Process and forming machine for the production of molded parts

Abstract

In a method for producing bent or straight shaped parts from an elongated workpiece, in particular a wire, sections of the workpiece of a predetermined length are successively conveyed parallel to a feed direction to a tool area of ​​the forming machine, formed there into a shaped part in a forming operation, and this part is then separated from the supplied workpiece material in a cutting operation. A slide feed device is used to convey the workpiece. This device has a linearly movable first gripping unit located closest to the tool area and at least one linearly movable second gripping unit located further away from the tool area. Working movements of the first gripping unit and of the second gripping unit, parallel to the feed direction, are generated by a first drive system and a second drive system, respectively, under the control of a control unit.During a forming operation, a component of a forming tool in the forming device performs a working movement that generates a reaction force component acting in the longitudinal direction of the workpiece material. The first gripping unit remains engaged with the workpiece and performs a linear traverse movement coordinated with the working movement of the forming tool to feed workpiece material.

Description

FIELD OF APPLICATION AND STATE OF THE ART

[0001] The invention relates to a method for producing two-dimensionally or three-dimensionally bent or straight shaped parts from an elongated workpiece, in particular a wire, and to a forming machine suitable for carrying out the method.

[0002] Forming machines are machine tools that, with the aid of suitable tools, can produce small or large series of shaped parts, sometimes with complex geometries, from elongated semi-finished products such as wire, tube, strip, or the like in an automated manufacturing process, primarily by forming. A forming machine can, for example, be a bending machine for producing two-dimensional or three-dimensional bent parts from wire, strip, or tube material by bending, or a spring manufacturing machine for producing compression springs, tension springs, torsion springs, or other spring-like shaped parts by spring coiling or spring winding.

[0003] Highly productive, computer-numerically controlled, multi-axis forming machines are used today for the efficient production of large quantities of molded parts. Such a forming machine has several controllable machine axes, a drive system with several electric drives for driving the machine axes, and a control device for the coordinated control of the working movements of the machine axes in a production process according to a computer-readable control program specific to the production process.

[0004] In the production of bent formed parts from "continuous material," the workpiece material is first straightened in a continuous flow using a straightening device on the forming machine under the control of an NC control program and then advanced or conveyed to a downstream forming device on the forming machine using a feed device on the forming machine. The fed workpiece material is formed into a spring or other formed part by the forming device downstream in the feed direction using at least one forming tool on the forming device. After completion of a forming operation, the finished formed part is separated from the fed workpiece material using a cutting device under the control of the NC control program. This process is repeated cyclically for each formed part to be produced.

[0005] There are different concepts for the design of intake systems, each with specific advantages and disadvantages.

[0006] In some variants, a feed device has at least one pair of feed rollers, each comprising two feed rollers arranged with parallel axes of rotation and capable of being driven in opposite directions. The profiled circumferential surfaces of the feed rollers of such a system ("roller feed") define a feed gap for the workpiece to pass through. By controlling the rotational speed and direction of the feed rollers, the feed speed and feed direction of the material to be processed can be specified. Roller feeds are considered cost-effective and robust. Slippage can occur when conveying smooth workpiece materials. This can be counteracted by increasing the clamping forces in the feed gap, although this is only possible to a limited extent with sensitive workpiece materials.

[0007] A feed device can also be designed as a belt feed device. It then has two counter-rotating conveyor belts, whose mutually facing outer surfaces define a conveyor gap elongated in the feed direction for guiding the workpiece. Belt feed devices are considered to be gentle on the workpiece because the engagement forces act over a longer distance and can therefore be kept relatively small locally.

[0008] There are also feed devices equipped with multiple, coordinately movable gripping units, which are referred to in this application as "slide feed devices." A slide feed device has at least two controllable gripping units or "pincers," namely a front gripping unit closer to the forming device and a rear gripping unit that can be moved linearly (by means of a slide). The front gripping unit can be controlled so that, after a feed stroke, it grips or clamps the fed workpiece section and holds it in position, while the movable rear gripping unit retracts, engages a new point on the workpiece, and then advances towards the forming unit for the next feed stroke. For this purpose, the front gripping unit is then opened. With slide feed devices, errors caused by slippage can be largely avoided.

[0009] Document DE 34 36 285 A1 discloses a forming machine with a slide feed device that operates with alternately movable grippers that move back and forth in the feed direction to selectively clamp (at least) one workpiece, feed the workpiece, and advance it in such a way that the workpiece remains clamped by either one or the other gripper during the feed. This is intended to prevent unwanted rotation of the workpiece material. The grippers can be controlled so that they open simultaneously before, during, or after shearing the workpiece to be fed, allowing the workpiece to relax.

