0040] The premolars 25, as particularly the Figures 2 and 6The embossing teeth 25 are characterized by two or four concavely rounded flanks 24a, 24b, such that the resistance of each embossing tooth 25 increases non-linearly with increasing penetration depth during the embossing process. Therefore, when embossing various ductile materials, depressions with a depth T are achieved that are sufficient to accommodate the retaining teeth 17. With even more ductile materials, the penetration depth is greater. However, the variability of the depth T is significantly less than the variability of the different materials under consideration. Additionally, the penetration depth during embossing can be monitored and controlled to a target value. Workpieces 10 can be made, for example, of aluminum, aluminum alloys, various other metals and metal alloys, or plastic.The rounding of the surface 24 ensures that even with soft materials, complete penetration of the embossing tooth 25 into the workpiece 10 is not to be expected.

[0041] As already mentioned, during clamping, the clamping surface 19 and the workpiece surface 20 are brought into contact with each other, while the retaining teeth 17 engage in the recesses 12. As shown Figure 7 As can be seen, the height h of a retaining tooth, measured in the clamping direction S, is preferably less than the depth T of the recess 12. During the clamping process, the ridge-like protrusion 27 is at least partially flattened by the clamping surface 19, so that material of the workpiece, particularly in zone 26, is further deformed and fits tightly around the retaining tooth 17. This can lead to further material flow, resulting in additional deformation. Figure 7This results in deformation areas 28, 29, shown in hatched relief. A large part of the clamping surface 20, preferably the entire clamping surface 20 and the outer surface (24a, 24b) of the retaining teeth 17, is thus used as a surface transmitting the clamping force. The material of the workpiece 10 rests with preload against the flanks and, optionally, also against the end face of the retaining teeth 17. Preferably, the depth of the recess 12 is such that the end face of the retaining tooth 17 does not rest against the bottom of the recess 12 when the workpiece 10 is clamped (see Figure 7 ).

[0042] The specified grid spacing, preferably 3 mm, ensures that the affected zones 26 of the various embossing teeth 25 in the workpiece 10 touch or overlap. This enables a quasi-continuous holding of the workpiece 10. Investigations show that both larger and smaller grid spacings result in lower workpiece holding forces. Figure 8This is illustrated in a diagram. The vertical axis (ordinate) shows the ratio of achievable holding force F to available clamping area A. To obtain comparable curves for different materials, the force F is normalized to the maximum holding force without retaining teeth.

[0043] The grid spacing R is plotted on the horizontal axis (abscissa). The grid spacing is the center-to-center distance of the embossing teeth 25, the center-to-center distance of the recesses 12, and the center-to-center distance of the retaining teeth 17. It is evident that the maximum achievable holding force F, relative to the area A, reaches its maximum at a grid spacing of 3 mm, while good holding force values ​​can still be achieved in the range between 2.5 mm and 3.5 mm. The decrease compared to the maximum holding force within this range is usually less than 30%, often less than 10%. This applies to almost all practically occurring materials that are at least somewhat ductile and thus embossable.

[0044] The holding force F is a force that acts perpendicular to the support surface 18 and thus attempts to pull the workpiece 10 clamped between the clamping jaws 14, 15 out of the clamping jaws 14, 15 (in Figure 1 vertically upwards).

[0045] Surprisingly, it has been shown that a grid spacing of 2.5 mm to 3.5 mm is optimal for a wide range of workpieces and materials, meaning that the presented clamping system does not require any specialization in specific materials or workpiece geometries. A universal clamping system can thus be offered that finds widespread application in practice.

[0046] How Figure 10 As illustrated, variations are possible. For example, the prefixing teeth and, accordingly, the retaining teeth 17 can have essentially flat flanks, while otherwise the previous description applies accordingly.

[0047] Furthermore, the Figure 11A further modification of the invention described above, wherein the workpiece 10 is held between four jaws 14, 15, 14a, 15a, each having retaining teeth 17, and for which the description of the clamping jaw 14 applies accordingly. Clamping jaws 14, 15, 14a, 15a, which are opposite each other, are moved towards or away from each other by clamping drives and can thus clamp the workpiece 10 on all four sides.

[0048] Figure 12 Figure 1 shows the clamping of a workpiece 10' on a cylindrical section thereof by means of corresponding cylindrical shell-shaped, adapted clamping jaws 14, 14a, 15, wherein the workpiece 10' as in all other embodiments of the invention has been provided with the necessary indentations in a preparatory work step, preferably by embossing, before clamping.

[0049] In the clamping method according to the invention, a workpiece 10 is first provided with recesses 12, which are arranged, for example, in a row or in a field on a grid with a 3 mm grid spacing. The grid spacing is measured as the center-to-center distance of the recesses 12, the depth T of which is preferably less than the length of the recess 12, measured in the direction of the row of recesses 12. The distances between the recesses 12 preferably correspond approximately to the length of the recesses 12.

