KR20090061690A - Main axis head displacement revision method of machine tool - Google Patents

Abstract

A main axis head displacement compensation method of the machine tool is provided, which maintains the surface roughness when processing machining. A main axis head displacement compensation method of the machine tool comprises: an input step(S120) that the present temperature is input from the first installed at the main axis head and second main axis temperature sensor; a calculation step(S160) calculating the difference temperature of the previous temperature and present temperature; a decision step(S170) comparing difference temperature and the maximum permissible difference temperature; a replacing step(S180) replacing the current temperature value with the previous temperature value; a data searching step(S190) searching index in data table; and a thermal deflection calculation step(S200).

Description

Main axis head displacement revision method of machine tool}

The present invention relates to a spindle head displacement correction method of a machine tool, and more particularly to effectively control the thermal displacement and axial movement of the spindle head of the machine tool to prevent scratches of the workpiece due to the spindle displacement when machining the workpiece. It relates to a spindle head displacement correction method of a machine tool.

In general, the machining accuracy of a machine tool is influenced by errors caused by the assembly and geometrical states of the components constituting the machine tool.

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

The thermal deformation error as described above is largely influenced by the machining error compared to the geometric error of the machine tool, and is mostly due to the thermal deformation error that occurs in the machine tool.

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

In addition, in the case of the static preload, which does not restrain the position of the bearing, there is a problem in that axial displacement of several tens of micrometers occurs instantaneously by high-speed rotation, and scratches occur in the workpiece.

Therefore, the technical problem to be achieved by the present invention is to prevent the workpiece machining accuracy from falling due to the error component caused by the temperature constant of the temperature and thermal displacement does not coincide with the high speed spindle, and calculates the amount of thermal displacement to compensate for the correction command. It is an object of the present invention to provide a spindle head displacement correction method of a machine tool for generating and maintaining a good surface roughness when machining a machine tool.

It is another object of the present invention to correct all displacement components due to axial movement immediately and at a predicted moment, and components due to thermal causes are components that gradually change with time, so that the correction values are gradually divided by time. It is an object of the present invention to provide a spindle head displacement correction method of a machine tool.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, another technical problem that is not mentioned can be clearly understood by those skilled in the art from the following description. There will be.

In order to achieve the above technical problem, a spindle head displacement correction method of a machine tool according to an embodiment of the present invention includes a shift value δ _A due to a shift value Z _th and an axis shift due to a thermal displacement. In the method for correcting the spindle head displacement of the machine tool by calculating the final zero point correction value ( Z _n ) by the summation, the current from the first and second spindle temperature sensors (41, 42) installed in the spindle head (40) An input step S120 of receiving a temperature T _n ; A calculation step (S160) of calculating a difference temperature ΔT _n between the current temperature T _n and the previous temperature T _n-1 ; A determination step (S170) of comparing and determining the difference temperature ΔT _n and the maximum allowable difference temperature ΔT _MAX ; A substitution step (S180) of replacing the current measured temperature value ( T _n ) with a previous measured temperature value ( T _n-1 ) if the difference temperature (Δ T _n ) is high in the determination step (S170); A data retrieval step of retrieving the index j in the data table to which the temperature value T _n currently measured after the difference temperature ΔT _n is low or after the replacement step S180 in the determination step S170. (S190); And a thermal displacement calculation step (S200) of calculating a thermal displacement (δ _{E, n} ) with respect to the temperature value ( T _n ) due to the linear interpolation, wherein the thermal displacement is calculated based on the thermal displacement (δ _{E, n} ). The movement value Z _th may be calculated to correct the spindle head displacement of the machine tool.

In addition, the calculation of the shift value δ _A by the axis shift includes the steps of: measuring and reading the fluctuating spindle speed S _{n of} the spindle; A data retrieval step (S610) of retrieving an index ( j ) from a data table to which the measured spindle speed ( S _n ) value belongs; And a step S170 of calculating a shift value δ _A of the axis shift with respect to the main shaft rotation speed S _n , wherein the shift value due to the axis shift obtained through this is obtained. Based on δ _A and the thermal displacement δ _{E, n} , the movement value Z _th is calculated to correct 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; Reading an axis shift correction value obtained by calculating from the shift value δ _A by the axis shift (S710); Reading the previous thermal displacement origin correction amount Z _{th, n-1} (S720); Comparing and determining the thermal displacement origin correction amount Z _{th, n-1} and the thermal displacement correction value δ _{E, n} (S730); Calculating a final zero point correction value ( Z _n ) if the thermal displacement zero point correction amount ( Z _{th, n-1} ) and the new correction value (δ _{E, n} ) do not change; And performing a home position correction function from the final home position correction value ( Z _n ) (S780).

