JPH07112646B2 - Screw processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a screw machining apparatus represented by a tap board.

"Conventional technology" Conventionally, tapping operation control in a screw machining device to which an NC device is applied is performed only by generating a feed command and a rotation command in the NC device according to the pitch of the screw to be machined The motor and the spindle rotation motor were controlled as independent servo systems. The deviation between the feed amount and the rotation amount, which occurs when the rotary motor is reversed, is absorbed by the mechanical expansion and contraction of the tapper with a tapper interposed between the tap tool and the spindle. For this reason, there are problems that the screwing speed is limited by the performance of the tapper, and the accuracy of the screw is reduced due to the force of expansion and contraction of the tapper.

Therefore, the actual rotation amount of the main shaft is detected, and the feed motor is driven according to the detected rotation amount (Japanese Patent Laid-Open No. 56-
33249) or the like, which detects the actual feed amount and drives the rotary motor in accordance with the feed amount (JP-A-60-155319).
No.) etc. have been proposed for controlling the feed motor and the rotary motor in synchronization with each other. Since these devices have high accuracy of synchronization between feed and rotation, screw processing can be performed without using a tapper in most cases.

[Problems to be Solved by the Invention] However, in recent years, there has been a demand for further shortening of machining time, and in screw machining, high-speed machining which is close to the limit of tap tools may be performed. In such a case, for example, in the conventional device that drives the rotary motor according to the feed amount,
Since a command is issued to the rotary motor after detecting that the feed shaft has actually moved, there is a problem in that a follow-up delay occurs and there is a limit to the improvement of screw machining accuracy. In particular, in machining with a small depth of thread machining or machining performed while stepping the tool with a small step width, the amount of machining in the transient state before the feed and rotation speeds become constant is large, so the error due to tracking delay is large. It becomes a problem.

The present invention has been made to solve the above problems, improves the followability of the spindle rotation with respect to the feed axis, high-precision tapping even in high-speed tapping close to the limit of tap tools. It is an object of the present invention to provide a screw machining device that can be used.

“Means for Solving Problems” A screw machining apparatus of the present invention made to achieve the above-mentioned object is a rotation position detecting means for detecting a rotation position of a spindle and a feed position detecting means for detecting a feed position of a machine. In a screw machining device that performs tapping operations by synchronously operating a rotary motor that rotates the spindle and a feed motor that drives the feed, calculates the feed deviation between the feed command value and the detected feed position of the machine. According to the feed deviation calculation means and the feed deviation,
Feed drive means for driving a feed motor, rotation command value calculation means for calculating a rotation command value for instructing the speed of the rotation motor based on the feed deviation and screw pitch, and the detected machine feed Based on the position and the screw pitch, a rotation correction value calculation means for calculating a rotation correction value for comparison with the rotation position of the spindle, and a rotation deviation between the rotation correction value and the detected rotation position of the spindle. Rotation deviation calculating means, correction means for correcting the rotation command value by the rotation deviation, and rotation driving means for driving the rotation motor in accordance with the rotation command value corrected by the correction means.

[Operation] In the present invention thus configured, the feed deviation calculation means calculates the feed deviation between the feed command value and the machine feed position detected by the feed position detection means. Then, the feed drive means drives the feed motor according to the feed deviation. That is, the feed motor is feedback-controlled by the feed position and independently controlled by the feed command value.

On the other hand, the rotary motor is controlled so as to synchronize with the feed motor as follows. That is, the rotation command value calculation means is
A rotation command value for commanding the speed of the rotary motor is calculated based on the feed deviation and the screw pitch. The rotation correction value calculation means calculates a rotation correction value for comparison with the rotation position of the spindle based on the machine feed position and screw pitch detected by the feed position detection means, and rotation deviation calculation means. Calculates the rotation deviation between the rotation correction value and the detected rotation position of the spindle. Then, the correction means
The rotation command value is corrected by the rotation deviation, and the rotation drive means drives the rotation motor in accordance with the rotation command value corrected by the correction means.

