JPH0323296B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention provides a system for suppressing rapid changes in spindle rotation speed.
The present invention relates to a method for controlling the spindle rotation speed in a 4-axis numerically controlled lathe.

(b) Background of the technology Normally, in this type of lathe, machining using one turret is often started while the other turret is working, but in such cases, the spindle rotation speed is As shown in Fig. 5, the rotation speed N _A suitable for machining with one tool post is changed to the rotation speed N _B suitable for machining with two tool rests.

(c) Prior art and problems FIG. 4 is a diagram showing the retracted state of the tool when switching the spindle rotation speed, and FIG. 5 is a conventional time chart showing how the spindle rotation speed changes.

Conventionally, as shown in Fig. 5, this switching of the spindle rotation speed was carried out in a very short time T _S , so the rotation speed suddenly changed, and the tool 1 during machining was changed accordingly. This has caused problems such as chipping, which deteriorates machining accuracy.

Therefore, when switching the spindle rotation speed, as shown in Fig. 4, the tools 1 of each tool rest 21, 22, including the tool 1 being processed up to that point, are evacuated from the workpiece 2 to stabilize the spindle rotation speed. Now, each tool 1
However, with this method, every time the spindle speed is changed, tool 1 is restarted.
Since it is necessary to remove the tool from the cutting state, the overall machining time becomes longer, and the tool rests 21, 2
There was a drawback that the machining program for controlling 2 became complicated.

(d) Purpose of the Invention In order to eliminate the above-mentioned drawbacks, the present invention eliminates the need to retract the turret no matter how the spindle rotational speed changes, and also enables machining without chipping or deterioration of machining accuracy. It is an object of the present invention to provide a method for controlling the main spindle rotation speed in a four-axis numerically controlled lathe, which allows continuous processing, shortens the overall machining time, and simplifies the machining program.

(e) Structure of the Invention In other words, the present invention provides a four-axis numerically controlled lathe having a memory in which a machining program is stored, a main spindle for holding a workpiece, and two tool rests, in which the center of the main shaft of the tool rest is At the same time, the spindle rotational speed is detected in accordance with the circumferential speed commanded in the machining program stored in the memory and the position of the tool post in the direction perpendicular to the axis. A first calculating means for determining the spindle rotational speed to be calculated is provided, and the target rotation is calculated every predetermined unit time according to a delay time from the time when the change command for the spindle rotational speed is outputted from the first calculating means. A second calculation determining means for calculating and determining a number is provided, and a control means for the main spindle is provided, and the rotation speed actually controlled by the main spindle control means and the main shaft rotation determined by the first calculation determining means are provided. The ratio of the difference between the number and the actual controlled rotational speed is calculated as a rate of change, and when the rate of change exceeds a predetermined value, the control means for the main shaft is instructed to perform the first calculation. A rotation speed comparison and determination means capable of instructing a switch from rotation speed control based on the output of the determining means to rotation speed control based on the output of the second calculation determining means is provided, and the rotation speed of the main shaft is controlled by the main shaft control means. , in the normal case, the first
When the rotation speed calculated and determined by the first calculation determining means suddenly changes, the control of the spindle control means is controlled by the first calculation determining means. The control is switched from the control based on the output of the calculation determining means to the control using the output of the second calculation determining means, thereby preventing a sudden change in the spindle rotation speed.

(f) Examples of the invention The present invention will be specifically described below based on the drawings.

Fig. 1 is a block diagram showing an example of the control part of a 4-axis numerically controlled lathe to which the present invention is applied, Fig. 2 is a time chart showing the control mode of the spindle rotation speed, and Fig. 3
The figure shows the machining mode of a 4-axis numerically controlled lathe.

The 4-axis numerically controlled lathe 3, as shown in FIG.
The main control section 5 includes a program memory 6, a target rotation speed calculation section 7, a rotation speed comparison and determination section 9, a spindle control section 10, a rotation speed calculation section 11, and a feed axis control section 12. etc. are connected via the bus line 13 etc. A main shaft drive motor 15 is connected to the main shaft control section 10, and a third motor is connected to the feed shaft control section 12.
Feed shaft drive motors 16 and 17 provided to drive the two tool rests 21 and 22 shown in the figure are connected. In addition, the feed shaft drive motors 16, 17
The transducers 16a and 17a are attached to the rotation speed calculating section 11.