In addition, if the thermal displacement origin correction amount Z _{th, n-1} and the new correction value δ _{E, n} vary in the step of comparing the determination S730, the thermal displacement origin correction amount Z _{th, n-1} . And the new correction value (δ _{E, n} ) is compared to determine which one is larger. When the thermal displacement origin correction amount ( Z _{th, n-1} ) is larger than the new correction value (δ _{E, n} ), the smoothing gain (K) is obtained. Initializing (S760) and increasing as much as one correction unit (S750 ~ S770) if it is small; may further include.

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

In the spindle head displacement correction method of the machine tool according to the embodiment of the present invention made as described above, in the case of a high speed spindle, the workpiece is processed by an error component generated due to a spike Sp because the time constant of temperature and thermal displacement does not coincide. It is possible to prevent the loss of accuracy, and to calculate the amount of thermal displacement to generate a correction command so as to maintain good surface roughness when machining the work piece.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

Like reference numerals refer to like elements throughout.

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.

1 is an exemplary view for explaining an example of a machine tool, Figure 2 is an exemplary view for explaining the configuration of the spindle head.

In the machine tool, as shown in FIG. 1, the column 20 is installed at the rear of the bed 10, the table 30 is disposed at the upper side of the bed 10, and the spindle head 40 is located in front of the column 20. ) Is placed.

The bed temperature sensor 11 may be disposed in the above-described bed 10, and the first and second spindle temperature sensors 41 and 42 may be disposed in the spindle head 40 at positions spaced vertically and downwardly, respectively. In addition, the servo motor 50 is disposed at one side of the above-described column 20 to drive the spindle disposed at the above-described spindle head 40.

In addition, the CNC machine 60 is arranged in the machine tool, and the resultant values measured by the above-described bed temperature sensor 11 and the above-mentioned first and second spindle temperature sensors 41 and 42 are CNC control described above. It is sent to the device 60, the above-mentioned CNC control device 60 to calculate the resulting value to control the above-described servo motor 50.

The configuration of the above-described spindle head 40 will be described in more detail with reference to FIG. 2.

The spindle head 40 is rotatably arranged in the head body 43 by the bearing 44 disposed on the upper and lower sides.

In addition, the above-mentioned spindle 45 is provided with a motor rotor 46, and the inside of the head body 43 is provided with a motor stator 47, the motor rotor 46 and the motor stator 47 Spindle 45 can be rotated by the interaction of

In addition, as shown in FIG. 2, the aforementioned first spindle temperature sensor 41 may be provided under the head body 43, and the second spindle temperature sensor 42 may include the motor stator 47. It may be provided on the side.

As shown in Fig. 1, the machine tool constructed as described above inevitably generates displacement δ at the tip of the axis due to centrifugal force, frictional heat, and the like caused by the spindle rotation.

Displacement (δ) generated in the case of the static preload high speed spindle has two components, and one of the displacements (δ) is an axis shift, which increases the outer ring pressure and the inner ring expansion due to the centrifugal force of the ball of the bearing 44. As the resultant component, as the main shaft rotates, centrifugal force is applied to the ball and pressure is applied to the outer ring.

In the hydrostatic preload bearing structure, the bearing outer ring which can be axially moved freely according to the pressure applied to the outer ring moves in the direction of the center of the main shaft at the same time as it rotates.

In particular, the axial movement displacement component is a displacement component that occurs transiently according to the rotation of the main shaft, and should be controlled separately from the thermal displacement correction based on the temperature.

The other one of the above-described displacements δ is thermal displacement with temperature rise, and this thermal displacement is a component that changes gradually over time.

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

FIG. 3 shows a small spike Sp, which is an axial shift measured at 4 hours, which is the point where the motor stops after 20,000 rpm rotation as a measure of thermal displacement of the high speed spindle. This is an axis shift.

