JPH11197998A - Thermal displacement correcting device of nc machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal displacement correcting device of an NC machine tool by which in the case where the thermal displacement of a spindle can not be measured correctly, the working accuracy can be prevented from being remarkably lowered by correction. SOLUTION: This device includes a thermal displacement measuring means 10 for measuring the thermal displacement of a spindle thermally displaced within a unit time at every unit time after the lapse of designated time since the rotating speed of a spindle is changed, a thermal displacement storing means 20 for storing the measured thermal displacement within a unit time, a correction amount determining means for determining the correction amount for shifting the mechanical coordinate system according to the measured thermal displacement of the spindle, and a correction command means 40 for outputting a correction command for shifting the mechanical coordinate system to NC device (a) based o the decided correction amount, wherein the correction amount determining means 30 compares the stored preceding thermal displacement with the measured this time thermal displacement to determine the correction amount according to the this time thermal displacement in the case where the preceding thermal displacement is larger than the this time thermal displacement, and determine the correction amount according to the preceding thermal displacement in the case where the this time displacement is larger than the preceding thermal displacement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal displacement compensating device for shifting a machine coordinate system of an NC machine tool when a main shaft of the NC machine tool undergoes thermal displacement due to a temperature rise.

[0002]

2. Description of the Related Art In an NC machine tool, a spindle, which is rotatably supported by a spindle head via a bearing, is rotated at a high speed by an electric motor, so that the heat generated by the electric motor itself and the rotational driving force of the electric motor are transmitted to the spindle. There has been a problem that the main shaft itself is heated and expands in the axial direction due to frictional heat of the power transmission mechanism and the bearing, and the tip portion is thermally displaced, thereby lowering machining accuracy.

For this reason, conventionally, NC machine tools include:
A thermal displacement measuring sensor that measures the thermal displacement of the spindle, and N based on the thermal displacement measured by the thermal displacement measuring sensor.
A correction amount determining means for determining a correction amount for shifting the machine coordinate system of the C machine tool, and a correction instruction means for outputting a correction instruction to the NC device for shifting the machine coordinate system based on the correction amount. A thermal displacement compensating device is provided, and during the operation of the NC machine tool, the thermal displacement of the main spindle is measured by a thermal displacement measuring sensor every unit time, and the measured thermal displacement is directly converted into a machine coordinate system. A correction amount for shifting is used, and the machine coordinate system is shifted every unit time based on the correction amount.

[0004]

However, in the above-described thermal displacement compensating device, the compensation amount is calculated based on the thermal displacement amount actually measured each time by the thermal displacement sensor. Even if the measurement sensor cannot correctly measure the thermal displacement of the main shaft, the correction corresponding to the thermal displacement is performed as it is, and such correction may adversely affect the processing accuracy. there were.

[0005] Therefore, an object of the present invention is to correct the correction amount so that the machining accuracy is not significantly reduced even if the thermal displacement amount of the spindle cannot be measured correctly due to some factor. An object of the present invention is to provide a thermal displacement correction device for an NC machine tool.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a thermal displacement of a spindle which is thermally displaced within a unit time after a lapse of a predetermined time after a rotation of a spindle of an NC machine tool changes. Thermal displacement amount measuring means for sequentially measuring the amount per unit time, thermal displacement amount storing means for storing the thermal displacement amount per unit time measured by the thermal displacement amount measuring means, and the thermal displacement amount measuring means On the basis of the measured thermal displacement of the spindle, a correction amount determining means for determining a correction amount for shifting the machine coordinate system of the NC machine tool, and a correction amount determined by the correction amount determining means, Correction command means for outputting a correction command for shifting a machine coordinate system to an NC device, wherein the correction amount determining means includes a previous thermal displacement amount stored in the thermal displacement amount storing means and a thermal displacement amount measuring means. Measured by If the previous thermal displacement is greater than the current thermal displacement, a correction amount is determined based on the current thermal displacement, and the current thermal displacement is calculated based on the previous thermal displacement. An object of the present invention is to provide a thermal displacement compensating device for an NC machine tool, in which when the thermal displacement is larger than the thermal displacement, the correction is determined based on the previous thermal displacement.