In addition, as shown in FIG. 3, the lathe 3 has two tool rests 21 and 22 arranged in a Z-axis 23 in the direction of the main shaft axis and in an X-axis direction perpendicular to the Z-axis 23, that is, arrows A and B. Furthermore, the workpiece 2 is held on the main shaft via a chuck (not shown) so as to be freely rotatable around the Z-axis 23.

The 4-axis numerically controlled lathe 2 has the following configuration.Actual machining is performed by the spindle control section 10 and feed axis control section 12 controlling the spindle drive motor 15 according to the machining program PRO in the machining program memory 6.
This is performed by controlling the rotation of the feed shaft drive motors 16 and 17. That is, the main shaft drive motor 1
5 is rotationally controlled so that machining is performed at the circumferential speed instructed by the machining program PRO, and the feed shaft drive motors 16 and 17 move the tool rests 21 and 22 to the machining positions indicated by the machining program PRO. Then, predetermined processing is performed. More specifically, the motors 16 and 17 are equipped with a transducer 16.
position pulses PS1 and PS2 are output from the transducers 16a and 17a to the rotational speed calculation section 11 in synchronization with the rotation of the motors 16 and 17. On the other hand, the rotation speed calculation unit 11 calculates the position of each tool rest 21, 22 in the X-axis direction, that is, in the direction of arrows C and D in FIG. 3, by integrating the position pulses PS1 and PS2. 22
The position of the cutting edge in the X-axis direction of the tool 1 attached to the machine is calculated periodically, and the rotational speed N _S of the spindle is calculated and determined from the circumferential speed indicated in the machining program PRO. It is periodically notified to the determination unit 9 as a rotation speed command. Furthermore, the spindle control unit 10 controls the rotation speed of the spindle, and thus the workpiece 2, to be N _S.
Controls the main shaft drive motor 15.

By the way, while machining with a single turret, another turret joins the machining and the machining program changes.
When the circumferential speed instruction by the PRO suddenly changes, the rotational speed N _S of the main shaft determined by the calculation section 11 also changes rapidly. Now, as shown in FIG. 2, suppose that machining by the tool rest 22 is started while the tool rest 21 is machining at a spindle rotation speed N _S of N ₁ , and as a result, the rotation speed calculation unit 11 is After that, change the rotation speed N _S
Suppose that the spindle control unit 10 is notified by a rotation speed command to change the rotation speed to _N2 . The rotation speed command for commanding the rotation speed N _S from the calculation section 11 is also output to the rotation speed comparison and determination section 9;
The rotation speed N _S indicated in the rotation speed command periodically input from the calculation unit 11 is latched, and when the rotation speed N _S input from the calculation section 11 changes, the rotation speed that was latched until then ( In this case, the latched rotation speed N ₁ is newly calculated and determined by the calculation section 11 as N ₁ ), which matches the actual rotation speed of the spindle controlled by the spindle control section 10, and is input as the rotation speed command. Find the rate of change K in the rotational speed (in this case N 2 ) after the time Δt (N ₂ in this case) = |N ₁ − N ₂ |/N ₁ (1), and find the rate of change K as a predetermined value of the rate of change. If it exceeds, the signal TS1 is changed from "0" to "1". In response to this, the spindle control section 10 switches the control of the spindle rotation speed from normal control based on the output from the rotation speed calculation section 11 to buffer control based on the output from the target rotation speed calculation section 7.

