GB2042958A

GB2042958A - Improvements in or Relating to Devices for Spark-erosion Machining of Workpieces

Info

Publication number: GB2042958A
Application number: GB7906107A
Authority: GB
Original assignee: EXNII METALLOREZHUS STANKOV
Current assignee: EXNII METALLOREZHUS STANKOV
Priority date: 1979-02-21
Filing date: 1979-02-21
Publication date: 1980-10-01
Also published as: GB2042958B

Abstract

A device for wire electrode- machining for instance of intricate shapes having an inclined generatrix in workpieces 6, for e.g. diesinking, includes wire guides 4, 5 located on opposite sides of the workpiece 6. One of the guides 5 is stationarily fixed on a C-frame 2, while the other guide 4 is located on a slide-block 8 mounted in a faceplate radial guide. The faceplate 9 is mounted on a gear wheel 10 and is selectively couplable with a fixed member 21 or with the gear wheel 10. The gear wheel 10 is rotatable by drive motor 23 around the axis of the guide 5. With the faceplate coupled to the member 21 such rotation, due to engagement of a dog 13 on the slide-block 8 with a thread 12 on the gear wheel, moves the slide block along the radial guide to vary the inclination of the wire. With the face plate coupled to the gear wheel, rotation of the gear wheel causes machining of e.g. a conical aperture in the workpiece. The coupling means are solenoids 16, (17), which can be numerically controlled, and manually-actuated clamps (18), (19). <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Devices for Spark-erosion Machining of Workpieces The present invention- relates to devices for spark-erosion machining or workpieces. Such a device may be used for spark-erosion machining of intricate-shaped workpieces having inclined walls by means of a wire electrode in numerically controlled diesinking machines.

Such a device may be used in diesinking machines for producing, for instance, the working elements of punching die sets.

Spark-erosion machining with the use of a wire electrode is extensively used for making the working elements of punching die sets (such as dies, punches, knockouts, etc.). Known machine toois enabling the machine of workpieces featuring inclined walls have made it possible to reduce refining bench work involved in making the dies of the punching die sets. A disadvantage of such known machines resides in their being devoid of automatic control for setting the angle of inclination of the wire electrode and hence in their being incapable of simultaneously machining the mating profiles of the punch and die.

According to the invention, there is provided a device for spark-erosion machining of a workpiece by a wire electrode, comprising at least two guides for the wire electrode arranged to be located on opposite sides of the workpiece when being machined, a gear wheel mounted on a body of the device and provided with a mechanical actuator for causing it to be swivelled around the axis ozone of the guides for the wire electrode, a faceplate interposed between the gear wheel and the body of the device and provided with a radial guide, a slide-block mounted in the radial guide of the faceplate and carrying the other of the guides for the wire electrode and stopping elements interposed between the faceplate, the body and the slide-block for selectively engaging the faceplate with the body and the gear wheel.

Such a machine can provide for automatic setting and maintaining of a preset angle of inclination of the wire electrode during the workpiece machining process. Also, the possibility of simultaneously machining the mating profiles of both the punch and the die can be provided. Further, the setting and maintaining of a preset angle of the wire electrode inclination may be actuated by the same drive.

Provision of the faceplate with the stopping elements makes it possible to automatically control the setting and maintaining of the angle of the wire electrode inclination in the course of machining, to dispense with manual setting-up operations and to automate the machining process.

In addition, operation of the device may be controlled from a single actuator, which makes it possible to make use of a two-dimensional coordinate contouring numerical control device.

The face of the gear wheel may have a thread and the slide-block may be provided with a driving dog operatively associated with the thread. Provision of the face screw thread in the gear wheel for engaging the driving dog which is fixed to the slide-block allows high-accuracy setting of the angle of the wire electrode inclination to be obtained with substantial simplification of the construction of the device.

Owing to the possibility of simultaneously machining the mating elements of a punch and die, much higher mating accuracy of the profiles of both the punch and the die may be attained, because the effects of the machine kinematic linkage imperfections and of inaccuracies of workpiece positioning are eliminated.