Thus, in the present invention, the rotation command value for commanding the speed of the rotary motor is calculated based on the feed deviation.
Since this feed deviation is a value that determines the control amount of the feed motor, it is possible to predict future changes in the feed position based on this value. In the present invention, since the rotary motor is controlled based on this feed deviation, the followability of the rotational position to the feed position is greatly improved.

Further, since the rotation command value is corrected by the actually detected feed position and rotation position, a steady error is prevented from occurring between the rotation position and the feed position, and the rotation position control accuracy is improved. improves.

[Examples] Examples of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing a screw processing device according to the present invention.

The machine body 1 of the screw machining device forms a vertical tap board, and a slider 4 is attached to a column 3 vertically arranged on a base 2.
The spindle head 5 is slidably supported in the vertical direction via the, and the spindle head 5 is engaged with the ball screw 6. The ball screw 6 is connected to a feed motor 7 composed of an AC servomotor and is rotationally driven to raise and lower the spindle head 5. The feed motor 7 is provided with a tachogenerator 8 that detects a rotation speed and a pulse generator 9 that detects a rotation position. The pulse generator 9 constitutes a feed position detecting means for detecting the feed position of the spindle head 5.

A main spindle 11 is rotatably supported by the main spindle head 5, and is rotationally driven by a rotary motor 12. The rotary motor 12 consists of an AC servo motor, and a tachogenerator 13 that detects the rotational speed.
And a pulse generator 14 for detecting the rotational position. The pulse generator 14 constitutes a rotational position detecting means for detecting the rotational position of the main shaft 11.

A tap tool 15 is directly attached to the lower end of the main shaft 11 without passing through a tapper, and a workpiece 17 having a prepared hole 16 is threaded.

A control circuit of a feeding system (referred to as Z axis) for moving the spindle head 5 up and down will be described.

Based on the data input from the input device 21, the calculator 22 calculates the feed command value Z and outputs it to the feed deviation counter 23 as a pulse train corresponding to the feed speed. A pulse corresponding to the rotation angle of the feed motor 7 is supplied to the feed deviation counter 23 as a position feedback pulse.
Input from. In the feed deviation counter 23, the feed command value Z
And the machine feed position z detected by the pulse generator 9 is calculated as a deviation E (Z) = Z−z, and the feed deviation E is calculated.
(Z) is sent as a speed command and output to the servo amplifier 24. A signal v corresponding to the actual speed from the tachogenerator 8 is sent to the feed servo amplifier 24 as a speed feedback signal.
(Z) is input to form a speed loop system to drive the feed motor 7. The control circuit of the above-mentioned feed system (Z axis) has the same circuit configuration as that used for normal feed control.

Next, a control circuit of a rotation system (referred to as an R axis) that controls the rotation of the main shaft 11 will be described. In the rotating system, the rotation command value R
Is not the data from the input device 21, but the feed deviation counter
It is calculated and controlled based on the feed deviation E (Z) from 23.

The feed deviation E (Z) from the feed deviation counter 23 is input to the rotation command value calculator 25. In the rotation command value calculator 25, the thread pitch P of the thread machining and the lead L of the ball screw 6 which are input from the pre-squeeze input device 21 and given through the calculator 22.
Then, the feed deviation E (Z) is multiplied by L / P, and the feed deviation E
The rotation command value R = E (Z) · L / P corresponding to (Z) is calculated. Then, the rotation command value R is output to the rotation servo amplifier 27 via the adder 26. Since the rotation command value R corresponds to the feed deviation E (Z), that is, the speed command value to the feed servo amplifier 24, the rotation command value R is a prediction of the movement of the spindle head 5.

The adder 26 corrects the rotation command value R. That is, the pulse generator 14 for detecting the rotational position r of the main shaft 11
The pulse from is input to the rotation deviation counter 28. On the other hand, the pulse from the pulse generator 9 for detecting the feed position z is input to the rotation correction value calculator 29, and the feed amount z is L / P from the thread pitch P of the thread machining and the lead L of the ball screw.
The rotation correction value r (z) corresponding to the feed position z is calculated (that is, the rotation correction value r (z) = z · L / P) and output to the rotation deviation counter 28. With the rotation deviation counter 28,
A rotation deviation E (r) between the rotation correction value r (z) and the rotation position r of the spindle 11 is calculated and output to the adder 26. Adder 26
Then, the rotation command value R from the rotation command value calculator 25 is corrected by the rotation deviation E (r), and the corrected rotation command value R
(E) = R + E (r) is output to the rotary servo amplifier 27.