In other words, the target rotation speed calculation section 7 is a calculation section arbitrarily determined by t=F(k)・K (2) K: rate of change k: parameter constant (can be arbitrarily set according to machining program, etc.) Find t (0 to ∞ seconds) from the time when the rotation speed command is input with the rotation speed from No. 11 as N ₂ , and calculate ΔN/Δt=(N ₂ −N ₁ )/t…(3) ∴ΔN= (N ₂ −N ₁ )·Δt/t (4) Δt: The rotational speed ΔN to be changed in time Δt is determined by calculating a predetermined unit time set in advance. Next, by calculating N _1-1 = N ₁ - ΔN (5), the target rotation speed N _1-1 after time Δt is calculated and notified to the spindle control unit 10. The main shaft control unit 10 controls the target rotation speed notified from the calculation unit 7.
Based on N _1-1 , after time Δt, the spindle rotation speed N ₁ is
The drive motor 15 is controlled so that N _1-1 . The target rotation speed calculation unit 7 calculates N _1-o = N _1-(o-1) −ΔN ...(6) n: 1, 2, 3, ... at each time Δt, and calculates the following at each time Δt. The spindle rotation speed to be achieved after Δt is calculated and output to the spindle control section 10. The spindle control section 10 controls the drive motor 15, and therefore the rotation speed of the spindle, based on the target rotation speed N1 _-o from the calculation section 7 as long as the signal TS1 is "1".

On the other hand, the machining by the tool rests 21 and 22 continues without the tool rests 21 and 22 retracting, and even during the time Δt, the positions of the tool rests 21 and 22, and thus their cutting edges in the X-axis direction, do not change. , therefore, the rotation speed calculation unit 11 outputs the rotation speed command to the spindle control unit 10 based on the circumferential speed specified in the machining program PRO (however, as long as the signal TS1 is “1”, the spindle control (The unit 10 ignores the output from the calculation unit 11.) The rotational speed N _S changes as N ₂ , N _2-1 , N _{2-2 ,} etc. every time Δt, as shown by the dashed line in FIG. 2. I will do it.

Therefore, the rotation speed comparison/judgment section 9 compares the rotation speed N _1-o output from the target rotation speed calculation section 7 and actually controlled by the spindle control section 10 and the rotation speed after Δt output from the rotation speed calculation section 11. Compare N _2-o and find KX=|N _1-o −N _2-o |/N _1-o ...(7) n: 1, 2...... The rate of change KX exceeds a predetermined value, and switching to control using the rotation speed N _2-o output from the rotation speed calculation unit 11 still causes a large change in the spindle rotation speed, which is inappropriate. In this case, the determination unit 9 continues to set the signal TS1 to “1”, and controls the control of the drive motor 15 by the spindle control unit 10 to the rotation speed output from the target rotation speed calculation unit 7.
Let it be done based on N _1-o . On the other hand, when the rate of change KX falls within a predetermined value and the spindle rotational speed does not change significantly even if control is performed using the rotational speed N _2-o (point P1 in Figure 2), is a signal
Return TS1 from "1" to "0". Then, the main shaft control section 5 performs buffer control based on the output from the target rotation speed calculation section 7, and performs the rotation speed calculation section 11.
Returns to normal control based on the output from (point P in the second figure)
2) Thereafter, control is performed based on the rotation speed N _S indicated in the rotation speed command output from the calculation unit 11.

In addition, in the above-mentioned embodiment, while one tool rest 21 is machining, the other tool rest 22 joins the machining,
Although the case of simultaneous machining has been described, in the present invention, any machining mode by the tool rests 21 and 22 may be used as long as the machining mode is accompanied by a rapid change in the spindle rotation speed. For example, first, double-edged turret 2
After simultaneous machining by 1 and 22, either one of the tool rests 21 or 22 stops machining, or during simultaneous machining of both tool rests 21 and 22, it is necessary to change the spindle rotation speed due to a change in the machining area. Various cases can be considered, such as when this occurs.

