KR101401848B1 - Main axis head displacement revision method of machine tool - Google Patents

Abstract

The present invention relates to a method of compensating a spindle head displacement of a machine tool, wherein a final origin correction value ( Z _n ) is calculated by summing a movement value ( Z _th ) by thermal displacement and a movement value (δ _A ) a method for correcting a spindle head displacement of a machine tool, the spindle head 40, first, the input stage receiving the current temperature (T _n) from the second main spindle temperature sensor (S120) is installed on, the current temperature (T _n) and a determination step of determining comparing previous temperature calculating step (S160), difference in temperature (Δ T _n) and (Δ T _mAX) the maximum allowable difference between the temperature to calculate a difference between the temperature (Δ T _n) in (T _n-1) ( S170), an alternative step S180 of replacing the currently measured temperature value T _n with the previous measured temperature value T _n-1 if the difference temperature T _n is high in the determination step S170, ( J ) in the data table to which the currently measured temperature value T _n belongs after the difference temperature? T _n is low in step S170 or after the replacement step S180, And a thermal displacement calculation step (S200) of calculating a thermal displacement (δ _{E, n} ) with respect to a temperature value ( T _n ) by linear interpolation _{, wherein the} thermal displacement (δ _{E, , n)} is the movement value (Z _th) is calculated on the basis of.

 Machine tool, spindle, spindle head, thermal displacement, compensation

Description

[0001] The present invention relates to a method for correcting head displacement of a machine tool,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for correcting displacement of a spindle head of a machine tool, and more particularly, to a method of correcting a displacement of a spindle head of a machine tool by effectively controlling thermal displacement and axial movement of the spindle head The present invention relates to a method for correcting a displacement of a spindle head of a machine tool.

In general, machining accuracy of a machine tool is influenced by the errors caused by the assembled state and the geometric state of each component constituting the machine tool.

In addition, machining accuracy of a machine tool is affected by cutting heat generated during machining of the workpiece, heat generated by high-speed rotation of the spindle, and frictional heat caused by repetitive transfer of the feed shaft and thermal deformation error due to ambient temperature changes.

As described above, the thermal deformation error is largely influenced by the machining error as compared with the geometrical error of the machine tool, and is largely due to the thermal deformation error occurring in the machine tool.

That is, the above-described spindle head causes axial displacement due to centrifugal force and heat generation due to high-speed rotation, and causes a large machining error in a machine tool requiring micrometer-level accuracy.

Further, in the case of a static preload that does not restrict the position of the bearing, axial displacement of several tens of micrometers occurs instantaneously due to high-speed rotation, thereby causing a problem of scratches in the workpiece.

Therefore, the technical problem to be solved by the present invention is to prevent the machining accuracy of the workpiece from being lowered due to an error component caused by the inconsistency of the time constants of the temperature and the thermal displacement in the case of the high-speed spindle, Wherein the surface roughness of the spindle head is compensated by the machining method.

Another object of the present invention is to compensate for the displacement component due to axial movement immediately at the predicted moment, and the component due to the thermal cause to gradually change with time. Therefore, And a method of compensating a spindle head displacement of a machine tool.

The present invention has been made in view of the above problems, and it is an object of the present invention to at least partially solve the problems in the conventional arts. There will be.

According to an aspect of the present invention, there is provided a method for correcting headstock displacement of a machine tool, the method comprising the steps of: calculating a displacement value Z _th by a thermal displacement and a displacement value δ _A by an axis shift, (42) provided on the main spindle head (40) to calculate a final origin correction value ( Z _n ) by summing the current spindle head position An input step (S120) of inputting a temperature ( T _n ); The calculation step of calculating the current temperature (T _n) and a previous temperature difference between the temperature (Δ T _n) in _{(T n-1) (S160} ); A determining step (S170) of comparing the difference temperature ( ΔT _n ) with a maximum allowable difference temperature ( ΔT _MAX ); Replacing the currently measured temperature value T _n with a previous measured temperature value T _{n -1} if the difference temperature T _n is high in the determining step S 170; A data retrieval step of retrieving an index j from a data table to which the currently measured temperature value T _n belongs after the difference temperature? T _n is low or after the replacement step S180 in the determining step S170; (S190); And a step of calculating thermal displacement (S200) for calculating the temperature value, thermal displacement (δ _{E, n)} for the (T _n) by a linear interpolation; including and to the mobile based on the thermal displacement (δ _{E, n)} The value Z _th may be calculated to correct the spindle head displacement of the machine tool.