[0010] Document DE 10 2020 213 931 A1 discloses a feeding device for the intermittent feeding of successive elongated workpiece sections of a wire or tube to a workstation of a wire or tube processing machine arranged downstream in the feed direction. The workpiece enters a bar processing machine parallel to the feed direction, which comprises, in this order along the feed axis of the workpiece, a straightening unit, a length measuring device, a stripping device, a brushing device arranged downstream of the stripping device, and the feed device arranged downstream of the stripping device. A cutting device is arranged downstream of the feed device, which cuts workpiece bars of a predefined length from the supplied wire material.The feeding device comprises a gripping unit that is movable back and forth along a linear guide device parallel to a feed direction over a stroke length by means of a feed drive and is designed to engage the workpiece section; as well as a front workpiece guide arranged between the gripping unit and the workstation or integrated into the workstation for guiding a feed movement of the workpiece section parallel to the feed direction. At least one traveling workpiece guide is provided between the gripping unit and the front workpiece guide. The front workpiece guide can be designed as a linearly movable gripping unit, thereby creating the functionality of a carriage feed device. TASK AND SOLUTION

[0011] Against this background, it is an object of the invention to provide a method for producing curved or straight molded parts from an elongated workpiece, which offers the advantages of a slide-feed device, is structurally inexpensive to implement, and can produce molded parts with high productivity whose shape exhibits only very small deviations from a desired shape. A further object is to provide a forming machine suitable for carrying out the method.

[0012] To achieve this object, the invention provides a method having the features of claim 1. Furthermore, a forming machine having the features of claim 10 is provided. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated into the description by reference.

[0013] According to one aspect of the invention, a method is provided for producing two-dimensionally or three-dimensionally bent or straight shaped parts from an elongated workpiece, which can in particular be a wire, but possibly also a tube. In the method, sections of a predetermined length of the workpiece are successively conveyed parallel to a feed direction into a tool area of ​​the forming machine. Components of a forming device are located in the tool area. The sections are then formed into a shaped part in a forming operation. In the production of bent shaped parts, the forming operation includes a bending operation. Variants for producing straight shaped parts do not produce bends in the fed workpiece section. The shaped part is finally separated from the fed workpiece material in a cutting operation. The forming machine can, for example, beIt could be a bending machine or a spring manufacturing machine.

[0014] To convey the workpiece, a carriage feed device is used which has a linearly movable first gripping unit closest to the tool area and at least one linearly movable second gripping unit arranged further away from the tool area. The first gripping unit carried by a first carriage is also referred to as the front gripping unit, and the second gripping unit carried by a second carriage is accordingly referred to as the rear gripping unit. The working movements of the first gripping unit running parallel to the conveying direction are generated using a first drive system, while the working movements of the second gripping unit running parallel to the conveying direction are generated independently using a second drive system. The working movements are each generated under the control of a control unit and can be coordinated using the control unit.

[0015] According to one formulation of the claimed invention, during a forming operation, a component of a forming tool of the forming device executes a working movement which generates a reaction force component acting in the longitudinal direction of the workpiece material, and the first gripping unit remains engaged with the workpiece and executes a linear travel movement coordinated with the working movement of the forming tool for feeding workpiece material.

[0016] The slide feed unit can therefore perform various tasks during forming operations. One task is the on-demand supply of workpiece material to the forming unit (also known as workpiece feed). In addition to this "classic" function, however, another function (tracking function) is performed, so that the first gripping unit fulfills a dual or multiple function. During a bending operation, the first gripping unit becomes a functional component of those tools that are actively and purposefully involved in the bending process.

[0017] The gripping unit of the slide feed device is not only able to open or close at a specific time, but also to precisely and coordinately guide workpiece material drawn in during the forming operation by means of the gripping unit, depending on the working movements of at least one forming tool during a forming operation in which active use of the gripping unit is important.

[0018] This allows the gripping units, especially the first gripping unit, to be used flexibly with respect to the forming process used. One advantage is that the gripping units, especially the first gripping unit, react in a way that is adapted to the forming process. This unit is actively involved in the forming process and contributes to ensuring that the formed parts have the desired target shape within the tolerances after the bending operation.

[0019] In particular, the workpiece material can be protected from excessive tensile stress and / or excessive longitudinal compression in the area between the forming tool and the first gripper. This reduces the risk of unwanted plastic deformation of the workpiece material, which has a positive effect on the shape of the finished molded part.

[0020] An important aspect is therefore that the first gripping unit can move along with the bending or forming operation using its own drive. This can be used wherever active movement of the gripping unit in the longitudinal direction of the workpiece, synchronized with the forming operation, is required.

[0021] According to a further development, the forming operation is a bending operation performed using at least one bending tool. In particular, this can be a bending operation in which a working movement of the bending tool during the bending operation generates a tensile force component on the workpiece material directed in the direction of the bending tool. The first gripping unit is guided in the direction of the tool area to reduce the tensile force components acting on the workpiece material.

[0022] It can thus be the case, for example, that during a bending operation a component of a bending tool of the forming device executes a working movement and the first gripping unit remains in engagement with the workpiece and executes a linear travel movement coordinated with the working movement of the bending tool in order to feed workpiece material.

