JPH04305707A - Numerical controller - Google Patents

Abstract

PURPOSE:To rapidly process distribution pulses applied to residual spindles of a tool especially at every program block in a numerical controller for controlling a machine tool such as a laser working machine. CONSTITUTION:An excess distribution variable S read out at the time of ending each program block is computed prior to its execution. An addition value commanding means 3 divides the variable S by an optionally set addition value N and the divided result is added to its preceding distribution variable having a preceding distribution period. Thereby, the excess distribution variable commanded from an acceleration/deceleration control circuit 4 always becomes zero and the reduction of a speed between blocks can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical control device for controlling a machine tool such as a laser processing machine, and more particularly to a numerical control device that can rapidly process pulses distributed to each tool axis for each program block.

0002

2. Description of the Related Art Conventionally, a pre-interpolation acceleration/deceleration function has been used to minimize errors in machining shapes in numerical control devices that control machine tools such as laser beam machines that require high machining accuracy. In the pre-interpolation acceleration/deceleration method, acceleration/deceleration is applied to the tangential speed command value of the moving path based on the feed command for each program block for the tool of the machine tool, and then distributed pulses that become interpolated data for each axis of the tool are formed. has been done.

0003

[Problem to be Solved by the Invention] By the way, in such acceleration/deceleration control, the distribution pulse for each unit distribution period is generally determined by dividing the command distance by the command speed, not only for acceleration/deceleration before interpolation. In addition, surplus distribution pulses may be left in the last distribution cycle of the commanded program block. If such surplus pulses occur when moving the command distance at a predetermined command speed, the command is output as a command that does not reach the command speed before and after the boundary distribution cycle, and this causes a shock to the machine tool at the joint between program blocks. For this reason, it is generally necessary to remove excess pulses during high-speed machining. However, if the amount of pulse distribution for each axis of the tool is determined by uniformly excluding surplus pulses, it will cause a decrease in the machining accuracy of the machine tool.

The present invention has been made in view of these points, and it is possible to eliminate shock between program blocks during high-speed machining required by laser processing machines, etc.
The purpose of this invention is to provide a numerical control device that enables smooth operation of machine tools.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a numerical control device that commands the pulse distribution amount for each axis of the tool, the total distribution amount in a unit program block and the distribution in one distribution cycle. calculation means for calculating the total number of distributions per block and the surplus distribution amount S generated in the final distribution cycle from the amount, and an additional value N for the number of times S/N of dividing the surplus distribution amount S by the number of divisions N. Provided is a numerical control device characterized by comprising an additional value command means for commanding each distribution amount in a distribution cycle.

[0006]

[Operation] The surplus distribution amount S read out at the end of one program block is calculated before execution. This surplus distribution amount S is divided by an arbitrarily set addition value N, and the
Add to the distribution amount of the preceding distribution cycle. Therefore, the surplus distribution amount actually commanded from the acceleration/deceleration control circuit is always zero, and a drop in speed between blocks can be prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of a numerical control device having a pre-interpolation acceleration/deceleration function. In the figure, an NC program is punched onto a command tape 1, and machining data is read block by block from the command tape 1 using a tape reader or the like.

Among the machining data, movement data D indicating the feed direction of each axis and a speed command value F in the tangential direction are input to the surplus distribution amount calculation circuit 2. The surplus distribution amount calculation circuit 2 calculates the total distribution amount per block from the total distribution amount in a unit program block determined from the movement data D and the distribution amount in one distribution cycle determined from the tangential speed command value F. The number of distributions and the surplus distribution amount S generated in the final distribution cycle are calculated.

This surplus distribution amount S and the added value N of the processed data are input to the added value command circuit 3. The additional value command circuit 3 assigns an additional value N to each distribution amount in the preceding distribution cycle.
Here, the added value N is given to the acceleration/deceleration control circuit 4 as many times as the surplus distribution amount S is divided by the added value N (S/N).

