JPH02232143A - How to compensate machine tools - Google Patents

Abstract

PURPOSE:To eliminate the necessity for an expensive measuring equipment and thermostatic chamber by measuring a distance between reference points set in the vicinity of a workpiece by a touch sensor compared in its measuring value with a reference value and correcting a work program by a calculated correction value. CONSTITUTION:A machine tool body 1 provides in its head 1a a table 2 mounting on it a workpiece 4 fixed to a pallet 3. An automatic dimension measuring device 5 can be moved in a direction of arrow head a-b by a feed mechanism 6 having a ball thread shaft 6a. Further a vertical direction movable measuring shaft 5a provides in its point end a touch sensor 5b, and a value measured thereby is fed to an NC unit 7. A distance between two or more reference pins 3a, 3b, set in the vicinity of the workpiece 4, is measured by this touch sensor 5b comparing its obtained measured value with a reference value, calculating a correction value while correcting a work program.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a correction device for a machine tool that corrects machining accuracy due to temperature.

[Conventional technology]

Generally, when machining is performed using a machine tool such as a machining center, machining is started first thing in the morning when the temperature of the machine body is low, and machining is performed when the temperature of the machine body has risen. Large variations in accuracy occur.

For this reason, in the past, in order to stabilize machining accuracy, a method was generally adopted in which the machine was warmed up until the temperature rose before starting machining. Since it does not contribute to production, there is a problem that leads to a decrease in productivity.

In order to improve this problem, we have installed high-precision measuring devices in each part of the machine body and corrected the control system based on the values detected by these devices to improve processing accuracy, or moved the machine body to a constant temperature room, etc. A method has also been proposed in which the processing accuracy can be increased by installing the machine in a thermostatic chamber and controlling the temperature of the constant temperature room.

[Problem to be solved by the invention]

However, both methods have drawbacks such as being uneconomical because they require expensive n1 constant equipment and facilities.

This invention was made with the aim of improving the above-mentioned problems, and aims to provide a correction device for a machine tool that can improve machining accuracy by using an automatic dimension measuring device installed in the machine tool. It is.

[Means and effects for solving the problem] In order to achieve the above object, the present invention provides a machine tool controlled by an NC device, in which a touch sensor is provided in the machine body, and the touch sensor is set near the workpiece. By measuring the distance between multiple reference points and calculating the calibration value by comparing the obtained measurement value with the reference value, and correcting the machining program using the calculated calibration value, it is possible to prevent heat generation from the machine body. The present invention provides a correction device for a machine tool that enables highly accurate machining even when there are temperature changes, changes in temperature at the installation location, changes in temperature distribution, etc.

〔Example〕

An embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a machine tool main body, which has a table 2 on a head 1a, and a workpiece 4 fixed to a pallet 3 is placed on the table 2.

Reference numeral 5 denotes an automatic dimension measuring device installed on the upper part of the machine body 1, which is movable in the directions of arrows a and b by a feed mechanism 6 having a ball screw shaft 6a, and also has a measuring device that is movable in the vertical direction. Touch sensor 5b at the tip of a-axis 5a
The value measured by the touch sensor 5b is sent to the NC device 7, and the machining program is corrected as follows.

Next, the above correction operation will be explained with reference to the flowchart shown in FIG.
The touch sensor 5b measures the positions of the reference pins 3a and 3b provided on the pallet 3 as shown in FIG. 1 or 2.

Then, the reference bins 3a and B measured in advance in step
A deviation value is calculated by comparing distance data L between distances b and the obtained deviation value is stored in the memory of the NC device 7 as a correction value in the X-axis direction in step (3).

Next, in step ■, move table 2 on which pallet 3 is placed to 9
The reference bins 3a and 3b are measured again using the touch sensor 5b in step (2).

Then, the obtained value in the Y-axis direction is compared with distance data L measured in advance to calculate a deviation value, and the obtained deviation value is stored in the memory of the NC device 7 in step (2).

When the deviation values in the X-axis and Y-axis directions are obtained as described above, the machining program of the NC device 7 is corrected, and the touch sensor 5b is removed in step (2). 1, it is possible to perform highly accurate machining without variations in machining accuracy due to temperature differences in the machine body 1.

Note that it is sufficient to perform the above measurement when the machine body 1 starts operating first thing in the morning and when it starts operating first thing in the afternoon.

In addition, in Fig. 4, the solid line shows the measured value after processing when processing is performed after correction based on the total nj value obtained by the touch sensor 5b, and the measurement after processing when no measurement or correction is performed. The value is indicated by the dashed line, and ΔII is indicated manually after processing.
The measured values for each case are shown by broken lines.

From this figure, the effect of correction based on the values obtained by measurement is clear.

By the way, the following results were obtained with and without correction.

Distance L between reference bins 3a and 3b when no correction is performed
A. Distance LB between reference pins 3a and 3b when performing correction
Assuming that the error between the temperature B of the ball screw shaft 6a and the temperature WA near the attachment part of the workpiece 4 is LE, 1. E/1β/1000 X O. OI. (B/ 'C
-WA 11') Note that 0 and 01 are the coefficients of thermal expansion of iron,
It shows that if the temperature increases by 1°C over a distance of 1m, it will expand by 0.01mm.

LA - β + LE LB - β + LE - LE (calibration value) β - 3 0 0 mm W A "If the temperature difference between C and B'C is 5°C, then LA - β + 0.015 LB - β is corrected. If this is done, the machining accuracy will be improved by 0.015 mm.

〔Effect of the invention〕

As detailed above, this invention attaches a touch sensor to an automatic dimension Δ-j determining device to two-dimensionally measure the distance between reference bins provided on a pallet, and corrects a machining program based on the obtained value. Since the machining accuracy can be improved by just using this method, it is economical because conventional expensive equipment such as ΔP1 equipment and thermostatic chambers are not required.

In addition, for large machine tools, direct measurement of the machine body makes it possible to correct the amount of thermal change based on the machine body.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, with Fig. 1 being an overall configuration diagram, Fig. 2 being a plan view of the pallet, Fig. 3 being a flowchart showing the operation, and Fig. 4 being a line diagram showing measurement results. be. 1 is the machine body, 4 is the workpiece, and 5b is the touch sensor.

Claims (1)

[Claims] In a machine tool controlled by an NC device, a touch sensor 5b is provided on the machine body 1, and the touch sensor 5b
Measure the distance between multiple reference points set near the workpiece 4, calculate the calibration value by comparing the obtained measurement value with the reference value, and correct the machining program using the calculated calibration value. A correction device for machine tools featuring: