EP2161101B1 - Device for tensioning a workpiece for processing in a grinding machine - Google Patents

Abstract

The device comprises a base body (30), which is mounted at a workpiece spindle of the grinding machine. A tension axle cuts the rotation axis of the workpiece spindle orthogonally. A clamping ram (46) is guided in a guiding block (40) in freely rotating manner. An actuator transfers clamping force to the clamping ram with transmission units, which allow an axial but not radial force transmission.

Description

The invention relates to a device for clamping a workpiece for machining in a grinding machine according to the preamble of patent claim 1.

In the grinding of disc-shaped workpieces, it is often necessary to grind the circumference of the workpiece and its contour. For example, in cutting inserts and in particular indexable inserts for cutting machine tools, the plan sides of the cutting insert are first ground in a first step. Subsequently, the periphery is ground to give the insert its shape, and finally the contour, that is, the cutting edge profile of the inserts is ground. For the two latter grinding operations, the cutting plates are clamped between two aligned in a clamping axis ram, which are acted upon on the one hand with an axial clamping force against each other to clamp the workpiece between the plungers, and on the other hand have a controlled rotary drive to the workpiece in the circumferential direction in Reference to the grinding wheel position.

Such a clamping device is for example from the EP 1 579 954 A1 known. This known device has a holding element, in which the one ram as counter-ram freely rotatable, but is mounted axially immovable. The holding element is guided axially freely displaceable on the serving as a clamping ram second plunger. The clamping ram can be used for rotary positioning be driven rotationally. On the holding element engages a lever which moves the holding element on the clamping plunger to initiate the axial clamping force in the fixed to the holding element counter-plunger. The holding element is C-shaped, wherein the one leg receives the counter-ram, while the other leg leads the clamping ram. The alignment of the two plungers in the clamping axis is thus determined by the dimensional stability of the C-shaped support member. Deformations of the holding element, for example due to thermal influences, can thus influence the exact alignment of the plungers and thus the accuracy of the grinding process.

The invention has for its object to provide a clamping device for workpieces during processing in a grinding machine, which ensures high precision in the tension and alignment of the workpiece.

This object is achieved by a device with the features of claim 1.

Advantageous embodiments of the invention are specified in the subclaims.

In the clamping device according to the invention the Gegenstöβel which is axially immovable and the axial clamping force is supported in a base body. In this body, a guide block is guided linearly displaceable parallel to the clamping axis. This guide block accommodates the clamping ram, which is freely rotatably and axially displaceably mounted in this guide block. An actuating device transmits the clamping force to the clamping ram, wherein this clamping force is introduced into the clamping ram so that only one axial

Force is transmitted, but not perpendicular to this axial force radial force component. The clamping ram is aligned in this way with high precision axially aligned with the counter-ram. The axial alignment is ensured by the linear guidance of the guide block on the base body, so that no deformations or transverse forces can occur in the clamping device, which affect this axial alignment.

In an advantageous embodiment, a servo motor, which causes the controlled rotary drive of the counter-ram, received in the main body of the device. Thus, the clamping device may be formed as a complete unit that can be used in a conventional grinding machine otherwise. In this embodiment, it is particularly possible to use the clamping device in a rotary workpiece axis of a grinding machine so that the clamping axis of the device intersects this rotary axis perpendicular. The workpiece can then rotate on the one hand to the clamping axis to grind the circumference of the workpiece. On the other hand, the clamping axis can be pivoted about the rotational axis of the grinding machine, so that the workpiece is pivoted relative to the grinding tool to grind the contour. Both grinding operations can be done in the same tension of the workpiece, which increases the precision of machining and saves time.

The introduction of the clamping force in the device can be carried out in an advantageous manner via an actuating rod, which is axially displaceable. In the direction of the clamping movement, the actuating rod is preferably acted upon axially by a spring force. To open the clamping device for a change of the workpiece, the tension rod is moved against this spring force, for example by a pneumatic unit.

Figur 1

schematisch den Grundaufbau einer Schleifmaschi- ne,

Figur 2

in perspektivischer Ansicht die für die erfindungsgemäße Ausgestaltung wesentlichen Teile der Schleifmaschine,

Figur 3

eine Figur 2 entsprechende Darstellung in einer anderen Arbeitsposition,

Figur 4

in perspektivischer Ansicht die Spann- vorrichtung,

Figur 5

die Spannvorrichtung in der in Figur 4 gezeigten Ansicht, jedoch teilweise geschnitten,

Figur 6

eine Teilansicht der Spannvorrichtung im geöffneten Zustand,

Figur 7

eine Figur 6 entsprechende Darstellung in geschlossenem Zustand und

Figur 8

eine Teildarstellung der Spannvorrichtung in geöffnetem Zustand der Figur 6.