The acceleration/deceleration control circuit 4 accelerates/decelerates the speed command value F in the tangential direction of the moving path, which is commanded by the feed speed command before interpolation, with a predetermined acceleration/deceleration time constant, and causes the interpolation means 5 to control the speed. It outputs a command value Fα. In this acceleration/deceleration control circuit 4, among the speed command values Fα outputted to the interpolation means 5, the remaining number of distributions during interpolation of the unit program block is equal to the number of times (S/N) determined by the addition value command circuit 3. After the feed speed command becomes equal, an override value corresponding to the addition value N is issued.

The interpolation means 5 selects either linear interpolation or curved interpolation such as circular interpolation based on the machining data on the instruction tape 1, creates necessary interpolation data, and sends data to the axis control circuits 6x and 6y. In contrast, the pulse distribution amount for each axis of the tool is commanded. That is, based on the movement data D and the speed command value Fα subjected to acceleration/deceleration control, the interpolation means 5 performs interpolation and distributes command pulses to the axis control circuits 6x and 6y, and then transmits the command pulses to each axis control circuit 6x and 6y via the servo amplifiers 7x and 7y. Axis servo motor 8x, 8
Drive y.

FIG. 2 is a diagram showing a comparison between the conventional distribution process (a) and the distribution process (b) in the numerical control device of the present invention. As shown in FIG. 2(a), when feed speed commands of the same speed F are input from program blocks N1 and N2, the total number of distributions per unit program block is determined from the distribution period T and the feed direction D. Ru. In this case, for example, in the last distribution cycle Tn of block N1, the number of pulses less than the command speed value always appears as the surplus distribution amount S, and the higher the speed F is the higher the command, the more the servo motors 8x, 8y of each axis The shock is transmitted to the tool driven by the

In the present invention, as shown in FIG. 2(b),
In the last distribution of each program block, the amount of distribution in the preceding distribution cycle is added to the amount of distribution in the preceding distribution cycle based on the predetermined addition value N so that no surplus pulses appear. For example, the additional value N
is determined to be 2 pulses, and if the surplus distribution amount S is determined in advance as 10 pulses, the additional value N, that is, 2 pulses, is equally added to the distribution amount F of the previous 5 distribution cycles, and each Increase the distance traveled in the distribution cycle gradually and evenly. As a result, the surplus distribution amount S that is actually given an acceleration/deceleration command from the acceleration/deceleration control circuit 4 is always zero, and a drop in speed between blocks can be prevented.

When the movement path is commanded by linear interpolation from the command tape 1, the total number of distributions per block is calculated by reading ahead the unit program block and from the movement distance commanded there and the distribution distance of one distribution cycle. Once determined, the surplus distribution amount S can be determined by the surplus distribution amount calculating circuit 2 as the number of surplus pulses. When the movement path is commanded by circular interpolation, the surplus distribution amount calculation circuit 2 can determine the total number of distributions per block from the arc center angle commanded in the unit program block and the distribution angle of one distribution cycle. can. In this case, the surplus distribution amount S is determined as a remainder angle.

FIG. 3 is a block diagram showing an example of hardware of the numerical control device (CNC) of the present invention. The processor 11 controls the entire numerical control device according to a system program stored in the ROM 12. The ROM 12 is an EPROM or an EEPROM. RAM
DRAM 13 is used to store various data. The nonvolatile memory 14 stores a machining program 14a read from an instruction tape or the like, various parameters, and the like. For example, the above-mentioned addition value N may be set in this nonvolatile memory 14 as a parameter. This nonvolatile memory 14 is a battery-backed CM
Since an OS or the like is used, the contents are retained even after the numerical control device is powered off. Note that this nonvolatile memory 14
Also stored are parameters such as allowable acceleration αmax and allowable speed difference ΔVmax for each axis between blocks.

A PMC (programmable machine controller) 15 receives commands for the M function, S function, T function, etc., decodes and processes the commands using a sequence program 15a, and outputs an output signal for controlling the machine tool. In addition, it receives limit switch signals from the machine side or switch signals from the machine operation panel, processes them in the sequence program 15a, and outputs output signals to control the machine side. Signals necessary for the numerical control device are sent via the bus 25 to the RAM 13 and read by the processor 11.

