JPH01153219A - Thread cutting nc device for nc lathe - Google Patents

Abstract

PURPOSE:To cancel synchronous errors by adding a synchronous correction amount obtained from detected rotational speed multiplied by thread magnification to a commanding position of a feed shaft to provide a temporary commanding position so that feed is controlled by speed corresponding to the deviation of detected position from said commanding position. CONSTITUTION:A spindle motor 3 is rotatably driven with set rotational speed thetaV and the rotational angle thereof is detected by a detector 4 to be sent to the input of a constant multiplier 5 and multiplied by thread multiplication KV so that a true commanding position theta of a feed shaft is given to a position adder 11. Also, the actual rotational speed thetaV of spindle motor 3 is detected by a detector 12 and multiplied by the thread magnification KV with a synchronous deviation amount calculator 10 to obtain a synchronous correction amount theta which is added to the true commanding position theta by a position added 11 to provide a temporary commanding position thetaC. The deviation (e) of position thetaC from a feed shaft position P detected by a detector 9 is obtained by a synchronous deviation calculator 6 to drive a feed servo motor 8 through a servo pump 7 with speed proportional to said deviation. Thus, synchronous errors are eliminated and the spindle and feed shaft can be run in synchronization with each other with high accuracy.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an NC device for thread cutting on an NC (numerically controlled) lathe, and in particular, to eliminate synchronization errors between the rotation of a spindle and the feed axis of a cutter. Related to improvements.

<Prior Art> Thread cutting on an NC lathe is performed by moving a feed shaft to which a cutter (tool) is attached in synchronization with the rotation of a spindle.

A conventional thread cutting NC device for this purpose has a block configuration shown in FIG. In FIG. 2, a spindle rotation speed (θV) is set by a spindle rotation fine setting device 1, and a spindle motor 3 is rotationally driven by a spindle servo amplifier 2.

The rotation angle (θ') of the spindle motor 3 is detected by the rotation angle detector 4, and the detected rotation angle is multiplied by the screw magnification (K,) determined by the screw lead by the screw constant multiplier 5, and the feed axis command is obtained. Output the position (θ).

On the other hand, the current position (P) of the feed axis is detected by the position detector 9, the position deviation (e) between the command position and the current position, that is, the synchronization deviation is calculated by the synchronization deviation calculator 6, and the The feed servo motor 8 is rotationally driven by the feed servo amplifier 7 at the same speed.

Here, the synchronization relationship is as follows.

First, let θ9 be the spindle rotation speed and t be the time.
The rotation angle θ' of the spindle motor 3 is θ'=θ・t...Equation (1) Also,
When the screw magnification is K, the command position θ output by the screw constant multiplier 5 is θ=K・θ' =K・θ・t...Formula (2) On the other hand, when the actual position of the feed axis is P , the synchronization deviation e of the position is e=θ−P =K ・θ ・t−P ・・Equation (3) Also,
The relationship between the synchronization deviation e and the current position P of the feed axis is P = e - t...Formula (4) Therefore, the synchronization deviation e is determined by Equation (3) and Equation (4), e = K.
θ ・' (11+t) −→ K , θ ...Equation (5) <Problem to be solved by the invention> As mentioned above, in the conventional technology, the spindle rotation speed θ is proportional to the rotation speed θ, and it depends on the time t. There is a synchronization deviation e, which causes an error in synchronization.

Therefore, when the spindle rotational speed θ changes or fluctuates, the synchronization deviation with the position of the feed shaft changes, resulting in a disadvantage that thread cutting accuracy deteriorates.

In addition, similar synchronization errors occur at the start and end of thread cutting when the feed rate changes, resulting in incomplete threads, but in order to minimize this, increasing the position loop gain,
The only option was to shorten the acceleration/deceleration time constant, which was not easy.

SUMMARY OF THE INVENTION In view of the problems of the prior art described above, it is an object of the present invention to provide a thread cutting NC device for an NC lathe that eliminates synchronization errors.

Means for Solving Problems> The thread cutting NC device for an NC lathe according to the present invention includes a spindle rotation speed setting means for setting the rotation speed of a spindle motor, and a spindle servo amplifier for rotating the spindle motor at the set rotation speed. , a rotation angle detection means for detecting the rotation angle of the spindle motor, a screw constant multiplication means for calculating the command position of the feed shaft by multiplying the detected rotation angle by a screw magnification, and a rotation speed for detecting the rotation speed of the spindle motor. a detection means, a synchronization deviation amount calculation means that calculates a synchronization correction amount by multiplying the detected rotational speed by a screw magnification, and a position that adds the synchronization correction amount to the command position of the feed axis to obtain a temporary command position of the feed axis. an addition means, a position detection means for detecting the position of the feed axis, a synchronous deviation calculation means for calculating the deviation between the temporary command position and the detected position, and a feed for driving the feed servo motor at a speed proportional to the calculated deviation. A servo amplifier.