(g) Effects of the Invention As explained above, according to the present invention, a memory such as the machining program memory 6 in which the machining program PRO is stored, the spindle holding the workpiece 2, the two turrets 21, 22, the positions of the tool rests 21 and 22 in the direction perpendicular to the spindle axis are detected, and the circumferential speed and speed commanded in the machining program stored in the memory are detected. A first calculation of the spindle rotation speed of the transducers 16a, 17a and the rotation speed calculation section 11, which calculates and determines the spindle rotation speed N _S according to the position of the tool rest in a direction perpendicular to the axis. A determining means is provided to determine the target rotational speed N _1- for each predetermined unit time Δt according to the delay time t from the time when a change command for the spindle rotational speed, such as a rotational speed command, is output from the first calculation determining means. ₁ , N _1-2 , N _1-3 . The ratio of the difference between the rotational speed N ₁ actually controlled by the control means and the spindle rotational speed N ₂ determined by the first calculation determining means to the rotational speed actually controlled is determined as a rate of change. K, and when the rate of change exceeds a predetermined value, the control means for the main shaft changes from the rotation speed control based on the output of the first calculation determining means to the rotation speed control based on the output of the second calculation determining means. A rotation speed comparison and determination means such as a rotation speed comparison and determination section 9 capable of instructing a switch to rotation speed control is provided, and the control of the rotation speed of the spindle by the spindle control means is normally controlled by the first calculation determination. When the rotation speed calculated and determined by the first calculation determining means suddenly changes, the control of the main shaft control means is performed based on the rotation speed calculated and determined by the first calculation determining means. Since the control is switched from the control based on the output of the above-mentioned second calculation determining means to the control based on the output of the second calculation determining means to prevent the spindle rotational speed from changing rapidly, the tool rests 21 and 22 can be moved relative to the work 2 Even if machining is continued without retracting, chipping will not occur or machining accuracy will deteriorate, and the overall machining time can be shortened, and the tool rests 21 and 22 can be retracted. This eliminates the need for a program for processing, which can also contribute to the simplification of machining programs.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of the control part of a 4-axis numerically controlled lathe to which the present invention is applied, Fig. 2 is a time chart showing the control mode of the spindle rotation speed, and Fig. 3
The figure shows the machining mode of a 4-axis numerically controlled lathe.
The figure shows the retracted state of the tool when switching the spindle rotation speed, and FIG. 5 is a conventional time chart showing the changes in the spindle rotation speed. 2... Workpiece, 3... 4-axis numerical control lathe, 7...
...Second calculation determining means (target rotation speed calculating section), 9
...Rotation speed comparison and judgment means (rotation speed comparison and judgment section),
10... Spindle control means (spindle control section), 11...
...first calculation determining means (rotation speed calculation section), 16a,
17a...first calculation determining means (transducer), 21, 22...turret, t...delay time,
Δt...Predetermined unit time, N _1-1 , N _1-2 , N _1-3 ,...
...Target rotation speed, N ₁ ...Rotation speed to be actually controlled,
N ₂ ... Spindle rotation speed determined by the first calculation means,
K... Rate of change.

Claims (1)

[Claims] 1. 4 having a memory in which a machining program is stored, a spindle for holding a workpiece, and two turrets.
In the axis numerically controlled lathe, the position of the tool post in a direction perpendicular to the spindle axis is detected, and the circumferential speed and the axis of the tool post commanded in the machining program stored in the memory are detected. A first calculation determining means for the spindle rotation speed is provided which calculates and determines the spindle rotation speed according to the position in a direction perpendicular to the rotation speed, and from the time when a change command for the spindle rotation speed is output from the first calculation determination means. a second calculation determining means for calculating and determining a target rotation speed for each predetermined unit time according to a delay time of the main shaft, a control means for the main shaft, and a rotation speed actually controlled by the main shaft control means. and the main shaft rotational speed determined by the first calculation determining means, the ratio of the difference to the actually controlled rotational speed is calculated as a rate of change, and if the rate of change exceeds a predetermined value; Further, the spindle control means is provided with a rotation speed comparison and determination means capable of instructing a switch from rotation speed control based on the output of the first calculation determination means to rotation speed control based on the output of the second calculation determination means. , the rotation speed of the spindle is normally controlled by the spindle control means based on the rotation speed calculated and determined by the first calculation determination means, and the rotation speed calculated and determined by the first calculation determination means is If the number suddenly changes, the control of the spindle control means is switched from control based on the output of the first calculation determining means to control based on the output of the second calculation determining means, and the spindle rotation speed is changed. A method for controlling the spindle rotation speed in a 4-axis numerically controlled lathe configured to prevent sudden changes.