[0023] This allows, for example, a variant of rotary draw bending to be implemented, whereby the front gripping unit remains engaged with the workpiece material drawn in during the bending operation. This makes it possible to feed the workpiece material as needed even during rotary draw bending, particularly without generating unnecessarily strong tensile stresses in the workpiece material. During rotary draw bending, the first gripping unit, located closest to the tool area, is moved synchronously and the workpiece is fed accordingly.

[0024] This functionality can also be used advantageously in eccentric bending. In eccentric bending, the workpiece, e.g. a wire, is bent around a non-centric pivot point of the bending tool. In order for the wire to be bent around this new pivot point, the bending tool must be moved. The distance by which the bending tool must be moved corresponds to the distance from the center of the bending tool (original pivot point) to the new pivot point. This therefore involves a shift of the pivot point, with the bending tool moving transversely to the wire feed direction. In eccentric bending, similar to rotary draw bending, workpiece material must be fed in. Shifting the pivot point by the said distance makes a corrective movement necessary.

[0025] Compensating movements of the first gripping unit can also be specifically generated during forming operations to avoid unfavorable compression of the workpiece material in the longitudinal direction. For example, this can occur if the forming operation is designed as a cutting operation for separating the bent formed part from the supplied workpiece material, or as a notching operation for creating at least one notch in the workpiece material, and / or as a chamfering operation for creating a tapered end of the formed part through material displacement.

[0026] During these forming operations, the workpiece material can deform plastically to such an extent that a difference in length, albeit a small one, occurs. This can be compensated for by a small gripper movement (possibly only in the millimeter range or by fractions of a millimeter) against the conveying direction. These minimal follow-up movements therefore occur in the reverse direction.

[0027] Such forming operations can occur in addition to one or more bending operations, but may also occur without an additional bending operation in the production of straight shaped parts, e.g. straight rods made of wire with tapered ends.

[0028] Some embodiments have exactly two gripping units. According to a further development, it can be provided that a carriage retraction device, in addition to the first and second gripping units, has at least one third gripping unit that can be driven independently of the first and second gripping units. The third gripping unit can be arranged between the first and second gripping units or even further away from the first gripping unit. It can be guided on the same linear guide system. In one operating mode, it is possible to continuously advance or convey the workpiece material with the aid of the second and third gripping units.

[0029] According to a further development, the first drive system and the second drive system each comprise a screw drive having a spindle that can be driven in rotation via a corresponding drive. The associated gripping unit is mounted on a carriage guided on a linear guide system and having a spindle nut guided on the spindle. This enables rapid feed movements of the gripping unit in both the forward and reverse directions with a precise speed profile, while simultaneously enabling sufficiently high feed forces in the conveying direction. The screw drive is preferably designed as a ball screw drive or recirculating ball screw and is therefore particularly low-friction.

[0030] According to a further development, the first gripping unit and the second gripping unit are guided for linear movement on a common linear guide system. The linear guide system can, for example, comprise two parallel guide rails along which the corresponding guide shoes of the gripping units run. The common linear guide system enables high positioning accuracies while simultaneously enabling a compact design.

[0031] A first spindle and a second spindle can be arranged next to each other in a common plane, allowing for a compact design in the vertical direction. One or more additional spindles can be provided in the same plane.

[0032] In addition to the screw drive (ball or trapezoidal), other drive types are also possible for the drive system. Alternatively, electric linear drives with motors, linear guides with rail guides, or traditional belt drives for the carriage can be used.

[0033] According to a further development, no component in contact with the workpiece is arranged between the first gripping unit and the second gripping unit. This results in a high degree of freedom regarding the relative movements of the two gripping units and allows for large strokes during the feed movement if necessary.

[0034] In some embodiments, a front workpiece guide is provided on the slide feed device, which, when the feed device is installed in the forming machine, is arranged between the first gripping unit and the tool area. This allows particularly precise axial feeding of the guided workpiece into the tool area. Preferably, a rear workpiece guide is located on the input side of the feed device, so that the gripping units of the feed device are arranged between a front workpiece guide and a rear workpiece guide. This also guides the workpiece in the area of ​​the gripping units so that it runs essentially coaxially with the feed axis. This makes it possible to control the effect of the gripping units on the conveyed material particularly precisely, since the material to be gripped is always close to or at its expected target position.

[0035] In order to ensure that the workpiece material is fed forward in a way that is gentle on the workpiece yet safe, a further development provides for a gripping unit to be pre-tensioned into a closed position by means of a pre-tensioning device with a pre-determinable closing force, and to open the gripping unit, the gripping unit is opened or can be opened against the closing force using an opening mechanism that is path-controlled. The closing force is the force with which the gripping unit engages the workpiece. This can be selected so that the engagement with the workpiece is sufficiently strong to prevent slipping, but by specifying the force, the workpiece is also treated gently. By controlling the path of the opening operation, the gripping unit can be disengaged from the workpiece material very quickly, so that immediately after the gripping unit is opened, the workpiece material can be moved again relative to the gripping unit.This allows for high feed rates of the workpiece. This aspect of preloading in the closed position, combined with the path-controlled opening, can also be provided independently of the other features of the claimed invention in generic methods and forming machines or in other gripping units.

