GB2103529A

GB2103529A - Method of changing work- pieces in high-speed metal-cutting processing machines, and a metal-cutting processing machine for performing the method

Info

Publication number: GB2103529A
Application number: GB08219757A
Authority: GB
Inventors: Horst Seitz
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1981-07-09
Filing date: 1982-07-08
Publication date: 1983-02-23
Also published as: FR2509208B3; DE3127130A1; JPH0118241Y2; JPS5827001U; GB2103529B; FR2509208A1

Abstract

The invention relates to a method of changing workpieces in high-speed metal cutting, processing machines, particularly high-speed lathes, in which the workpiece to be machined is clamped between the centre (7) of a motor-driven headstock spindle (1) and the centre (5) of a tailstock spindle (3). The workpieces are changed during continued rotation of the headstock spindle (1) by accelerating the workpiece (9), when it is decoupled from the headstock spindle with respect to driving torque, from zero to a rotational speed corresponding at least approximately to the rotational speed of the headstock spindle by driving the tailstock spindle which is positively rotatably coupled to the workpiece. The workpiece is positively rotatably coupled to the headstock spindle after this rotational speed has been attained. For this purpose, the tailstock spindle (3) is connected to a second drive motor (6) which has lower power than the main drive and whose rotational speed can be adjusted from zero to its maximum rotational speed. <IMAGE>

Description

SPECIFICATION Method of changing workpieces in highspeed metal-cutting processing machines, and a metal-cutting processing machine for performing the method The invention relates to a method of changing workpieces in high-speed metal-cutting processing machines, particularly high-speed lathes, and to metal-cutting processing machines for performing this method.

In order to increase productivity, constant endeavours are being made to increase the metal-cutting capacity of metal-cutting processing machines, particularly lathes. With the use of high-grade tools, such as ceramic tools, it is possible to increase the metal cutting capacity by, for example, increasing the machining rate, that is to say, by increasing the rotational speed of the spindles and by increasing the drive power.

Although the metal-cutting capacity of the processing machine is substantially improved by perceptibly increasing the rotational speed of the spindles to, for example, 10,000 r.p.m.

or even to 15,000 r.p.m., this improvement may not be fully effective, since the ratio between the cutting time, that is to say, the active machining of the workpiece, and the setting-up time, that is to say, the time required for clamping and unclamping the workpiece, is preceptibly impaired. This impairment is not only caused by the fact that the metal-cutting operation itself is performed more rapidly, but also by the fact that the increased drive power now required for the headstock spindle requires the use of a larger motor having larger rotating masses. The deceleration and re-acceleration of this large drive motor not only takes place relatively sluggishly, but also requires a relatively large amount of power.

The object of the invention is to develop a method of changing workpieces in high-speed metal-cutting processing machines, and a metal-cutting processing machine, such that there is a decided improvement in the ratio between the metal-cutting time and the setting-up time and also a reduction in the wear on the processing machine.

In accordance with one aspect of the present invention there is provided a method of changing work-pieces in high-speed metal-cutting processing machines in which the workpiece to be processed is clamped between the centre of a motor-driven headstock spindle and the centre of a tailstock spindle, characterised in that, with the headstock spindle continuing to rotate, running exchange of the workpiece is performed by accelerating the workpiece, decoupled from the head-stock spindle with respect to torque, from zero to a rotational speed corresponding at least approximately to the rotational speed of the headstock spindle by the tailstock spindle positively rotatably coupled to the workpiece, the workpiece being positively rotatably coupled to the headstock spindle after this rotational speed has been attained.

According to another aspect of the invention there is provided a metal-cutting processing machine for performing the method in which the workpiece is mounted between centres, which processing machine has a headstock spindle which has a main centre and which is positively rotatably couplable to the workpiece and which is drivable by a drive motor whose power is adapted to the required metal-cutting capacity, and a tailstock spindle having a tailstock centre, characterised in that the tailstock spindle is mounted in the tailstock and is axially displaceable under the action of a drive means which acts upon the tailstock spindle in an axial direction, which tailstock spindle has a tailstock centre provided with a driver means which is positive rotatably couplable to the workpiece, the tailstock spindle being drivable by a second drive motor whose rotational speed is controllable or regulatable from zero to a maximum rotational speed, and that the main centre is rotatable in the headstock spindle separately from a driver means, rigidly connected to the headstock spindle and serving for the positive rotatable coupling of the workpiece and is mounted so as to be axially insertable against the force of a spring arrangement.