As described above, when the previous thermal displacement is larger than the current thermal displacement, a correction amount is determined based on the current thermal displacement, and the current thermal displacement is set to be smaller than the previous thermal displacement. If it is larger, the NC machine tool determines the correction amount based on the previous thermal displacement amount, as shown in FIG. 7, after the start of spindle rotation or after a change in the number of revolutions of the spindle (spindle rotation). including the stop), except for the main shaft rotation start immediately and spindle speed changes the initial time immediately after the (time to T _0), always
This is because it has been found that the spindle has a thermal displacement characteristic in which the rate of increase and decrease of the thermal displacement of the spindle decreases with time (T ₁ , T ₂ ,...), And thus the correction amount is determined. Thus, even when the thermal displacement of the main shaft cannot be measured correctly due to some factor, it is possible to effectively prevent a reduction in machining accuracy due to improper thermal displacement correction.

The correction command means divides the correction amount determined by the correction amount determination means, and outputs a correction command based on the divided correction amount a plurality of times before the next measurement of the thermal displacement amount. , The machine coordinate system can be gradually shifted so as not to cause a step on the machined surface even when a large thermal displacement occurs in the main spindle within a unit time. In particular, it is desirable that the correction command unit does not output a correction command when the NC machine tool is performing a specific process such as a screw hole process or during automatic tool change.

[0009]

Embodiments will be described below with reference to the drawings. As shown in FIG. 1, the thermal displacement compensator 1 includes a thermal displacement measuring means 10 for measuring a thermal displacement of a spindle of an NC machine tool A, and a thermal displacement of the spindle measured by the thermal displacement measuring means 10. Thermal displacement storage means 20 for storing the displacement, and correction for determining a correction amount for shifting the machine coordinate system of the NC machine tool A based on the thermal displacement of the spindle measured by the thermal displacement measuring means 10. An amount determining means 30, a correction command means 40 for outputting a correction command to the NC device a of the NC machine tool A based on the correction amount determined by the correction amount determining means 30, the thermal displacement amount measuring means 10, The control unit 50 controls the displacement amount storage unit 20, the correction amount determination unit 30, and the correction instruction unit 40.

As shown in FIG. 2, the thermal displacement measuring means 10 is attached to the spindle head near the rear end of the spindle supported by the spindle head of the machine tool A, and is mounted on the spindle head from a reference position. A thermal displacement measuring sensor 11 such as a gap sensor for sequentially measuring the thermal displacement (L) of the main spindle for each unit time (ΔT), and a thermal displacement (L) measured by the thermal displacement measuring sensor 11 are stored. And a thermal displacement amount (L _n-1 ) at the previous measurement time point (T _n-1 ) stored in the storage unit 12
And the thermal displacement (L _n ) at the current measurement time (T _n ) measured by the thermal displacement measuring sensor 11 to determine the difference between the previous measurement time (T _n-1 ) and the current measurement time (T _n). ), That is, the unit time (Δ
T _n) is composed of a calculation unit 13 for calculating the thermal displacement of the spindle thermally displaced ([Delta] L _n) into the thermal displacement amount in the unit was calculated time by the calculating unit 13 ([Delta] L _n) is ,
It is sequentially output to the control means 50 at each measurement time.

The thermal displacement amount storage means 20 is a RAM or P
The control means 5 comprises a memory such as a ROM.
This is for temporarily storing the thermal displacement amount (ΔL _n ) per unit time calculated by the thermal displacement amount measuring means 10 output from 0, and is stored in the thermal displacement amount storing means 20. The amount of thermal displacement (ΔL _n ) per unit time is used when the correction amount determining means 30 determines the correction amount, as described later.