In the following the invention will be explained in more detail with reference to an embodiment shown in the drawing. Show it

FIG. 1

schematically the basic structure of a grinding machine,

FIG. 2

3 is a perspective view of the essential parts of the grinding machine according to the invention;

FIG. 3

a FIG. 2 corresponding representation in another working position,

FIG. 4

in a perspective view the tensioning device,

FIG. 5

the tensioning device in the in FIG. 4 shown view, but partially cut,

FIG. 6

a partial view of the clamping device in the open state,

FIG. 7

a FIG. 6 corresponding representation in the closed state and

FIG. 8

a partial view of the clamping device in the open state of FIG. 6 ,

In FIG. 1 schematically shows the basic structure of a grinding machine, which can be equipped with the inventive device for clamping a workpiece, in particular a cutting insert or indexable insert. The grinding machine has a machine bed 10 with a vertical rear wall 12. On the machine bed 10, a table 14 is arranged, which is movable in a horizontal Y-axis perpendicular to the front operator side and the rear wall 12 controlled. On the rear wall 12, a cross slide is arranged, which is controlled in a direction perpendicular to the Y-axis horizontal X-axis and in a direction perpendicular to the X-axis and the Y-axis vertical Z-axis movable. At the bottom of the carriage 16, there is disposed a grinding spindle unit 18, which is rotatably supported in the carriage 16 about a C-axis parallel to the Z-axis and rotationally driven about this C-axis. In the grinding spindle unit 18, a grinding spindle is horizontally mounted, which is driven by a spindle motor 20 and carries at its free end a grinding tool 22, which is in particular designed as a cup-shaped grinding wheel. On the table 14, a workpiece spindle unit 24 is arranged, which receives a workpiece spindle 26. The workpiece spindle 26 is rotatable by means of a motor 28 numerically controlled about its axis parallel to the X-axis A-axis. In that regard, the grinding machine corresponds to the state of the art.

As in the Figures 2 and 3 can be seen, on the workpiece spindle 26, a clamping device mounted as in FIG. 4 is shown.

The tensioning device has a main body 30. On the main body 30 coupling means are mounted, with which the base body 30 can be fixedly connected to the workpiece spindle 26. The coupling agent consist in the illustrated Embodiment of a shaft taper 32 which is inserted into the receiving flange of the workpiece spindle 26 and screwed thereto. The main body 30 is thus controlled via the workpiece spindle 26 pivotable about the A-axis.

In the main body 30, a servo motor 34 is firmly received. On a flange 36 of the motor shaft of the servo motor 34, a counter-ram 38 is mounted, which is coaxially aligned with the motor shaft of the servomotor 34. The counter-ram 38 can be numerically controlled by means of the servomotor 34 about its central axis, which is referred to as the clamping axis, are rotated. The servo motor 34 and the counter-ram 38 are arranged in the base body 30 so that the axis of the counter-ram 38, ie the clamping axis orthogonally intersects the central axis of the shaft cone 32 and thus the A-axis. Accordingly, the clamping axis can also be referred to as B-axis, as in FIG. 2 is indicated.

Below the clamping axis and spaced therefrom, a guide block 40 is mounted in the base body 30. The guide block 40 is guided linearly displaceable in the main body 30 in a direction parallel to the clamping axis direction. For this purpose, the base body 30, for example, a recess in which the guide block 40 is arranged and slides on guides 42 which extend parallel to the clamping axis and are mounted in the base body 30. The guides 42 are formed in the illustrated embodiment as guide rods. The guide block 40 can move freely on the guides 42 with a stroke of, for example, about 10 millimeters.

On the guide block 40, a guide bush 44 is attached. The guide bush 44 is axially aligned with the central axis the counter-ram 38 aligned. In the guide bushing 44, a clamping ram 46 is guided free of play both axially and rotationally freely movable. The clamping ram 46 is preferably formed conically at its end facing the counter-ram 38 end. A workpiece, in particular an indexable insert 48, can be tensioned between the counter-ram 38 and the clamping ram 46 by the indexable insert 48 is arranged centrally to the clamping axis and the clamping ram 46 is moved by force against the counter-ram 38. The clamping ram 46 can penetrate into a clamping recess or clamping bore of the indexable insert 48 in order to clamp it centered on the counter-ram 38.