[0036] In some embodiments, the carriage retraction device is designed as a rotatable carriage retraction device and configured such that the carriage retraction device as a whole can be rotated about a rotational axis running parallel to the conveying direction by means of a rotary drive under the control of a control unit. This rotational operation can be used, for example, in a bending machine to change the bending plane between two consecutive forming operations. For this purpose, the carriage retraction device can then be rotated about the rotational axis in at least one phase of a forming operation.

[0037] As a further special feature, it can be provided that the positions of the first and second gripping units along the conveying direction are detected by means of a position measuring system independent of the drive systems, and measurement signals representing the positions are processed by the control unit to control the first and second drive systems. Corresponding devices (gripping units, drive systems) are provided in the forming machine, with the control unit being configured to control the first and second drive systems depending on the measurement signals of the position measuring system independent of the drive systems.

[0038] This measure is based, among other things, on the following findings of the inventors. Many modern drive systems for generating linear working movements of components that are to be moved in a straight line or linear manner have integrated encoders (e.g., displacement encoders or rotary encoders) to determine the position of the moving component based on encoder signals. For example, in servo-motor-driven ball screws, a rotary encoder integrated into the servo drive can be used to determine the position of the linearly driven part. This is sufficient for many applications.

[0039] However, it has been discovered that, particularly in the case of forming machines operating at high unit output in continuous operation, previously unexplained length errors can occasionally occur in the manufactured products. One cause of errors identified when using screw drives, particularly ball screws, is a previously unnoticed thermal expansion of the spindle, the effect of which on the position accuracy of the driven component cannot be detected by an encoder integrated into the spindle drive. Thus, the encoder signals from an encoder integrated into the drive do not represent the position of the driven part with sufficient accuracy. The invention remedies this problem by providing a position measuring system independent of the drive systems for detecting the positions of the first and second gripping units along the conveying direction.The measurement signals from the position measuring system represent the actual positions of the driven gripping units with high accuracy, regardless of whether, and if so, to what extent, heat-induced expansion of drive train components occurs. By applying this concept, length errors could be significantly reduced, allowing molded parts to be produced even at high unit outputs with shapes, especially their length along the workpiece material, that exhibit only very small deviations from the target shape.

[0040] The separate, independent position measuring system can also be provided in generic methods and forming machines independently of the features characteristic of the claimed invention and can bring great benefits.

[0041] Preferably, the positions of the gripping units are detected without contact, in particular with a magnetic position measuring system.

[0042] The position measuring system can, for example, comprise a measuring system component that extends parallel to a guide rail of the linear guide system and interacts with a component attached to the respective gripping unit. The length measuring system can, for example, be designed as a magnetic length measuring system, in particular as a non-contact magnetic length measuring system. This can comprise a magnetic strip in a guide rail or parallel to a guide rail, which interacts with a measuring sensor integrated into a gripping unit. Other measuring principles are also possible, for example, electromechanical or optical. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Further advantages and aspects of the invention emerge from the claims and from the following description of preferred embodiments of the invention, which are explained below with reference to the figures. Fig. 1 shows an oblique perspective view of a forming machine designed as a leg spring machine according to an embodiment; Fig. 2 shows a schematic plan view of the feed device of the forming machine; Fig. 3 shows a section through a gripping unit; Fig. 4A to 4E show different phases of workpiece feed in a bending process with a pin-and-mandrel tool; Fig. 5A to 5E show different phases of workpiece feed in a bending process with a rotary draw bending tool; Fig. 6A to 6C show different phases of a continuous workpiece feed in an embodiment with three gripping units. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] Fig. 1 shows an oblique perspective view of a forming machine 100 designed as a leg spring machine according to an embodiment. Fig. 2 shows a schematic plan view of the components of the feed device of the forming machine. Fig. 3 shows a section through a gripping unit.

[0045] The forming machine 100 is configured to produce complexly bent shaped parts in the form of coil elements for electric motors. A starting material (also referred to as workpiece W) is processed, which comprises a wire-shaped electrical conductor material (e.g., copper) with a substantially flat, rectangular cross-sectional shape, which is coated with an electrically non-conductive insulating layer of varnish or the like. The starting material is in the form of a wound material supply (coil). The workpiece is also referred to below as "wire" or "flat material" for short.

[0046] The computer-numerically controlled, multi-axis forming machine 100 has a plurality of machine axes controllable via a control unit 190, a drive system with a plurality of electric drives for driving the machine axes, and a control device for the coordinated control of working movements of the machine axes in a manufacturing process according to a computer-readable control program specific to the manufacturing process.