The invention will now be described further hereinafter, by way of example only, with reference to one embodiment illustrated in the accompanying drawings, in which: Figure 1 is a partially diagrammatic side elevation of a high-speed high power lathe in accordance with the invention, Figure 2 is a fragmentary section through a detail, drawn to a larger scale, of the machine of Fig. 1, and Figures 3 and 4 each show diagrammatically a portion of Fig. 2 at various times during changing of workpiece.

The heavy-duty high speed lathe illustrated in Fig. 1 chiefly comprises a work table 15, a headstock spindle 1, a tailstock spindle 3 and metal-cutting tools 12.

A headstock spindle support 16 and a tailstock 2, axially displaceable relative to thereto, are spaced apart on the work table 15.

The headstock spindle 1 is rotatably mounted in the headstock spindle support 16 on the one hand and, on the other hand, a highpower drive motor 14 for driving the headstock spindle is secured to the headstock spindle support 16, the drive power of the motor 14 being adapted to the level of the required metal-cutting capacity.

The tailstock spindle 3 is rotatably mounted in the tailstock 2. Furthermore, a second drive motor 6 of smaller power than the first drive motor 14 is secured to the tailstock and can drive the tailstock spindle 3, as will be explained in greater detail below.

The workpiece 9 to be machined is mounted between centres, one end of the workpiece being mounted on a centre 7 of the headstock spindle 1 and its other end being mounted on a centre 5 of the tailstock spindle 3. In the first instance, it appears that it is highly unconventional to mount the workpiece between centres at these high rotational speeds. However, it offers very accurate and very reliable mounting. The use of chuck-type clamping devices or the like is virtually impossible at the desired high rotational speeds of the spindles, owing to centrifugal forces which would then occur.

In the present embodiment, two horizontally and vertically displaceable tool supports 12 are provided which are rotatable about their horizontal longtudinal axes and to each of which is secured, for example, a plurality of cutting tools 1 7.

In order to use the heavy-duty lathe to an optimum extent, the workpieces are changed when the machine is running. Thus, the headstock spindle 11 driven by the drive motor 14 continues to run at full speed during changing of the workpiece, that is to say, when the workpiece 9 to be machined is being introduced into the machine and when the machined workpiece is being removed from the machine. For this purpose, the second drive motor 6 is provided on the one hand and, on the other hand, the main centre 7 and the headstock spindle 1 on the one hand and, on the other hand, the tailstock centre 5 and the tailstock spindle 3 are constructed and arranged in a special manner.

Details of the construction of the headstock spindle and of the tailstock are shown in Fig.

2.

The tailstock spindle 3 is rotatably mounted in the tailstock 2 and can also be axially displaced in the tailstock 2 or slide unit by the action of a drive device 4 in the form of a hydraulic power cylinder which acts upon the tailstock spindle 3 in an axial direction. The centre 5 of the tailstock spindle 3 is provided with a driver device by which the tailstock centre or the tailstock spindle 3 can be positively rotatably coupled to the workpiece 9.

The driver device can be in the form of a claw coupling or the like in which substantially radially extending notches, grooves or the like, disposed in the end face of the workpiece 9 are engaged by complementary projecting parts on the end face of the tailstock spindle.

In the case of the headstock spindle 1, in contrast to the tailstock spindle 3, a headstock centre 7 and a driver device 8 are fully separated from one another with respect to their function. While the drive device 8, which can be constructed in the same or a similar manner to the corresponding driver device of the tailstock spindle 3, is rigidly connected to the headstock spindle 1, the headstock centre 7 is mounted in the headstock spindle 1 so as to run freely independently thereof. The headstock centre can be pushed axially into the headstock spindle 1 to a slight extent against the force of a spring arrangement 13.