As shown in FIG. 3, the correction amount determining means 30 calculates the thermal displacement (ΔL) of the main shaft thermally displaced within the unit time (ΔT _n ) measured by the thermal displacement measuring means 10 at the time of the current measurement. _n ) and a data capturing unit 31 for capturing the thermal displacement amount (ΔL _n-1 ) within the unit time (ΔT _n-1 ) at the previous measurement time point stored in the thermal displacement amount storage means 20;
A data judging unit 32 that compares the two data taken into the data acquiring unit 31 to determine which thermal displacement is larger, and the data judging unit 32 allows the thermal displacement (ΔL _{n) at the} time of the previous measurement. _-1) determines the correction amount in thermal displacement amount (thermal displacement at the time the current measurement when [Delta] L _n) is greater than (currently measured point on the basis of the [Delta] L _n) (T _n) at the time the current measurement, current measurement Thermal displacement at the time (ΔL
_{If n} ) is larger than the thermal displacement amount (ΔL _n-1 ) at the previous measurement time, the correction amount at the current measurement time (T _n ) is determined based on the thermal displacement amount (ΔL _n-1 ) at the previous measurement time. And a correction amount determining unit 33.

The amount of thermal displacement at the time of the current measurement (ΔL
_n) the thermal displacement amount before measurement time point (if [Delta] L _n-1) greater than the thermal displacement amount before measurement time point ([Delta] L _n-1)
Is stored in the thermal displacement storage means 20 as the thermal displacement at the current measurement time (ΔL _n ), and the thermal displacement at the previous measurement (L _n-1 ) and the thermal displacement at the previous measurement (ΔL _{n−). 1)} the sum of _{(L n-1 + ΔL n} -1) is stored in the storage unit 12 of the thermal displacement measurement unit 10 as the thermal displacement amount (L _n) at the current measurement time point.

As shown in FIGS. 1 and 4, the correction command means 40 includes a state signal input section 41 to which a machining state signal of the machine tool A output from the NC device a is input via the control means 50. The correction amount input unit 42 to which the correction amount determined by the correction amount determination unit 30 is input via the control unit 50, and the machining state signal and correction output from the state signal input unit 41 and the correction amount input unit 42, respectively. The determination / processing unit 43 performs a predetermined determination based on the amount and performs processing based on the determination, and an output unit 44 that outputs the correction amount processed by the determination / processing unit 43 to the NC apparatus a. .

The judgment / processing section 43 receives the machining state signal output from the state signal input section 41, and
Does not output the correction amount to the output unit 44 so as not to perform the correction when the specific processing such as the screw hole processing or the automatic tool change is performed.

The determining / processing unit 43 determines that the correction amount determined by the correction amount determining means 30 is a predetermined unit correction amount (for example, a predetermined coefficient is set to a minimum shift amount capable of shifting the machine coordinate system of the machine tool). If the correction amount is larger than the multiplication amount, the correction amount is divided into a plurality of unit correction amounts, and the division is performed between the current measurement time point (T _n ) and the next measurement time point (T _{n + 1} ). The unit correction amount is sequentially output to the output unit 44 a plurality of times.

The thermal displacement compensator 1 configured as described above
Will be described in detail below with reference to the flowcharts shown in FIGS.

When the power of the NC machine tool A is turned on, the thermal displacement compensator 1 is also activated at the same time, and it is first determined whether or not machining has been started, that is, whether or not the spindle has started to rotate (step). S1) When it is determined that the machining has been started, the timer is reset in step S2, and then the process is started, and the process proceeds to step S3. If the processing has not been started in step S1, the process returns to step S1 and waits until the processing is started.

In step S3, it is determined whether or not the initial time has elapsed since the start of machining. If it is determined that the initial time has elapsed, the process proceeds to step S4, where the timer is reset and started. Step S
If the initial time has not elapsed in step 3, the process returns to step S3 again and waits until the initial time has elapsed.