[0047] In the exemplary embodiment, the forming machine has a rectangular machine coordinate system MK, designated by lowercase letters x, y, and z, with a vertical z-axis and horizontal x- and y-axes. In the example shown, the x-axis runs parallel to the feed axis 310 or the feed direction. The coordinate axes x, y, and z are to be distinguished from the controlled machine axes, whose drives are controlled by the control unit of the forming machine.

[0048] The forming machine 100 has a machine frame that supports a vertically oriented front wall 105 at its front. Located at the front of the front wall is the tool area of ​​the forming machine, in which components of a forming device are housed. The forming device 200 of the forming machine, mounted on the front wall and accessible from the front, includes, among other things, several forming units 220, 230, and 240 that can be advanced radially to the feed axis, and a forming unit 250 that can be advanced obliquely to the yz-plane and the feed axis. Each of the forming units has a tool head on which a single-piece or multi-component forming tool can be used.

[0049] The workpiece W, i.e., the wire, emerges from the guide device 110, equipped with a guide bushing, perpendicular to the front wall 105, coaxial with a horizontal feed axis 310 of the forming machine, running parallel to the x-axis of the machine coordinate system MK, into the area of ​​the forming device 200. The guide bushing has a guide opening with a rectangular cross-section adapted to the rectangular cross-section of the flat material.

[0050] The wire is formed into a three-dimensionally bent shaped part using numerically controlled tools of the forming device 200. The finished or largely finished formed part is then separated from the supplied wire with a scissor cut by a cutting unit 280. The cutting unit 280, equipped with a movable cutting blade, is positioned at a 45° angle to the vertical direction.

[0051] Behind the front wall 105 there is, among other things, a feed device 300 for drawing in the elongated workpiece material from a material supply and for pushing or conveying or transporting the workpiece W parallel to the feed axis 310 into the area of ​​the forming device 200 and a straightening unit (not shown in the figures) connected upstream of the feed device 300 for straightening the workpiece coming from the workpiece supply before it enters the feed device 300. The straightening unit has straightening rollers which are mounted in planes oriented perpendicular to one another and which, through appropriate infeed, eliminate the residual stress in the workpiece material and any residual curvatures in it or produce a workpiece which is as straight as possible.

[0052] The feed device 300 downstream of the straightening unit is designed as a slide feed device 300, which can feed successive workpiece sections of the workpiece material coming from the material supply and straightened by the straightening unit with a numerically controlled feed speed profile in the horizontal transport direction more or less coaxial with the feed axis 310 through the downstream guide device 110 into the area of ​​the forming device 200.

[0053] The feed device 300 is rotatable by means of a servo-electric drive about a feed rotation axis 310 corresponding to the feed axis 310 in both directions of rotation by predetermined angles of rotation (e.g. + / - 180°). A vertical rear wall 115 is provided at a distance behind the front wall 105, which is or can be firmly connected to the front wall in the lower and upper areas. Coaxial pivot bearing points are formed in the front wall and the rear wall, in which a support frame 320 is rotatably mounted about the feed axis 310. Inside the support frame, the Fig. 2 shown main component of the feed device 300 is mounted.

[0054] The straightening unit can rotate synchronously with the carriage feed device about the feed axis. For this purpose, a support frame of the straightening unit is mechanically connected in a rotationally fixed manner to a support frame (320) for the feed device (300).

[0055] In the following, details on the structure and function of the feed device 300 are given based on the Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5 explained.

[0056] The components of the feed device 300 responsible for the workpiece feed are mounted on an elongated rectangular base plate 330, which is fastened eccentrically to the feed axis in the support frame 320 such that the workpiece material guided along the feed axis runs coaxially to a through-feed axis 332 of the feed device.

[0057] On the Fig. Two parallel, straight guide rails 341, 342 of a linear guide system 340 are attached to the top side of the base plate, as shown in Figure 2, in the longitudinal edge areas. Directly adjacent to the guide rail 341, a magnetic strip 372 of a magnetic position measuring system 370 runs parallel to it.

[0058] Two gripping units 350-1 and 350-2 are arranged on the guide rails so that they can be moved back and forth on the guide rails parallel to the throughput axis 332. The first gripping unit 350-1, which is closer to the forming device, is also referred to as the front gripping unit, while the second gripping unit 350-2, which is arranged further back, is referred to as the rear gripping unit. Fig. 3 shows a vertical section through one of the gripping units.

[0059] A separate drive system is provided for each of the gripping units to generate the working movements parallel to the feed direction. The first drive system 360-1 belonging to the first gripping unit has a recirculating ball screw 362-1 aligned parallel to the feed axis, on which a spindle nut 363 arranged on the underside of the gripping unit runs. A servomotor drive (not shown) is connected to the ball screw drive via a toothed belt to drive the ball screw drive. The first recirculating ball screw extends almost to the end 331 of the base plate near the tool; the travel path of the first gripping unit is shorter than half the base plate. The first recirculating ball screw has a relatively low pitch, so that relatively large forces can be transmitted if necessary for short travel paths.

