JPH0740143A - Screw working device - Google Patents

Abstract

PURPOSE:To provide a screw tapping device which can carry out the stable tapping work in a short working time independently of the working speed. CONSTITUTION:A main spindle accelerating speed calculating circuit 24 outputs the max. accelerating speed As of a main spindle which is the value obtained by dividing the max. revolution speed Sm of the main spindle by the min. time St necessary for obtaining the max revolution speed of the main spindle, and a Z-axis accelerating speed calculating circuit 25 outputs the max. Accelerating speed Az of the Z axis which is the value obtained by dividing the max. shift speed Zm of the Z axis by the min. time Zt necessary for obtaining the max. speed of the Z axis. A comparison circuit 26 compares each max. accelerating speed As, Az, and outputs the less value as the accelerating speed A, and an acceleration//deceleration control circuit 27 acceleration/deceleration-controls the distribution pulse Pz according to the accelerating speed A obtained by the comparison circuit 26. Accordingly, even in the case where the tapping working speed is a high speed, the drive over the capacity of a motor is prevented, and overshoot, etc., can be prevented. Further, even in the case where the tapping working speed is a low speed, the necessary time for obtaining the set speed is shortened, and the working time can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw machining device for a numerically controlled machine tool, and more particularly to a screw machining device capable of performing stable tapping in a short machining time.

[0002]

2. Description of the Related Art Conventionally, in tapping processing, it has been strongly required to shorten the processing time. In particular,
When tapping metal such as aluminum,
Not only the processing time is shortened, but also high processing accuracy is required, so that the rotation speed of the spindle and the feed speed of the Z axis must be accurately synchronized. Therefore, in place of tapping processing using a conventional floating tapper, for example, a screw machining apparatus that synchronizes the spindle with the Z-axis by generating a spindle rotation command pulse from a Z-axis movement command pulse is disclosed in JP-A-63-63. No. 251121. Further, Japanese Patent Laid-Open No. 64-58425 discloses a screw machining device that synchronizes the spindle with the Z-axis by generating a Z-movement command pulse from a spindle rotation command pulse.

[0003]

However, in these tapping processes, as shown in FIG. 5, the time T required until the set speed is reached after the drive of the spindle motor and the feed motor is started is high or low. Regardless of this, since a constant value was constantly used, inconvenience occurred due to the high or low setting speed.

For example, when this time T is large (see FIG. 5)
In (A), there is a problem in that when tapping is performed at a low speed L, the acceleration is small, so that it takes a long time to reach the set speed L, and as a result, the processing time becomes long. On the other hand, when this time T is small (Fig. 5
(See (B)) is good because the performance of the motor can be utilized to the maximum when tapping is performed at a low speed L, but when performing tapping at a high speed, a load exceeding the capacity of the motor is exhibited. However, there was a problem that problems such as overshoot would occur.

The present invention has been made to solve the above-mentioned problems, and provides a screw machining apparatus capable of performing stable tapping in a short machining time regardless of the machining speed. is there.

[0006]

In order to achieve this object, the present invention synchronizes a spindle motor M1 for rotating a spindle and a feed motor M2 for feeding a spindle along the spindle, as illustrated in FIG. In the screw machining device that performs the tapping machining operation, the maximum spindle acceleration calculation means that calculates the maximum acceleration of the spindle motor M1 using the preset maximum rotation speed of the spindle motor M1 and the minimum time required to reach that speed. M3, a feed maximum acceleration computing means M4 for computing the maximum acceleration of the feed motor M2 using a preset maximum rotation speed of the feed motor M2 and a minimum time required to reach that speed, and a maximum of the spindle motor M1. The selecting means M5 for selecting the smaller one of the acceleration and the maximum acceleration of the feed motor M2, and the maximum selected by the selecting means M5. Based on the speed, the spindle motor M
The acceleration and deceleration control means M6 for controlling the rotation speed of 1 or the feed speed of the feed motor M2.

[0007]

In the thread machining apparatus of the present invention having the above-mentioned structure, the spindle maximum acceleration calculating means M3 and the feed maximum acceleration calculating means M4 calculate the respective maximum accelerations, and the selecting means M5 calculates the spindle maximum acceleration and the feed maximum acceleration. The smaller one of them is selected, and the acceleration / deceleration control means M6 controls either or both of the feed speed of the feed and the rotation speed of the spindle according to the selected acceleration. For example, when the rotation speed of the spindle motor M1 is controlled, tapping is performed by synchronizing the feed speed of the feed motor M2 with the controlled rotation speed. Conversely, when the feed speed of the feed motor M2 is controlled, the spindle motor M1 is set to the controlled feed speed.
The tapping process is performed by synchronizing the rotation speeds of. Further, the rotation speed of the spindle motor M1 and the feed motor M2
The tapping process may be performed while simultaneously controlling the feed rate of the.

