EP3885071A1 - Device and method for clamping workpieces - Google Patents

Abstract

The embossing device (10) according to the invention is used to prepare a mixed positive and frictional clamping of a workpiece (11) in a corresponding chuck. The embossing device (10) has jaws (13, 14) with embossing teeth which are formed on insert bodies (28 to 31). The insert bodies (28 to 31) each have a penetrating edge (36) with which they penetrate the workpiece surface in order to produce a recess with defined dimensions. For this purpose, a workpiece contact surface (39) is formed on the insert body (28), preferably in the vicinity of the strip-like projection (32), which stops the penetration process of the strip-like projection (32) as soon as the workpiece contact surface (39) is also involved in the embossing process comes into contact with the workpiece surface. Then the force required to move the jaw (14) rises steeply, from which a control device generates a switch-off signal for the actuating device (15).

Description

The invention relates to a device and a method for clamping workpieces, in particular round workpieces, and in particular a device and a method for preparing workpieces for clamping.

For machining workpieces in machine tools, especially for machining, the workpieces must be firmly clamped and held in suitable clamping positions. In this case, even greater forces acting on the workpiece during machining operations must not lead to the workpiece moving in the clamping device or being released from it. On the other hand, the workpiece should be as easily accessible as possible in order to be able to carry out as many machining operations on the workpiece as possible one after the other in a single clamping.

the EP 1 071 542 B1 proposes a tensioning method in which, in a preparatory work step, evenly spaced depressions are made on the workpiece, which only serve as coupling elements when tensioning with a corresponding tensioning device, but otherwise have no function. After this preparatory work step, the workpieces are held in vices, which have contact surfaces for frictional holding on their clamping jaws and which have form-locking elements that are complementary to the recesses of the workpiece for positive positioning and securing. The workpiece is mixed with it and clamped positively and frictionally. This PT system has basically been used for both Tried and tested workpieces with straight clamping surfaces as well as workpieces with rounded clamping surfaces.

An essential element of the post-tensioning system EP 1 071 542 B1 is an embossing station that is used to make a series of indentations on the workpiece. These depressions must match the clamping teeth of the vices, between the jaws of which the workpiece is to be clamped. These depressions must be dimensionally accurate.

It is the object of the invention to provide a method for preparing a workpiece for clamping, with which dimensionally accurate depressions can be produced on a large spectrum of workpieces consisting of different materials.

The method according to the invention for clamping workpieces is based on the fact that recesses are made on workpieces, in particular workpieces with curved clamping surfaces such as for example at least partially cylindrical clamping surfaces, into which the projections of the clamping jaws engage when the workpiece is clamped. In particular, the depressions are applied to the workpiece 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, the distance between which can be adjusted. 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 a stamping 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 a desired one with its projection Measure into the workpiece and create a recess at this point. The insert body forms a stamping tooth, the projection provided on the insert body and the surface areas adjoining its edge being used as stamping teeth. It has been shown that the insert body is only subject to slight wear and tear and has a long service life with a wide variety of materials. In particular, a specially shaped insert body with a projection provided thereon can be used as the embossing tooth. The insert body can be a body provided separately for this purpose or, alternatively, an indexable insert.

The adjustment of the distance between the jaws and the abutment is preferably force-limited and / or path-controlled. In this way, provided that a maximum force is not exceeded, a predetermined depth of penetration of the insert body into the workpiece is achieved. In this way, the depressions produced on the workpiece have a desired uniform shape regardless of the material properties of the workpiece.

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 that have clamping surfaces with clamping teeth attached to them. The clamping teeth fit into the recesses and create a form fit. The clamping surfaces lie against the workpiece in the vicinity of the depressions and additionally clamp it with a friction fit. A secure storage of the workpiece in the clamping means is thus achieved with little space requirement. The periphery of the workpiece is largely freely accessible and can therefore be machined, for example.

The embossing device according to the invention, which is provided for applying plastic deformation to a workpiece, has at least one first jaw with at least one seat for receiving an insert body. An insert body is arranged on the seat and fastened thereto. An abutment opposite the insert body is provided on a second jaw. This can be formed, for example, by a flat or curved contact surface or by one or more insert bodies against which the workpiece is pressed during the stamping process. An actuator is also provided to move at least one of the jaws toward and away from the other jaw.

This stamping device has at least one projection designed as a stamping tooth. The embossing tooth has, in particular, an edge and adjoining surface areas which enclose a wedge angle with one another. This 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 exchanged if necessary. The insert body has a polygonal border, for example, and preferably has two or more rotational symmetry. The insert bodies can thereby be attached to the jaw in two or more positions. In this way, the insert body can be fastened in a different position on the seat after it has been worn accordingly, in order to continue to serve as a stamping tooth.

The projection of the insert body can have a strip-like shape and extends along a side surface of the insert body. This projection forms a stamping tooth which is set up to produce a recess with a precisely predetermined shape on the workpiece.

