Tool for machining workpieces, especially sheet metal

Abstract

Tool for machining workpieces (12), in particular sheet metal, comprising an upper tool (21) which receives a machining tool (62) and a lower tool (22) which receives a counter-holder (45), wherein the upper tool (21) and the lower tool (22) can be arranged opposite each other, so that the counter-holder (45) is positioned on one side and the machining tool (62) on the other side of the workpiece (12) which can be arranged between them, and the counter-holder (45) is designed as a rollable body and has at least one outer edge zone (55) which has a lower surface hardness than the workpiece (12) to be machined or the workpiece surface of the workpiece (12) to be machined, characterized in that, in the case of a workpiece (12) to be machined with a Vickers hardness in the range of 200 to 10.000 MPa at least the outer edge zone (55) of the rollable body is formed from a material with a Vickers hardness of less than 200 MPa.

Description

[0001] The invention relates to a tool for machining workpieces, in particular sheet metal, which has an upper tool with a machining tool and a lower tool with a counterholder, wherein the upper tool and the lower tool can be arranged opposite each other, so that the counterholder is positioned on one side and the machining tool on the other side of a workpiece that can be arranged in between.

[0002] From DE 690 10 505 T4, a device for producing blanks from corrugated cardboard, rigid fiberboard, or similar materials is known, through which waste sections from die-cut blanks are removed. For this purpose, a first and a second roller are provided, each having a layer of elastically compressible or deformable material. A scraper pin is provided on one of the rollers, which acts on the waste piece so that it is clamped by the opposite roller and transported away for disposal.

[0003] From EP 2 125 262 B1, a method for producing a structured material web with a multidimensional structure is known. A perforated sheet is fed to a pressure roller, which forms a gap with a support element roller through which the sheet is guided. This support element roller has hexagonal support elements consisting of recesses. The elastic pressure roller has such hardness that the sheet, passed between the pressure roller and the support element roller, is pressed into the recesses of the support elements.

[0004] From EP 2 450 120 A1, a burr removal machine is known which includes a tool for this purpose. This tool consists of an upper tool with a machining tool, such as a striking pin, and a lower tool which accommodates a counter-holder. The counter-holder is designed as a spring-loaded steel ball. During machining of the workpiece, the steel ball rests against one side of a cut edge of the workpiece. On the opposite side of the cut edge, a striking pin is used to remove the burr, with the ball counteracting the working force of the striking pin.

[0005] US Patent 2006 / 0042341A1 describes a deburring tool in which an upper tool with a machining tool is located on one side of the workpiece to be processed, and a lower tool with a counter-holder is located on the opposite side. For deburring the workpiece, it is proposed that both the machining tool and the lower tool be designed as spheres made of steel, in order to smooth out the burr through a contact force during a traversing movement.

[0006] US patent 2007 / 0122224A1 describes another tool for machining workpieces, especially sheet metal. An upper tool accommodates a marking tool as the machining tool. Opposite this, the lower tool includes a ball as a counter-holder.

[0007] To machine the workpieces with the aforementioned tools, they are moved between the upper and lower tools, with the upper and lower tools positioned against the workpiece. This ensures that the ball rests against one side of the workpiece, while the machining tool engages the workpiece on the opposite side, applying pressure against the opposing ball. This process can cause scratches, marks, or indentations on the surface of the workpiece on the side facing the ball, which can impair the workpiece's quality.

[0008] The invention is based on the objective of proposing a tool for machining workpieces, in particular sheet metal, in which damage to the workpiece surface of the workpiece to be machined, on which a counter-holder of the tool engages, is avoided.

[0009] This problem is solved by a tool with the features of claim 1, comprising a counterholder designed as a rollable body, which has at least an outer edge zone with a lower surface hardness than the workpiece or workpiece surface to be machined. For a workpiece with a Vickers hardness in the range of 200 to 10,000 MPa, at least the outer edge zone of the rollable body on the counterholder is designed with a Vickers hardness of less than 200 MPa. This makes the rollable body softer than the workpiece or workpiece surface to be machined, so that despite the contact force between the upper and lower tools, neither indentations nor scratches occur on the workpiece surface. This improves the machining quality of such workpieces.

[0010] According to a preferred embodiment of the invention, the outer edge zone of the rollable body is designed as a coating applied to a core. This allows for the simple manufacture of such a counterholder. Furthermore, this coating can also be used as a wear indicator. As soon as this coating shows damage, flaking, or perforations, wear of the counterholder can be detected and it can be replaced.

