JPH06182666A - Numerically controlling device for grinding machine machine - Google Patents

Abstract

PURPOSE:To provide the numerically controlling device for a grinding machine capable of preventing the breakage of a tool due to overloads. CONSTITUTION:The instruction position based on the NC program 1 and the actual machine position detected by a position detector 6 are compared, and the position of a grinding tool is controlled by a servo motor 5 so that both of them coincide in the numerically controlled device of a grinding machine. When overloads of the servo motor 5 and a main spindle motor 11 are detected by an overload detector 3, a proper load searching unit 7 sends a command to shift the machine coordinates to a shift command generator 2. The servo motor 5 is controlled by the shift command generator 2 to move the grinding tool in the direction to reduce the load.

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 a grinding machine, and is particularly useful when applied to a workpiece to be ground where there is an element such as a step that causes an increase in the grinding load. is there.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing a mode during general grinding by a grinding machine. As shown in the figure, at the time of grinding, the grinding tool 8 rotating at a high speed is moved to the + position of the Z axis from the grinding surface of the work 9 (see FIG. 4).
After that, the workpiece 9 is moved in parallel with the ground surface to perform predetermined grinding (see FIG. 4B). Grinding tool 8
When the tool has passed over the work 9, the grinding tool 8 is moved in the opposite direction of the X-axis this time (see FIG. 4C). These Figure 4
Grinding is performed by repeating the operations of (a) to FIG. 4 (c).

FIG. 5 is a block diagram showing a numerical control apparatus for a grinding machine according to the prior art. The numerical control device for a grinding machine shown in the same drawing is created by sequentially interpreting and executing the commands of an NC program, which is created in advance so as to command the movement of the machine, like the numerical control device for a general cutting machine. The processing is realized.

That is, the NC program 1 specifies the moving direction of the machine (X axis, Y axis, Z axis, etc.) and the movement end point coordinates of each axis or the movement amount from the current position. Movement command generator 2
Interprets the movement command of the NC program 1, and detects the position detector 6
A movement command is output to the servo motor 5 via the servo amplifier 4 so that the current position of the machine detected in step 1 and the position instructed by the NC program 1 match. In this way, the position control is executed based on the coordinate value commanded by the NC program and the current position detected by the position detector 6.

The spindle motor 11 is driven under the control of the spindle controller 10. Further, the overload detector 3 monitors the currents flowing in the servo motor 5 and the spindle motor 11 via the servo amplifier 4 and the spindle controller 10, and when these abnormalities are detected, the machine is stopped or an alarm is issued. Output a message.

[0006]

As described above, the numerical control device according to the prior art controls so that the coordinate values instructed by the NC program 1 and the position of the machine match.

However, since the grinding machine 8 used in the grinding machine is made of a fragile material such as a grindstone as compared with a general cutting machine, it is easily damaged when the load applied to the grinding tool 8 increases. There's a problem. That is, for example, as shown in FIG. 4D, when the work 9 has a step due to poor cutting accuracy, when the grinding tool 8 reaches the step, the load on the grinding tool 8 increases. If the load is large, the grinding tool will be damaged.

In view of the above-mentioned prior art, the present invention has an object to provide a numerical control device for a grinding machine capable of preventing damage to a tool due to overload.

[0009]

The structure of the present invention which achieves the above object is to compare a commanded position based on an NC program with an actual machine position detected by the position detecting means so that the two agree with each other. In the numerical control device of the grinding machine that controls the position of the grinding machine, monitor the current of each motor during grinding, and if this current value indicates overload, move the grinding tool in the direction to reduce the load. It is characterized by having an appropriate load search means for changing the machine coordinate command value and shifting the machine coordinate.

[0010]

According to the present invention having the above-described structure, when it is detected that an overload condition has occurred, the grinding tool moves in a direction in which the load is reduced.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that the same parts as those of the conventional technique are denoted by the same reference numerals, and overlapping description will be omitted.

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, in the present embodiment, an appropriate load search device 7 is added to the numerical control device according to the prior art shown in FIG.

The proper load search device 7 shifts the machine coordinates so that the grinding tool 8 moves away from the work 9 when an overload signal output by the overload detector 3 detecting a motor overload is input. The command to perform is output to the movement command generator 2. This shift command is issued by the servo motor 5 detected via the servo amplifier 4 and the spindle controller 10.
And the current value of the spindle motor 11 is output until it becomes the same as the time average value of the current values until the overload signal is received.

Further, when the movement instructed by the NC program 1 is completed, the proper load search device 7 outputs a movement command for the amount by which the machine coordinates are shifted in order to grind the instructed amount.

The appropriate load search device 7 as described above can be easily formed by using a microcomputer and devising its software. A flowchart in this case is shown in FIG.

In the above embodiment, if the grinding process as shown in FIG. 3 (a) progresses and the grinding tool 8 approaches a step during grinding as shown in FIG. 3 (b), the servo motor 5 and the main shaft are rotated. The load on the motor 11 increases and the current value increases. When each current value is larger than a certain value, the overload detector 3 outputs an overload signal to the proper load search device 7. Upon receiving this overload signal, the proper load search device 7 shifts the machine coordinates in the direction in which the grinding tool 8 is moved away from the work 9. As a result, a difference occurs between the coordinate value designated by the NC program 1 and the current machine position, so the movement command generator 2 outputs a movement command to the servo amplifier 4. Thus, FIG.
As shown in (c), the grinding tool 8 is moved away from the work 9 by the shift amount, and the loads on the servo motor 5 and the spindle motor 11 are reduced. This operation is repeated until the current values of the servo motor 5 and the spindle motor 11 become the same as the time average value of the current values until the overload is detected. As a result, the load increased due to the step can be reduced and damage to the grinding tool 8 can be prevented.

Further, when the movement instructed by the NC program 1 is completed, a movement command for further adding the grinding amount in the Z direction by the shifted machine coordinates is outputted, and the amount instructed by the NC program 1 is ground.

[0018]

As described above in detail with reference to the embodiments, according to the present invention, the mechanical coordinates are shifted by the load of the motor during grinding, and the relative distance between the grinding tool and the work is changed to increase the mechanical coordinates. The load can be reduced and damage to the grinding tool can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the proper load search device in the embodiment.

FIG. 3 is an explanatory view showing a mode of grinding processing in the embodiment.

FIG. 4 is an explanatory view showing a mode of grinding processing in a conventional technique.

FIG. 5 is a block diagram showing a numerical controller according to a conventional technique.

[Explanation of symbols]

 1 NC program 2 Movement command generator 3 Overload detector 4 Servo amplifier 5 Servo motor 6 Position detector 7 Appropriate load searcher 8 Grinding tool 9 Workpiece 10 Spindle controller 11 Spindle motor

Claims (1)

[Claims] 1. A numerical controller of a grinding machine for controlling a position of a grinding tool such that a commanded position based on an NC program and an actual machine position detected by a position detection means are compared with each other so that the two coincide with each other. The current of each motor inside is monitored, and when this current value indicates an overload, it is appropriate to change the machine coordinate command value and shift the machine coordinate so that the grinding tool moves in the direction that reduces the load. A numerical control device for a grinding machine, comprising a load search means.