Function> In the above configuration, the rotation speed of the spindle motor is set to θ9.
, when the screw magnification is Kv, the synchronization correction amount Δθ is the same as the conventional synchronization deviation amount, and Δθ=K ・θ
...Equation (6) Also, if the rotational speed of the spindle motor is θ', the true command position θ of the feed axis is θ=K ・θ′ − as shown in (2), and θ, t ・・・Equation (2) Therefore,
θ. If θ is a temporary command position, then θ = θ + Δθ 201 K · θ = θ, (1+t) = Equation (7), which is a value that takes into account the amount of synchronization deviation in advance.

On the other hand, if the actual position of the feed axis is P, then the tentative command position θ. The synchronization deviation e from
And, as in Equation (4), P=e −t ... From Equation (4), Equation (8), and Equation (4), the synchronization deviation amount e is e=K ・θ
...Equation (9) is obtained, but this synchronization deviation amount e is with respect to the temporary command position θ-, and the equation (
7), the truer command position θ is θ=θ. -, ·θ, so the true synchronization deviation is zero.

Therefore, synchronization errors between the rotation of the spindle and the movement of the feed shaft of the cutter are eliminated, thread cutting becomes highly accurate, and incomplete threads are shortened.

Embodiment Example With reference to FIG.
An example of the device will be described. The thread cutting NC device of the embodiment shown in FIG. 1 is constructed by adding a synchronization deviation it calculator 10, a position adder 11, and a rotational speed detector 12 to the conventional device shown in FIG.

In FIG. 1, the spindle rotation speed setting device 1 sets the rotational progress θ of the spindle motor 3, and the spindle servo amplifier 2 sets the rotational progress θ of the spindle motor 3rf! Rotates according to the set speed.

With respect to the rotation of the spindle motor 3, a rotation angle θ' is detected by a rotation angle detector 4, and the detected angle θ' is provided to a Ness constant multiplier 5. The screw constant multiplier 5 multiplies the detected angle θ' by a screw magnification K determined by the lead of the screw, and provides the position adder 11 with the true commanded position θ of the feed shaft.

Further, the actual rotational speed θ of the spindle motor 3 is detected by the rotational speed detector 12, and the detected speed θ9 is provided to the synchronization deviation calculator 10.

The synchronization deviation calculator 10 multiplies the screw magnification by the detected speed θ, and provides the synchronization correction amount Δθ to the position adder 11. Δθ
= K, ·θ9, and Δθ is the same as the conventional synchronization deviation amount.

A position adder 11 adds the true command value θ and the synchronization correction amount Δθ, and sets θ+Δθ as a temporary command position θ. It is given to the synchronization deviation calculator 6 as .

The synchronization deviation calculator 6 calculates a temporary command position θ. The deviation e between the position P and the position P of the feed axis detected by the position detector 9 is determined and given to the feed servo amplifier 7.

The feed servo amplifier 7 drives the feed servo motor 8 at a speed proportional to the deviation e.

As for the operation, since the synchronization deviation amount e=K,·θ9 is expected in advance for the tentative command position θ0 as described above, the synchronization deviation with respect to the true command position θ becomes zero. That is, the synchronization error between the rotation angle of the spindle motor and the feed axis of the cutter becomes zero.

8. As a result, the synchronization deviation amount Δθ only needs to be added to the command position θ, so the calculations do not necessarily have to be performed by separate and independent equipment, and the combination of calculations can be changed as appropriate.

<Effects of the Invention> According to the present invention, synchronization errors are eliminated by allowing for synchronization deviation in the command position of the feed axis, and the system is not affected by changes in the rotation of either the spindle motor or the feed servo motor. The rotation of the spindle and the feed axis can be operated in synchronization with high precision. Therefore, the thread cutting accuracy becomes high and the incomplete thread portion becomes short.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example. In the drawing, 1 is a spindle rotation speed setting device, 2 is a spindle servo amplifier, 3 is a spindle motor, 4 is a rotation angle detector, 5 is a screw constant multiplier, 6 is a synchronization deviation calculator, 7 is a feed servo amplifier, 8 1 is a feed servo motor, 9 is a position detector, 10 is a synchronous deviation calculation device, 11 is a position adder, and 12 is a rotation speed detector.

Claims (1)

[Scope of Claims] A thread cutting NC device for an NC lathe that performs thread cutting by synchronizing the rotation of a spindle and the movement of a feed shaft equipped with a cutter, comprising: a spindle rotation speed setting means for setting the rotation speed of a spindle motor; a spindle servo amplifier that rotates the spindle motor at the specified rotation speed, a rotation angle detection means that detects the rotation angle of the spindle motor, and a screw constant multiplier that calculates the command position of the feed axis by multiplying the detected rotation angle by a screw magnification. means, a rotation speed detection means for detecting the rotation speed of the spindle motor, a synchronization deviation amount calculation means for calculating a synchronization correction amount by multiplying the detected rotation speed by a screw magnification, and a synchronization correction amount for the command position of the feed axis. position adding means for adding up to obtain a temporary command position of the feed axis; position detection means for detecting the position of the feed axis; synchronous deviation calculation means for calculating the deviation between the temporary command position and the detected position; A thread cutting NC device comprising a feed servo amplifier that drives a feed servo motor at a speed proportional to the deviation.