In the screw machining apparatus of the present invention, the selecting means M5
Since the smaller maximum acceleration is selected, there is no fear that a load will be applied to both the spindle motor M1 and the feed motor M2 beyond the capacity of the motor. Therefore, overshooting and the like can be prevented even when the tapping setting speed is high. Further, since the maximum acceleration is used even when the set speed of tapping processing is low, the time required to reach the set speed is shortened as compared with the related art, and as a result, the processing time is shortened.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a block diagram showing an embodiment of the screw machining device according to the present invention. The machine body 1 of the screw machining device forms a vertical tap board, and a spindle head 5 is vertically slidably supported via a slider 4 on a column 3 arranged upright on a base 2, and a spindle head is provided. 5 is engaged with a ball screw 6. Ball screw 6 is AC
The spindle head 5 is moved up and down by being rotationally driven by being connected to the feed motor 7 which is a servo motor. The feed motor 7 has
A pulse generator 9 for detecting the rotational position is provided. The pulse generator 9 detects the feed position of the spindle head 5.

The spindle 11 is rotatably supported by the spindle head 5 and is rotationally driven by a spindle motor 12 which is an AC servomotor. The spindle motor 12 is provided with a pulse generator 14 that detects the rotational position. The pulse generator 14 detects the rotational position of the spindle 11.

The tap tool 15 is directly attached to the lower end of the main shaft 11 without using a tapper, and threads a workpiece 17 having a prepared hole 16 therein. Next, a control circuit of a feed system (referred to as Z axis) for moving the spindle head 5 up and down will be described.

The numerical controller 20, as shown in FIG.
Calculator 22, pulse distribution circuit 23, main axis acceleration calculation circuit 24, Z axis acceleration calculation circuit 25, comparison circuit 26, acceleration / deceleration control circuit 27, deviation counters 28, 29, Z axis pulse conversion circuits 31, 32, adder 33. Is equipped with. The numerical control device 20 executes each process based on the data input from the input device 21, and outputs it to the Z-axis servo amplifier 34 and the main-axis servo amplifier 35.

Based on the data input from the input device 21, the computing unit 22 feeds the Z-axis feed speed F, the pitch P of the screw to be tapped, the maximum rotation speed Sm of the spindle, the maximum movement speed Zm of the Z-axis, The minimum time St required to reach the maximum rotation speed of the main shaft and the minimum time Zt required to reach the maximum rotation speed of the Z axis are output to predetermined circuits. The minimum times St and Zt are values determined depending on the capacities of the spindle motor 12 and the feed motor 7, respectively. Also,
The maximum rotation speed Sm of the main shaft is corrected so as to be synchronized with the moving speed of the Z axis, and is output as a pulse / second together with the maximum moving speed Zt of the Z axis.

The pulse distribution circuit 23 outputs a distribution pulse Pz for moving the Z-axis to the acceleration / deceleration control circuit 27 based on the Z-axis feed speed F input from the calculator 22. The spindle acceleration calculation circuit 24 corresponds to the spindle maximum acceleration computing means of the present invention, and compares the spindle maximum acceleration As which is the value obtained by dividing the spindle maximum rotation speed Sm input from the computing unit 22 by the minimum time St. Output to the circuit 26.

The Z-axis acceleration calculation circuit 25 corresponds to the maximum feed acceleration calculation means of the present invention, and is a value of the Z-axis which is a value obtained by dividing the maximum movement speed Zm of the Z-axis input from the calculator 22 by the minimum time Zt. The maximum acceleration Az is output to the comparison circuit 26. The comparison circuit 26 corresponds to the selection means of the present invention, and compares the maximum acceleration As of the main axis and the maximum acceleration Az of the Z axis, and the smaller one is set as the acceleration A, and the acceleration / deceleration control circuit 27.
Output to. Here, the smaller one is selected because the spindle motor 12 and the feed motor 7 are synchronously operated, and it is necessary to apply a load so as not to exceed the capacity of either motor. is there.

The acceleration / deceleration control circuit 27 corresponds to the acceleration / deceleration control means of the present invention, and the acceleration / deceleration described later is generated by the distribution pulse Pz input from the pulse distribution circuit 23 and the acceleration A input from the comparison circuit 26. Control is performed and the output pulse Qz is output to the deviation counter 28.

The deviation counter 28 includes an acceleration / deceleration control circuit 27.
It is counted up by the output pulse Qz input from and is counted down by the feedback pulse described later. Therefore, inside the deviation counter 28, the output pulse Q
There is a difference between z and the feedback pulse, which is converted into an analog command signal by a DA converter (not shown) and output to the Z-axis servo amplifier 34. The Z-axis servo amplifier 34 controls the rotation of the feed motor 7. The feed motor 7 is connected to the ball screw 6, and thereby the main shaft 11 moves in the Z-axis direction. The pulse generator 9 coupled to the feed motor 7 generates a feedback pulse according to the rotation of the feed motor 7. The velocity feedback loop is omitted in FIG. These form a velocity feedback loop by a known method.

