JPS5911420B2 - Control method for machine tool slide table stop position - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling the stop position of a slide table of a machine tool, and relates to a machine tool that brings the slide table into contact with a stopper and stops it to process a workpiece on the slide table with high precision, especially for finishing. Suitable for use in polling machine tools.

In more detail, the position of the stopper that can be moved forward and backward is corrected based on the average value of the measurement data of the machined workpiece, and the machining accuracy such as center-to-center machining can be maintained at a high level even when the ambient temperature changes. .

Conventionally, for example, when determining the center-to-center dimension of a hole by moving a slide table on which a work is placed during precision poling processing, there have been two methods: a method using a fixed stopper, in which the slide table is positioned by abutting against a fixed stopper; There is a numerical control method that positions the slide table without contacting the stopper.

In the method using fixed stoppers, the slide table moves between fixed stoppers set at intervals determined by gauges, etc., and when it comes into contact with the stoppers, the slide table stops and is positioned, so the positioning of the slide table is repeated. Accuracy is relatively stable.

However, as a result of structural members expanding and contracting due to changes in ambient temperature, the distance between the once fixed stoppers changes according to the temperature, so especially during long-term operation, the stop position of the slide table will change depending on changes in ambient temperature. cannot be corrected.

On the other hand, numerical control methods are suitable for positioning a slide table at multiple locations, but are not suitable for repeatedly positioning the same location in terms of accuracy, and it is extremely difficult to stably obtain repeatable positioning accuracy of, for example, 1 μm. It is difficult to

Moreover, it is similar to the above-mentioned method using a fixed stopper that correction for ambient temperature cannot be made.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a method for controlling the stop position of a slide table of a machine tool, which can maintain the stop position of the slide table with high precision. In order to machine two holes in a workpiece, both ends of the slide table are positioned by stoppers so that the polling head can move by a length corresponding to the distance between the centers of the two holes, and one stopper is moved by a drive source. A polling device whose position can be adjusted measures the center-to-center distance of the processed workpiece,
Calculates the average value of a predetermined number of measured values, compares the average value with the set value, and obtains a correction signal that electrically indicates this difference when the difference between the average value and the set value exceeds a tolerance range. The electric signal is obtained by operating the drive source based on the correction signal to correct the position of the one stopper by the difference, and detecting the amount of displacement of the stop position of the slide table due to this correction operation. The present invention is characterized in that the correction operation is re-corrected as necessary so that the displacement amount matches the difference within a predetermined range using the displacement amount signal.

Hereinafter, embodiments of the method of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of a control device embodying the method of the present invention for use in controlling the center-to-center dimension of a finish-poling machine tool.

As shown in the figure, the stopper 2 of the machine tool 1 is connected to the bed 3.
A stopper 4 facing this stopper 2 is provided on the bed 3 so as to be movable after cutting.

In other words, the stopper 4 is a fixed member 5 fixed to the bed 3.
The wedge 6, which can be reciprocated, is pressed by a biasing force such as a spring (not shown), and the slant 4a of the stopper 4 and the slant 6a of the wedge 6 are in close contact with each other.

The wedge 6 is connected to a drive source 1, which is a pulse motor in this case, by a gear mechanism (not shown), and is moved in the vertical direction in the figure by the operation of the drive source 7.

Since the slope 4a of the stopper 4 is pressed against the slope 6a of the wedge 6, when the wedge 6 moves upward, the stopper 4 retreats to the left in the figure, and conversely, when the wedge 6 moves downward, the stopper 4 moves to the right. move forward in the direction.

In this case, the operating amount of the drive source 7 is converted into a fine displacement amount of the stopper 4 by the reduction ratio of the gear mechanism and the inclination of the slopes 4a, 6a.

In other words, the position of the stopper 4 is minutely changed and adjusted by the operation of the drive source γ, and as a result, the position of the slide table 8 at which it comes into contact with the stopper 4 and stopped is minutely changed and adjusted.

The control device that controls the stop position of the slide table 8 is shown in FIG.
It is composed of a second comparator 14 and a drive source driving device 15.

A hole 16a machined by the measuring instrument 9 in the machine tool 1 at the position where the workpiece 16 abuts against the stopper 4 of the slide table 8 and stops; and a hole 16a formed by the machine tool 1 at the position where the workpiece 16 abuts against the stopper 2 of the slide table 8 and stops. The center-to-center dimension d with respect to the hole 16b machined is sequentially measured for each workpiece 16, and a measurement data signal electrically representing the measurement data is output to the average value calculation device 10.

In this average value calculation device 10, the measurement data signal manually inputted from the measuring device 9 is stored in a built-in storage section, and the average value (that is, a moving average) of the N pieces of measurement data measured most recently is averaged. The value calculation device 10 calculates and outputs an average value signal, which is an electric signal of the average value, to the first comparator 13 .

Note that the value of N is not constant and may be varied.

On the other hand, the set value signal generator 11 outputs the design center value of the center-to-center dimension d, that is, the set value, to the first comparator 13 as an electrical set value signal.

In this case, the set value is set in the set value signal generator 11 by a human operation such as a keyboard, switch, or dial, or is set by an electrical signal or the like from another device.

As described above, the first signal receives the average value signal and the set value signal.
The comparator 13 compares both signals and sends the correction signal to the second comparator 1.
Output to 4.

This correction signal is generated when the average value exceeds the appropriate tolerance range set above and below the set value, and is an electrical signal corresponding to the difference between the average value and the set value. It also includes information for identifying cases in which the range is exceeded and cases in which the average value falls below the set value and exceeds the permissible range.