Note that the "initial time" referred to herein is the one shown in FIG.
As shown in, NC machine tool means a time zone thermal displacement amount of the rate of change of the main shaft is small immediately after the processing starts immediately and the rotation speed of the change of the main shaft of the machine, after a lapse of the initial time (T ₀₎ As shown in FIG. 3, the thermal displacement characteristic shows that the rate of change of the thermal displacement of the main shaft once increases and then decreases with time. Further, it is necessary to appropriately set the initial time (T ₀ ) in accordance with the thermal displacement characteristics of each NC machine tool.

Next, in step S5, the thermal displacement amount (L ₀ ) of the main shaft at the time point (T ₀ ) at which the initial time has elapsed is measured by the thermal displacement amount measuring sensor 11 of the thermal displacement amount measuring means 10. The calculation unit 13 outputs the amount (L ₀ ) to the control means 50 as the thermal displacement amount (ΔL ₀ ) in which the main shaft is thermally displaced from the start of machining to the time (T ₀ ) at which the initial time has elapsed, and measures the amount this time. After storing the thermal displacement amount (L ₀ ) in the storage unit 12, the process proceeds to step S6.

In step S6, the thermal displacement (ΔL ₀ ) output to the control means 50 is output to the correction amount determining means 30, and after the correction amount is determined based on the thermal displacement (ΔL ₀ ) The correction amount is output to the correction instruction means 40 via the control means 50, and the correction instruction means 40 outputs a correction instruction based on the correction amount to the NC device a.

Next, in step S7, it is determined whether or not the unit time (ΔT) has elapsed since the initial time (T ₀ ), and if the unit time (ΔT) has not yet elapsed, the step is repeated. The process returns to S7 and waits until the unit time (ΔT) elapses. In this embodiment, the unit time (ΔT) is set to about 10 to 20 minutes.

On the other hand, if it is determined in step S7 that the unit time (ΔT) has elapsed, the process proceeds to step S8.
, The timer is reset and then started, the process proceeds to step S9, and the following processing is performed.

In step S 9, first, the thermal displacement amount (L ₁ ) of the main shaft at the time point (T ₁ ) at which the unit time has elapsed is measured by the thermal displacement amount measuring sensor 11.
By calculating the difference between the previously measured thermal displacement (L ₀ ) and the currently measured thermal displacement (L ₁ ) stored in the memory, the current measuring time (T ₁ ) from the previous measuring time (T ₀ ) The calculation unit 13 calculates the amount of thermal displacement (ΔL ₁ ) during which the main shaft has undergone thermal displacement, outputs it to the control unit 50, and stores the amount of thermal displacement (L ₁ ) measured this time in the storage unit 12. On the other hand, the thermal displacement (ΔL ₁ ) output to the control means 50 is
Is output to the thermal displacement storage means 20 and stored in the thermal displacement storage means 20.

In the next step S10, the amount of thermal displacement (ΔL ₁ ) output to the control means 50 is determined by the correction amount determining means 30.
After the correction amount is determined based on the thermal displacement amount (ΔL ₁ ), the correction amount is output to the correction instruction means 40 via the control means 50, and the correction instruction means 40 After outputting a correction command based on this to the NC device a, the process proceeds to a predetermined thermal displacement correction processing routine S11.

In the thermal displacement correction processing routine in step S11, as shown in FIG. 6, first, in step S21, it is determined whether or not a unit time (ΔT) has elapsed since the previous measurement time (T ₁ ). If the unit time (ΔT) has not elapsed, the process returns to step S21 and waits until the unit time (ΔT) has elapsed.

On the other hand, if it is determined in step S21 that the unit time (ΔT) has elapsed from the previous measurement time point (T ₁ ), in step S22, the timer is reset and then started.