On the other hand, in order to synchronize the rotation speed of the main spindle 11 with the movement speed of the Z axis, the Z axis pulse conversion circuit 31 uses Z
The output pulse of the axis deviation counter 28 is converted into a spindle pulse according to the pitch P of the screw to be tapped, and output to the adder 33. Further, the Z-axis pulse conversion circuit 32 is
The feedback pulse of the Z-axis pulse generator 9 is converted into a spindle pulse by the pitch P of the screw to be tapped,
It is sent to the deviation counter 29. The deviation counter 29 is Z
It is counted up by the feedback pulse of the shaft and counted down by the feedback pulse of the main shaft which will be described later. Therefore, there is a difference between the feedback pulses of the Z axis and the main axis inside the deviation counter 29, and this difference is output to the adder 33. Then, the output of the adder 33 is converted into an analog command signal by a DA converter (not shown), and the spindle servo amplifier 35
Output to. The spindle servo amplifier 35 is used for the spindle motor 12
Control the rotation. The main shaft motor 12 is coupled to the main shaft 11, and thereby the main shaft 11 rotates. The pulse generator 14 coupled to the spindle motor 12 generates a feedback pulse according to the rotation of the spindle motor 12.
The velocity feedback loop is omitted in FIG. These form a velocity feedback loop by a known method.

Instead of providing each circuit such as the spindle acceleration calculation circuit 24, the Z-axis acceleration calculation circuit 25, the comparison circuit 26 and the deviation counters 28 and 29, these may be realized as a computer function. Next, the acceleration / deceleration control circuit 27
Will be described in detail with reference to FIGS. 3 and 4. Figure 3
Is a flowchart in which acceleration / deceleration control is realized as a function of a computer.

In the acceleration / deceleration control circuit 27, this processing is repeatedly executed at predetermined intervals. When the n-th processing is executed, the distribution pulse is Pz (n) and the output pulse is Q.
z (n), the maximum acceleration input from the comparison circuit 26 is A
(Constant) First, in step 110, it is determined which of the acceleration, constant speed, and deceleration states. Specifically, Pz
(N) and Qz (n-1) are compared, and Pz (n)
> Qz (n-1) accelerates, Pz (n) = Qz (n)
If so, it is determined to be constant speed, and if Pz (n) <Q (n-1), it is determined to be deceleration.

Then, when it is judged to be accelerated in step 110, Qz (n) ← Qz (n-1) + A is performed (step 120), and the process is terminated. If it is determined at step 110 that the speed is constant, Qz (n) ← Pz (n) is performed (step 130), and the process ends.

Further, when it is determined that the vehicle is decelerating in step 110, Qz (n) ← Qz (n-1) -A is performed (step 140), and the process ends. FIG. 4 is a speed pattern diagram in which the acceleration / deceleration control is performed in this manner. FIG. 4 (A) shows when the tapping processing is set at a high speed, and FIG.
Shows the distribution pulse Pz (n) and the output pulse Qz (n) when the set speed of tapping is low.

FIG. 4A shows Pz (n) = H (n = 1 to 1).
s and H are high speed settings), Pz (n) = 0 (n> s)
And the case where Qz (t) = Pz (t) at n = t is shown. Therefore, when n = 1 to t, Q
Since z (n-1) <Pz (n), step 110
Is determined to be acceleration, and in step 120, Qz (n) ← Qz
(N-1) + A is executed. Also, n = (t + 1)-
Since Qz (n-1) = Pz (n) for s, it is determined at step 110 that the speed is constant, and at step 130 Qz
(N) ← Pz (n) is executed. Furthermore, n = (s +
1) to (s + t), Qz (n-1) <Pz (n), so it is determined that the vehicle is decelerating in step 110, and step 1
At 40, Qz (n) ← Qz (n-1) -A is executed.

At this time, the acceleration A does not exceed the capacity of the feed motor 7 because it is the maximum acceleration of the spindle motor 12 or the feed motor 7, whichever is smaller, and is synchronized with the feed motor 7. It does not exceed the capacity of the spindle motor 12. Therefore, there is no risk of problems such as overshoot.

In FIG. 4B, Pz (n) = L (n = 1 to 1)
u and L are low set speeds (L <H), Pz (n) = 0
(N> u), Qz (v) = Pz (v) when n = v is shown. Since this is almost the same as FIG. 4A, its description is omitted. However, Qz
The time required for (n) to reach the set speed L is shortened compared to the time required for it to reach the set speed H (see FIG. 3A). Therefore, the processing time can be shortened.