The calculation of the moving value (? _A ) by the axis shift may be performed by measuring (S600) the variable spindle rotational speed ( S _n ) of the main spindle; The measured spindle rotation speed _(n S) data search step of searching for the value of the index (j) in the data table belongs (S610); And calculating a movement value (? _A ) of an axis shift with respect to the main shaft rotation number ( S _n ) (S170). The movement value (? the moving value Z _th is calculated on the basis of the thermal displacement δ _A and the thermal displacement δ _{E, n} , thereby correcting the spindle head displacement of the machine tool.

Further, the step of correcting the displacement spindle head, the thermal displacement (δ _{E, n)} is a step (S700) are calculated by reading the thermal displacement correction values obtained (δ _{E, n)} from a; _A step (S710) of reading an axis shift correction value calculated from the movement value (? _A ) by the axis shift; A step (S720) of reading the previous thermal displacement origin correction amount ( Z _{th, n-1} ); (S730) comparing and comparing the thermal displacement origin correction amount ( Z _{th, n-1} ) with the thermal displacement correction value (? _{E, n} ); If the thermal displacement origin correction amount ( Z _{th, n-1} ) and the new correction value (? _{E, n} ) do not fluctuate, calculating (S740) the final origin correction value ( Z _n ); And performing an origin correction function from the final origin correction value ( Z _n ) (S780), thereby correcting the spindle head displacement of the machine tool.

Also, the comparison determination (S730) step thermal displacement origin correction amount (Z _{th, n-1)} and the new correction value (δ _{E, n)} is if the variation, the thermal displacement origin correction amount (Z _{th, n-1)} in which and a new correction value (δ _{E, n)} which value is no comparison is determined by thermal displacement origin correction amount (Z _{th, n-1)} the new correction value is greater is greater than (δ _{E, n)} in the smoothed gain (K) (S760), and if it is small, incrementing the number by a predetermined unit (S750 to S770).

The details of other embodiments are included in the detailed description and drawings.

In the spindle head displacement compensation method of a machine tool according to an embodiment of the present invention as described above, the time constant of the temperature and the thermal displacement do not coincide with each other in the case of the high speed spindle, It is possible to prevent the accuracy from being deteriorated, and also it is possible to maintain a good surface roughness when the work is machined by generating a correction command by calculating the amount of thermal displacement.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings.

Like reference numerals refer to like elements throughout the specification.

Hereinafter, a configuration of a spindle head of a machine tool according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an exemplary view for explaining an example of a machine tool, and FIG. 2 is an exemplary view for explaining a configuration of a spindle head. FIG.

1, the machine tool is provided with a column 20 on the rear side of the bed 10, a table 30 on the upper side of the bed 10, and a spindle head 40 .

The bed temperature sensor 11 may be disposed in the bed 10 and the first and second main shaft temperature sensors 41 and 42 may be disposed at positions spaced vertically from the main shaft head 40 A servomotor 50 is disposed on one side of the above-described column 20 to drive a spindle disposed on the spindle head 40 described above.

The CNC control device 60 is disposed in the machine tool and the resultant values measured by the bed temperature sensor 11 and the first and second main shaft temperature sensors 41 and 42 described above are controlled by the CNC control And is sent to the apparatus 60, and the above-described servo motor 50 is controlled by calculating the resultant value in the above-described CNC control device 60.

The structure of the spindle head 40 will be described in more detail with reference to FIG.

In the spindle head 40, a spindle 45 is rotatably disposed inside the head body 43 by bearings 44 arranged on the upper and lower sides.

The motor rotor 46 is provided on the spindle 45 and the motor stator 47 is provided on the inside of the head body 43. The motor rotor 46 and the motor stator 47 The spindle 45 can be rotated.

