JPH05228792A - Temperature compensating device for machine tool - Google Patents

Abstract

PURPOSE:To reopen accurate working operation without generating any error of dimensional accuracy in an extreme short time so as to improve working efficiency by providing a control means to reopen working operation after raising temperature up to nearby the temperature before interruption. CONSTITUTION:An interruption detecting means to detect interruption of working operation of a machine tool and a timer means 23 to measure the interruption time of working operation are provided. Next, the machine tool is operated at high speed in non-working condition for a set time according to the interruption time detected by the timer means 23 after interruption, the temperature of a drive part is raised up to nearby the temperature before interruption of working operation by generated friction heat, and then working operation is reopened. Hereby, working operation can be reopened in the balanced temperature condition similar to the condition before interruption, and hence error of the dimensional accuracy can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool, and more particularly to a technique for avoiding the influence of interruption of machining operation.

[0002]

2. Description of the Related Art A machine tool such as a lathe has a headstock and a tool base mounted on a bed, and a tool held by the headstock is mounted on a ball screw and a tool held by the tool base.
Processing is carried out while being transferred by a nut mechanism or the like. By the way, in such a machine tool, the machining operation may have to be interrupted during the machining operation of the workpiece in order to remove chips and replace the cutting tool.

In this case, if the machining operation is resumed as it is after the work, since the spindle stock and the tool base are cooled during the interruption of the machining operation, the thermal deformation of these parts causes an error in the machining dimensional accuracy.

[0004]

For this reason, it is usual to carry out a running-in operation (operation in a non-processing state) after the operation is stopped, and restart the processing operation after reaching the saturation temperature, but the interruption time is prolonged. If it does, it takes time to return to the saturation temperature. When running in at the same speed as when machining,
It is necessary to run in for approximately the same time as the interruption time.

A method in which a heating means such as a heater is installed in a machine tool to heat the machine tool and then the machining operation is restarted is conceivable, but it is costly and it is difficult to obtain a heat generation distribution characteristic similar to that during operation. Therefore, it is difficult to correct it well. The present invention has been made in view of such conventional problems, and a good temperature compensation function can be obtained without adding a special heating means, so that the machining operation can be restarted in a short time. An object is to provide a temperature compensation device for a machine tool.

[0006]

Therefore, the temperature compensating device for a machine tool according to the present invention, as shown by the solid line in FIG.
Interruption detecting means for detecting interruption of machining operation of the machine tool,
A time measuring means for measuring the interruption time of the machining operation and a high speed operation in a non-machining state for a time set according to the interruption time detected by the time measuring means after the interruption, and the temperature of the driving part is processed by the generated friction heat. The control means restarts the processing operation after the temperature is raised to near the temperature before the operation was interrupted.

Further, as shown by a chain line in FIG. 1, it is more preferable to include means for detecting the ambient temperature around the machine tool, and to correct the time set by the control means according to the ambient temperature.

[0008]

When the machining operation of the machine tool is interrupted, the drive unit is cooled, its temperature is lowered, and heat shrinks. The amount of temperature decrease during the interruption depends on the interruption time, while the amount of temperature increase due to heat generation in the high-speed break-in operation after the interruption also depends on the operation time. Therefore, the operation time until the temperature of the drive unit, which rises due to the high-speed break-in operation after the interruption, reaches near the temperature before the interruption can be obtained corresponding to the interruption time.

Therefore, the temperature of the drive unit can be raised to near the temperature before the interruption by performing a break-in operation at a high speed for a time set according to the interruption time detected by the time measuring means after the interruption. The machining operation can be restarted under the same equilibrium temperature conditions as before, and the error in dimensional accuracy can be suppressed. Also, to be precise, the amount of temperature decrease during interruption is somewhat affected by the environmental temperature around the machine tool, so
By correcting the environmental temperature and setting the running-in time for high-speed operation, the error in dimensional accuracy can be further reduced.

[0010]

EXAMPLES Examples of the present invention will be described below. In FIG. 2, a headstock 3 is supported at one end on a bed 2 of a machine tool (lathe) 1. The spindle headstock 3 includes a spindle 5 having a chuck 4 for holding a work W at its tip, and the spindle 5
And a hydraulic cylinder (not shown) for opening and closing the chuck 4, and the like.