The invention will be further described, by way of example with reference to the accompanying drawings, wherein: Figure 1 is a longitudinal sectional view of a device constituting a preferred embodiment of the invention and its mounting on a diesinking machine C-frame; Figure 2 is a section taken along the line Il-Il in Figure 1; Figure 3 is a diagram illustrating setting of the required angle of the wire electrode inclination; Figure 4 is a diagram illustrating setting of the required angle of the wire electrode inclination when making a punch and die from a single blank; and Figure 5 is-a diagram illustrating following of the profile of a workpiece by the wire electrode.

The device is mounted on the top portion of a C-frame 2 of a diesinking machine through an arm 1 (Figs. 1, 2).

A wire electrode 3 passes through a top guide 4 and a bottom guide 5 located on both sides of a workpiece 6 and held on a table 7 of the machine.

The bottom guide 5 is stationarily fixed on the Cframe of the machine.

The device also incorporates a mechanism for radial traversing of the top guide 4, the mechanism comprising a slide-block 8 which carries the top guide for the wire electrode 3 and is traversable along the slot (not shown) of a faceplate 9, and a gear wheel 10 set in a bearing 11 and provided with a face screw thread 12 adapted to engage a driving dog 13 made fast on the slide-block 8. The faceplate 9 is arranged coaxially with the gear wheel 10 and is secured thereto through a ring 14 seated in a circular groove thereof. The faceplate 9 and the slideblock 8 are interlinked by a spring 1 5.

The device also comprises stopping elements incorporating solenoids 1 6 and 1 7 (Fig. 2) for the device to operate on an automatic cycle, and retainers 1 8 and 1 9 for the device to operate on a manually assisted cycle. The solenoid 1 6 is mounted in an outer stationary race 20 of the bearing 11 to couple the faceplate 9 to a body 21 of the device. The solenoids 1 7 are made fast on the faceplate 9 so as to link it to the gear wheel 10. The coil ends of the solenoids 1 7 are brought to slip rings 22. Both of the solenoids 16, 17 can be controlled by any of the known conventional methods, e.g., from a numerical control system (not shown in Figs. 1 and 2).The retainer 18 linked to the gear wheel 10 is located in the faceplate 9, whereas the retainer 1 9 connected to the faceplate 9, is located in the body 21.

A drive motor 23 (Fig. 1) mounted on the body 21, is associated with the gear wheel 10 through a gear pinion 24.

The device operates as follows: Prior to machining, the guides 4 and 5 of the wire electrode 3 (Fig. 3) are set vertically and coaxially with each other, and the wire electrode 3 is passed into a production hole 25 in the workpiece 6 (shown by a dotted line). By engineering the solenoid 1 6 and de-energizing the solenoids 17, the faceplate 9 is brought into engagement with the body 21 and to brake the faceplate. Then, the top guide 4 is made to traverse over a required length L computed by the formula L=H tg a, where H stands for the guide spacing, and a denotes the angle of the wire electrode inclination.

Traversing of the guide 4 is caused as a result of rotation of the motor 23 which is imparted through the gear pinion 24 to the gear wheel 10.

As a result, the driving dog 1 3 slides along the screw thread 12, thus making the slide-block 8 travel likewise. The clearance between the driving dog 13 and the bottom of the screw thread 12 is taken up continuously by the spring 15, while the bottom guide 5 remains stationarily fixed. As soon as the wire electrode 3 reaches the working position (shown by a solid line), the solenoid 1 6 is de-energized and the solenoids 1 7 are energized, whereby the faceplate 9 engages the gear wheel 10, and the profile to be cut starts to be followed by the wire electrode 3. As the gear wheel 10 rotates, the faceplate 9 rotates along with the slide-block 8 and the top guide 4 round the vertical axis passing through the bottom guide 5.

Whenever it becomes necessary in the course of tracing the profile of the workpiece being machined, the angle of inclination of the wire electrode 3 can be altered by switching over the solenoids 16 and 17 and radially traversing of the top guide 4 as described above.

The control of the solenoids 1 6 and 1 7, the motor 23 and the actuators (not shown) of the two-dimensional coordinate feed traverse is effected by virtue of the numerical control device (not shown). Manual changing over of the faceplate 9 by means of the retainers 18 and 1 9 is also provided.