2, the first spindle temperature sensor 41 may be provided below the head body 43, and the second spindle temperature sensor 42 may be disposed below the head body 43, .

In the machine tool constructed as described above, displacement (delta) of the tip of the pivot shaft is unavoidably caused by centrifugal force, frictional heat or the like due to rotation of the main shaft as shown in Fig.

One of the displacements (δ) is the axial shift, which is caused by the increase of the outer ring pressure due to the centrifugal force of the ball of the bearing (44) and the expansion of the inner ring The centrifugal force acts on the ball as the main shaft rotates as a resultant component, and a pressure is applied to the outer ring.

In the static preload bearing structure, the bearing outer ring, which can freely move axially according to the pressure applied to the outer ring, is moved in the direction of the center of the main spindle simultaneously with rotation.

In particular, the axial movement displacement component is a displacement component that occurs transversely with the spindle rotation, and should be controlled separately from the thermal displacement correction based on the temperature.

The other of the above-mentioned displacements? Is a thermal displacement due to a rise in temperature, and this thermal displacement is a component that gradually changes with the lapse of time.

When the correction for the thermal displacement is performed, the surface of the workpiece may be scratched if the predicted correction amount is temporarily corrected.

FIG. 3 is a graph showing the measured thermal displacement of the high-speed spindle. In FIG. 3, there is a small spike Sp when looking at the main spindle displacement at the fourth hour after the rotation after 20,000 rpm.

4 is a graph showing an example in which thermal displacement correction is performed, and is an example of correction based on data values measured by the first and second spindle temperature sensors 41 and 42. FIG.

4, δ is the actual spindle displacement, δ _A is the displacement prediction through the first spindle temperature sensor 41, and δ _B is the displacement prediction through the second spindle temperature sensor 41.

The predicted value by the first spindle temperature sensor 41 is predicted and corrected faster than the actual spindle displacement to generate the error e _A and the second spindle temperature sensor 42 predicts and corrects the actual spindle displacement more slowly than the actual spindle displacement, e _B ). < / RTI >

That is, since the time constant of the temperature increase and the displacement increase are different from each other, an error occurs in the transient state, and scratches may occur on the surface of the workpiece, particularly as shown in FIG.

In other words, when correction is performed only considering temperature increase and displacement increase, accurate correction can not be made, and in particular, the surface roughness of the workpiece may be partially roughened.

6, when the temperature is measured, the correction calculation is used in a state in which the abnormal value due to the external electrical interference (noise) is not removed, so that the spike Sp is generated Or does not filter out minutely fluctuating temperature measurements, resulting in vibrations.

FIG. 7 is a graph for explaining the dwell time according to the time constant difference, and FIG. 8 is a graph for explaining an example in which the error according to the time constant difference applied to the present invention is improved.

FIG. 9 is a flowchart for explaining the calculation of the thermal displacement according to the temperature variation to which the present invention is applied. Here, the thermal displacement calculation section can be used as a basic data of the temperature-column data table shown in FIG. 15 of the accompanying drawings.

The above-described temperature-thermal displacement data table shown in FIG. 15 can be separately configured according to the number of temperature sensors, and in the present invention, the temperature-thermal displacement data table shown in FIG.

10 is a flowchart for explaining calculation of a delay correction value to which the present invention is applied, and the rotation number-delay correction value table shown in FIG. 16 of the accompanying drawings can be used as a basic data.

16 may be separately configured according to the number of revolutions. In the present invention, the delay correction value is determined in advance for various revolutions, for example.

Fig. 11 is a flowchart for explaining smoothing calculation of the thermal displacement command value to which the present invention is applied. In this case, as the basic data, the rpm-temperature time constant gain data table and the rpm- A gain minimum value data table can be used.

FIG. 12 is a flowchart for explaining the calculation of the axis movement to which the present invention is applied. Here, the axis-shift calculation section can be used as a basic data of the rotation-axis movement data table shown in FIG.

13 is a graph for explaining an example of the correction to which the present invention is applied.

