JPH04229305A - Controller for nc machine tool - Google Patents

Abstract

PURPOSE:To obtain the controller for the NC machine tool which corrects the shape errors of necessary places sufficiently and automatically reduces or eliminates the shape error correction of unnecessary places without any operator's intervention. CONSTITUTION:The controller consists of a machining program memory block 1, a program analytic block 2, an alteration block 3, an interpolative arithmetic block 4, a predictive control arithmetic block 5, and a position control block 6. Then conditions deciding whether the shape error correction is required or not for track control are stored and the conditions of a case wherein the shape error correction is required or not required are found at the time of the calculation of track variation based upon a program, an indication code or alteration code is given to the corresponding program to set or reset the shape error correction or vary the constant of the shape error correction.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is capable of providing a specification code for specifying shape error correction such as feedforward control and predictive control to a necessary step in a program for contour control of an NC machine tool, and a change code. The present invention relates to a control device for an NC machine tool that is capable of canceling shape error correction or changing shape error correction constants by applying the following to the step.

0002

2. Description of the Related Art Generally, when performing contour control in a machine tool, it is known that errors occur in the trajectory due to problems in the response of the servo system. Feedforward control, predictive control, etc. are used to correct this trajectory error.

0003

In the above-mentioned conventional technology, while contour control is being performed, shape error correction is usually fixedly applied at a constant constant. This state apparently indicates that the gain of the position loop of the servo system is very high, and it can be said that the servo system is in a state where it is difficult to stabilize. In addition, once shape error correction is set, shape error correction is always applied, so shape error correction remains applied even in places where shape error correction is not required or in places where the feed speed is slow, making it difficult for the servo system to stabilize. They often induce vibrations that are detrimental to the machine.

To eliminate the above-mentioned vibration, either run the program on a trial basis and manually cancel the form error correction of the step where the vibration occurred from the program, or reduce the gain of the form error correction to such an extent that the above-mentioned vibration does not occur. It has to be a constant value. That is, at present, there are problems in that it is troublesome to rely on human hands, and that shape error correction is not performed much on parts that are not really needed, and that it is not easy to perform sufficient shape error correction on parts that are necessary.

In view of the above-mentioned problems, the present invention provides an NC machine that performs sufficient shape error correction in necessary locations, and automatically weakens or eliminates shape error correction in unnecessary locations without manual intervention. The purpose is to provide a control device for machines.

[0006]

[Means for Solving the Problems] The control device for an NC machine tool of the present invention is capable of giving a designation code for designating shape error correction to a required step in a program for controlling the contour of an NC machine tool, and In a control device for an NC machine tool in which shape error correction can be canceled or constants for shape error correction can be changed by giving a change code to the step, the shape error correction is unnecessary and the shape error correction is necessary for contour control. However, when a change in the trajectory is calculated based on the program, there is a storage means that stores the conditions when it is necessary to change the constant of the shape error correction, and when the change in the trajectory is calculated based on the program, it is stored in the storage means at a step in the program. and a program resetting means that assigns the specified code or change code corresponding to the found condition to the corresponding step when a condition is found, or if an excessive error occurs when the program is executed. When an excessive error occurs, the error step correction means includes a storage means for storing the step in which the excessive error has occurred, and an error step correction means for assigning the change code to the step in which the excessive error has occurred based on the contents stored in the storage means.

[0007]

[Operation] The storage means stores the conditions under which shape error correction is necessary or unnecessary for trajectory control, and when the trajectory change is calculated based on the program, the conditions under which shape error correction is necessary or unnecessary are discovered. In this case, the program resetting means assigns a designation code or a change code to the corresponding program to set or cancel the shape error correction or change the shape error correction constant.

Furthermore, if an excessive error occurs when the program is executed, the storage means stores the step where the error occurred, and the error step correction means adds a specified code or a change code to the program of the stored step. Add this to set or cancel shape error correction, or change the shape error correction constant.

[0009]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a control device for an NC machine tool according to the present invention.

Machining program memory block 1 (hereinafter referred to as
A machining program instructing a predetermined machining is written in advance in the program block 1 (abbreviated as program block 1). The program analysis block 2 reads out the machining program from the program block 1, analyzes and translates it, and outputs it to the modification block 3.

The code automatic insertion and modification block 31 (hereinafter abbreviated as the code modification block 31) of the modification block 3 includes a step in which the program from the program analysis block 2 includes a designation code for designating shape error correction. Check to see if it exists.

If there is a step that includes a specified code, the condition stored in the condition storage block 32 is used to determine whether shape error correction is necessary for that step based on the calculation of the change in trajectory associated with that step. See and decide. If shape error correction is necessary, determine whether or not it is necessary to change the constant for shape error correction. If not, leave shape error correction valid, and if necessary, change the constant and assign a code. (in this embodiment, the constant KF of the predictive control calculation block 5 or the constant KFS of the function KFS of the position control block 6). If shape error correction is not necessary, a change code for disabling shape error correction is assigned to that step. If there is no step that includes the specified code, it is determined from the calculation of the change in trajectory associated with each step whether shape error correction is necessary for that step, with reference to the conditions stored in the condition storage block 32. If necessary as a result of the reference, a designation code designating shape error correction is given to that step even if it is not designated in the machining program. Further, when the machining program has already been executed and the occurrence of an excessive error is stored in the excessive error detection storage block 34, a corresponding change code is assigned based on the stored step and error content. Therefore, when a change code for changing a constant is assigned to a program, the code change block 31 changes the constant of the predictive control calculation block 5 or the constant KF of the function KFS of the position control block 6 in this embodiment. When a designation code is given to a program, when a designation code of a program is made valid, or when a designation code of a program is invalidated, a valid or invalidation instruction is given to the switch control block 33, respectively.