When simultaneous machining of a die 26 and a punch 27 (Fig. 4) from a single blank is required, working edges 28 and 29 are mated due to an inclined position of the wire electrode. Thus, by appropriate changing the angle of the wire electrode inclination, either a clearance or an interference fit in mating the edges 28 and 29 can be obtained. The required angle of inclination of the wire electrode 3 can be found from the following formula: h.sin or=(d+2A)+X cos , where h is the height of the blank; d is the diameter of the wire electrode; A is the electrode gap; and a is the required amount of interference (+) or clearance (-) between the working edges of the die and punch.

Such being the case, a production hole 30 in the workpiece 6 is machined at an angle exceeding the angle a and the top guide 4 of the wire electrode 3 is preliminarily displaced with respect to the bottom guide 5 by the device by the length L which depends upon the angle of inclination of the production hole 30. After the wire electrode 3 has been passed into the hole 30 (shown by a dotted line), the top guide 4 is traversed by the device by a length Lr+L2 concurrently with traversing of the C-frame carrying the top guide 4 and the bottom guide 5 by virtue of one of the actuators of the twodimensional coordinate feed motion of the machine (not shown) by a length L2. The traversing of the top guide 4 and the C-frame are correlated and are directed oppositely.As a result the top guide 4 traverses over a length L1 from the initial position, and the bottom guide 5 over a length L2, whereby the wire electrode 3 assumes its working position (shown by a solid line). Some slits in the punch 27 and the die 26 resulting from the above motions, however, affect neither the strength nor the operability of both as the slits occur on the nonoperative areas of the above elements.

Once the wire electrode 3 has reached the working position, it starts tracing the profile of the workpiece being machined by virtue of the two dimensional coordinate traverses of the machine and the device.

When the profile of the workpiece is being traced, the required angle of inclination of the wire electrode 3 in the section must be maintained normal to the profile. Fig. 5 shows a diagram of tracing the workpiece profile by the wire electrode 3 in the clockwise direction. The link K is in fact the pathway of the bottom guide 5 of the wire electrode 3, the line M is the pathway of the top guide 4, the segment AB representing the position of the wire length between the guides 4 and 5.

When machining a straight portion of the workpiece profile the angle made by the wire electrode 3 with the coordinate axes X and Y remains constant as the segment AB is parallel to the segment A,B, so that no control signal arrives from the numerical control system at the actuator of the device. As soon as the curvilinear portion A1A3 of the workpiece profile starts to be machined, the angle of inclination of the wire electrode 3, while remaining constant with respect to the profile being machined, should continuously vary with respect to the coordinate axes X and Y. As the wire electrode 3 changes from the position A,B1 to the instant position A2B2, the angle A y of a required turn of the top guide with respect to the bottom one equals the centre angle Sy, formed by the radius of curvature of the profile portion being machined. Thus,

where AX, AY are the amounts of instant traverse along the coordinate axes X and Y; and R is the radius of curvature of the profile being machined.

All the required control signals for actuating the traversing along the coordinate axes X and Y for swivelling the top guide by the angle Ay are delivered from the numerical control device of the machine.

Claims

1. A device for spark-erosion machining of a workpiece by a wire electrode, comprising at least two guides for the wire electrode arranged to be located on opposite sides of the workpiece when being machined, a gear wheel mounted on a body of the device and provided with a mechanical actuator for causing it to be swivelled around the axis of one of the guides for the wire electrode, a faceplate interposed between the gear wheel and the body of the device and provided with a radial guide, a slide-block mounted in the radial guide of the faceplate and carrying the other of the guides for the wire electrode, and stopping elements interposed between the faceplate, the body and the slide-block for selectively engaging the faceplate with the body and the gear wheel.

2. A device as claimed in Claim 1, wherein the face of the gear wheel has a thread and the slideblock is provided with a driving dog operatively associated with the thread.

3. A device for spark-erosion machining of a workpiece, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

4. A diesinking machine including a device as claimed in any one of the preceding claims.