FIG. 14 is a flowchart for explaining a correction amount command method to which the present invention is applied. The correction value command method portion is a portion for determining a command value for driving the servo motor in the configuration of the present invention.

Hereinafter, the operation of the spindle head displacement correction method of the machine tool according to the embodiment of the present invention will be described.

1 can be expressed by the following equation (1) when the thermal displacement? Is estimated by measuring one temperature value T by the first spindle temperature sensor 41 shown in FIG.

For bars with linear thermal expansion, the thermal expansion can be calculated by multiplying the temperature rise, the thermal expansion coefficient and the length, and the coefficient (a) corresponds to the product of the thermal expansion coefficient and length.

In addition, as shown in FIG. 2, when correction is performed using the two temperature values ( T0 , T1 ) by the first and second main shaft temperature sensors 41 and 42, it can be expressed by the following equation (2).

That is, the above equation can be used when the temperature fluctuation of two points affects the displacement of the main shaft tip.

In addition, since the expression of the temperature value represents the absolute value rather than the relative temperature variation, it is possible to calculate the thermal displacement separately at low temperature and at high temperature. If the temperature state is the same, An estimate can be obtained.

That is, by adding the respective column displacements based on the two data tables, the final thermal displacement correction value is obtained in consideration of the sign.

On the other hand, if the difference between the reference temperature T0 of the bed temperature sensor 11 in the bed 10 and the head temperature T1 of the first spindle temperature sensor 40 is corrected, (3) and (4).

At this time, coefficients having opposite sign to each other are inputted to the data table.

As described above, when the data table is corrected using the temperature-thermal displacement relation, the roughness of the surface of the workpiece can be smoothly displayed in a state where the temperature does not fluctuate greatly, but when the temperature suddenly changes, do.

This is because the temperature value is multiplied by the coefficient obtained from the data table as shown in Equations (2) and (4) described above, so that errors may occur when the time constants of the thermal displacement and the temperature increase are different.

The situation in which an error occurs in the transition period according to the above-mentioned time constant difference is shown in Fig.

And if in Fig. 7 is used to heat the displacement δ and δ _A are faster than the thermal time constant displacement point temperature, δ _B is if the time constant is a slow temperature point.

Also, assuming that the magnitude of the thermal displacement is 1, the errors can be expressed as e _A and e _B , respectively.

In the case of using a temperature point having a time constant higher than that of the thermal displacement, it is possible to easily reduce the error. If the time is adjusted by using the ratio of the thermal displacement and the time constant, the following equation (5) Lt; / RTI >

Where t is the time, τ is the thermal time constant, τ _A is the temperature point A temperature time constant, and τ _B is the temperature point B temperature time constant.

At this time, if the time constant is faster than the time constant of thermal time constant, it is comparatively easy to solve by using the time constant ratio, but if it is slow, a separate method should be provided since it does not know the future data.

To this end, the final thermal displacement prediction value? Is calculated by adding the delay correction value? _D to the thermal displacement? _T according to the existing temperature-to-thermal displacement data table.

The delay correction value? _D described above can increase the accuracy of the prediction by using an exponential function as shown in the following Equation (6).

Here,? _{D and I} are initial values of the delay correction value, and can be easily programmed as shown in Equation (7) as a difference form.

Here, G is a change gain (Gain) and has a correlation as shown in Equation (8) below.

Where τ _s is the sampling time of the digital control system and can be used, for example, 1 second for thermal displacement correction.

The thermal displacement calculated using the delay correction value is finally smoothed to determine the value used in the actual correction command.

The smoothing is suitably performed using the following exponential smoothing, and the gain K _n is set to a numerical value that changes from the change in the number of rotations to minimize the time delay due to smoothing. 9.

Where δ _{E, n} is a smoothed value and is entered into the correction command section.

K _n is a value between 0 and 1, and the closer to 1, the smaller the averaging effect. In case of 1, the averaging is not performed, but the time delay due to smoothing does not occur. This will be described with reference to FIG. 8 attached hereto.

FIG. 8 shows the error e _B of FIG. 7 according to various calculation conditions, where a is an error when a constant gain is used, and b is a case where the gain is varied.

