JPH0682296B2 - Numerically controlled machine tool - Google Patents

Description

The present invention relates to a numerically controlled machine tool (NC machine tool).

<Prior Art> As shown in the block diagram of the conventional numerical control type machine tool of FIG. 7 and the conventional flow chart of FIG. A machining device 11 for machining, a machining feed device 12 for moving the machining device 11 relative to the workpiece, a control circuit 13 for outputting a movement command to the machining feed device 12, Control circuit 13
And a program input means 14 for inputting a program to the control circuit 13.
Based on the program input by
A movement command output means 13h having an interpolation calculation means 13g for outputting a movement instruction to 12 is provided.

Further, in this configuration, the created program is executed as it is read without being processed in the control circuit at the optimum processing speed. In this case, it is possible to enter a machining speed command in advance, but in the case of shape machining, since the amount of information is large, it is only necessary to enter the machining speed command several times at the beginning or in the middle of the program.

<Problems to be solved by the invention> Therefore, since the machining speed does not change despite the machining shape changing moment by moment, the shape accuracy at the end of machining deteriorates and the radius of curvature of the workpiece is reduced. The smaller the load, the larger the cutting load, which adversely affects the cutting conditions. However, in a normal machining program, the machining speed is preliminarily set in the program, which is not preferable in terms of machining accuracy and cutting blade life. Further, it is problematic in terms of programming that the processing speed is finely set in the program.

<Means for Solving Problems> The means for solving problems according to the present invention includes, as shown in FIGS. 1 to 6, a processing apparatus 1 for processing a workpiece 6 and the workpiece 6. A machining feed device 2 for relatively moving the machining device 1, a control device 3 for outputting a movement command to the machining feed device 2, and a block of a program consisting of a large number of blocks to the control device 3 are first. Program pre-reading means 4a for reading and inputting, program inputting means 4 for inputting a program to the control device 3, and the workpiece 6
The optimum precision setting means 5 for setting the optimum machining precision for each shape, and the control device 3 stores the program input by the program input means 4 and the program storage means 3a. Shape recognition calculation means 3b for obtaining the shape of the processed part of the workpiece 6 based on the contents of the block read in advance by the read-ahead means 4a as a reference, and the output of the shape recognition calculation means 3b and the optimum Optimal machining speed calculation means 3d for obtaining the optimum machining speed of the machining apparatus 1 capable of machining within the optimum machining accuracy based on the optimum machining accuracy set by the accuracy setting means 5 for each block, and the optimum machining speed calculation means 3d The processing speed storage means 3e for storing the calculation result of the above, and the optimum processing speed obtained by the optimum processing speed calculation means 3d is for the previous block. The machining speed correction means 3f that corrects the previously stored optimum machining speed when it changes abruptly as compared with the optimum machining speed, and the optimum machining speed obtained and the contents of the program are moved to the machining feed device 2. It comprises a movement command output means 3h for outputting a command.

<Operation> In the problem solving means, first, the operator inputs the finish accuracy value of the workpiece 6 to the control device 3 using the optimum accuracy setting means 5. Next, the program input means 4
Enter more programs and start machining. At the same time, as shown in FIG. 2, the following processing is performed on the M-th block which is several tens of blocks after the N-th block currently being processed. The program pre-reading means 4a pre-reads the program contents from the Nth block to the Mth block, and the shape recognition calculating means 3b reads the shape (curvature radius) up to the Mth block.
Are sequentially requested.

Here, as a cause of the shape error at the time of processing,
There is a follow-up feed of the servo system, that is, a position loop gain, which is a characteristic that differs from machine to machine. Generally, when cutting an arc with a shape (radius of curvature) of R (mm), a processing speed of F (mm / min), and a position loop gain of kp (sec ^-1 ),
It is known that when the shape error is ΔR, the following equation is obtained.

When this equation is transformed, If is replaced by a proportional constant K unique to each machine, Becomes The proportional constant K may take into consideration the influence of mechanical inertia and the like in addition to the position loop gain.

Therefore, the allowable error set by the optimum accuracy setting means 5 is Δr, the proportional constant is K, and the shape recognition calculation means is
When the shape (curvature radius) in the Mth block obtained by 3b is R (M), the processing speed F (M) in the Mth block can be obtained by the following equation.

The machining speed F (M) obtained by this equation is the maximum speed that can be machined within a certain allowable error Δr input by the operator for the shape in the Mth block, and this is the optimum machining speed. The optimum processing speed is calculated by the optimum processing speed calculation means 3d and the processing speed storage means 3e is obtained.
If the ratio exceeds a permissible amount such as a speed change rate allowed by the machine, the speed is changed to M-th block before the M-th block and compared with the speed F (M-1) of the M-th block. -1 Block speed correction is performed. Then, the corrected F (M-
Similarly, 1) and F (M-2) are compared and correction is performed if necessary, and the same processing is performed until the correction is no longer required over multiple blocks. The workpiece is machined on the basis of the optimum machining speed for each block thus obtained.