[0011] Alternatively, the outer edge zone can also be formed by a cladding applied to the inner core. Such a cladding is usually significantly thicker than a coating. This also allows for a wider selection of materials that can form such a cladding. This, in turn, enables the use of various manufacturing processes. For example, the cladding can be produced by vulcanization as well as by other polymerization processes. Like a coating, such a cladding can act as a wear indicator. The core of the rollable body can be made of a harder material than the coating or cladding.

[0012] An alternative embodiment of the invention provides that the rollable body is formed from a solid material whose surface hardness is lower than that of the workpiece to be machined. This enables the cost-effective production of such counterholders.

[0013] Preferably, at least the outer edge zone of the rollable body, or the rollable body itself, is made of a thermoset, a thermoplastic, a thermoplastic elastomer, an elastomer, a synthetic fiber material, a non-ferrous metal, or an elastic natural product such as a natural fiber, felt, cork, fur, or leather. These materials are particularly suitable for preventing surface scratches and deformations. At the same time, cost-effective manufacturing is possible. Non-ferrous metals, such as brass or similar materials, which are softer than the workpieces typically made of steel, can also be used for the outer edge zone or for a rollable body made of solid material.

[0014] Furthermore, a coating may be applied to the outer edge zone of the rollable body. This could be, for example, a layer of paint or varnish. Such an additional layer of paint or varnish serves as a wear indicator, enabling timely replacement of the counter-holder when signs of wear appear.

[0015] An alternative design of the counter-holder provides that the outer edge zone consists of two or more layers with differing material properties, wherein the outer layer is more wear-resistant than the inner layer, but has a lower surface hardness than the workpiece or workpiece surface to be machined. This allows the outer edge zone to be flexible relative to the core of the rolling body, yet still exhibit increased wear potential without affecting the workpiece surface.

[0016] The counterholder can be arranged in a receptacle of the lower tool, which is open towards the workpiece. The counterholder is equipped with a holding device for positioning it within the receptacle, allowing it to be flexibly held along a longitudinal axis of the lower tool. This enables the counterholder to move within a predetermined tolerance range during machining, thus preventing overloading of the workpiece surface.

[0017] The holding device can be designed as a spring element, which has a receiving section for arranging the counter-holder and fastening sections for fixing the spring element to the base of the lower tool, and includes strip-shaped expansion sections in between. Such a spring element allows for simple positioning of the counter-holder relative to the lower tool. Simultaneously, the strip-shaped expansion sections of the holding device allow for simple adjustment of the counter-holder's compliance relative to the lower tool.

[0018] Another preferred embodiment of the holding device provides that, in the event of an overload of the lower tool, the counter-holder fully immerses itself in the receptacle opposite an outer edge of the receptacle, and the expansion sections of the holding device are plastically deformed. Thus, the holding device serves as overload protection and simultaneously as an indicator of an overload, which may be caused, for example, by unevenness in the sheet metal, incorrect machining parameters, collisions, sheet metal vibrations, or operator error.

[0019] The machining tool in the upper or lower tool can be designed, for example, as a marking, embossing, foil cutting, engraving, roller deburring, or roll forming tool, in particular a roll forming tool. In all these machining tools, the counter-holder, designed as a rollable body, can be used with at least one outer edge zone that has a lower surface hardness than the workpiece or workpiece surface to be machined.

[0020] A preferred embodiment provides that, in the case of a workpiece to be machined, a Vickers hardness in the range of 1000 to 10,000 MPa (N / mm²) 2 ), such as steel, steel alloys, or stainless steel, when using plastics with a Vickers hardness of less than 200 MPa. This allows for a preferential improvement in the machining quality of such workpieces.

[0021] Another alternative embodiment provides that, in the case of a workpiece to be machined with a Vickers hardness in the range of 200 to 1,000 MPa, preferably from 200 to 500 MPa, which is made, for example, of a non-ferrous metal, at least the outer edge zone of the rollable body is formed with a Vickers hardness of less than 200 MPa. In this application, when non-ferrous metals are being machined, at least the outer edge zone of the rollable body is made of plastic.

[0022] The counter-holder, designed as a rollable body, can, for example, be a sphere, allowing it to be used without needing to align with the cutting edge. Alternatively, the rollable body can be a cylinder, such as a roller, rotating around an axis of rotation, particularly one parallel to the workpiece or machine table. This cylindrical body has an outer layer with a surface hardness lower than that of the workpiece. This outer layer may extend only partially along the length of the axis of rotation. Furthermore, the rollable body can be designed as a torus.