The graphic control circuit 16 converts the data stored in the RAM 13, such as the current position and amount of movement of each axis, into a display signal and sends it to the display device 16a, which displays it. As the display device 16a, a CRT, liquid crystal display, or the like is used. The keyboard 17 is used to input various data.

The axis control circuit 18 receives a position command from the processor 11 and outputs a speed command signal for controlling the servo motor 20 to the servo amplifier 19. The servo amplifier 19 amplifies this speed command signal and drives the servo motor 20. A pulse coder 21 that outputs a position feedback signal is coupled to the servo motor 20. pulse coder 2
1 feeds back a position feedback pulse to the axis control circuit 18. In addition to the pulse coder 21, a position detector such as a linear scale may be used. These elements are required for the number of axes, but since the configuration of each element is the same, only one axis is shown here.

The input/output circuit 22 exchanges input/output signals with the machine side. In other words, the limit switch signal on the machine side,
The PMC 15 receives the switch signal from the machine operation panel and reads it. It also receives an output signal from the PMC 15 for controlling a pneumatic actuator, etc. on the machine side, and outputs it to the machine side. The manual pulse generator 23 outputs a pulse train for precisely moving each axis according to the rotation angle, and is used to precisely position the machine. Manual pulse generator 2
3 is usually mounted on the machine operation panel.

In the figure, a spindle control circuit, a spindle amplifier, a spindle motor, etc. for controlling the spindle are omitted. Further, although there is one processor here, a multi-processor system using a plurality of processors can be used depending on the system.

In the above explanation, when the remaining number of distributions during interpolation becomes equal to the number of distributions determined by the surplus distribution amount S, the additional value N is commanded, but the additional value is determined by the total distribution period. , it is also possible to absorb the surplus distribution amount S by adding it from the first distribution cycle of the unit program block. Further, although the above embodiment describes acceleration/deceleration before interpolation, it can be similarly applied to acceleration/deceleration after interpolation.

[0022]

[Effects of the Invention] As explained above, the present invention eliminates the surplus distribution amount actually commanded from the acceleration/deceleration control circuit.
The speed at the end of distribution can be kept constant. Therefore, since it is possible to prevent the tool speed from dropping between program blocks, it can be used to control machine tools such as laser processing machines that require both processing speed and processing accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the main parts of a numerical control device having a pre-interpolation acceleration/deceleration function according to the present invention.

FIG. 2 is a diagram showing a comparison between a conventional distribution process (a) and a distribution process (b) in the numerical control device of the present invention.

FIG. 3 is a block diagram showing an example of hardware of a numerical control device (CNC) of the present invention.

[Explanation of symbols]

1 Command tape 2 Surplus distribution amount calculation circuit 3 Addition value command circuit 4 Acceleration/deceleration control circuit 5 Interpolation means

Claims (4)

[Claims] Claim 1: A numerical control device that commands the amount of pulse distribution for each axis of a tool, which calculates the total number of times of distribution per block and the final distribution period from the total amount of distribution in a unit program block and the amount of distribution in one distribution cycle. calculation means for calculating the surplus distribution amount S generated in the above distribution period; and addition for instructing the addition value N to each distribution amount in the preceding distribution cycle by the number of times (S/N) that the surplus distribution amount S is divided by the addition value N. A numerical control device comprising: value command means. 2. When the movement path is commanded by linear interpolation, the calculation means calculates 1 from the movement distance commanded by the unit program block and the distribution distance of one distribution cycle.
2. The numerical control device according to claim 1, wherein the total number of distributions per block is determined, and the surplus distribution amount S is obtained as the number of surplus pulses. 3. When the movement path is commanded by circular interpolation, the calculation means calculates the total number of distributions per block from the arc center angle commanded in the unit program block and the distribution angle of one distribution cycle. 2. The numerical control device according to claim 1, wherein the surplus distribution amount S is determined as a remainder angle. 4. The additional value command means determines that the remaining number of distributions during interpolation of the unit program block is the number of times (
2. The numerical control device according to claim 1, wherein an override value corresponding to the additional value N is commanded for the feed speed command after the feed speed command becomes equal to S/N.