[0060] The second ball screw 362-2, which is coupled to the second gripping unit 350-2 to drive it, is located at the same height as the first ball screw on the underside of the base plate opposite the gripping units, relative to the plate plane of the base plate. It is driven in rotation by a second servomotor drive via a toothed belt and carries a spindle nut that is attached to the slide part of the second gripping unit 350-2. The pitch of the second ball screw is greater than that of the first, so that with the same degree of rotation, larger travel distances can be achieved than with the first gripping unit.

[0061] Based on Fig. 3, the structure of the gripping unit 350-1 is explained in more detail. Mounted on the base plate 352, which carries a sensor 374 of the magnetic position measuring system, the spindle nut 363, and the guide shoes of the linear guide system on its underside, are components of a bearing unit 351. These bearing units carry, among other things, two clamping jaws 352-1, 352-2 that can be moved toward and away from each other perpendicular to the direction of travel and symmetrically to it. The clamping jaws are interchangeably accommodated in a corresponding jaw holder, which is guided for linear displacement in a base body of the gripping unit. The gripping unit can also be referred to as a pair of pliers, and the clamping jaws are accordingly referred to as gripping jaws.

[0062] The clamping jaws are preloaded toward a closed position. For this purpose, spring elements are combined into a spring assembly, whose forces acting on the clamping jaws can be adjusted using an adjustment device 353, for example, depending on the workpiece. The closing movement thus occurs automatically with a certain closing force if no opposing forces are acting.

[0063] To open the clamping jaws, an electric motor drive 354 is provided. This drives a crankshaft 355, on which coupling elements are mounted like connecting rods, which are coupled to the clamping jaws. Thus, rotation of the crankshaft causes the clamping jaws to open, allowing the workpiece to be released. The end position of each clamping jaw closest to the workpiece can be preset using an adjustable stop.

[0064] A front workpiece guide 332 facing the forming tools is mounted on the tool-side end 331 of the base plate, and a rear workpiece guide 334 is mounted on the rear end. Their guide openings are arranged coaxially to the feed axis 310 and help to guide the guided workpiece as precisely as possible along the feed axis in the area of ​​the clamping jaws of the gripping units.

[0065] The working movements of the gripping units, both with regard to the movement parallel to the feed axis and with regard to the closing and opening movements of the clamping jaws, are controlled via a control unit 190 of the forming machine.

[0066] Based on the Fig. 4 ff., different phases of working movements of the gripping units during different bending operations are explained. Fig. Figures 4A to 4E show different phases of a pin-and-mandrel bending operation, in which the workpiece is bent using a pin-and-mandrel bending tool 400. Between the beginning and end of the bending operation, the wire is not advanced any further. The front gripping unit 350-1 facing the tool always remains in the same place or position. One advantage of this is that the distance between the clamping and bending points remains constant, thus compensating for the same elongation. Fig. Figure 4A shows the feed stroke of the rear gripping unit 350-2 to convey a new piece of workpiece material into the area of ​​the forming tools. During this phase, the front gripping unit 350-1 is open, and the rear gripping unit is closed. Then, by closing the front gripping unit, the workpiece is secured in the axial direction, and the rear gripping unit opens ( Fig. 4B) and returns to the Fig. 4A, to advance a new piece of workpiece material after the bending operation has been completed. For this purpose, the rear gripping unit is closed and the front gripping unit is opened ( Fig. 4D) and then the rear gripping unit pushes the released tool material forward ( Fig. 4E).

[0067] Based on the Fig. 5A to 5E now explain the working movements of the slide feed device when the workpiece material is advanced toward a rotary bending tool 500 for performing a rotary bending process. This tool has a bending mandrel 510 located in the area of ​​the rotation axis with an outer contour, which defines the inner contour of the bend to be created in terms of radius. An outer tool 520, which can be rotated with the bending mandrel about the bending axis, can be advanced to clamp the workpiece material laterally to the bending mandrel ( Fig. 5B). At the beginning of the operation, the workpiece material is gripped by opening the front gripping unit 520-1 and closing the rear gripping unit 520-2. The front gripping unit is then opened, and the rear gripping unit moves forward toward the tool to bring the workpiece material into the engagement area of ​​the bending tool 500. This tool now performs a rotary draw bending operation. For this purpose, the workpiece material is clamped to the bending mandrel ( Fig. 5B) and then, as the rotary bending tool rotates, the workpiece material is pulled around the bending mandrel, so that workpiece material must be fed in from the feed side.