<Example> An example of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is a block diagram showing a numerically controlled machine tool of the present invention, FIG. 2 is the same flow chart, and FIG. 3 is a diagram showing a program state at a certain point during cutting.
The figure is also a diagram showing an example of the radius of curvature of the cutting blade locus and the optimum cutting speed, FIGS. 5 (a), (b) and (c) are illustrations of the processing speed correcting means, and FIG. 6 is also the present invention. FIG. 3 is a schematic side view in which is applied to a milling machine.

Then, as shown in the figure, the numerical control type machine tool of the present invention has a processing apparatus 1 for processing a workpiece 6 such as a die, and a processing apparatus 1 for moving the processing apparatus 1 relative to the workpiece 6. Machining feed device 2, a control device 3 for outputting a movement command to the machining feed device 2, a program input means 4 having a program pre-reading means 4a for inputting a program to the control device 3, and the machining target. An optimum accuracy setting means 5 for setting an optimum processing accuracy for each shape of the object 6; and the control device 3 stores a program input by the program input means 4 in the program storage means.
3a, shape recognition calculation means 3b for obtaining the shape of the processed portion of the workpiece 6 based on the stored contents of the program storage means 3a,
The output of the shape recognition calculation means 3b and the optimum accuracy setting means 5
Optimum machining speed calculation means 3d for obtaining the optimum machining speed (feed speed) of the machining apparatus 1 based on the conditions set by
A machining speed storage means 3e for storing the calculation result of the optimum machining speed calculation means 3d, a machining speed already stored in the machining speed storage means 3e and the optimum machining speed calculation means
When the calculation result of 3d changes abruptly, the machining speed correction means 3f for correcting the stored machining speed, the machining speed storage means 3e, and the contents of the program storage means 3a are used to command the machining feed device 2 to move. And a movement command output means 3h having an interpolation calculation means 3g for outputting. The above processing is executed while performing processing.

Further, the processing apparatus 1 is provided with a cutting blade 9 (for example, a ball end mill) detachably attached to the chuck, and a cutting blade driving motor for rotationally driving the cutting blade 9, and the motor is a program. It is rotated or stopped by a command from the above or a manual switch.

The machining feed device 2 is composed of three servomotors 2A, 2B, 2C for moving the machining device 1 back and forth, left and right, and up and down, respectively. Servo amplifiers 2a, 2b, 2c are connected.

The control device 3 is composed of a general microcomputer and is composed of a central processing unit (CPU), an input / output device (I / O), a memory, a timer, a clock oscillator, and the like.

The program pre-reading means 4a has a function of pre-reading tens of blocks among the contents of the program divided into a large number of blocks. The program input means 4 comprises a keyboard, a paper tape reader (PTR), a magnetic disk device, a data communication interface or a memory device such as a semiconductor memory or a core memory.

In the above configuration, first, the operator inputs the finish accuracy value of the workpiece 6 to the control device 3 using the optimum accuracy setting means 5.

Next, a program is input from the program input means 4 to start machining. At the same time, as shown in FIG. 2, the following processing is performed on the M-th block which is several tens of blocks after the N-th block currently being processed.

First, the shape recognition calculation means 3b sequentially reads the program contents from the Nth block to the Mth block, and sequentially obtains the shapes (curvature radius) up to the Mth block.

Then, the optimum processing speed calculation means 3d has the allowable error Δr and the proportional constant K set by the optimum accuracy setting means 5, and the shape (curvature radius) R (in the M-th block obtained by the shape recognition calculation means 3b. M) To obtain an optimum processing speed F (M) such that Δr becomes constant. This optimum processing speed F (M) is the Mth
It is the maximum speed that can be machined within a certain allowable error Δr input by the operator for the shape of the block.

The result is stored in the processing speed storage means 3e, and the speed F (M-block of the (M-1) th block one block before the Mth block is stored.
Compared with 1), if the ratio exceeds a certain value, speed correction of M-1 block is performed.

That is, as shown in FIG. 5 (a), when the speed F (M-1) of the M-1th block can be reduced to the speed F (M) of the Mth block at the M-th block start point, no correction is performed. Also, as shown in FIG. 5 (b), at the M-th block start point, the M-th block
When it is not possible to decelerate from the speed F (M-1) of one block to the speed F (M) of the Mth block, as shown by the broken line in the figure,
Correct (M-1) to decelerate to Fo (M-1).
The corrected F (M-1) [that is, Fo (M-1)]
And F (M-2) are similarly compared, correction is performed if necessary, and the same processing is performed until correction is no longer necessary.