[0050] Preferably, these recesses 12 are formed using embossing tools having embossing teeth 25 with rounded flanks 24a, 24b. Preferably, the flanks 24a, 24b are concavely rounded.

[0051] The embossing process is preferably carried out such that raised areas 27 are formed between the recesses 12, which, when the workpiece 10 is clamped between clamping jaws 14, 15, are the first to come into contact with its flat clamping surface 19. Deformation of these raised areas 27 during the clamping process increases the holding force.

[0052] A grid spacing of 2.5 mm to 3 mm has proven optimal for a wide range of usable workpieces and materials. Reference symbol:

[0053] 10, 10'Workpiece 11Deformations 12Recesses 13Clamping device 14Clamping jaws 15Abutment 16Positive locking elements 17Retaining teeth 18Support surface 19Clamping surface RRaster 20Workpiece surface 21Embossed die 22Support surface 23Ridge 24Recesses 24a, bFlanks of the embossing tooth 25 25Embossed teeth 25aFace surface of an embossing tooth 25HHeight of the embossing teeth 25TDepth of the recesses 12 26Influenced zone 27Rim-like elevation SClamping direction hHeight of a retaining tooth 17FHolding force AArea of ​​the clamping surface 20 28, 29Deformation areas 30Force generating device

Claims

1. A method for clamping workpieces (10) made of ductile materials, in which, in a preparatory process step, deformations (11) are applied to the workpieces (10) in a defined grid (R), which deformations exclusively serve as positioning and coupling elements during clamping in a corresponding clamping device (13), in which the workpieces (10) are then clamped in a combined friction-fit and form-fit manner by means of clamping jaws (14, 15) which have contact surfaces (19) for frictionally holding the workpiece (10) and which have form-fit elements (17) matching the deformations (11) for form-fit positioning and securing the position of the workpiece (10), characterized in that the deformations (11) are arranged in the grid (R) with a center-to-center distance of 2.5 mm to 3.5 mm relative to each other and have a depth of between 0.2 mm and 2 mm.

2. The method according to claim 1, characterized in that the deformations (11) are depressions (12) which are introduced into the workpiece (10) by plastic deformation by means of an embossing device (21), in that each depression (12) is created by means of one embossing tooth (25) by material displacement.

3. The method according to claim 2, characterized in that a distance to the workpiece (10) is maintained between adjacent embossing teeth (25) during embossing in order to allow an elevated deformation (27) of the workpiece surface (20).

4. The method according to claim 2, characterized in that the depressions (12) are formed on a workpiece surface (20) which is curved multiple times between the depressions (12).

5. The method according to claim 4, characterized in that planar clamping surfaces (19) provided on the clamping jaws (14, 15) are brought into surface contact with the workpiece surface (20) when the workpiece (10) is clamped.

6. The method according to claim 5, characterized in that the workpiece surface (20) is transformed into a planar shape when the workpiece (10) is clamped.

7. An embossing device for preparing the clamping of a workpiece (10) made of ductile material and associated clamping device (13) for subsequent clamping of the workpiece (10), wherein the embossing device comprises at least one embossing die (21) having an embossing structure (25) defining a grid (R) with a grid dimension, wherein the clamping device (13) comprises at least one movable clamping jaw (14) and a counter support (15) associated therewith, and wherein the clamping jaw (14) comprises a series of form-fit elements (16), characterized in that the grid dimension of the embossing structure (25) is between 2.5 mm and 3.5 mm and the embossing device is arranged to create depressions (11) on the workpiece (10) with a depth of between 0.2 mm and 2 mm.

8. The embossing device according to claim 7, characterized in that the embossing device (21) comprises a counter support for the workpiece (10), wherein the counter support is arranged opposite the embossing die (21).

9. The embossing device according to claim 8, characterized in that the counter support is configured as a further embossing die (21).

10. The embossing device according to anyone of claims 8 or 9, characterized in that a force-generating device (30) is arranged between the counter support (21') and the embossing die (21).

11. The embossing device according to anyone of the preceding claims, characterized in that the embossing die (21) comprises at least two, preferably several, embossing teeth (25), a center-to-center distance of which corresponds to the grid dimension (R).

12. The embossing device according to claim 11, characterized in that each embossing tooth (25) has at least one concavely rounded flank (14a, 14b).

13. The embossing device according to claim 11 or 12, characterized in that an interstice (24) following a cylinder contour is defined between two adjacent embossing teeth (25).

14. The embossing device according to anyone of claims 11 to 13, characterized in that the embossing teeth (25) are formed on a bar projection (23).