[0068] This could be achieved by opening the first and second gripping units so that the workpiece material is pulled forward simply by rotating the bending tool. Instead, however, the front gripping unit 350-1 is left in the gripping position, while the rear gripping unit can open and retract. The front gripping unit 350-1 therefore remains in engagement with the workpiece W during tool rotation and executes a linear movement coordinated with the working movement of the bending tool to feed the workpiece material. This ensures that the workpiece material lying between the front gripping unit 350-1 and the bending tool remains sufficiently well clamped without excessive tensile forces acting on it. The feed is therefore better controlled than in a case without a moving front gripping unit. This allows bending geometries to be improved and the workpiece material is not subjected to excessive tensile loads.This benefits the dimensional stability of the finished molded parts.

[0069] After completion of the bending operation (see Fig. 5D) the first gripping unit is opened again and moves back to its starting position, while the rear (second) gripping unit closes for the next feed process ( Fig. 5E).

[0070] In the embodiments described above, exactly two gripping units are provided. The rear gripping unit (second gripping unit) 350-2 provides the large stroke during the feed, which is why this gripping unit is also referred to as a feed unit or feed tongs. The front, first gripping unit does not participate in the workpiece feed, which is carried out before the start of a new bending operation. It can, as in the example of the Fig. 4, remain stationary during the entire bending operation or, as in the example of rotary draw bending of Fig. 5, clamp the workpiece material during the bending operation and move in a coordinated manner with the bending movement. The front gripper unit is therefore also referred to as the bending pliers.

[0071] There are also designs with more than two independently movable gripping units. This allows for continuous feed at high speed. Fig. 6, the structure and possible uses of such a carriage feed device 600 with a total of three gripping units are explained.

[0072] The feed device 600 has a front gripping unit 650-1, a first rear gripping unit 650-2 and a second rear gripping unit 650-3, which is arranged even further away from the first gripping unit on the same linear guide system and which is also referred to here as the third gripping unit.

[0073] Fig. Figure 6A shows a phase in which the third gripping unit 650-3 has gripped the workpiece, advanced it toward the tools, and has now reached the feed rate of the still-open middle gripping unit 650-2. This gripping unit is now closed and takes over the workpiece material, while the rearmost feed unit is accelerated back to its starting position against the feed direction. Fig. Figure 6B shows the situation in which the third gripping unit 650-3 has returned to the rear starting position and the front feed unit is feeding the wire toward the tool at a continuous speed. Now, the third gripping unit 650-3 accelerates again in the feed direction to reach the feed speed. In the situation of Fig.At 6C, the wire material is transferred again. The third gripper unit (rear feed unit) has reached the feed speed again and clamps the wire. The front feed unit (second gripper unit) opens and accelerates back to its starting position, counter to the feed direction.

[0074] In all process variants, the positions of the first and second gripping units along the feed direction are recorded using the contactless position measuring system. The measurement signals from sensors 374, which represent these axial positions, are transmitted wired or wirelessly to the control unit 190. This unit processes the measurement signals or the position information contained therein to control the first and second drive systems (and, if necessary, a third drive system). QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 34 36 285 A1

[0009] DE 10 2020 213 931 A1

[0010]