In the next step S23, the NC machine tool A
It is determined in the determination and processing unit 43 whether or not is performing a specific processing such as screw hole processing and automatic tool change,
When it is determined that the specific processing or the like is being performed, a series of processes from the measurement of the thermal displacement amount to the output of the correction command to the NC device a as described below is not performed, that is, the thermal displacement The thermal displacement correction processing routine is ended without performing the correction, but when the specific processing or the like is not performed, the process proceeds to step S24, and the following processing is performed.

In step S24, first, the thermal displacement amount (L ₂ ) of the main shaft at the current measurement time (T ₂ ) at which the unit time (ΔT) has elapsed from the previous measurement time (T ₁ ) is measured by the thermal displacement amount measurement sensor 11. The difference between the previously measured thermal displacement (L ₁ ), which has been measured and already stored in the storage unit 12, and the currently measured thermal displacement (L ₂ ) is calculated from the previous measurement time (T ₁ ). The calculation unit 13 calculates the amount of thermal displacement (ΔL ₂ ) of the main shaft thermally displaced up to the current measurement time point (T ₂ ), outputs the amount of thermal displacement (ΔL ₂ ) to the control unit 50, and measures the current time. The obtained thermal displacement (L ₂ ) is stored in the storage unit 12.

In the next step S25, the previous step S2
Thermal displacement amount in the current measurement time point (T ₂₎ calculated in 4 (ΔL ₂₎ already thermal displacement amount before measurement time point stored in the thermal displacement amount storage unit _{20 (T 1) (ΔL 1} ) control The data is output to the data capturing section 31 of the correction amount determining means 30 through the means 50, and it is determined whether the thermal displacement (ΔL ₂ ) or the thermal displacement (ΔL ₁ ) captured by the data capturing section 31 is larger. When the thermal displacement (ΔL ₁ ) at the previous measurement time is larger than the thermal displacement (ΔL ₂ ) at the present measurement time, the heat displacement measurement sensor 11 determines the heat of the spindle of the NC machine tool A by the data determination unit 32. Since it is considered that the correct amount of thermal displacement according to the displacement characteristics has been measured,
In step S26, the correction amount determination unit 33 determines the correction amount based on the thermal displacement amount (ΔL ₂ ) at the time of the current measurement, outputs the correction amount to the control unit 50, and then proceeds to step S28.

On the other hand, in step S25, when the thermal displacement (ΔL ₂ ) at the current measurement time is larger than the thermal displacement (ΔL ₁ ) at the previous measurement time, the thermal displacement of the main shaft of the machine tool is caused by some factor such as noise. Since it is considered that the correct amount of thermal displacement according to the characteristic has not been measured, in step S27, the correction amount determining unit 33 determines the amount of correction based on the amount of thermal displacement (ΔL ₁ ) at the time of the previous measurement, and corrects the amount. After outputting the amount to the control means 50, the process proceeds to step S28. As described above, when it is considered that the thermal displacement (ΔL) is measured as a value considerably larger than the actual value, the NC is determined by determining the correction amount based on the previously properly measured thermal displacement (ΔL). The machine coordinate system of the machine tool is not shifted more than necessary, and a decrease in machining accuracy caused by improper thermal displacement correction can be minimized.

In step S28, normally, in step S2
4, the thermal displacement amount (ΔL) output to the control means 50
₂ ) is output from the control means 50 to the thermal displacement storage means 20 and stored in the thermal displacement storage means 20. The thermal displacement (ΔL ₂ ) at the present measurement time (ΔL ₂ ) is the thermal displacement at the previous measurement time (ΔL ₂ ). ΔL ₁ ), that is, when the correction amount is determined based on the thermal displacement amount (ΔL ₁ ) at the previous measurement time, the thermal displacement amount (ΔL ₁ ) at the previous measurement time is the thermal displacement amount at the current measurement time. (ΔL ₂ ) is stored in the thermal displacement amount storage means 20, and the sum (L ₁ + ΔL ₁ ) of the thermal displacement amount (L ₁ ) at the previous measurement time point and the thermal displacement amount (ΔL ₁ ) at the previous measurement time point is obtained. Thermal displacement at the time of current measurement (L
₂ ) is stored in the storage unit 12 of the thermal displacement measuring means 10.