A tool base 7 is supported on the bed 2 on the side opposite to the headstock 3. The tool base 7 includes a Z-axis slide 8 that is slidable in the Z-axis direction parallel to the axis of the main shaft 5 with respect to the bed 2, and an X-axis direction (on the front and back sides of the paper) perpendicular to the Z-axis slide 8 on the Z-axis slide 8. Direction) and an X-axis slide 9 held slidably in
A tool rest 11 for holding 10 is provided. The Z-axis slide 8 is driven in the Z-axis direction via a Z-axis servo motor 12 and a Z-axis ball screw / nut mechanism 13, and the X-axis slide 9 also has an X-axis servo motor and an X-axis ball screw / nut mechanism (any one). (Not shown), and is driven in the X-axis direction.

The spindle 5, the Z-axis slide 8 and the X-axis slide 9 are driven by control signals according to NC programs from the control unit 14, respectively, and the blade 10 is controlled while controlling the positions in the X-axis direction and the Z-axis direction. It moves so as to cut the workpiece W into a predetermined shape by the blade 10. Further, the drive motors of the respective parts can control the drive speed variably within a set range, for example, the blade 10 can move at a high speed during non-machining as compared to the speed during normal machining operation. ..

Next, the part according to the present invention will be described. In addition to the NC control unit, a temperature compensation control unit that copes with interruption of machining operation is provided in the control device 14. FIG. 3 is a control block diagram of the temperature compensation controller. The ON and OFF signals from the power switch 21 are input to the control circuit 22 including a microcomputer and the like.
22 is provided with a timer 23 as a time measuring means for measuring the interruption time when the continuous machining operation is interrupted. On the other hand, a temperature sensor 24 as temperature detecting means for detecting the environmental temperature is provided on the outer wall of the machine tool 1, and the temperature signal detected by the temperature sensor 24 is also input to the control circuit 22 to perform the temperature correction described later. Be seen.

In the control circuit 22, a storage unit such as a ROM 25 stores a map of a high-speed break-in operation time performed after the interruption of the machining operation of the machine tool 1 after the interruption. Here, the relationship between the interruption time and the corresponding high-speed break-in operation time is set as follows. First, for each type of work (including machining), check the temperature and thermal displacement of the spindle 5 and tool rest 4 when the workpiece is continuously machined and then interrupted, and obtain the characteristic curve. Put (Figure 4
O-A-B-C). Here, the continuous processing state is a state in which heat is generated due to the processing operation, the temperature rises, the saturation temperature is reached, and the machine is in an equilibrium state. The saturation temperature differs depending on the type of work because the processing load varies. For example, a hard work has a large processing load, so that the amount of heat generated by friction is large, resulting in a high saturation temperature. Therefore, the thermal displacement with respect to the interruption time also differs depending on the type of work.

Next, the state of thermal displacement due to the temperature rise due to the high-speed running-in operation after the interruption is examined to obtain the characteristic curve. Here, as shown in FIG. 5, each interruption end time point C _{1 to} C
_The high-speed break-in operation is started from _N and the temperature around
The characteristics of the operating time and the thermal displacement when returning to _{1 to DN} ) can be regarded as a substantially straight line regardless of the length of the interruption time, and the slope thereof is also considered to be substantially constant.

Therefore, the relationship between the thermal displacement at the end of the interruption and the operating time of the high-speed running-in operation is obtained, and the operating time of the high-speed running-in operation is set using the interruption time as a parameter and stored in the ROM or the like. Next, the processing control operation including the temperature compensation control by the temperature compensation control unit will be described with reference to the flowchart shown in FIG.

Step (denoted by S in the figure. The same applies hereinafter) 1
Then, the power switch 21 of the machine tool 1 is turned on to perform a break-in operation, and the temperature of each drive unit of the machine tool 1 is raised to the saturation temperature (between OA in FIG. 4). In step 2,
Whether or not the break-in operation has been completed is determined by whether or not the saturation temperature has been reached. After it is determined that the saturation temperature has been reached, the routine proceeds to step 3.