As the method of variation, the gain is exponentially decreased with time, and the prediction error is reduced by varying the gain with time.

Also, c is the case of adding the delay correction value (δ _d ) to improve the transient follow-up, and the thermal displacement can be predicted through the temperature measurement with the smallest error.

In the case of the axial shift, since the phenomenon appears immediately at a constant value with respect to the change in the number of revolutions, the amount of movement of the shaft according to the number of revolutions is simply calculated based on the data table of FIG. 19 without applying any other smoothing function.

9 is a diagram for explaining a process of calculating a thermal displacement according to a temperature variation, which starts with checking the state of the temperature input module reading the temperature (S100).

And whether or not the measured temperature is the temperature abnormality warning value is checked first (S110).

If the temperature measured in the temperature input module status checking step S100 is within the normal range, the process goes to the next step S120. If an abnormality occurs in the measured temperature value, And terminates.

The function abnormality warning (S130) may be a form that can be recognized visually or audibly, and can transmit an electric signal to the CNC control device (60).

When one or more steady state in the presence or absence determination step (S110) described above to read the current temperature (T _n) (S120).

The current temperature (T _n) is the best temperature range allowed (T _MAX) temperature value whether or not determined (S140), and the current temperature (T _n) is the maximum temperature range (T _MAX) is higher than generating a warning over the temperature in (S150 If the present temperature T _n is lower than the maximum temperature range T _MAX , the process proceeds to the next step S160.

That is, the previously calculated temperature (T _n-1) and the temperature difference (Δ T _n) of the current temperature (T _n) (S160).

Then, the difference in temperature (Δ T _n) and the maximum allowed difference in temperature (Δ T _MAX) of comparison is determined (s170) and the difference temperature (Δ T _n) is high, discard the current measured temperature value (T _n) of the previous measured temperature value replacement (S180) to (T _n-1) to move on to the next step (S190).

If the difference temperature? T _n is lower than the difference temperature? T _n and the maximum allowable difference temperature? T _MAX , the currently measured temperature value T _n is maintained, (S190).

At this time, the spike (Sp) of the predicted thermal displacement as shown in FIG. 6 of the accompanying drawings can be effectively removed.

Then, the current temperature value ( T _n ) in the temperature-column data table shown in FIG. 15 is searched for the index j (S 190).

Thereafter, the thermal displacement (δ _{E, n} ) with respect to the current temperature value ( T _n ) is calculated by the linear interpolation method (S200) and the process is terminated.

FIG. 10 is a flow chart for calculating a delay correction value to be added to the thermal displacement with temperature.

First, the main spindle rotational speed S _n is read ( S 300), and the previous main spindle rotational speed S _n-1 is compared with the currently measured main shaft rotational speed S _n (S310) .

If there is no change in the previous main spindle revolution number S _n-1 and the currently measured main spindle revolution number S _n in the above-described S310 step, 隆 _d ( _n ) is calculated using the rotation number-temperature time constant gain data table shown in Fig. The variation gain G is calculated (S320).

Also, the number before the main shaft rotation in the S310 step above (S _n-1) and the rotation speed main shaft of the currently measured (S _n) when there is a change spindle can rotate the index (j) in the data table belongs to (S _n) of (S330).

Then, the delay correction value initial value? _{D, I} value for the main shaft rotation number S _n is calculated (S340).

Then, the delay correction value? _{D, n} is initialized (S350), and the process proceeds to step S320 described above, and the? _D change gain G is calculated (S320) using the rotation number-temperature time constant gain data table shown in FIG.

Thereafter, the delay correction value? _{D, n} due to the exponential decay is calculated (S360) and the process ends.

11 is a flowchart showing a process of smoothing the thermal displacement command value.

First reads the count the total thermal displacement (δ _n) (S400), and the main shaft rotation number (S _n) (S410).

Thereafter, it is determined whether there is a variation by comparing the currently input spindle revolution speed S _n with the previous spindle revolution speed S _n-1 (S420).

If the result of the determination of the presence or absence of the fluctuation of the spindle rotation speed S _n described above (S420) fluctuates, the process goes to the step of calculating the gain F of the gain K change (S430).