Then, in the next step S29, after the judgment / processing section 43 performs a predetermined process on the correction amount input to the correction amount input section 42, the output section 44 issues a correction command to the NC unit a. Is output and the thermal displacement correction processing routine ends. At this time, the determination / processing unit 43 first determines that the correction amount determined in step S26 or step S27 is a predetermined unit correction amount (a minimum shift amount that can shift the machine coordinate system of the machine tool is multiplied by a predetermined coefficient). It is determined whether or not the correction amount is larger than the unit correction amount. If the determined correction amount is larger than the unit correction amount, the correction amount is divided into a plurality of unit correction amounts, and the next correction amount is calculated from the current measurement time (T ₂ ). Until the measurement time point (T ₃ ), the divided unit correction amounts are sequentially output to the output unit 44 a plurality of times. Therefore, the correction based on the determined correction amount is not performed at once, but is corrected a plurality of times for each unit correction amount, and the machine coordinate system is gradually changed so as not to generate a step on the processing surface. Can be shifted.

As described above, the measurement, storage, and thermal displacement correction of the thermal displacement (L, ΔL) are not performed during specific machining such as thread machining, but thread hole machining and automatic tool machining are not performed. The time required for specific processing such as replacement is generally short, and such specific processing always involves a change in the number of revolutions of the spindle. Therefore, in the next step S12, be sure to return to step S1. Is repeated from the beginning, so that the thermal displacement correction processing which is not performed because the specific processing is being performed is not repeatedly accumulated, and is measured in the subsequent step S5 as described later. The amount of thermal displacement (ΔL ₀ ) is calculated by calculating the difference between the amount of thermal displacement (L) measured and stored before the specific machining and the amount of thermal displacement (L ₀ ) measured in step S5, Specific addition Unless the work is being performed, the correction amount that should be corrected is added at this point, so there is no particular problem.

When the thermal displacement correction processing in step S11 is completed as described above, it is determined in step S12 whether or not the rotational speed of the main shaft has been changed. If the rotational speed of the main shaft has not been changed, the process proceeds to step S13. Transition. Here, when the rotation speed of the spindle is changed, the process returns to step S1 and the above processing is repeated from the beginning.

However, at the start of processing, as described above,
In step S5, the measured thermal displacement (L ₀ )
The thermal displacement amount spindle is thermally displaced between the intact machining start point to the initial time point (T ₀₎ (ΔL ₀₎
However, immediately after the rotation speed of the spindle is changed, the calculation unit 13 stores the thermal displacement amount (L _n ) corresponding to the previous measurement time point already stored in the storage unit 12 and the initial time from the time point of the rotation speed change of the spindle. Is obtained from the thermal displacement amount (L ₀ ) of the spindle measured at the time (T ₀ ) after the passage of the rotation speed, the thermal displacement of the spindle from the rotation speed change time to the initial time lapse (T ₀ ). The calculated thermal displacement (ΔL ₀ ) is calculated.

In the final step S13, the NC machine tool A
It is determined whether or not the processing has been stopped. If the processing has not been stopped, the processing returns to the thermal displacement correction processing routine of step S11 again, and the thermal displacement correction processing after the next measurement point (T ₃ , T _4, ...) Is repeated. Do it. On the other hand, when the machining of the NC machine tool A is stopped in step S13, the correction processing by the thermal displacement correction device 1 ends.

In this embodiment, the NC machine tool A
The thermal displacement at the rear end of the spindle is measured and this thermal displacement is used as it is as the thermal displacement at the tip of the spindle, but strictly speaking, the thermal displacement at the rear end of the spindle and the thermal displacement at the tip of the spindle are Is different, the correlation between the thermal displacement at the rear end of the spindle and the thermal displacement at the tip of the spindle is determined in advance, and based on this correlation,
It is desirable to calculate the thermal displacement at the front end of the spindle by correcting the measured thermal displacement at the rear end of the spindle, and to adopt the calculated thermal displacement at the front end of the spindle.

