JPS58165951A - Main shaft rotation control system in machine tool - Google Patents

Abstract

PURPOSE:To remove the phenomenon of cutting stick-slip by controlling the number of revolutions of a main shaft with the period and amplitude of the increase and decrease of said set number of revolutions when the cutting stick- slip is detected in a machine tool where the main shaft is turned for cutting process. CONSTITUTION:When a stick-slip detection signal SIG is inputted from a cutting stick-slip detector to an operating circuit 1, the operating circuit 1 output an instruction Sn of the number of revolutions to provide a periodically (T) changing (Sa) rotation, forming a triangular wave following an increasing decreasing step amount DS operated in an operating circuit 5 under input receiving status, a maximum amplitude Smax operated in an adder 3, and a minimum amplitude Smin operated in a subtractor 4. Namely, when the stick-slip detection signal SIG is inputted at time tO, the operating circuit 1 repeats an operation in compliance with a formula Sn=Sn-1+ or -DS and outputs the instruction Sn of the number of revolutions changing in the period T and the increasing decreasing step amount DS between the maximum amplitude Smax and the minimum amplitude Smin, so that the stick-slip in a cutting work may be removed.

Description

[Detailed Description of the Invention] This invention relates to a spindle rotation control method in a machine tool,
*Related to a shaft rotation control system for eliminating chatter during cutting operations.

When the spindle rotates, it becomes difficult to rotate the spindle. [In machine tools that are designed to perform cutting operations, conventionally, when cutting chatter occurs, the spindle rotation speed or feed rate command must be changed and input again, or It took 5K to cut by changing the override switch for rotation speed or feed speed. Therefore, the operator is required to carry out the above-mentioned change operation every time cutting chatter occurs, which is complicated. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a spindle rotation control system that automatically eliminates cutting chatter even if it occurs during cutting work.

This invention will be explained below.

The present invention relates to a spindle rotation control method for a machine tool that performs cutting work by rotationally driving the spindle.The present invention relates to a spindle rotation control method for a machine tool that performs cutting work by rotationally driving the spindle. The cutting chatter is set in advance, and when the cutting chatter is detected by the cutting chatter detector, the cutting chatter is removed by controlling the rotational speed of the spindle with the set period and amplitude.

FIG. 1 shows an example of a device to which this invention method is applied, in which a command rotation speed of 8 (rp
m) is the arithmetic circuit 1. Arithmetic unit 2. Adder 3 and subtracter 4
The chatter detection signal 8IG from the cutting chatter detector separately installed in the drive system of the main spindle of the machine tool is input to the arithmetic circuit lk, and the increase/decrease in the spindle rotation speed when the chatter detection signal SIG is output. Command amplitude B for commanding amplitude
(%) is input to the calculator 2. Then, the amplitude 8. which is calculated by the calculator 2 and which is actually increased or decreased. (rpm) is
A command period T (sec
) is also input to the arithmetic unit 5, and the increase/decrease step amount D8 (rpm) calculated by the arithmetic unit 5 is input to the arithmetic circuit 1.

Furthermore, the maximum value Sm of the rotational speed amplitude calculated by the adder 3
, x is input to the arithmetic circuit 1 and is calculated by the subtracter 4, which is the minimum value 8 of the rotational speed amplitude.

is input to the arithmetic circuit 1, and the spindle rotation speed command Sn calculated by the arithmetic circuit 1 is input to the spindle drive system.

In such a configuration, if the chatter detection signal 8IG is not output from the cutting chatter detector, the arithmetic circuit 1 outputs the command rotation speed 8 as it is as the rotation speed command 8n, so the spindle rotates at the command rotation Bs. Then it becomes k. Further, the command amplitude B and the command cycle T are set in advance by an operator or the like. Therefore, computing units 2 and 5. Adder 3 and subtracter 4 calculate the set command rotation speed 8. The command period T and the command amplitude B are calculated by calculating the increase/decrease step amount D8, the maximum amplitude -8, and the minimum amplitude width 11, and these data are input to the calculation circuit 1.

That is, the arithmetic unit 2 calculates an amplitude value (P − P ) consisting of the command rotation speed 8 and the command amplitude B. Find this amplitude value S
Add a63. Subtractor 4. Input to calculation 185. Here, the command rotation speed 8 is inputted to the adder 3 and the subtracter 4, and the adder 3 and the subtracter 4 respectively set the maximum amplitude S and the minimum amplitude 8 m2 according to the following formulas. Calculate.

Then, based on the amplitude SJl from the computing unit 2 and the set command period T, the computing unit 5 calculates the increase/decrease step amount D according to the following formula.
Find 8. That is, . Here, in the above formula, 1/100 means that the period for adding and subtracting the increase/decrease step amount D8 is 1/100.
This is because it is performed every (s@c). In this way, the increase/decrease step amount DS is obtained by the calculator 5.

The maximum amplitude SmJlx1 obtained by the adder 3 and the minimum amplitude Sm1n obtained by the subtracter 4 are respectively calculated by the arithmetic circuit 1.
has been entered.

Therefore, from the arithmetic circuit IK cutting chatter detector as shown in Fig. 2 (
5), when the chatter detection signal 81G shown in FIG. )K outputs a rotational speed command 8m that rotates by increasing and decreasing (8,) periodically with a triangular wave as shown in . The calculation according to formula % (5) K is repeated and a rotation speed command 8fl that changes with a period T and an increase/decrease step amount D8 between the maximum vibration -8m1x and the minimum amplitude 8min is output, so the main shaft is operated with one cycle of such amplitude. K is driven so that the rotational speed changes with
Become. As a result, chatter in the cutting operation is removed. For example, at time t1, the chatter is removed, so that the chatter detection signal 81G is no longer output. After this, the gate control is performed on the frequency signal at the commanded times. As described above, according to the method of the present invention, it is possible to detect the maximum vibration of -8 m, When chatter is detected, the rotational speed of the spindle changes with two preset amplitude cycles, so that chatter during cutting can be automatically and reliably removed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a device to which the method of the present invention is applied, and FIG. 2 (A) and (A) are time charts showing an example of its operation.

Claims (1)

[Claims] In a machine tool that performs cutting work by rotationally driving a spindle, a cutting chatter detector is provided in the drive system for the cutting work, and a period of increase/decrease and an amplitude of increase/decrease in the rotation speed of the spindle are set. A machine tool characterized in that when cutting chatter in the cutting operation is detected by a detector, the rotational speed of the spindle is controlled with the set period and amplitude to remove the cutting chatter. spindle rotation control method.