The strip-like projection is preferably oriented parallel to the workpiece support surface of the jaw. This enables the workpiece to be fastened later in a particularly secure manner in a chuck prepared for this purpose.

The strip-like projection preferably has a triangular cross-section. This makes the embossing process easier. The projection is preferably straight and adjoins at least one of its two flanks on a surface that is designed as a workpiece contact surface. This defines the depth and shape of the embossed recess on the workpiece.

In a preferred embodiment, the seats provided for receiving the insert bodies are designed as pockets from which the insert bodies protrude when they are arranged therein. The jaws preferably have a workpiece support surface over which the insert bodies protrude. When embossing, the workpiece is placed on the workpiece support surface of each jaw, after which the embossing process is initiated and carried out by reducing the distance between the jaws. This configuration clearly defines the axial position of each recess produced in relation to the end face of a cylindrical workpiece. The embossing device according to the invention is therefore robust, durable and accurate.

• Figur 1 eine Prägestation zum Vorbereiten eines Werkstücks zum Spannen in einem geeigneten Spannfutter, in perspektivischer schematisierter Darstellung,
• Figur 2 die Prägestation nach Figur 1, in Draufsicht,
• Figur 3 die Prägestation, in einer ausschnittsweisen perspektivischen Darstellung,
• Figur 4 einen Einsatzkörper in Draufsicht,
• Figur 5 den Einsatzkörper nach Figur 4 in Seitenansicht,
• Figur 6 eine abgewandelte Ausführungsform eines Einsatzkörpers und eines zugehörigen Werkstücks, in schematisierter Vertikalschnittdarstellung,
• Figur 7 eine weiter abgewandelte Ausführungsform einer Prägestation, in vereinfachter Vertikalschnittdarstellung.

Advantageous embodiments of the invention are the subject matter of the dependent claims, the drawing and the associated description. Show it:

• Figure 1 an embossing station for preparing a workpiece for clamping in a suitable chuck, in a perspective schematic representation,
• Figure 2 the embossing 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 sectional view,
• Figure 7 a further modified embodiment of an embossing station, in a simplified vertical sectional view.

In Figure 1 a stamping device 10 is illustrated, which is used to prepare a workpiece 11 for clamping in a chuck equipped for this purpose. The workpiece 11 is symbolized by a ring. Workpieces 11 can, however, also have other shapes, in which case they follow a cylinder, at least in sections, only in a lower zone 12 of their circumferential surface adjoining the base surface. The workpiece 11 can later be received in a rotating chuck, for example in order to carry out turning operations, turn-milling operations or the like.

The embossing device 10 includes two jaws 13, 14, the distance from one another of which can be adjusted in a controlled manner by means of an actuating device 15.

The two jaws show how from the Figures 2 and 3 emerges, on their upper side in each case a workpiece support surface 16, 17, which are preferably arranged lying in a common plane. The jaw 14 has at least one, preferably a plurality of seats 18 to 22, which can be embodied, for example, as pockets with a polygonal border. 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. In at least one, preferably several of the seats 18 to 22; Insert bodies 28, 29, 30, 31 are attached to 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 also as abutments for the respective opposing embossing tooth.

The insert bodies 28 to 31, like the seats 18 to 27, are designed to be identical to one another. The in Figures 4 and 5 The illustrated insert bodies 28 and the description thereof below are therefore representative of all the insert bodies 28 to 31 used on the embossing device 10.

In plan view, the insert body 28 has, for example, a hexagonal, non-equilateral, but three-fold rotationally symmetrical outline. On the three shorter edges of this hexagonal outline, strip-like projections 32 to 34 are formed, which protrude radially outward and form embossing teeth.

Below its hexagonal head, the insert body 28 according to FIG Figure 5 a polygonal, for example hexagonal shaft 35, which can also have a hexagonal outline and fits into the seats 18 to 27 with little play. The hexagonal shaft 35 preferably has a non-equilateral contour with three-fold rotational symmetry. In other words, the shaft 35 can be inserted into the relevant pocket 19 in three positions rotated by 120 ° in relation to one another.

The strip-like projection 32 corresponds to the strip-like projections 33, 34 and has, as now Figure 5 shows, preferably a wedge cross-section in which two wedge surfaces 37, 38 adjoin a penetrating edge 36. The penetrating 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 a 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 penetrating edges 36 of all strip-like projections 32 to 34 and is preferably oriented parallel to the workpiece support surface 17.

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

The penetration body 28 can consist of powder steel, a hard metal, ceramic or another hard material.

