EMBOSSING DEVICE FOR CLAMPING WORKPIECES

Description

[0001] The invention relates to a device and a method for clamping workpieces, in particular round workpieces, and in particular to an embossing device for preparing workpieces for clamping.

[0002] When machining workpieces in machine tools, especially for metal cutting, the workpieces must be firmly clamped and held in suitable clamping positions. Even large forces acting on the workpiece during machining operations must not cause the workpiece to move in or out of the clamping fixture. At the same time, the workpiece should be as accessible as possible to allow as many machining operations as possible to be performed consecutively on the workpiece in a single setup.

[0003] EP 1 071 542 B1 proposes a clamping method in which, in a preparatory step, evenly spaced recesses are applied to the workpiece. These recesses serve solely as coupling elements when clamped with a corresponding clamping device, but are otherwise functionless. After this preparatory step, the workpieces are held in vices that have contact surfaces on their clamping jaws for frictional holding and have form-locking elements complementary to the recesses in the workpiece for positive positioning and positional security. The workpiece is thus clamped in a mixed manner and clamped with both form and friction. This clamping method has proven itself in principle for workpieces with straight clamping surfaces as well as for workpieces with rounded clamping surfaces.

[0004] A key element of the clamping system according to EP 1 071 542 B1 is a stamping station, which serves to create a series of recesses on the workpiece. These recesses must fit the clamping teeth of the vices between whose jaws the workpiece is to be clamped. These recesses must be dimensionally accurate.

[0005] Furthermore, EP 2 724 817 A1 discloses a vice with two jaws that can be adjusted toward each other and have triangular pockets for accommodating carbide clamping inserts. Each clamping insert has two rows of teeth that dig into the workpiece for clamping.

[0006] Also for clamping workpieces, DE 10 2012 000 905 A1 proposes clamping jaws with screws inserted into them, the conical head of which has a toothed edge that is able to dig into the workpiece to be clamped.

[0007] A similar system is known from DE 20 2006 020 457 U1. This document describes clamping jaws with clamping elements inserted into them, which are suitable for clamping round workpieces. For this purpose, the clamping elements have a laterally flattened head with teeth on the flattened side.

[0008] The object of the invention is to provide an embossing device with which dimensionally accurate depressions can be produced on a wide range of workpieces made of different materials.

[0009] On workpieces, particularly workpieces with curved clamping surfaces such as at least partially cylindrical clamping surfaces, recesses are made into which projections of the clamping jaws engage when the workpiece is clamped. The recesses are made on the workpiece in particular in a preparatory operation in which the workpiece is plastically deformed, for example by embossing. For this purpose, an embossing device is used which has at least one jaw and an abutment whose distance from one another is adjustable. The jaw has at least one seat for at least one insert body which has a projection with an edge directed towards the workpiece. To carry out an embossing process, the distance between the jaws and the abutment is adjusted until the insert body touches the workpiece with at least one point of the projection.By further reducing the distance between the abutment and the jaw, the insert body penetrates the workpiece with its projection by the desired amount, creating a depression at that point. The insert body forms a stamping tooth, with the projection provided on the insert body and the surface areas adjacent to its edge serving as the stamping tooth. It has been shown that the insert body is subject to only minimal wear and has a long service life when cutting a wide variety of materials. A specially shaped insert body with a projection provided on it can be used as the stamping tooth. The insert body can be a body specially provided for this purpose or, alternatively, an indexable insert.

[0010] The distance between the jaw and the abutment is preferably adjusted using force-limiting and / or displacement-controlled adjustment. This ensures that, as long as a maximum force is not exceeded, a specified penetration depth of the insert into the workpiece is achieved. This ensures that the indentations created on the workpiece have a desired, uniform shape, regardless of the workpiece's material properties.

[0011] The workpiece is then clamped in a clamping device, for example in the form of a vice with two or more movable jaws or in the form of a chuck with, for example, three or more jaws, which have clamping surfaces with attached clamping teeth. The clamping teeth fit into the recesses and create a positive connection. The clamping surfaces rest against the workpiece near the recesses and additionally clamp it with frictional engagement. This ensures secure storage of the workpiece in the clamping device while requiring minimal space. The circumference of the workpiece is largely freely accessible and can therefore be machined, for example, by machining.

[0012] The embossing device according to the invention is defined in claim 1.

[0013] This embossing device has at least one projection designed as an embossing tooth. The embossing tooth has, in particular, an edge and adjoining surface areas that enclose a wedge angle with one another. This angle is preferably between 45° and 90° and is preferably 60°. The insert bodies are preferably releasably attached to the respective seat and can thus be replaced as needed. The insert body has a polygonal border and exhibits two- or morefold rotational symmetry. The insert bodies can thus be attached to the jaw in two or more positions. This allows the insert body to be attached to the seat in a different position after sufficient wear to continue serving as an embossing tooth.

[0014] The projection of the insert body can have a strip-like shape and extend along a side surface of the insert body. This projection forms a stamping tooth, which is designed to create a recess of a precisely predetermined shape on the workpiece.