In the main body 30, an actuating rod 50 is arranged, which leads coaxially through the shaft cone 32 and with an in FIG. 5 52 designated stroke is axially displaceable. The actuating rod 50 is biased with a spring force which pushes the actuating rod 50 out of the shaft taper 32. In the illustrated embodiment, this preload is generated by a package of cup springs 54 which are supported at one end on the stem cone 32 and the other end to an outer collar of the actuating rod 50. The coaxially through the shaft cone 32 in the workpiece spindle 26 leading end of the actuating rod 50 is further connected to a non-visible in the drawing pneumatic unit through which the actuating rod 50 against the spring force of the plate springs 54 can be pushed inwardly into the base body 30. The inner end of the actuating rod 50 is pivotally connected via tabs 56 with an arm of a pivot lever 58 which is pivotally mounted about a pivot point 60 in the base body. The pivot lever 58 has two approximately perpendicular arms, one of which is hinged to the actuating rod 50 and substantially perpendicular to this runs. In the free end of the other arm of the pivot lever 58 is freely rotatable but axially supported a ball 62 mounted, with which the pivot lever 58 rests against the end face of the clamping ram 46 facing away from the counter-ram 38. The free arm of the pivoting lever 58 is freely pivotable between the guide block 40 with the guide bushing 44 and a stop 64 which limits the pivotal movement of the free arm of the pivot lever 58 of the guide block 40 and the guide bushing 44 away. In the illustrated embodiment, this stop 64 is formed by the head of a screw which is screwed into the guide block 40 and whose shaft passes through a slot in the arm of the pivot lever 58. The pivoting of the pivot lever 58 is thus limited to the length of the screw shank of the stop 64. Finally, a locking ring 66 is still placed on the clamping ram 46 at its rear end, which protrudes from the guide bush 44 against the ball 62.

The clamping device works in the following way:

To change the workpiece to be ground, for example an indexable insert 48, the actuating rod 50 is pressed by means of the pneumatic unit against the force of the disc springs 54 in the main body 30. The actuating rod 50 thereby pivots the pivot lever 58 in the representation of FIG. 5 in the counterclockwise direction. The free arm of the pivot lever 58 thereby moves on the shaft of the screw of the stop 64 until the pivot lever 58 abuts against the stop 64 of the screw head. In the further pivoting movement of the pivot lever 58, this takes over the stop 64 with the guide block 40 with. The guide block 40 takes with its guide bush 44 while the clamping ram 46, since the guide bushing 44 on the locking ring 66 of the clamping ram 46th comes to the plant. The clamping ram 46 is thus pulled away axially from the counter-ram 38, so that the tensioned and finished, ground indexable insert 48 is released.

The indexable insert 48 can be detected, for example, by a handling gripper 68, which is moved by means of the cross slide 16. The handling gripper 68 places the ground indexable insert 48, for example in a cassette 70, removes the cassette 70 from an unpolished indexable insert 48 and brings it into the clamping position between the counter-ram 38 and the clamping ram 46.

Then, the pressure of the pneumatic unit on the actuating rod 50 is released, so that the plate springs 54 now pull the actuating rod 50 back out of the main body 30 due to their bias. As a result, the pivoted on the actuating rod 50 pivot lever 58 in FIG. 5 pivoted clockwise. The free arm of the pivot lever 58 now presses with his ball 62 the Spannstöβel 46 against the counter-ram 38, wherein the clamping ram 46 engages the clamping recess of the insert 48 and the indexable insert 48 clamped under the clamping force generated by the plate springs 54 against the counter-ram 38. The indexable insert 48 is thus tensioned for grinding by means of the grinding wheel 22. In this case, only an axial compressive force is exerted on the clamping ram 46 as a clamping force on the rotatably mounted ball 62. A force transverse to the axis, the ball 62 is not transmitted to the clamping ram 46. The guide block 40 is freely displaceable in this clamping position on the guides 42, wherein the guide bushing 44 can move freely on the clamping ram. There are therefore no forces transmitted from the guide block 40 on the clamping ram 46, so that any thermal Expansions of the main body 30 can not be transferred to the clamping ram 46 and the exact alignment of the counter-ram 38 and clamping ram 46 can not affect.

The workpiece, namely the indexable insert 48, can now be ground by means of the grinding wheel 22. By means of the cross slide 16, the grinding wheel 22 is delivered in the X-axis and the Z-axis, while a feed movement in the Y-axis via the table 14 can take place. For circumferential grinding of the indexable insert 48, the clamping device is pivoted about the A-axis so that the clamping axis defined by the counter-ram 38 and the clamping ram 46 is horizontal, i. parallel to the Y-axis. The circumference can now be ground by the counter-ram 38 is rotated by means of the servo motor 34 about the clamping axis. In this case, the workpiece, the indexable insert 48 frictionally rotated and also the clamping plunger 46 rotates freely in the guide bush 44. Subsequently, the cutting contour of the insert 48 can be ground in the same voltage, for which purpose the clamping device is pivoted about the A-axis by means of the motor 28 , As a result, the angle of attack of the clamping axis is pivoted against the axis of the grinding wheel 22 to produce, for example, chamfers of the cutting edge, free cutting surfaces on the circumference and any troughs in the plate planes.