The embossing device 10 described so far operates as follows:
In preparation for the later clamping of the workpiece 11, it 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 that the workpiece 11, as in FIG Figure 1 and 2 indicated, 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 stationary 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 between them automatically, so that all four insert bodies 28 to 31 with their strip-like projections 32 on the lower zone 12 of the outer circumferential surface of the workpiece 11 are in contact. Furthermore, the strip-like projections 32 penetrate into the workpiece 11 with a constant increase in the penetration force until the penetration force rises abruptly as a result of the contact between the workpiece contact surface 39 and the workpiece 11. With this procedure, regardless of the material properties and the geometric properties of the workpiece 11, for example its spring properties, a uniform embossing depth achieved. In this case, the actuation device 15 is designed so that it monitors the actuation force during the stamping and, if a limit value of the actuation force or a limit value of the change in force is exceeded, switches off and moves the jaws 13, 14 apart again to release the workpiece.

The invention has been explained above with reference to insert bodies 28 to 31 specially prepared for the embossing process. However, instead of the specially shaped insert bodies 28, it is also possible to use other elements, for example hard metal bodies, such as are used as indexable inserts, as insert bodies 28 ′. Figure 6 shows an example in which the cutting edge of the indexable insert used as the embossing tooth is used as the penetration edge 36 '.

It is also possible to use the insert body 28 ', such 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 with a standard component, such as an indexable insert, when used as an insert body 28 ', which with respect to a horizontal plane (plane , which is parallel to the workpiece support surface 16) is symmetrical.

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, which are formed on insert bodies 28 to 31. The insert bodies 28 each have a penetrating edge 36 with which they penetrate the workpiece surface in order to produce a recess with defined dimensions. For this purpose, on the insert body 28, preferably in the vicinity of the strip-like projection 32, a Workpiece contact surface 39 is formed, 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 when the embossing process is carried out. If the workpiece contact surface 39 meets the workpiece 11, the force required to move the jaw 14 rises steeply, from which a control device generates a switch-off signal for the actuating device 15.

Such a control or monitoring of the embossing process makes it possible to prepare workpieces 11 of different geometries and made of different materials in an embossing process for the later clamping process without the embossing device 10 having to be readjusted to the geometry or the material of the workpiece 11.

Reference number:

10

Embossing device

11

workpiece

12th

lower zone of the outer peripheral surface

13, 14

to bake

15th

Actuator

16, 17

Workpiece support surfaces

18-22

Baking 14 seats

23-27

Baking seats 13

28 - 31

Insert body

32 - 34

strip-like projections

35

shaft

36

Penetration edge

37, 38

Wedge surfaces

39

Workpiece contact surface

40

level

Claims (15)

Method for clamping workpieces (11) in which, in preparation for clamping: at least one insert body (28) is inserted and fastened in at least one seat (19) which is provided in at least one jaw (14), the workpiece (11) is positioned between the insert body (28) and an abutment (13, 30, 31), the distance between the jaw (14) and the abutment (13, 30, 31) is adjusted until the insert body (28) touches the workpiece (11) with at least one point (36), further adjustment of the distance between one jaw (14) and the abutment (13, 30, 31) until the insert body (28) has penetrated the workpiece (11) by a desired amount. Method according to Claim 1, characterized in that each insert body (28) touches the workpiece (11) with an edge (36) or with a corner. Method according to one of the preceding claims, characterized in that at least one jaw (14) is moved in a force-limited or force-change-limited manner. Method according to one of the preceding claims, characterized in that the workpiece (11) after the insert body (28) into the The workpiece (11) has penetrated and has thereby caused a local plastic deformation, is clamped in a clamping device with clamping jaws that match the deformations. Embossing device (10) for applying plastic deformations to a workpiece (11),
with a first jaw (14) which has at least one seat (19) for receiving an insert body (28),
with an insert body (28) which is arranged on the seat (19) and attached thereto,
with a second jaw (13) which is at least one abutment (13, 30, 31) opposite the insert body (28),
with an actuating device (15) which is adapted to move at least one of the jaws (14) towards and away from the other jaw (13). Device according to Claim 5, characterized in that the seat (19) is formed by a polygonally delimited pocket. Device according to one of Claims 5 or 6, characterized in that the jaw (14) has several seats (18-22) for receiving several insert bodies (28, 29). Device according to one of the preceding claims 5 to 7, characterized in that the abutment (13, 30, 31) is provided by one or more insert bodies (30, 31) includes. Device according to one of the preceding claims 5 to 8, characterized in that the insert bodies (28-31) each have strip-like projections (32-34) which are arranged to act as an embossed structure on the workpiece (11). Device according to one of Claims 5 to 9, characterized in that the insert bodies (28 - 31) are hard material bodies or powder steel bodies. Device according to one of Claims 5 to 10, characterized in that the insert body (28) has a strip-like projection (32) which extends along a side surface of the insert body (28). Device according to claim 11, 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). Device according to one of Claims 5 to 12, characterized in that the strip-like projection (32) has a triangular cross-section. Device according to one of Claims 5 to 13, characterized in that the strip-like projection (32) is straight. Device according to one of claims 5 to 14, characterized in that the strip-like projection (32) on at least one of its two sides to a surface which is designed as a workpiece contact surface (39).

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