[0023] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The features that can be derived from the description and the drawings can be applied individually or in any combination according to the invention. The drawings show: Fig. 1. A perspective view of a machine tool, Fig. 2 a schematic sectional view of a tool for a machine tool according to Fig. 1 with an upper and a lower tool in a starting position, Fig. 3 a schematic sectional view of the tool according to Fig. 2 in a processing position, Fig. 4 a schematic sectional view of the tool according to Fig. 2 in an overload situation, Fig. 5 a schematic view of a holding device for receiving a counter-holder in the lower tool according to Fig. 2, Fig. 6 a perspective view from below of an alternative embodiment of a counterholder Fig. 2, Fig. 7 a schematic side view of the counterholder according to Fig. 6 and Fig. 8 another schematic side view of the counterholder according to Fig. 6.

[0024] In Fig. Figure 1 shows a machine tool 11 for machining workpieces 12, in particular plate-shaped workpieces 12, such as sheet metal. Machining of workpieces can include punching, bending, marking, embossing, engraving, deburring, roll forming, especially roll forming, as well as film cutting on the workpiece surface. The machine tool 11 has a C-shaped base frame 14 with an upper frame leg 15 and a lower frame leg 16. A conventional coordinate guide 17 is housed in a recess between the upper frame leg 15 and the lower frame leg 16. This guide serves to position or move the workpiece 12 relative to a machining station 18 of the machine tool 11, as well as for magazine storage and for changing tools 20 at the machining station 15.

[0025] At machining station 18, a tool 20 is installed, comprising an upper tool 21 and a lower tool 22. The lower tool 22 is mounted in a lower tool holder 23 on a machine table 25, which in turn rests on the lower frame leg 16 of the machine frame 14. The upper tool 21 is mounted on an upper tool holder 24 of a ram 26. The ram 26 can be moved up and down on the upper frame leg 15 of the frame 14 in the direction of a double arrow 27, for example, hydraulically. Both the upper tool 21 and the lower tool 22 can be adjusted or moved about a stroke axis 28 of the ram 26 in the direction of a double arrow 29. These positioning movements, as well as the other essential machine functions, are controlled by a schematically depicted control unit 30 of the machine tool 11.

[0026] The workpiece 12 is held by means of a gripping device 32 during machining with the tool 20 and positions the workpiece 12, which rests on the machine table 25, relative to the machining station 18. After completion of a machined workpiece 34, it is removed from the machining station 18, for example by lowering a table segment 35 of the machine table 25.

[0027] In Fig. Figure 2 is a schematically enlarged representation of the tool 20, where, for example, an upper tool 21 is arranged above and a lower tool 22 below the workpiece 12. The arrangement of the upper tool 21 and the lower tool 22 can also be reversed. The representation in Fig. 2 is only an example.

[0028] The upper tool 21 comprises a base body 41, which includes a holding shank 42 and a downwardly open receptacle 43. A counter-holder 45 with a counter-holder receptacle 46 is arranged in this receptacle 43 and is spring-mounted by a holding device 47. The counter-holder 45 is a rollable body, which, according to the first embodiment, is designed as a ball 48 that is freely rotatable in the counter-holder receptacle 46. The counter-holder receptacle 46 has a cylindrical guide section 49 that is slidably guided along a longitudinal axis 50 of the tool 20 in a recess 51 in the base body 41.

[0029] In a starting position, the holding device 47 receives the counter-holder 45 such that a portion of the counter-holder 45, or a spherical segment, projects beyond an outer edge 52 of the receptacle 43. According to a first embodiment, the counter-holder 45, designed as a sphere 48, consists of a core 54 and an outer edge zone 55 that completely surrounds the core 54. The outer edge zone 55 forms a rolling surface. The outer edge zone is made of a material that has a lower surface hardness than the workpiece 12 or the workpiece surface to be machined. The outer edge zone 55 is softer than the workpiece surface. The surface hardness is determined by the Shore hardness of a material. The thickness of the outer edge zone 55 can be in the form of a coating.This can also be formed by a covering or casing, which, for example, can also encompass half or three-quarters of the radius of the sphere 48. The core 24 can, for example, be made of a harder material than the outer edge zone 55. Likewise, the core 54 can also be made of a softer material than the outer edge zone 55.

[0030] In an embodiment not shown in detail, the core 54 and the outer edge zone 55 can be made of the same material, meaning that the sphere 48 is made of a single material. The sphere 48 can be designed as a hollow sphere or as a solid sphere. However, the material used is selected such that it has a lower surface hardness than the workpiece 12 or the workpiece surface to be machined. Furthermore, the sphere 48 can alternatively consist solely of the outer edge zone 55, without any other components or parts.