[0015] The strip-like projection is preferably oriented parallel to the workpiece support surface of the jaw. This ensures particularly secure subsequent fastening of the workpiece in a specially designed chuck.

[0016] The strip-like projection preferably has a triangular cross-section. This facilitates the stamping process. The projection is preferably straight and borders on at least one of its two flanks a surface designed as a workpiece contact surface. This determines the depth and shape of the stamped recess on the workpiece.

[0017] In a preferred embodiment, the seats provided for receiving the insert bodies are designed as pockets from which the insert bodies protrude when arranged therein. The jaws preferably have a workpiece support surface over which the insert bodies project. During stamping, the workpiece is placed onto the workpiece support surface of each jaw, after which the stamping process is initiated and carried out by reducing the distance between the jaws. This configuration clearly defines the axial position of each created depression relative to the end face of a cylindrical workpiece. The stamping device according to the invention is thus robust, durable, and precise.

[0018] Advantageous embodiments of the invention are the subject of subclaims, the drawings, and the associated description. They show: Figure 1a stamping station for preparing a workpiece for clamping in a suitable chuck, in a perspective schematic representation, Figure 2 the minting station after Figure 1 , in plan view, Figure 3 the embossing station, in a partial perspective view, Figure 4 an insert body in plan view, Figure 5 the insert body after Figure 4 in side view, Figure 6 a modified embodiment of an insert body and an associated workpiece, in a schematic vertical section, Figure 7 a further modified embodiment of an embossing station, in a simplified vertical section.

[0019] In Figure 1Illustrated is a stamping device 10, which serves to prepare a workpiece 11 for clamping in a chuck designed for this purpose. The workpiece 11 is symbolized by a ring. However, workpieces 11 can also have other shapes, in which case they only follow a cylinder, at least in sections, in a lower zone 12 of their circumferential surface bordering the base surface. The workpiece 11 can later be mounted in a rotating chuck, for example, to perform turning operations, turn-mill operations, or the like.

[0020] The embossing device 10 includes two jaws 13, 14, the distance between which can be adjusted in a controlled manner by means of an actuating device 15.

[0021] The two cheeks point, as can be seen from the Figures 2 and 3As can be seen, each of the jaws has a workpiece support surface 16, 17 on its upper side, which are preferably arranged in a common plane. The jaw 14 has at least one, preferably a plurality of seats 18 to 22, which can be designed, for example, as polygonally bordered pockets. The jaw 13 also has a plurality of seats 23 to 27, which are preferably designed as polygonally delimited pockets, which preferably correspond in shape and size to the seats 18 to 22. Insert bodies 28, 29, 30, 31 are attached to at least one, preferably a plurality of the seats 18 to 22; 23 to 27 of the two jaws 13, 14 and are each secured with a suitable fastening means, for example a screw. The insert bodies 28 to 31 serve as embossing teeth or as abutments for the respective opposite embossing tooth.

[0022] The insert bodies 28 to 31, as well as the seats 18 to 27, are of identical design. Figures 4 and 5 The illustrated insert body 28 and its subsequent description therefore represent all insert bodies 28 to 31 used on the embossing device 10.

[0023] In plan view, the insert body 28, for example, has a hexagonal, scalene, yet triple-rotationally symmetrical outline. Strip-like projections 32 to 34 are formed on the three shorter edges of this hexagonal outline, which project radially outward and form embossed teeth.

[0024] Below its hexagonal head, the insert body 28 has Figure 5a polygonal, for example hexagonal, shaft 35, which can also have a hexagonal outline and fits into the seats 18 to 27 with minimal play. Preferably, the hexagonal shaft 35 has a scalene outline with triple rotational symmetry. In other words, the shaft 35 can be inserted into the respective pocket 19 in three positions, each rotated by 120° relative to the other.

[0025] The strip-like projection 32 corresponds to the strip-like projections 33, 34 and has, as now Figure 5preferably has a wedge cross-section in which two wedge surfaces 37, 38 adjoin a penetration edge 36. The penetration edge 36 is oriented in the circumferential direction with respect to the workpiece 11 as well as with respect to the insert body 28. The radius of curvature of the penetration edge 36 is preferably greater than zero, but again preferably less than one-tenth of the length of the wedge surface 37, measured from the penetration edge 36 to the adjacent workpiece contact surface 39. The wedge angle defined by the wedge surfaces 37, 38 has an angle bisector which lies in a plane 40 which contains all the penetration edges 36 of all the strip-like projections 32 to 34 and is preferably oriented parallel to the workpiece support surface 17.

[0026] The wedge surface 38 merges into a side surface of the insert body 28, which is set back from the workpiece contact surface 39.

[0027] The indenter 28 can be made of powder steel, a hard metal, ceramic or another hard material.