The workpieces are changed in the following manner: It will be assumed that the headstock spindle 1 is being driven at the full rotational speed by the drive motor 14 and a workpiece 9 is not clamped in position. A conveyor device 10, such as a lifting beam arrangement which is guided through the machine transversely of the longitudinal axis of the centres in the region between the two centres 5 and 7 in a horizontal plane located below these centres, places the workpiece to be machined between the headstock centre 7 and the tailstock centre 5 in a position in which the longitudinal axis of the workpiece 9 is in alignment with the axes of the headstock spindle 1 and of the tailstock spindle 3. This position is illustrated in Fig. 3.In the first instance, the workpiece 9 is not in engagement with the headstock centre 7 rotating with the headstock spindle 1 as a result of friction, or with the stationary headstock centre 5. Upon actuation of the drive device 4, the non-rotating tailstock spindle 3 is advanced axially, whereby the tailstock centre 5 in the first instance enters a centering bore disposed in the end face of the workpiece 9, and at the same time a positive rotary coupling is established between the workpiece 9 and the drive device 18 of the headstock centre 5. During further axial movement of the headstock spindle 3, the other end face of the workpiece is pushed onto the headstock centre 7 which thereby stops if it should rotate with the headstock spindle 1 as a result of friction.The tailstock spindle 3 is moved axially only to the extent that, although the workpiece 9 is being pushed onto the centre 7 of the headstock spindle, the driver device 8 of the headstock spindle rotating at full speed does not yet engage the workpiece.

This position is shown in Fig. 4.

After this position has been reached, the second drive motor 6 of controllable or regulable rotational speed rapidly accelerates the tailstock spindle 3 from zero to a rotational speed at least approximately corresponding to the rotational speed of the headstock spindle 1, it being appreciated that the tools 17 are out of engagement during this period of time.

As soon as the rotational speed of the workpiece 9 at least approximately corresponds to the rotational speed of the headstock spindle 1 driven by the drive motor 4, this being detected by known devices for measuring and comparing rotational speeds, the drive device 4 displaces the tailstock spindle 3 further toward the headstock spindle 1 in an axial direction until the driver device 8 is coupled to the workpiece 9 in a frictional or positively rotatable manner, whereby the actual changing of the workpiece is ended and the metal-cutting machining of the workpiece can commence.

Basically, the second drive motor 6, which only has, for example, 2 to 5 percent of the power of the main drive motor 14, could continue to run during the machining operation or, alternatively, could run freely with no load. However, it is more advantageous to separate the second drive motor 6 from the workpiece 9 with respect to torque, as soon as. the workpiece has been positively rotatably coupled to the headstock spindle 1. For this purpose, in the present embodiment, a freewheeling device 11 is interposed between the tailstock spindle and the second drive motor 6. As already mentioned above, the speed of the second drive motor 6 will only increase to a speed which lies slightly below the rotational speed of the rotating headstock spindle 1.This speed difference separates the tailstock spindle from the second drive motor 6 when the positive rotary coupling between the headstock spindle 1 and the workpiece 9, and thus also between the headstock spindle 1 and the tailstock spindle 3, is established. The second drive motor 6 can then be stopped again.

The workpieces are changed again after the machining of the workpiece 9 has been completed. The finished workpiece is removed and a fresh workpiece to be machined is inserted.

When removing the finished workpiece, the above-described method steps are performed in a substantially reverse sequence. After the metal-cutting tools 17 have been retracted, with the drive motor 6 running, the drive device 4 withdraws the tailstock spindle 3 (to the right as viewed in Fig. 2) to an extent that the workpiece, then axially displaced in the same direction under the action of the spring arrangement 13, is separated from the driver device 8 of the headstock spindle 1 with respect to torque. The workpiece 9 is subsequently decelerated by reducing the rotational speed of the second drive motor 6. The tailstock spindle 3 is then fully retracted, and the finished workpiece is deposited onto the conveyor means 10.