In step 3, the machining operation of the work W is started according to the machining program set by the NC control section. In step 4, it is determined whether or not the machining operation of the work W is interrupted by whether or not the power switch 21 is turned off. The function of step 4 corresponds to the interruption detecting means.

When it is determined in step 4 that the interruption has been performed, the timer 23 is activated in step 5 to start measuring the interruption time. In step 6, it is determined whether or not the interruption is completed, depending on whether or not the power switch 21 is turned on. If it is determined in step 6 that the interruption has ended,
Proceed to step 7 and subsequent steps to start the high-speed break-in program.

In step 7, the type of the workpiece W currently being machined is read from the interruption time t ₁ measured by the timer 23, the environmental temperature T detected by the temperature sensor 24, and the NC program. In step 8, from the setting map of the high-speed run-in operation time for each work W stored in the ROM based on the interruption time t, the basic operation time of the high-speed run-in operation of the spindle 5 drive motor 6 and the Z-axis servomotor 12 is performed. Then, t ₀₂ is searched for, and the final high-speed running-in time t ₂ is set by multiplying the basic operation time t ₀₂ by the temperature correction coefficient based on the ambient temperature.

In step 9, the main shaft 5 drive motor and the Z-axis servomotor 12 are run-in at high speed. Incidentally, Z
Since the Z-axis slide 8 has a limited movement range, the axis servo motor 12 is reversely driven at a predetermined cycle so as to reciprocate within the predetermined range. In step 10, for each motor, it is determined whether or not the set time t ₂ for the high-speed run-in operation has elapsed, and when the set time t ₂ has passed, the drive of each motor is reduced to the speed during the machining operation and the run-in operation is performed. The functions of steps 6 to 10 described above correspond to the control means.

In step 11, the machining program after the interruption is read and the machining operation is restarted. With this configuration, even if the interruption time of the machining operation is prolonged, the temperature of each drive section is raised to near the temperature before the interruption in a short time by the high-speed break-in operation, and the dimensional error of the thermal displacement is stabilized. The machining operation can be restarted while suppressing the occurrence.
In this embodiment, the motor for rotating the main shaft and the motor for sliding the Z-axis are acclimated at a high speed. However, for simplicity, only one of the motors may be driven. It may be configured to drive a motor for axial sliding.

Further, in order to suppress the overshoot of the temperature rise due to the high-speed break-in operation, it is possible to perform a highly accurate control such that the speed is slightly reduced near the end.

[0024]

As described above, according to the present invention, after the machining operation of the machine tool is interrupted, the break-in operation is performed at a high speed for a time set according to the interruption time, and after the temperature is raised to the temperature before the interruption. Since the processing operation is restarted, it is possible to restart a highly accurate processing operation that does not cause a dimensional accuracy error in an extremely short time, thus improving work efficiency.

Further, by correcting the high-speed running-in operation time depending on the environmental temperature, the dimensional accuracy error can be further eliminated and the processing accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a temperature compensation device for a machine tool according to the present invention.

FIG. 2 is a side view showing a configuration of a machine tool according to an embodiment of the present invention.

FIG. 3 is a control block diagram showing temperature compensation control according to the embodiment.

FIG. 4 is a time chart showing changes in thermal displacement in the above-mentioned embodiment.

FIG. 5 is a time chart showing the relationship between the interruption time and the high-speed running-in time.

FIG. 6 is a flowchart showing a temperature compensation control routine.

[Explanation of symbols]

 1 Machine tool 6 Motor for spindle drive 12 Z-axis servo motor 13 Z-axis ball and nut mechanism 21 Power switch 22 Control circuit 23 Timer 24 Temperature sensor 25 ROM

Claims (2)

[Claims] 1. An interruption detecting means for detecting interruption of a machining operation of a machine tool, a timing means for measuring an interruption time of the machining operation, and a interruption time detected by the timing means after interruption. Control means for operating at high speed for a non-machining state for a period of time, and restarting the machining operation after raising the temperature of the drive unit to near the temperature before the interruption of the machining operation by the generated friction heat,
A temperature compensation device for machine tools, characterized in that 2. A temperature compensating device for a machine tool according to claim 1, further comprising means for detecting an environmental temperature around the machine tool, wherein the time set by the control means is corrected according to the environmental temperature. ..