The effects of this embodiment will be described below. Since tapping is performed on the basis of the smaller maximum acceleration A of the spindle motor 12 or the feed motor 7, even if the set speed for tapping is high, the tapping is not driven beyond the capacity of the motor and overshoots. Etc. can be prevented. Further, even when the set speed of tapping processing is low, the time required to reach the set speed is shortened, so that the processing time is shortened. In particular, when the screw pitch P is large, the feed speed of the feed motor 7 is high even if the rotation speed of the spindle motor 12 is low. Can be prevented and the processing time can be shortened. Further, since the acceleration / deceleration control is performed using the maximum acceleration A, the processing itself is simple and the processing speed can be sufficiently increased.

It is needless to say that the present invention is not limited to the above-mentioned embodiments and can be carried out in various modes without departing from the gist of the present invention. For example,
In the present embodiment, the synchronous operation is performed by causing the feed motor to follow the spindle motor, but the reverse, that is, by controlling the speed of the spindle motor by the acceleration / deceleration control circuit, the feed motor is caused to follow the spindle motor. Synchronous operation may be performed. Further, both the feed motor and the spindle motor may be controlled.

In this embodiment, the linear acceleration / deceleration control is performed by treating the acceleration A as a constant value.
By treating the acceleration A as a variable input from the outside or stored in the inside, for example, an exponential function type or s
It is also possible to perform acceleration / deceleration control of an arbitrary function such as an in-function type. In this case, in view of the capacity characteristics of the motor, a larger acceleration can be set instantaneously than when the acceleration is constant, so that the machining time is further shortened.

[0029]

As is apparent from the above description,
According to the screw machining device of the present invention, stable tapping can be performed in a short machining time regardless of the machining speed.

That is, when the set speed for tapping is low, the time required to reach the set speed is shortened because the maximum acceleration of the spindle motor or the feed motor is used for control. In addition, when the set speed for tapping is high, there is no risk of driving beyond the capacity of the motor, so problems such as overshoot do not occur.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the present invention.

FIG. 2 is a block diagram of the present embodiment.

FIG. 3 is a flowchart of an acceleration / deceleration control circuit of this embodiment.

4A and 4B are speed pattern diagrams of the present embodiment, where FIG. 4A is a speed pattern diagram when the tapping setting speed is high, and FIG. 4B is a speed pattern diagram when the tapping setting speed is low.

5A and 5B are speed pattern diagrams of a conventional technique, in which FIG. 5A is a speed pattern diagram when a time T required to reach a set speed after driving of a motor is large, and FIG. 5B is a speed pattern diagram when the time T is small. is there.

[Explanation of symbols]

1 ... Machine body, 2 ... Base, 3 ... Column, 4 ...
.Slider, 5 ... Spindle head,
7 ... Feed motor, 9 ... Pulse generator,
11 ... Spindle, 12 ... Spindle motor,
14 ... Pulse generator, 15
... Tap tool, 20 ... Numerical control device, 21 ... Input device,
22 ... arithmetic unit, 23 ... pulse distribution circuit,
24 ... Spindle acceleration calculation circuit, 25 ... Z
Axial acceleration calculation circuit, 26 ... Comparison circuit, 2
7 ... Acceleration / deceleration control circuit, 28, 29 ...
..Deviation counter, 31, 32 ... Z-axis pulse conversion circuit, 33 ... Adder, 34 ... Z-axis servo amplifier, 35 ... Spindle servo amplifier,

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[Procedure amendment]

[Submission date] August 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

In the acceleration / deceleration control circuit 27, this processing is repeatedly executed at predetermined intervals. When the n-th processing is executed, the distribution pulse is Pz (n) and the output pulse is Q.
z (n), the maximum acceleration input from the comparison circuit 26 is A
(Constant) First, in step 110, it is determined which of the acceleration, constant speed, and deceleration states. Specifically, Pz
(N) and Qz (n-1) are compared, and Pz (n)
> Qz (n-1) accelerates, Pz (n) = Qz (n-
If 1), it is determined as constant speed, and if Pz (n) < Qz (n-1), it is determined as deceleration.

Claims (1)

[Claims] 1. A screw machining apparatus for performing a tapping machining operation by synchronizing a spindle motor that rotates a spindle and a feed motor that feeds the spindle along the spindle, in a preset maximum rotation speed of the spindle motor and its speed. The maximum spindle acceleration calculation means for calculating the maximum acceleration of the spindle motor using the minimum time required to reach, and the maximum rotation speed of the feed motor set in advance and the minimum time required to reach that speed, Based on the maximum feed rate acceleration calculating means for calculating the maximum acceleration, a selecting means for selecting the smaller one of the maximum acceleration of the spindle motor and the maximum acceleration of the feed motor, and the maximum acceleration selected by the selecting means. hand,
An acceleration / deceleration control means for controlling the rotation speed of the spindle motor or the feed speed of the feed motor.