If the second drive motor 6 is connected to the tailstock spindle 3 by way of a freewheeling device 11, the latter must be equipeed with an engageable locking means in order to enable deceleration of the tailstock spindle.

The invention not only enables optimum use of a high-speed processing machine owing to the fact that the workpieces can be changed very rapidly, but also perceptibly reduces the wear on the main drive which has relatively large rotating masses and which has to be constantly decelerated and re-accelerated in conventional processing machines.

Claims

1. A method of changing workpieces in high-speed metal-cutting processing machines in which the workpiece to be processed is clamped between the centre of a motor-driven headstock spindle and the centre of a tailstock spindle, characterised in that, with the headstock spindle continuing to rotate, running exchange of the workpiece is performed by accelerating the workpiece, decoupled from the headstock spindle with respect to torque, from zero to a rotational speed corresponding at least approximately to the rotational speed of the headstock spindle by the tailstock spindle positively rotatably coupled to the workpiece, the workpiece being positively rotatably coupled to the headstock spindle after this rotational speed has been attained.

2. A method as claimed in claim 1, characterised in that a second drive motor driving the tailstock for accelerating the workpiece up to speed is released from the workpiece with respect to torque, and the workpiece is positively rotatably coupled to the headstock spindle.

3. A method as claimed in claim 1 or 2, characterised in that the workpiece is changed automatically by aligning the workpiece to be machined into a position axially parallel to the axis of the headstock spindle and the axis of the tailstock spindle by a conveyor means passing through the processing machine, and is clamped between the centre of the headstock and the centre of the tailstock and is positively rotatably coupled to the tailstock spindle.

4. A metal-cutting processing machine for performing the method as claimed in one of the claims 1 to 3, in which the workpiece is mounted between centres, which processing machine has a headstock spindle which has a main centre and which is positively rotatably couplable to the workpiece and which is drivable by a drive motor whose power is adapted to the required metal-cutting capacity, and a tailstock spindle having a tailstock centre, characterised in that the tailstock spindle is mounted in the tailstock and is axially displaceable under the action of a drive means which acts upon the tailstock spindle in an axial direction, which tailstock spindle has a tailstock centre provided with a driver means which is positive rotatably couplable to the workpiece, the tailstock spindle being drivable by a second drive motor whose rotational speed is controllable or regulatable from zero to a maximum rotational speed, and that the main centre is rotatable in the headstock spindle separately from a driver means, rigidly connected to the headstock spindle and serving for the positive rotatable coupling of the workpiece and is mounted so as to be axially insertable against the force of a spring arrangement.

5. A metal-cutting processing machine as claimed in claim 4, characterised in that the power of the second drive motor is at least not substantially greater than that necessary to accelerate the workpiece, not in metalcutting engagement, efficiently from zero to the rotational speed of the headstock spindle and to declerate it from the rotational speed of the headstock spindle to zero for the purpose of removing the workpiece.

6. A metal-cutting processing machine as claimed in claim 4 or 5, characterised in that the second drive motor is decouplable from the tailstock spindle after positive rotary coupling of the workpiece to the headstock spindle.

7. A metal-cutting processing machine as claimed in claim 6, characterised in that a free-wheeling device is interposed between the tailstock spindle and the second drive motor.

8. A metal-cutting processing machine as claimed in claim 7, characterised in that the free-wheeling device is equipped with an engageable locking means.

9. A metal-cutting processing machine as claimed in one of the claims 4 to 8, characterised by a conveying means which is guided through the machine transversely of the longitudinal axis of the centres in the region between the two centres and in a horizontal plane located below the centres, by means of which conveying means the workpiece can be brought automatically into a position coaxially of the centre of the headstock and of the tailstock, through the intermediary of a lifting device if required.

10. A method of changing work pieces in high-speed metal-cutting processing machines substantially as hereinbefore described with reference to the accompanying drawings.

11. A metal cutting processing machine constructed and arranged and adapted to operate subtantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.