In this embodiment, the unit time (Δ
In T), the correction amount is determined based on the thermal displacement amount (ΔL) in which the main shaft is thermally displaced. However, the thermal displacement amount (L) measured at each measurement time point (T ₀ , T ₁ ,. It is also possible to perform the thermal displacement correction by outputting the thermal displacement (L) corrected by performing the above-described predetermined processing to the thermal displacement (L) to the NC device a as it is as a correction amount.

[0041]

As described above, the thermal displacement compensating device for an NC machine tool according to the present invention takes into account the thermal displacement characteristics of the spindle,
If a measured amount of thermal displacement is greater than a previously measured amount of thermal displacement after a predetermined time has elapsed from the time when the rotational speed of the spindle of the machine tool has changed, a correction amount is determined based on the amount of thermal displacement of the previous time. Therefore, even if the thermal displacement of the spindle cannot be measured correctly for some reason,
The machine coordinate system of the NC machine tool is not shifted more than necessary, and the deterioration of machining accuracy caused by improper thermal displacement correction can be prevented, and the reliability of thermal displacement correction can be improved. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a thermal displacement correction device according to the present invention.

FIG. 2 is a block diagram showing a thermal displacement amount measuring means in the thermal displacement correction device of the above.

FIG. 3 is a block diagram showing a correction amount determining means in the thermal displacement correction device of the above.

FIG. 4 is a block diagram showing a correction command unit in the thermal displacement correction device according to the first embodiment;

FIG. 5 is a flowchart showing the content of processing of the entire thermal displacement correction apparatus of the above.

FIG. 6 is a flowchart showing the content of a thermal displacement correction process of the thermal displacement correction device of the above.

FIG. 7 is a graph showing a thermal displacement characteristic of a spindle of a machine tool.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal displacement correction device 10 Thermal displacement amount measuring means 20 Thermal displacement amount storing means 30 Correction amount determining means 40 Correction command means 50 Control means A NC machine tool a NC device

Claims (3)

[Claims] 1. A thermal displacement amount measuring means for sequentially measuring, every unit time, a thermal displacement amount of a main shaft thermally displaced within a unit time after a predetermined time elapses after a rotation speed of a main shaft of an NC machine tool changes, A thermal displacement amount storing means for storing a thermal displacement amount per unit time measured by the thermal displacement amount measuring means; and a NC machine tool based on the thermal displacement amount of the spindle measured by the thermal displacement amount measuring means. Correction amount determining means for determining a correction amount for shifting the machine coordinate system; and a correction command for outputting a correction command for shifting the machine coordinate system to the NC device based on the correction amount determined by the correction amount determining means. Means, the correction amount determination means compares the previous thermal displacement amount stored in the thermal displacement amount storage means with the current thermal displacement amount measured by the thermal displacement amount measuring means, Thermal displacement now If the thermal displacement amount is larger than the thermal displacement amount, the correction amount is determined based on the current thermal displacement amount.If the current thermal displacement amount is larger than the previous thermal displacement amount, the correction amount is determined based on the previous thermal displacement amount. A thermal displacement compensating device for an NC machine tool to be determined. 2. The correction commanding means divides the correction amount determined by the correction amount determining means, and outputs a correction command based on the divided correction amount a plurality of times before the next measurement of the thermal displacement amount. 2. The method according to claim 1, wherein the output is sequentially performed over
3. The thermal displacement compensating device for an NC machine tool according to claim 1. 3. The NC machine according to claim 1, wherein the correction command means does not output a correction command when the NC machine tool is performing a specific processing or during automatic tool change. Machine thermal displacement compensation device.