Further, as a concrete correction method, as shown in FIG. 5 (c), the movement amount of the cutting blade 9 at the M-1th block is set to 1 [c].
m], and the allowable acceleration (deceleration) is α [cm / sec ² ], F (M−1) −F (M)> α · t ₁ Corrects time and obtains the Fo (M-1) -F ( M) = α · t 1 become as Fo (M-1), which is a correction value.

The example of deceleration has been described above, but the same applies to the case of acceleration.

As a result of the above processing, it is possible to perform processing in real time at an optimum cutting speed for each block of the entire program. Then, simply by setting the accuracy, the control device selects the optimum processing speed that matches the processing shape, so the processing accuracy of the work piece can be set to the set value, and the life of the cutting blade can be extended. In addition, since the machining speed correction means is provided, it is possible to prevent dripping of the locus of the cutting blade due to rapid speed fluctuation, and further improve the cutting accuracy.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, although a milling machine is shown in this embodiment, the present invention is NC
Of course, it can be applied to other NC machine tools such as lathes and NC drilling machines. Further, the number of servomotors of the work feeding device may not be three depending on the machine. Further, in the above-described embodiment, an example in which the position of the processing device is moved while the position of the processing device is fixed is shown, but the present invention is not limited to this, and the processing device may be configured to move with respect to the processing object.

<Effects of the Invention> As is apparent from the above description, in the present invention, since the blocks of the program are read in advance and the optimum processing speed for each block that can be processed within the set processing accuracy is obtained, the setting is performed in all steps. It is possible to process the workpiece with high accuracy within the specified processing accuracy.

In addition, since the optimum processing speed of each block is monitored by pre-reading the blocks, even if there is a sudden change in the processing speed at the seam of each block, the optimum processing speed is corrected across multiple blocks. Therefore, it is possible to prevent the trajectory of the cutting blade from dripping and improve the processing accuracy.

Further, when machining at a constant machining speed as in the past, the machining accuracy becomes significantly poor at a portion with a small radius of curvature when the machining speed is fast, so the entire machining is performed to the extent that the machining accuracy does not deteriorate at a portion with a small radius of curvature. Although there is a tendency to suppress the speed, in the present invention, since the optimum processing speed changes depending on the shape, it is possible to increase the processing speed in a portion having a large radius of curvature, which is excellent in that the average processing speed can be increased. There is an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a numerically controlled machine tool of the present invention, FIG. 2 is a flow chart, and FIG. 3 is a diagram showing a program processing state at a certain point during cutting.
FIG. 4 is a diagram showing an example of the radius of curvature of the cutting blade locus and optimum cutting speed, FIGS. 5 (a), (b) and (c) are explanatory views of the processing speed correction means, and FIG. 6 is the same. FIG. 7 is a schematic side view in which the present invention is applied to a milling machine, FIG. 7 is a block diagram of a conventional numerically controlled machine tool, and FIG. 8 is a flow chart. 1: Machining device, 2: Machining feed device, 3: Control circuit, 3a: Program storing means, 3b: Shape recognition computing means, 3d: Optimal machining speed computing means, 3e: Machining speed storing means, 3f: Machining speed correcting means ,
3g: interpolation calculation means, 3h: movement command output means, 4: program input means, 4a: program pre-reading means, 5: optimum accuracy setting means, 6: workpiece.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Fujita, Shin-Nippon Koki Co., Ltd., 2-44, Kitakuhoji-cho, Higashi-ku, Osaka-shi, Osaka (56) Reference JP-A-59-231608 (JP, A)

Claims (1)

[Claims] 1. A processing device for processing a workpiece, a processing feed device for moving the processing device relative to the workpiece, and control for outputting a movement command to the processing feed device. Device, program pre-reading means for pre-reading and inputting a block of a program consisting of a large number of blocks to the control device, program inputting means for inputting the program to the control device, and each shape of the workpiece The optimum accuracy setting means for setting the optimum processing accuracy for, the control device, the program storage means for storing the program input by the program input means, the program pre-reading means Shape recognition calculation means for obtaining the shape of the processed portion of the work piece based on the contents of the block read in advance on the basis of the block, and the output of the shape recognition calculation means. And an optimum processing speed calculation means for obtaining an optimum processing speed of the processing device capable of processing within the optimum processing accuracy for each block based on the optimum processing accuracy set by the optimum accuracy setting means, and the optimum processing speed calculation means. Machining speed storage means for storing the calculation result, and stored when the optimum machining speed obtained by the optimum machining speed calculation means changes abruptly as compared with the optimum machining speed for the immediately preceding block. Numerical control characterized by comprising a machining speed correction means for compensating the optimum machining speed before the operation, and a movement command output means for outputting a movement command to the machining feeding device based on the obtained optimum machining speed and the contents of the program. Machine tool.