[0031] Furthermore, the counterholder 45 can include a paint or lacquer coating, which serves as a wear indicator. Likewise, the outer edge zone 55 itself can serve as a wear indicator. Wear is indicated when the outer edge zone or the coating shows damage, perforations, or flaking, meaning that damage has occurred to the outer edge zone 55 of the counterholder 45 when the ball 48 rolls on the workpiece surface of the workpiece 12.

[0032] Opposite the upper tool 21 is the lower tool 22, which can also be referred to as a die. A base body 61 of the lower tool 22 receives a machining tool 62, which is driven by a ram (not shown) guided by the lower frame leg 16. The lower tool 22 is supported by its bearing shoulder 64 on the lower tool holder 23. The machining tool 62 is held in a receptacle 63. The receptacle 63 is held by a guide 65, which forms part of a support surface 67 on its outer side. Furthermore, the receptacle 63 is positioned and preloaded relative to the guide 65 by one or more energy storage elements 68. The receptacle 63 and the machining tool 62, which are connected to each other, can be displaced downwards into the base body 61 in the event of an overload.

[0033] In the embodiment according to Fig. For example, in Figure 2, the counterholder 65 is assigned to the upper tool 21 and the machining tool 62 to the lower tool 22. This arrangement can be reversed, as can the positioning of the upper tool 21 and lower tool 22 relative to the workpiece 12. This means, for example, that the upper tool 21 can hold the machining tool 62 and is assigned to the lower side of the workpiece 12. A reversal of this arrangement is also possible.

[0034] In Fig. 2 the tool 20 is arranged in a starting position 66 at the beginning or end of a machining step, that is, the upper tool 21 and lower tool 22 are positioned at a distance from the respective workpiece surface of the workpiece 12.

[0035] To machine workpiece 12, the upper tool 21 and the lower tool 22 are brought onto the workpiece surface of workpiece 12. Such a machining position 69 of the tool 20 is in Fig. 3 shown.

[0036] The machining tool 62 engages or penetrates the workpiece surface on one side of the workpiece 12, as is the case, for example, when signing or engraving, as shown in Fig. Figure 3 shows the counter-holder 45 engaging the workpiece 12 on the opposite side and counteracts the force exerted on the workpiece 12 by the machining tool 62 to prevent deformation. During machining, the workpiece 12 can be moved relative to the tool 20 or the machining station 12. The machining tool 62 engages the workpiece surface of the workpiece 12 continuously or alternately. The rolling body 48 rests against the workpiece surface of the workpiece 12 continuously or alternately during the movement. In such a machining position 69, there is no or only a slight deflection of the holding device 47, so that the contact point of the ball 48 on the workpiece surface of the workpiece 12 continues to protrude relative to the edge 52 of the receptacle 43 of the upper workpiece 21.

[0037] The Fig. Figure 4 shows the tool 20 in an overload position 71. In this overload position 71, the outer edge 52 of the receptacle 43 of the upper tool 21 rests on the workpiece surface of the workpiece 12, with the ball 48 fully immersed in the receptacle 43. The holding device 47 receives this immersion movement and maintains it after the upper tool 21 is lifted from the workpiece 12, as shown below. Fig. As described in section 5, this ensures that no deformation or other damage occurs to the workpiece surface. It also signals any existing overload.

[0038] The holding device 47 has, for the performance of these functions, an exemplary embodiment according to Fig. 5. The holding device 47 is designed as a spring element, which is, for example, made from a plate-shaped workpiece. A receiving section 73, which is, for example, circular, allows for easy arrangement and positioning of the counter-holder receptacle 46, which is preferably cylindrical. The guide section 49 of the counter-holder receptacle 46 can be inserted into the receiving section 73 and rests against the receiving section 73 with a shoulder of the counter-holder receptacle 46. The holding device 45 is preferably fastened in the receptacle 43 by means of fastening sections 74. Strip-shaped expansion sections 75 are formed between the fastening sections 74 and the receiving section 73. These sections are elastically deformable within a predetermined stroke or compression movement, but are plastically deformed under stress according to the overload position 71.Such plastic deformation can be determined and selected by the choice of material as well as the cross-section of the expansion sections 75.