If there is no change in the result of the presence or absence of the fluctuation of the main shaft speed S _n (S420), the smoothing gain K is initialized (S440).

After the smoothing gain K is initialized (S440), the index j is searched for in the data table to which the main shaft rotation number S _n belongs (S450).

Thereafter, the smoothed gain minimum value K _MAX for the main shaft rotation number S _n is calculated (S460) and the gain F of the gain K change is calculated (S430).

Then, the gain K _n by the exponential decay is calculated (S470).

The comparison determines (S480) the gain (K _n) and gain Min (K _MAX) calculated by the above-described sense posts index.

If the gain K _n calculated by the exponentiation is smaller than the gain minimum value K _MAX in the result of the comparison (S480), the gain K _n by the exponential reduction is calculated (S500) and the process is terminated .

If the above-described comparison determination (S480), calculated by the exponential decrease post on a result of the gain (K _n) is larger gain Min (K _MAX) to fixed (S490) and, after a sense index post than the gain Min (K _MAX) the gain (K _n) is calculated by (S500) and ends.

Next, in order to change the gain K _n , it is checked whether or not the spindle revolution speed fluctuates.

When the number of revolutions has changed, the gain is initialized and the lower limit value of the gain is determined according to the rotation number-smoothed gain minimum value data table shown in Fig.

In determining the gain F , a table of the number-of-rotations-temperature temporal gain data of Fig. 17 can be used.

The gain ( K _n ) is calculated by using the exponential decreasing formula, and then the smoothed thermal displacement prediction value (δ _{E, n} ) is finally obtained.

12 is a flowchart showing an algorithm for calculating an axial shift, and a data value required for the axial movement calculation is obtained by performing linear interpolation using the rotation-axis shift data table of FIG. 19 And calculates an axial movement correction amount? _A at a specific number of revolutions.

The calculation of the above-described axial shift will be described in more detail with reference to FIG.

First, the main shaft rotation number S _n is read (S600) and the index j is searched in the data table to which the main shaft rotation number S _n belongs (S610).

Thereafter, the axial movement correction amount? _A for the main shaft rotation number S _n by linear interpolation is calculated (S620).

As described above, the thermal displacement prediction value? _{E, n} and the axial movement correction value? _A are calculated, and an actual correction command is made based on the final calculated result, .

14 is a flowchart showing an example in which actual correction is performed in the spindle head.

Thermal displacement, unlike axial shift, occurs during continuous surface machining and has the property of increasing or decreasing with time.

Accordingly, when the calculated thermal displacement prediction value (? _{E, n} ) is corrected all at once by the same method as the axial shift, there is a fear that the machined surface is scratched.

As an example, if a sudden transfer of 2 占 퐉 occurs in the direction of the main axis, scratches appear in the shape of a line, which is apparently visible to the naked eye.

In order to minimize this phenomenon, it is necessary to use the time dispersion correction and reduce the correction unit as shown in Fig. 13 for the thermal displacement correction.

The time dispersion correction refers to the correction of the unit correction amount by a certain period of the calculated correction value.

In the case where the thermal displacement correction value is estimated to be 10 mu m, and the unit correction amount is 1 mu m and the correction period is 1 second, the total correction is performed by 1 mu m every 1 second.

Of course, until the end of the calibration, the thermal displacement estimate is continuously calculated, followed by the time variance correction, and the unit correction amount is corrected at every calibration period.

The correction period should be determined so as to sufficiently follow the thermal displacement generated at the time of high-speed rotation, and the unit correction amount is preferably the minimum amount that the machine can respond to.

The order in which the actual correction is performed will be described with reference to FIG.

First, the smoothed thermal displacement correction value? _{E, n} and the axis shift correction value? _A are read (S700) (S710), and the previous thermal displacement origin correction amount Z _th, (S720).

Next, the thermal displacement origin correction amount ( Z _{th, n-1} ) and the new correction value? _{E, n} are compared with each other (S730).

The final origin correction value Z _n is calculated in step S740 if the thermal displacement origin correction amount Z _{th, n-1} and the new correction value? _{E, n} do not fluctuate in the comparison determination step S730 _, do.

