JPH03208542A - Backlash correction system numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To have backlash correction which best suits the feed speed and is precise even in case bit-in phenomenon occurs when the guadrant is changed over, by preparing a correction data optimum for the command speed from a correction data which is accumulated for each piece of a plurality of feed speeds, and supplying this prepared optimum data to a drive motive. CONSTITUTION:The type of processing command and the command speed are identified by a data analyzing part 4 of a command data 2, and backlash correction amount data corresponding to the command speed and positions is read out of correction data parts 14a-14n according to the command speed and position data. A backlash correction amount calculating part 16 calculates the backlash correction amount and pulse rate from the backlash correction data and pulse rate data, and they are supplied to a servo motor 8 through a speed control part 6. This enables a backlash correction optimum for the feed speed in case circular are interpolation is to be made, and backlash correction is made practicable which is precise even in case bite-in phenomenon occurs when the quadrant is changed over and with gentle rising.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a numerically controlled machine tool, and more specifically, it performs optimal deformation correction in response to various feed speeds in curve machining using circular interpolation, etc. This paper relates to a backlash correction method for numerically controlled machine tools.

[Conventional technology] Conventionally, machine tools that perform three-dimensional cutting, etc.
Three-dimensional three-dimensional machining1 is realized by moving the machining tool or workpiece using drive mechanisms arranged for each axis, Y-axis, and Z-axis. This NC device, which is often used as a programmable NC device, analyzes the movement angle command value for each axis based on externally input data and a predetermined operation program, and then transmits the data for each axis to the machine tool. It is also C that sequentially outputs to the drive mechanism of each axis and executes the desired operation set by the operation program 1.

Here, the drive mechanism described above includes a servo motor as a drive source for moving the workpiece, a transmission mechanism such as a C ball screw or gear train for transmitting the rotation of the motor to each axis, and a motor. It supplies a drive signal for rotational driving, and also includes a control circuit such as a position and speed control loop for detecting position and speed and feeding it back to the drive signal.

In this drive mechanism, backlash occurs due to the transmission mechanism when moving a processing tool or a workpiece. Therefore, various techniques have been devised to correct this pack lash.

Generally, backlash correction in such an NC device is performed by setting the feed speed in curve control such as cutting feed, rapid feed, or circular interpolation to a certain speed, measuring the amount of backlash that occurs at that time, and calculating this as the backlash correction amount. A method that is often used is to store the data as a value and supply it to the speed control system of the drive mechanism for correction.

[Problems to be Solved by the Invention] In curve control such as circular interpolation, simultaneous control of two axes is required when performing perfect circle machining, but backlash correction in this case requires adjusting the amount of backlash correction for each axis. This is done for each axis using By the way, in such machining, when switching quadrants, that is, when the feed direction of one axis changes from 10 to -
Alternatively, when normal backlash correction is performed when changing from 1 to 10, a so-called bite phenomenon may occur.

FIG. 4 is a diagram showing this situation, and shows the trajectory S of the machining tool before backlash correction and the trajectory S' after backlash correction with the error with the command value enlarged. (a)
→(B) shows the case where the backlash correction works normally and no digging-in phenomenon occurs, and (C)→(B) shows the case when the backlash correction does not work normally and the digging-in phenomenon occurs. There is.

This biting phenomenon is due to the structure of the mechanical system.
This does not occur when the rise is sharp as in A when switching quadrants, but it occurs when the rise is slow as in B. Note that BL is the amount of pack lash.

Here, in normal backlash correction, a pulse corresponding to the amount of backlash correction is added at one time during one sampling time of servo motor drive and is supplied to the servo motor via the speed control system, so the rise is sharp when switching quadrants. However, if the rise is slow, the trajectory after backlash correction will draw a trajectory that bites into the inside of the circular arc to be machined, resulting in a biting phenomenon.

Fig. 5 is a diagram showing the biting phenomenon shown in Fig. 4 as the movement of the mechanical system. This shows a case where backlash correction does not work properly and a bite phenomenon occurs.

In the figure, C indicates the NC command value, M indicates the state before backlash correction, N indicates the state after backlash correction, and BL indicates the amount of backlash.

If the backlash correction works correctly and the digging phenomenon does not occur, the mechanical system is stopped during the backlash, whereas if the backlash correction does not work correctly and the digging phenomenon occurs, then the mechanical system stops during the backlash. During backlash, the mechanical system moves back little by little, so if normal backlash correction is performed, it will bite inward from the desired trajectory, which will reduce the accuracy of circular interpolation and curve machining. This will reduce the

The reason for this is, as mentioned earlier, in normal backlash correction, pulses equivalent to the amount of backlash correction are added at one time during one sampling time of servo motor drive, and the pulses are supplied to the servo motor via the speed control system. Therefore, if the rise is slow at the time of quadrant switching, the trajectory after pack lash correction will draw a trajectory that cuts inside the arc to be machined.