[0028] The embossing device 10 described so far works as follows: In preparation for the subsequent clamping of the workpiece 11, the workpiece is inserted into the embossing device 10. For this purpose, the jaws 13, 14 are first moved apart by means of the actuating device 15 so far that the workpiece 11, as in Figure 1 and 2indicated, can be placed on the workpiece support surfaces 16, 17 without touching the insert bodies 28 to 31. In the next step, the actuating device 15 is activated so that it moves the jaws 13, 14 towards one another, for example by moving the movable jaw 14 towards the fixed jaw 13. The workpiece 11 comes into contact with the strip-like projections 32 (i.e. the embossing teeth) of the individual insert bodies 28 to 31 and centers itself automatically between them so that all four insert bodies 28 to 31 soon rest with their strip-like projections 32 on the lower zone 12 of the outer peripheral surface of the workpiece 11. The strip-like projections 32 then penetrate into the workpiece 11 with a constant increase in the penetration force until the penetration force increases abruptly as a result of the contact between the workpiece support surface 39 and the workpiece 11.This procedure achieves a uniform stamping depth regardless of the material properties and geometric characteristics of the workpiece 11, such as its spring properties. In this case, the actuating device 15 is designed to monitor the actuating force during stamping and, if a limit value for the actuating force or a limit value for the force change is exceeded, switches off and moves the jaws 13, 14 apart again to release the workpiece.

[0029] The invention was explained above using insert bodies 28 to 31 specially prepared for the stamping process. However, it is also possible to use other elements, such as hard metal bodies such as those used as indexable inserts, as insert bodies 28' instead of the specially shaped insert bodies 28. Figure 6shows an example in which the cutting edge of the indexable insert used as a embossing tooth is used as the penetration edge 36'.

[0030] Furthermore, it is possible to insert the insert body 28', as Figure 7 shows, to be supported on a surface or a seat 19 which is inclined towards the receiving surface 16 in order to achieve a recess which is symmetrical with respect to a horizontal plane (plane which is parallel to the workpiece support surface 16) even with a standard component, such as an indexable insert, when used as an insert body 28'.

[0031] An embossing device 10 according to the invention is provided for preparing a mixed positive and frictional clamping of workpieces 11 in a corresponding chuck. The embossing device 10 has jaws 13, 14 with embossing teeth formed on insert bodies 28 to 31. The insert bodies 28 each have a penetration edge 36 with which they penetrate into the workpiece surface to create a recess with predetermined dimensions. For this purpose, a workpiece contact surface 39 is formed on the insert body 28, preferably adjacent to the strip-like projection 32, which stops the penetration process of the strip-like projection as soon as the workpiece contact surface 39 comes into contact with the workpiece surface during the embossing process.When the workpiece contact surface 39 hits the workpiece 11, the force required to move the jaw 14 increases steeply, from which a control device generates a switch-off signal for the actuating device 15.

[0032] Such control or monitoring of the stamping process makes it possible to prepare workpieces 11 of different geometries and made of different materials in one stamping process for the subsequent clamping process without the stamping device 10 having to be readjusted to the geometry or the material of the workpiece 11. Reference symbol:

[0033] 10 Embossing device 11 Workpiece 12 Lower zone of the outer peripheral surface 13, 14 Jaws 15 Actuating device 16, 17 Workpiece support surfaces 18 - 22 Seats of jaw 14 23 - 27 Seats of jaw 13 28 - 31 Insert body 32 - 34 Strip-like projections 35 Shank 36 Penetrating edge 37, 38 Wedge surfaces 39 Workpiece contact surface 40 Plane

Claims

1. An embossing device (10) for applying plastic deformations to a workpiece (11), comprising a first jaw (14) which has at least one seat (19) for receiving an insert body (28), an insert body (28) which is arranged on the seat (19) and fastened thereto, a second jaw (13) which is at least an abutment (13, 30, 31) opposite the insert body (28), an actuating device (15) which is configured to move at least one of the jaws (14) towards and away from the other jaw (13), characterized in that the seat (19) is formed by a polygonally delimited pocket and that the insert body (28) is polygonally bordered and has a two- or multi-fold rotational symmetry.

2. The device according to claim 1, characterized in that the jaw (14) has a plurality of seats (18 - 22) for receiving a plurality of insert bodies (28, 29).

3. The device according to anyone of the claims 1 or 2, characterized in that the abutment (13, 30, 31) comprises one or more insert bodies (30, 31).

4. The device according to anyone of the preceding claims, characterized in that the insert bodies (28 - 31) each have strip-like projections (32 - 34) which are arranged to act as an embossing structure on the workpiece (11).

5. The device according to anyone of the preceding claims, characterized in that the insert bodies (28 - 31) are hard material bodies or powder steel bodies.

6. The device according to anyone of the preceding claims, characterized in that the insert body (28) has a strip-like projection (32) which extends along a side surface of the insert body (28).

7. The device according to claim 6, characterized in that the jaw (13, 14) has a workpiece support surface (16, 17) and that the strip-like projection (32) extends parallel to the workpiece support surface (16, 17).

8. The device according to anyone of the preceding claims, characterized in that the strip-like projection (32) has a triangular cross-section.

9. The device according to anyone of the preceding claims, characterized in that the strip-like projection (32) is straight.

10. The device according to anyone of the preceding claims, characterized in that the strip-like projection (32) borders on at least one of its two sides on a surface which is designed as a workpiece contact surface (39).