If the above-described comparison determination (S730) thermal displacement origin correction amount in the step of (Z _{th, n-1)} and the new correction value (δ _{E, n)} (Z _th is if there is fluctuation, the thermal displacement origin correction _{value, n-1} ) And the new correction value (? _{E, n} ) is larger (S750).

If the thermal displacement origin correction amount Z _{th, n-1} is larger than the new correction value? _{E, n} in the comparison determination step S750, the smoothing gain K is initialized (S760) Z _n ) is calculated (S740).

If small, as long as one of the correction unit of thermal displacement origin correction amount than the thermal displacement home position correction amount (Z _{th, n-1)} the new correction value (δ _{E, n)} in the step of the above-described comparison determination (S750) (Z _th) (S770), and then the final origin correction value Z _n is calculated (S740).

After the final origin correction value Z _n is calculated (S740) as described above, the origin correction function is performed (S780).

Therefore, the final origin correction value Z _n is a final command value input to the CNC origin moving function in an integer unit. Accordingly, the servomotor 50 receives a command to move the transfer system, and the origin moving value Z _n is a thermal displacement movement value (Z _th) and the moving shaft is made by the sum of the movement values (δ _a) by (axis shift).

Further, as shown in Fig. 13, the movement value ( Z _th ) by the thermal displacement is subjected to time dispersion correction, and the axis shift (Axis shift) is immediately corrected.

As described above, when the workpiece is subjected to the correction by the spindle head displacement correction method of the machine tool according to the embodiment of the present invention, the surface of the workpiece is smoothly processed as shown in Fig.

On the other hand, FIG. 20 shows the measurement of axial movement of the machine tool, and the data are shown in the table below as a table.

On the other hand, FIG. 21 is a graph showing changes in the rotational speed of the main shaft before the correction of the axial movement (black) and after the correction of the axial movement (gray) at 10,000 rpm, 20,000 rpm and 30,000 rpm Results.

As shown in FIG. 21, it can be seen that the state after the correction is smoother in the change of the displacement (占 퐉) over time than in the state before the correction. At this time, And the component that gradually changes in the gray graph after correction is the thermal displacement component.

FIG. 23 shows the temperature variation and the displacement graph by measuring the temperature and the displacement when the main shaft rotation number is changed as shown in FIG. 22 after correcting the axis shift.

23, the temperature-thermal displacement data table as shown in Table 2 below can be created.

FIG. 24 shows a graph before and after correction according to the spindle rotation cycle of FIG.

The thermal displacement after correction shows a small value, and thus a smooth surface can be obtained as shown in FIG. 25.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. will be.

It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

The spindle head displacement compensation method of the present invention can be applied to a machine tool in which the main axes are arranged in the vertical direction. Especially, since variables such as spikes are generated and abrupt correction can be avoided, It can be processed smoothly and precisely.

1 is an exemplary view for explaining an example of a machine tool.

2 is an exemplary view for explaining the configuration of the spindle head.

3 is a graph for explaining an example of a main shaft displacement of the spindle head.

4 is a graph for explaining an example for correcting thermal displacement of the spindle head.

5 is a photograph showing an example of processing by applying thermal displacement correction of the spindle head.

6 is a graph for explaining vibration due to a spike due to an abnormal value and a correction command.

Fig. 7 is a graph for explaining the oocyte according to the time constant difference.

FIG. 8 is a graph for explaining an example in which the error according to the time constant difference applied to the present invention is improved.

FIG. 9 is a flowchart for explaining the calculation of the thermal displacement according to the temperature variation to which the present invention is applied.

FIG. 10 is a flowchart for explaining a delay correction value calculation to which the present invention is applied.

11 is a flowchart for explaining smoothing calculation of a thermal displacement command value to which the present invention is applied.

Fig. 12 is a flowchart for explaining the calculation of the axis shift to which the present invention is applied.

13 is a graph for explaining an example of the correction to which the present invention is applied.

FIG. 14 is a flowchart for explaining a correction amount command method to which the present invention is applied.

15 to 19 are data tables for explaining data applied to the present invention.