On the other hand, in the NC device described in Japanese Patent Application Laid-Open No. 60-172444, as a backlash correction method for a mechanical system having a slow rise as described above, a pulse corresponding to the backlash correction amount is generated during one sampling time of the servo motor drive. is added at one time and not supplied to the servo motor via the speed control system. Instead, backlash correction data is prepared by dividing the amount of backlash that occurs during circular interpolation into multiple position intervals, and the amount of backlash correction is gradually increased for each moving position. Disclosed is a method for adding.

According to this method, it is possible to considerably improve the above-mentioned biting phenomenon, but there are disadvantages in the following points.

In other words, the first point is that the amount of the above-mentioned biting phenomenon changes depending on the feed speed, so simply performing backlash correction based on the amount of backlash measured at a certain feed speed will not result in complete correction. The second reason is that, corresponding to the divided position, pulses corresponding to the amount of backlash correction at the divided position are supplied to the servo motor via the speed control system during one sampling time of servo motor drive. , the backlash correction does not follow the change in slope of the slow rising part.

The second point will be explained in detail as follows. If we analyze in detail the blow crush that has a slow rise, it can be divided into a sharp rise part A and a slow rise part B, as shown in Figure 3 (the error from the command value is shown enlarged). In the slow rising portion B, the slope gradually changes according to the division distances Ll, L2, and L3 for each position.Therefore, the speed control system is adjusted based on the pack lash correction amount according to the position. Accurate backlash correction cannot be performed unless the pulse rate per sampling time supplied to the servo motor via the servo motor is changed.

As explained above, in the conventional backlash correction method, when circular interpolation is performed, backlash correction that is optimal for the feed speed is not performed, and
In the case where the start-up is slow and a biting phenomenon occurs when switching quadrants, accurate backlash correction is not performed, resulting in a disadvantage in that machining accuracy decreases.

The present invention has been made in order to overcome the above-mentioned disadvantages, and when performing circular interpolation, it is possible to perform backlash correction that is optimal for the feed rate, and also to correct the slow rise. The object of the present invention is to provide a backlash correction method for a numerically controlled machine tool, which enables accurate backlash correction and improves machining accuracy even in cases where a biting phenomenon occurs when switching quadrants. .

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention applies a driving force to each pongee through a driving force transmission mechanism based on a predetermined operation program. In a semi-closed-loop numerically controlled machine tool that performs operations such as a correction data section that stores pulse rate data for calculating the pulse rate supplied to the drive source according to each of the plurality of feed speeds; backlash correction data is read from the correction data section, and the backlash correction data is read out from the correction data section; a backlash correction amount calculation unit that calculates a backlash correction amount adapted from the speed and the positional interval and the pulse rate data; and supplying the backlash correction amount calculated by the backlash correction amount calculation unit to the speed control system. Features.

[Function] Since the numerically controlled machine tool according to the present invention is constructed as described above, it exhibits the following functions.

That is, backlash correction data is obtained by dividing the amount of backlash generated during circular interpolation into multiple position intervals as backlash correction amount data, and the pulse rate supplied to the drive source via the speed control system according to the divided positions. The pulse rate data for calculating the
M is multiplied in the correction data section corresponding to each feed speed, and first, based on the command data, corresponding backlash correction data and pa JL slate data are extracted from the correction data section based on the command speed and the position interval. Read out.

Next, in the backlash correction amount calculation section, based on the commanded speed and position, for example, by interpolation calculation etc. from the backlash correction amount corresponding to the speed before and after the commanded speed, the optimum correction amount corresponding to the commanded speed is calculated. Optimal backlash correction data is generated from pulse rate data corresponding to the divided position in accordance with the position, and is supplied to the drive source via the speed control system.

Therefore, it is possible to perform backlash correction that is optimal for the feed speed, and even in cases where there is a slow rise and a biting phenomenon occurs when switching quadrants, it is possible to perform accurate backlash correction, resulting in machining accuracy. It becomes possible to improve the

[Embodiment] Next, preferred embodiments of the numerically controlled machine tool according to the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a diagram showing the structure of an NC device according to this embodiment.

In FIG. 1, command data 2 input from the outside is analyzed by a data analysis section 4 for command contents such as the type of machining command, command speed and position, and a single drive signal for each wheel is generated. This drive signal is supplied to the servo motor 8 via the speed control section 6 to rotate the ball screw 12. The ball screw 12 converts the rotational motion of the servo motor 8 into linear motion, thereby moving the movable table 10 to the commanded position.

Reference numeral 18 is a mechanical encoder for position detection, and a detected position signal from this encoder 18 is supplied to the speed control section 6, forming a well-known feedback loop.