Claims

[1] Method for producing two-dimensionally or three-dimensionally bent or straight shaped parts from an elongated workpiece, in particular a wire, comprising the following steps: Successive conveying of sections of a predetermined length of the workpiece parallel to a feed direction to a tool area of ​​the forming machine; Forming supplied workpiece material into a molded part in a forming operation; separating the molded part from the supplied workpiece material in a cutting operation; wherein a carriage feed device is used to convey the workpiece, which has a linearly movable first gripping unit closest to the tool area and at least one linearly movable second gripping unit arranged further away from the tool area, wherein working movements of the first gripping unit running parallel to the feed direction are generated by means of a first drive system and of the second gripping unit by means of a second drive system under the control of a control unit; characterized by , that during a forming operation, a component of a forming tool of the forming device executes a working movement which generates a reaction force component acting in the longitudinal direction of the workpiece material, and that the first gripping unit remains in engagement with the workpiece and executes a linear travel movement coordinated with the working movement of the forming tool for feeding workpiece material. [2] Method according to claim 1, characterized bythat the forming operation is a bending operation which is carried out by means of at least one bending tool, wherein preferably a working movement of the bending tool during the bending operation generates a tensile force component on the workpiece material directed in the direction of the bending tool and the first gripping unit is guided in the direction of the tool area in order to reduce tensile force components acting on the workpiece material. [3] Method according to claim 2, characterized by that the bending operation is carried out as a rotary draw bending operation. [4] Method according to one of the preceding claims, characterized bythat the forming operation comprises a cutting operation for separating the bent shaped part from the supplied workpiece material or a notching operation for producing at least one notch in the workpiece material and / or a chamfering operation for producing a tapered end of the shaped part by material displacement, wherein the travel movement of the first gripping unit for feeding the workpiece material takes place counter to the feed direction in order to avoid unfavourable compression of the workpiece material. [5] Method according to the preamble of claim 1, in particular according to one of the preceding claims, characterized by that positions of the first and second gripping units along the feed direction are detected by means of a position measuring system independent of the drive systems, and measurement signals of the position measuring system representing the positions are processed by the control unit for controlling the first and second drive systems. [6] Method according to claim 5, characterized by that the positions of the gripping units are recorded without contact, in particular with a magnetic position measuring system. [7] Method according to one of the preceding claims, characterized by that a gripping unit is pre-tensioned into a closed position with a predeterminable closing force and is opened in a path-controlled manner against the closing force to open the gripping unit. [8] Method according to one of the preceding claims, characterized by that the slide feed device is rotated in at least one phase of a forming operation by means of a rotary drive under the control of the control unit about a rotational axis running parallel to the feed direction. [9] Method according to one of the preceding claims, characterized bythat a feed device has, in addition to the first and the second gripping unit, at least a third gripping unit which can be driven independently of the first and the second gripping unit, wherein preferably in one operating mode the workpiece is continuously advanced. [10] Forming machine (100) for producing two-dimensionally or three-dimensionally bent or straight shaped parts from an elongated workpiece (W), in particular a wire, comprising a carriage feed device (300) for successively conveying sections of a predeterminable length of the workpiece parallel to a feed direction (310) to a tool area of ​​the forming machine having a forming device; wherein the carriage feed device a linearly movable first gripping unit (350-1) closest to the tool area and a linearly movable second gripping unit (350-2) arranged further away from the tool area and a first drive system (360-1) for generating working movements of the first gripping unit parallel to the feed direction and a second drive system (360-2) for generating working movements of the second gripping unit parallel to the feed direction characterized by , that a control unit (190) of the forming machine is configured in at least one operating mode such that during a forming operation a component of a forming tool of the forming device executes a working movement which generates a reaction force component acting in the longitudinal direction of the workpiece material and that the first gripping unit (350-1) remains in engagement with the workpiece (W) and executes a linear travel movement coordinated with the working movement of the forming tool for feeding workpiece material. [11] Forming machine according to claim 10, characterized bythat the drive systems (360-1, 360-2) for each of the gripping units have a screw drive, in particular a ball screw drive, with a spindle (362-1, 362-2) rotatable about a spindle axis and a spindle nut coupled to the gripping unit, wherein preferably the spindle axes of the spindles (362-1, 362-2) lie next to one another in a common plane which lies parallel to a plane spanned by guide rails (341, 342) of a linear guide system (340). [12] Forming machine according to claim 10 or 11, characterized by that the first gripping unit (350-1) and the second gripping unit (350-2) are guided in a linearly movable manner on a common linear guide system (340). [13] Forming machine according to the preamble of claim 1, in particular according to one of the preceding claims, characterized bya position measuring system (370) independent of the drive systems is provided for detecting positions of the first and second gripping units (350-1, 350-2) along the feed direction (310) and generating measurement signals representing these positions, and that the control unit is configured to control the first and second drive systems in dependence on the measurement signals of the position measuring system. [14] Forming machine according to claim 13, characterized bythat the position measuring system (370) has a measuring system component (372) which extends parallel to a guide rail of the linear guide system (340) and interacts with a component (374) attached to the respective gripping unit and / or that the position measuring system is designed as a contactless position measuring system, in particular as a magnetic position measuring system which has a magnetic strip (372) in a guide rail or parallel to a guide rail, which interacts with a measuring sensor (374) integrated in a gripping unit. [15] Forming machine according to one of claims 10 to 14, characterized by that no component in contact with the workpiece is arranged between the first gripping unit (350-1) and the second gripping unit (350-2). [16] Forming machine according to one of claims 10 to 15, characterized bythat the carriage retraction device (300) has, in addition to the first gripping unit and the second gripping unit, at least one third gripping unit (650-3) which can be driven independently of the first and the second gripping unit. [17] Forming machine according to one of claims 10 to 16, characterized by a front workpiece guide (332) arranged between the first gripping unit (350-1) and the tool area, wherein a rear workpiece guide (334) is preferably arranged on an input side of the feed device, so that the gripping units of the carriage feed device are arranged between a front workpiece guide (332) and a rear workpiece guide (334). [18] Forming machine according to the preamble of claim 10, in particular according to one of claims 10 to 17, characterized bythat a gripping unit (350-1, 350-2) has a pretensioning device which is designed such that it pretensions the gripping unit into a closed position with a predeterminable closing force, and that the gripping unit can be opened in a drive-controlled manner against the closing force by means of an opening mechanism. [19] Forming machine according to one of claims 10 to 18, characterized by that the carriage feed device (300) can be rotated by means of a rotary drive about a feed rotation axis coaxial with the feed axis (310) by predeterminable rotation angles. [20] Forming machine according to one of claims 10 to 19, characterized bythat the forming machine (100) is designed as a bending machine or as a spring manufacturing machine and has a forming device in the tool area and / or that the forming machine has a straightening device upstream of the slide feed device (300) for straightening the workpiece before it enters the slide feed device (300).

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