FIG. 20 is a graph for explaining the displacement amount to which the present invention is applied and which is axially moved according to the number of revolutions.

21 is a graph for explaining the axial movement correction to which the present invention is applied.

22 is a graph showing the spectrum of the spindle rotation to which the present invention is applied.

23 is a graph for explaining an example of determining the thermal displacement correction coefficient to which the present invention is applied.

24 is a graph for explaining an example of thermal displacement correction to which the present invention is applied.

25 is a photograph showing a surface of a workpiece processed by applying the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS (S)

10: Bed 11: Bed temperature sensor

20: Column 30: Table

40: spindle head 41, 42: first and second spindle temperature sensors

43: head body 44: bearing

45: spindle 46: motor rotor

47: motor stator 50: servo motor

60: CNC control device

Claims (4)

_A method of correcting the spindle head displacement of the machine tool by calculating the final origin correction value Z _n by summing the movement value by thermal displacement ( Z _th ) and the movement value (隆_A ) by axis shift As a result, An input step (S120) of receiving the current temperature ( T _n ) from the first and second main spindle temperature sensors (41) and (42) provided on the spindle head (40); The calculation step of calculating the current temperature (T _n) and a previous temperature difference between the temperature (Δ T _n) in _{(T n-1) (S160} ); A determining step (S170) of comparing the difference temperature ( ΔT _n ) with a maximum allowable difference temperature ( ΔT _MAX ); Replacing the currently measured temperature value T _n with a previous measured temperature value T _{n -1} if the difference temperature T _n is high in the determining step S 170; A data retrieval step of retrieving an index j from a data table to which the currently measured temperature value T _n belongs after the difference temperature? T _n is low or after the replacement step S180 in the determining step S170; (S190); And And a thermal displacement calculation step (S200) of calculating a thermal displacement (? _{E, n} ) with respect to a temperature value ( T _n ) by a linear interpolation method, And the moving value ( Z _th ) is calculated based on the thermal displacement (? _{E, n} ) to correct the headstock displacement of the machine tool. The method according to claim 1, The calculation of the moving value (? _A ) by the axis shift is carried out, The number of revolutions of the main spindle to change the main axis at step (S600) to (S _n) to read the measurement; The measured spindle rotation speed _(n S) data search step of searching for the value of the index (j) in the data table belongs (S610); And _A step (S170) of calculating a shift value (? _A ) of an axis shift with respect to the main shaft rotation number ( S _n ); And the moving value Z _th is calculated on the basis of the movement value δ _A by the axis shift and the thermal displacement δ _{E, n} obtained through the calculation, A method for compensating displacement of a spindle head of a machine tool. 3. The method of claim 2, The step of correcting the spindle head displacement includes: Step to the thermal displacement (δ _{E, n)} calculated by reading the thermal displacement correction values obtained (δ _{E, n)} from (S700); _A step (S710) of reading an axis shift correction value calculated from the movement value (? _A ) by the axis shift; A step (S720) of reading the previous thermal displacement origin correction amount ( Z _{th, n-1} ); (S730) comparing and comparing the thermal displacement origin correction amount ( Z _{th, n-1} ) with the thermal displacement correction value (? _{E, n} ); If the thermal displacement origin correction amount ( Z _{th, n-1} ) and the new correction value (? _{E, n} ) do not fluctuate, calculating (S 740) the final origin correction value ( Z _n ); And Performing an origin correction function from the final origin correction value ( Z _n ) (S780); Wherein the displacement of the main spindle head of the machine tool is corrected. The method of claim 3, The comparison determines thermal displacement zero at (S730) step that the correction amount (Z _{th, n-1)} and the new correction value (δ _{E, n)} is if the variation, the thermal displacement origin correction amount (Z _{th, n-1)} and a new correction value (δ _{E, n)} which value is no comparison is determined by thermal displacement origin correction amount (Z _{th, n-1)} the new correction value is larger in the larger than reset the smoothed gain _{(K) (δ E, n} ) ( S760), and if it is smaller, incrementing it by one unit (S750 to S770); And correcting the displacement of the spindle head of the machine tool.

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