Reference numeral 14 (14a to 14n) is a correction data section, which includes backlash correction data obtained by dividing the amount of backlash generated during circular interpolation into a plurality of position intervals as backlash correction amount data, and the Pulse rate data for calculating the pulse rate to be supplied to the servo motor via the speed control system is stored in the correction data sections 14a to 14n corresponding to each of a plurality of feed speeds.

FIG. 2 is a diagram showing the contents of the correction data accumulated in the correction data sections 14a to 14n.

F, to F. is the feed rate, D0 to D. is the division position, and for each feed rate F, to F,, and for each division position D
o to D. Backlash correction data B is obtained by dividing the amount of backlash that occurs during circular interpolation into multiple position intervals.
Lo to BL. According to the divided positions, pulse rates f-9La to f-9L for calculating the pulse rate to be supplied to the servo motor 8 via the speed control section 6 are stored.

Reference numeral 16 is a backlash correction amount calculating section, which reads correction data from the correction data sections 14a to 14n in accordance with the commanded speed, and calculates the backlash correction amount and the pulse rate adapted from the commanded speed and the position interval. It is calculated and supplied to the speed control section 6.

The NC device according to the present invention is basically constructed as described above, and its functions and effects will be explained in detail below.

The data analysis section 4 identifies the type of machining finger and the command speed of the command data 2 inputted from the outside. When the machining command is circular interpolation such as perfect circular machining, the drive signal for the axis that has reached the quadrant switching position is sent from the correction data sections 14a to 14n to the backlash corresponding to the command speed and position according to the command speed and position data. Correction amount data is read out.

For example, when the command speed is F1 and the position is D, the divided backlash correction data BL. shown in FIG. According to the divided position, the pulse rate }f1 is read out for calculating the pulse rate to be supplied to the servo motor 8 via the speed control section 6. In the backlash correction amount calculation section 16, this backlash correction data BL
．． The backlash correction amount and the pulse rate are calculated from the pulse rate data L11 and the pulse rate data L11.

The pulse rate for backlash correction is the amount of movement in the X-axis direction, and in the above example, is pulse rate data L++. This is supplied as backlash correction data to the servo motor 8 from the backlash correction amount calculation la16 via the speed control section 6.

When the command speed is a value between the speeds for which backlash correction amount data has been accumulated, the backlash correction amount data corresponding to the adjacent speeds (speeds before and after the command speed) are read out,
The backlash correction amount calculation unit 16 calculates the amount by interpolation.

For example, in FIG. 2, when the speed F8 is FIO00, the speed F is F2000, and the command speed is F1400, the backlash correction data BL++ at the position D1 is BL. ．． + (B L , 2-B L ..)x
(400/1000), and similarly, the pulse rate data L. is L++ 10 (Lea L++) X (400/1000
).

[Effects of the Invention] Since the backlash correction method for the numerically controlled machine tool according to the present invention is configured as explained above, when circular interpolation is performed, the optimum feed rate is adjusted for the feed rate. Backlash correction is possible, and accurate backlash correction is also possible even in cases where there is a slow rise and a bite phenomenon occurs when switching quadrants.
It is possible to improve the machining accuracy of semi-closed loop numerically controlled machine tools.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the structure of the numerically controlled machine tool according to the present invention, Fig. 2 is a diagram showing an example of the contents stored in the correction data section, and Fig. 3 is a diagram illustrating backlash when there is a slow rise. FIG. 4 is a diagram explaining the gouge phenomenon in circular interpolation, and FIG. 5 is a diagram showing the gouge phenomenon in FIG. 4 as a movement of a mechanical system. ...Command data 4...Data analysis section...
Speed control unit 8...Servo motor 0...Moving table 12...Ball screws 4, 14a to 14n
...Correction data section 6...Backlash correction amount calculation section 8...Encoder before backlash correction After backlash correction Before backlash correction After backlash correction (b) If there is a bite Continue from page 1 @ Inventor Jun Fujita Toshiba Machine Co., Ltd. Numazu Office, 2068-3 Ooka, Numaichizu City, Shizuoka Prefecture

Claims (1)

[Claims] (1) In a semi-closed loop numerically controlled machine tool that executes operations on machining tools, workpieces, etc. by applying driving force to each axis via a drive force transmission mechanism based on a predetermined operation program. Backlash correction data obtained by dividing the backlash amount of the driving force transmission mechanism that occurs during circular interpolation of the command value into multiple position intervals, and pulse rate data for calculating the pulse rate supplied to the drive source according to the divided positions. and a correction data section stored correspondingly to each of a plurality of feed speeds; and backlash correction data is read from the correction data section, and the backlash correction amount and the pulse rate data adapted from the command speed and the position interval are calculated. 1. A backlash correction method for a numerically controlled machine tool, comprising: a backlash correction amount calculation section for calculating, and supplying the backlash correction amount calculated by the backlash correction amount calculation section to a speed control system.