As can be seen from the drawings, the counter-ram 38 is shaped so that its diameter decreases conically from the end flanged to the shaft flange of the servomotor 34 against the end abutting the workpiece 48. As a result, the plungers 38 and 46 on both sides of the tensioned indexable insert 48 has a small diameter, so that sufficient space is available to even with a cup-shaped Grinding wheel 22 on both sides of the insert 48 to attack.

After completion of the grinding operation, the finished workpiece 48 is released again by acting on the actuating rod 50 by means of the pneumatic unit, so that the cycle described can start again.

LIST OF REFERENCE NUMBERS

10

machine bed

12

rear wall

14

table

16

carriage

18

Grinding Spindles

20

spindle motor

22

grinding tool

24

Workpiece spindle unit

26

Workpiece spindle

28

engine

30

body

32

taper shank

34

servomotor

36

flange

38

against ram

40

guide block

42

guides

44

guide bush

46

clamping rams

48

Indexable insert

50

actuating rod

52

stroke

54

Disc springs

56

tabs

58

pivoting lever

60

pivot point

62

Bullet

64

attack

66

circlip

68

Handling grippers

70

cassette

Claims (11)

1. An apparatus for clamping a workpiece for machining in a grinding machine, with two rams, namely a clamping ram (46) and a counter ram (38), which are in alignment in a clamping axis and between which the workpiece is clamped, wherein one ram is capable of being acted upon in the clamping axis with an axial clamping force, whilst the other ram forms the abutment in order to support the clamping force, and wherein a ram is rotatable about the clamping axis whilst driven in a controlled manner, whilst the other ram is mounted so as to be freely rotatable about the clamping axis, characterized in that the apparatus has a base member (30) which is capable of being mounted with coupling means on a workpiece spindle (26) of the grinding machine capable of being driven in a rotating manner, wherein the clamping axis intersects the axis of rotation (A-axis) of the workpiece spindle (26) at a right angle, the counter ram (38) is received axially non-displaceably and in a manner capable of being driven rotatably in the base member (30), a guide block (40) is guided in the base member (30) so as to be displaceable in a linear manner parallel to the clamping axis, the clamping ram (46) is guided in the guide block (40) so as to be freely rotatable and freely displaceable axially, and an actuating device mounted in the base member (30) transmits the clamping force to the clamping ram (46) with transmission means which permit only an axial, but not a radial, transmission of force.
2. An apparatus according to claim 1, characterized in that a servo motor (34) driving the counter ram (38) in a rotating manner is received in the base member (30).
3. An apparatus according to claim 1 or 2, characterized in that the actuating device has an actuating rod (50) which is mounted in the base member (30) so as to be axially displaceable, is acted upon with a spring force in an axial displacement direction in order to produce the clamping force and is movable in the opposite axial displacement direction by a controllable force contrary to the spring force.
4. An apparatus according to claim 3, characterized in that the spring force is produced by a compression spring enclosing the actuating rod (50) coaxially, in particular by disc springs (54).
5. An apparatus according to claim 3 or 4, characterized in that the controllable force is produced by a pneumatic unit.
6. An apparatus according to any one of the preceding claims, characterized in that the actuating device transmits the axial clamping force to the axially rear end face of the clamping ram (46) by a ball (62) mounted so as to be freely rotatable and supported axially against the clamping force.
7. An apparatus according to claim 3, characterized in that the actuating rod (50) is in alignment coaxially with the workpiece spindle (26) and passes through the coupling means coaxially, and the axial movement of the actuating rod (50) is deflected into the clamping axis by way of an angled pivoting lever (58).
8. An apparatus according to any one of the preceding claims, characterized in that the guide block (40) is guided in the base member (30) so as to be freely movable axially, the clamping ram (46) is entrained by the guide bush (44) when the latter moves away from the counter ram (38), and the guide block (40) is entrained by the actuating device when the latter is actuated in the opening direction.
9. An apparatus according to claim 8, characterized in that the clamping ram (46) has a securing ring (66) against which the guide bush (44) abuts for entrainment purposes.
10. An apparatus according to claim 8, characterized in that the guide block (40) has a stop (64) which permits a reciprocating path of the actuating device with respect to the guide block (40) in the direction of the clamping axis and entrains the guide block (40) when the actuating device comes to rest against this stop (64) in the opening direction.
11. An apparatus according to any one of the preceding claims, characterized in that in order to grind cutting plates, in particular indexable cutting plates (48), the counter ram (38) and the clamping ram (46) have a small diameter in the region of their ends engaging on the cutting plate, so that a free space is present on both sides of the cutting plate for the pivoting-in of a grinding disc (22), in particular a cup-shaped grinding disc of the grinding machine.

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