Based on the instruction from the code change block 31, the switch control block 33 turns the switches SW1 and SW2 to the predictive control calculation block 5 side and the switch SW3 to the on side when it is valid, and turns each switch SW1 to the on side when it is invalid. , SW2, and SW3 are switched to the opposite side from when they are enabled.

The interpolation calculation block 4 performs interpolation calculations on the program from the program analysis block 2 inputted via the code change block 31 and the switch control block 33, and
Alternatively, it is directly output to the position control block 6. The predictive control calculation block 5 performs predictive control calculations.

The position control block 6 controls the position of the motor M according to the deviation between the output of the switch SW2 and the output of the pulse generator PG connected to the motor M. When the switch SW3 is on, feedforward control is performed using the function KFS, and when the switch SW3 is off, no feedforward control is performed. In the position control block 6, KF is a feedforward gain, KV is a velocity loop gain, and KP is a position loop gain.

In the above embodiment, when shape error correction is necessary, it is further determined whether or not the shape error correction constant needs to be changed, and if necessary, a predetermined change code is assigned to the corresponding constant. However, if the predetermined constant is smaller than a predetermined threshold value, shape error correction may not be performed. In this case, calculation time is shortened.

Next, an example of an actual program will be explained with reference to FIG. 2, which shows a locus to be machined.

A program P1 for machining along a trajectory as shown in FIG. 2 is created as follows. Program P1 O 100: N1 G91 G01 F6000; N2 Y25. ; N3 G02 I25. ; N4 Y25. ; N5 M30; However, when machining is performed using the above program P1, the radius decreases. This reduction in radius is generally calculated using the following formula (1
).

[0020] △R=1/2・{T2 + (1/KP)2
}・F2/R... (1) However, R = Command radius (m/m) T = Cutting time constant (sec) KP = Position loop gain (1/sec) F = Feed rate (mm/sec) However , in the case of this embodiment, F> is stored in the condition storage block 32.
In the case of G01 when the number is 500, it is stored that shape error correction should be performed, and an instruction code COMP1ON is given, and when the instruction code COMP1ON is no longer necessary, a change code COMP1OFF is given. Therefore, program P1 is changed to program P2 below. Program P2 O 100: N1 G91 G01 F6000; N2 Y25. COMP1ON; N3 G02 I25. ; N4 Y25. COMP1OFF; N5 M30; Shape error correction is performed by this program P2, and the above △
R becomes zero. In this way, processing contents can be automatically instructed by the conditions set in the condition block 32 and the designation code and change code set corresponding to the conditions.

It will also be clear that excessive errors detected by excessive error detection storage block 34 can be dealt with in a similar manner.

[0022]

Effects of the Invention As explained above, the present invention is applicable to the conditions stored in the storage means when shape error correction is not necessary and when shape error correction is necessary but constants for shape error correction need to be changed. By being able to automatically change the program based on
This has the effect of making it easy to perform sufficient shape error correction on the necessary portions while not performing too much shape error correction on the portions that are not so necessary.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a control device for an NC machine tool of the present invention.

FIG. 2 is a diagram showing a specific example of a locus to be processed in the embodiment.

[Explanation of symbols]

1 Machining program memory block 2 Program analysis block 3 Change block 4 Interpolation calculation block 5 Predictive control calculation block 6 Position control block 31 Code change block 32 Condition storage block 33 Switch control block 34 Excessive error detection storage block

Claims (3)

[Claims] Claim 1: A designation code specifying shape error correction can be given to a required step in a program that performs contour control of an NC machine tool, and a change code can be given to the step to cancel or cancel shape error correction. In a control device for an NC machine tool that is capable of changing constants for shape error correction, cases in which the shape error correction is not necessary for contour control and cases in which the shape error correction is necessary but the constant for shape error correction needs to be changed. a storage means for storing conditions;
When a change in trajectory is calculated based on the program, if a condition stored in the storage means is found in a step in the program, the specified code or change code corresponding to the found condition is sent to the corresponding step. An NC characterized in that it has a program resetting means for assigning a program.
Machine tool control device. 2. A designation code specifying shape error correction can be given to a required step in a program for controlling the contour of an NC machine tool, and a change code can be given to the step to cancel or cancel shape error correction. In a control device for an NC machine tool capable of changing constants for shape error correction, if an excessive error occurs when the program is executed, a storage means for storing the step in which the excessive error occurred and its contents; A control device for an NC machine tool, comprising error step correction means for assigning the change code to the step in which the excessive error has occurred based on the content stored in the storage means. 3. A storage means for storing conditions for whether or not the shape error correction is necessary for contour control and a case where the shape error correction is necessary but a constant change for the shape error correction is required; A program that, when a condition stored in a storage means is found in a step in the program when calculating a change in the trajectory based on the above-mentioned information, gives the specified code or change code corresponding to the found condition to the corresponding step. 3. The control device for an NC machine tool according to claim 2, further comprising a reset means.