The above tolerance range is a so-called dead width determined by the required tolerance of the center-to-center dimension d and the measurement accuracy of the measuring instrument 9. For example, if the required tolerance is ±5 μm, the dead width is determined to be ±2 μm.

The displacement amount signal is input to the second comparator 14 together with the correction signal.

This displacement amount signal is outputted by the displacement amount detector 12, which is an induction scale in this case, and the displacement amount of the stop position of the slide table 8 is detected as an electric signal. indicates a displacement of zero.

Therefore, the correction signal input to the second comparator 14 is outputted to the drive source driving device 15 as is for the time being.

The drive source driving device 15 that has received this correction signal corrects the position of the stopper 4 by the difference between the average value and the set value according to the content of the correction signal (if the average value is larger than the set value, it moves forward; (If it is smaller than the value, the stopper is moved backward) A drive signal is applied to the drive source 7 of the stopper 4.

In this case, if the drive source 7 is a pulse motor, the drive signal is an appropriate number of pulse signals, but the content of the drive signal is determined as appropriate depending on the type of drive source 7.

When the position of the stopper 4 is corrected based on the correction signal, the displacement detector 12 detects the old position of the slide table 8 that came into contact with the stopper 4 before the position correction and the stopper 4 after the position correction. The amount of displacement from the new position of the slide table 8 that has come into contact and stopped is detected, and is input to the second comparator 14 as the displacement amount signal.

At this time, if the displacement amount signal matches the correction signal within a predetermined range, no signal is output from the second comparator 14, which means that the above-described correction operation based on the correction signal has been performed accurately.

Conversely, if the displacement amount signal differs from the correction signal, it means that the correction operation based on the correction signal was inaccurate, and the second comparator 14 outputs a re-correction signal to the drive source driving device 15.

Based on this re-correction signal, the stopper 4 is
This re-correction operation is repeated until the displacement signal matches the correction signal within a predetermined range.

In addition, when detecting the displacement amount of the stop position of the slide table 8 with the displacement amount detector 12, if a change in the stop position of the slide table 8 is detected after the slide table 8 collides with the stopper 4 back and forth several times, the collision is detected. It is also possible to further improve the stopping accuracy during this time.

By the way, when a workpiece with a different center-to-center dimension is required, for example, for a center-to-center dimension of up to ±30 μm of the drawing dimension, the setting value of the set value signal generator 11 can be changed to the desired center-to-center dimension. It should be added that since the stop position of the table 8 is corrected, the workpiece can be easily machined to the desired center-to-center dimension.

Next, a description will be given of the dance suppression device shown in FIG. 2, which is the control device shown in FIG. 1 with a printout device 17 and a manual correction signal generator 18 added. The output of the comparator 18 and the output of the first comparator 13 are switched by a switch 19 and input to the drive source driving device 15.

That is, the printout device 17 can print and record the measurement data of each workpiece 16 measured by the measuring device 9 and the corrected displacement amount of the stop position of the slide table.

Further, the correction signal generator 18 is used to arbitrarily correct the stop position of the slide table 8 manually when there is no measurement data signal from the measuring device 9.

In the above-mentioned actual case, most of the electrical signals are handled digitally, and it is convenient and advantageous to use a mini-computer, etc., especially for the portions surrounded by dashed lines in FIGS. 1 and 2.

As explained above in detail with the embodiments, according to the method of the present invention, the machining dimensions of the machined workpiece are measured, and the position of the stopper that can be moved forward and backward based on the difference between the average value of the measured values and the set value. Since the stop position of the slide table is controlled by correcting the stop position, it is possible to prevent changes in machining accuracy over a relatively long cycle such as changes in the dimensional relationship of various parts due to temperature changes, etc. Since the amount of displacement of the table stop position is detected and fed back to correct the stopper position, the slide table stop position can be reliably corrected.

In this way, it is possible to stably maintain the accuracy of a machine tool that requires a high processing accuracy of 1 μm, for example, even against temperature changes.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing an embodiment of the method of the present invention and an example of its application, respectively. In the drawing, 1 is a machine tool, 2 and 4 are stoppers, 7 is a driving source, 8 is a slide table, 9 is a measuring device, 10 is an average value calculation device, 11 is a set value signal generator, and 12 is a displacement detection device. 13 is a first comparator, 14 is a second comparator, 15 is a drive source drive device, 16 is a workpiece, 16a and 16b are holes, and d is a center-to-center dimension.

Claims (1)

[Claims] 1 In order to machine two holes in a workpiece, both ends of the slide table are positioned by stoppers so that the polling head can move by a length corresponding to the distance between the centers of the two holes, and one stopper is is a polling device whose position can be adjusted by a drive source, measures the center-to-center distance of the machined workpiece, calculates the average value of a predetermined number of measured values, and compares the average value with the set value to obtain the above-mentioned result. When the difference between the average value and the set value exceeds the allowable range, a correction signal is obtained that electrically indicates this difference, and the drive source is actuated based on this correction signal to change the position of the one stopper by the amount of the difference. On the other hand, if necessary, the displacement amount signal, which is an electric signal obtained by detecting the amount of displacement of the stop position of the slide table due to this correction operation, is used to adjust the amount of displacement as described above so that the amount of displacement matches the difference within a predetermined range. A method for controlling a stop position of a slide table of a machine tool, characterized by re-correcting a correction operation.