A signal v (r) corresponding to the speed from the tachogenerator 13 is supplied to the rotary servo amplifier 27 as a speed feedback signal.
Is input to form a speed loop system to drive the rotary motor 12 in accordance with the corrected rotation command value R (E).

The control circuit described above is a circuit that performs digital calculation except for the servo amplifiers 24 and 27.
3, 28, the rotation command value calculator 25, the rotation correction value calculator 29, the adder 26, etc. are realized as internal calculation processing using a microcomputer.

The feed motor 7 is driven by inputting data such as the screw pitch, the feed stroke (tap depth), and the feed speed from the input device 21, and the rotary motor 12 rotates in synchronization with the feed motor 7. It is driven and screw processing is performed.

In this embodiment, since the rotary motor 12 is synchronously operated on the basis of the feed deviation E (Z), a transient follow-up is provided as compared with the conventional device which performs the synchronous operation on the basis of the feed amount z. The delay could be greatly reduced.

For example, diameter 6mm, pitch 1.0 (M6, P1.0), tap depth 1
According to the experimental results when a 2 mm screw was processed at a high speed of 3000 rpm, the lead / lag error in the screw feed direction (Z axis) based on the screw rotation position was compared to the conventional device. With the example device, it was possible to reduce by about 25%.

In the above embodiment, the deviation counter 23 serves as the feed deviation computing means, the feed servo amplifier 24 serves as the feed driving means, the rotation command value computing unit 25 serves as the rotation command value computing means, and the rotation correction value computing unit 29 serves for the rotation correction. The deviation counter 28 corresponds to the rotation deviation calculating means, and the adder 26 corresponds to the correcting means.

"Effects of the Invention" As described in detail above, in the screw machining device of the present invention, the rotation command value is calculated based on the feed deviation, and the rotation motor is controlled based on the rotation command value. The followability with respect to the feed position can be improved very well. Further, since the rotation command value is corrected by the actually detected feed position and rotation position, it is possible to prevent a steady error from occurring between the rotation position and the feed position, and to control the rotation position accurately. Can be improved.

Therefore, according to the present invention, it is possible to obtain the effect that the followability of the rotational position to the feed position is good even during high-speed machining, and highly accurate screw machining can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control circuit of a screw machining device according to the present invention. 3 ... column, 5 ... spindle head, 7 ... feed motor,
9 ... Pulse generator (feed position detection means), 11 ...
Spindle, 12 ... Rotation motor, 14 ... Pulse generator (rotational position detection means), 24 ... Feed servo amplifier, 25 ... Rotation command value calculator, 26 ... Adder (correction means), 27 ... Rotation Servo amplifier, 29 ... Rotation correction value calculator.

Claims (1)

[Claims] 1. A rotary position detecting means for detecting a rotary position of a main shaft and a feed position detecting means for detecting a feed position of a machine, wherein a rotary motor for rotating the main shaft and a feed motor for driving the feed are synchronously operated. In a screw machining device that performs tapping machining operation, a feed deviation calculation means that calculates the feed deviation between the feed command value and the detected machine feed position, and a feed drive means that drives the feed motor according to the feed deviation. , Based on the feed deviation and the screw pitch, a rotation command value calculation means for calculating a rotation command value for commanding the speed of the rotary motor, and based on the detected feed position and screw pitch of the machine,
A rotation correction value calculation means for calculating a rotation correction value for comparison with the rotation position of the spindle, a rotation deviation calculation means for calculating a rotation deviation between the rotation correction value and the detected rotation position of the spindle, and its rotation A screw machining apparatus comprising: a correction unit that corrects the rotation command value based on a deviation; and a rotation drive unit that drives a rotation motor according to the rotation command value corrected by the correction unit.