[0039] In Fig. Figure 6 shows an upper tool 21 in which the counter-holder 45, designed as a rollable body, is formed by a roller 50. The roller 50 has, for example, a bearing axis 77 by which the counter-holder 45 is rotatably mounted in the base body 41. A coating 78 is provided on the bearing axis 77, which has a lower surface hardness than the workpiece to be machined. For example, a plastic coating can be applied, which can also be reapplied to the bearing axis 77 after wear. Alternatively, the coating 78 could be designed as a plastic sleeve or the like, which can be slipped onto the bearing journal 77, so that only the coating 78 needs to be replaced in case of wear.The bearing axis 77 is fixedly aligned in the base body 41 and rotatably mounted about a rotary axis 79; alternatively, the bearing axis 77 can also be fixedly arranged in the base body 41, and the casing 78 rotates about the bearing axis 77. The bearing axis 77 can also be rotatably mounted in the base body 41. The bearing axis 77 is aligned in a plane parallel to the machine table 25 or to the surface of the workpiece 12. With such a top tool 21, it is necessary that the roller 50 be guided by a rotation of the base body 41 about the stroke axis according to the double arrow 29. Fig. 1 occurs so that the rolling direction follows the course of the cutting edge.

[0040] As an alternative to active tracking of the upper tool, it can also be provided that the counter support 45, such as the roller 50, is mounted in the receptacle 43 of the base body 41 so as to be freely rotatable on a horizontal plane - i.e. passively - so that it can rotate freely in the horizontal plane and an independent tracking to the cutting edge on the workpiece 12 follows.

[0041] Furthermore, the counterholder 45 can be designed as a torus according to an embodiment not shown in detail.

[0042] The embodiments and design possibilities described using the example of the sphere 48 with regard to the outer edge zone 55 and the inner core 54 apply analogously to other rollable bodies, such as cylinders or torus.

Claims

[1] Tool for machining workpieces (12), in particular sheet metal, comprising an upper tool (21) which receives a machining tool (62) and a lower tool (22) which receives a counterholder (45), wherein the upper tool (21) and the lower tool (22) can be arranged opposite each other, so that the counterholder (45) is positioned on one side and the machining tool (62) on the other side of the workpiece (12) which can be arranged between them, and the counterholder (45) is designed as a rollable body and has at least one outer edge zone (55) which has a lower surface hardness than the workpiece (12) to be machined or the workpiece surface of the workpiece (12), characterized by, that in the case of a workpiece (12) to be machined with a Vickers hardness in a range of 200 to 10,000 MPa, at least the outer edge zone (55) of the rollable body is formed from a material with a Vickers hardness of less than 200 MPa. [2] Tool according to claim 1, characterized by , that the outer edge zone (55) of the rollable body is designed as a coating or sheathing which is applied to an inner core (54). [3] Tool according to claim 1, characterized by , that the outer edge zone (55) extends over the entire cross-section of the rollable body and the rollable body is made of a solid material. [4] Tool according to any one of the preceding claims, characterized by, that at least the outer edge zone (55) of the rollable body is made of a thermoset, a thermoplastic, a thermoplastic elastomer, an elastomer, a synthetic fiber material, a non-ferrous metal, or an elastic natural product. [5] Tool according to claim 1, characterized by , that a paint or varnish coating is applied to the outer edge zone (55) of the rollable body. [6] Tool according to claim 1, characterized by , that the outer edge zone (55) of the rollable body consists of two or more layers with different material properties, wherein the outer layer has a higher surface hardness than the inner layer. [7] Tool according to any one of the preceding claims, characterized by, that the counterholder (45) is arranged in a receptacle (43) of the lower tool (22), which is open towards the workpiece (12) and a holding device (47) is provided for positioning the counterholder (45) in the receptacle (43), by which the counterholder (45) is flexibly received along a longitudinal axis (50) of the lower tool (22). [8] Tool according to claim 7, characterized by , that the holding device (47) is designed as a spring element which has a receiving section (73) for a counter-holding receptacle (46) and at least one fastening section (74) for fixing to or in the receptacle (43) and includes strip-shaped expansion sections (75) in between. [9] Tool according to claim 7 or 8, characterized by, that in the event of an overload of the lower tool (22) the counterholder (45) fully immerses itself in the receptacle (43) opposite an outer edge (52) of the receptacle (43) and the expansion sections (75) of the holding device (47) are plastically deformable. [10] Tool according to claim 1, characterized by , that the processing tool (62) is designed as a marking, embossing, foil cutting, engraving, roller deburring or roll forming tool. [11] Tool according to claim 1, characterized by , that in a workpiece (12) to be machined with a Vickers hardness in a range of 200 to 10,000 MPa at least the outer edge zone of the rollable body in a range of 200 to 1,000 MPa is made of plastic with a Vickers hardness of less than 200 MPa. [12] Tool according to claim 1, characterized by , that the rollable body is designed as a sphere (48), as a cylinder (50) or as a torus.

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