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

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

The predicted value by the first spindle temperature sensor 41 predicts and corrects faster than the actual spindle displacement, thereby generating an error e _A , and the second spindle temperature sensor 42 predicts and corrects slower than the actual spindle displacement and corrects the error ( e _B ) can be seen.

That is, an error occurs in the transition period because the time constants of the temperature increase and the displacement increase are different, and in particular, scratches may occur on the surface of the workpiece as shown in FIG. 5.

That is, when the correction is made only by considering the temperature increase and the displacement increase, precise correction cannot be performed, and in particular, the surface roughness of the workpiece may be partially roughened.

Examples of the scratches as described above include the spike calculation caused by the use of the correction calculation in the state that the abnormal value due to external electric interference (noise) or the like is not removed during temperature measurement as shown in FIG. This phenomenon is caused by the vibration caused by filtering out the temperature measurement which is changed or is slightly changed.

Figure 7 is a graph for explaining the error according to the time constant difference, Figure 8 is a graph for explaining an example of improving the error according to the time constant difference to which the present invention is applied.

In addition, Figure 9 is a flow chart for explaining the thermal displacement calculation according to the temperature variation to which the present invention is applied, wherein the thermal displacement calculation portion may be used as a basic data using the temperature-thermal displacement data table shown in the accompanying drawings.

The above-described temperature-heat displacement data table shown in FIG. 15 may be configured separately according to the number of temperature sensors. In the present invention, as an example, the temperature-heat displacement data table is configured with heat displacement data preset for various temperatures.

10 is a flowchart illustrating the calculation of the delay correction value to which the present invention is applied, and the rotation speed-delay correction value data table shown in FIG. 16 may be used as the basic data.

The various types shown in Fig. 16 may be configured separately according to the rotational speeds. In the present invention, for example, the delay correction values are determined in advance for the various rotational speeds.

11 is a flow chart for explaining the smoothing calculation of the thermal displacement command value to which the present invention is applied, wherein the rotation speed-temperature time constant gain data table and the rotation speed-smoothing shown in the attached drawings FIGS. 17 and 18 as basic data are shown. A gain minimum data table can be used.

12 is a flowchart illustrating the calculation of the axis movement to which the present invention is applied. In this case, the rotational speed-axis movement data table shown in FIG. 19 may be used as the basic data.

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

14 is a flowchart for explaining a correction amount command method to which the present invention is applied, and a correction value command method part is a part for determining a command value for driving a servomotor in the configuration of the present invention.

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

When the thermal displacement δ is estimated by measuring one temperature value T by the first spindle misleading sensor 41 shown in FIG. 1, it may be represented by Equation 1 below.

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

In addition, as shown in FIG. 2, when two or more temperature values T0 and T1 are corrected by the first and second spindle temperature sensors 41 and 42, they may be expressed as Equation 2 below.

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

In addition, since the expression of the temperature value represents the absolute value rather than the relative temperature variation, the thermal displacement can be calculated separately at the low temperature and the high temperature, and if the temperature is the same, the absolute thermal displacement regardless of the operation of the machine An estimate can be obtained.

In other words, by summing the respective thermal 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 correction is based on 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, Equations 3 and 4 are the same.

At this time, coefficients having opposite signs to each other are input to the data table.

As described above, when correcting using the data table and the temperature-thermal displacement relationship, the surface roughness of the workpiece may appear smoothly in the state where the temperature does not fluctuate, but the error may occur greatly in the transient period in which the temperature fluctuates rapidly. do.

As shown in Equations 2 and 4, since the temperature value is multiplied by the coefficient obtained from the data table, an error may occur greatly when the time constant of the thermal displacement and the temperature increase is different.

The situation in which the error occurs during the transitional period according to the above-described time constant difference is shown in FIG. 7.

In FIG. 7, δ is a thermal displacement, δ _A is a case where a temperature constant is faster than a thermal displacement, and δ _B is a case where a temperature constant is slow.

In addition, it is assumed that the magnitude of the thermal displacement is 1, so that the errors may be represented by e _A and e _B , respectively.

In the case of using a temperature point whose time constant is faster than the thermal displacement, it is possible to easily reduce the error, and when the time is adjusted using the ratio of the thermal displacement and the time constant, it can be expressed by the following Equation 5. This becomes possible.

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

In this case, the time constant is faster than the time constant thermal displacement time constant, but it is solved relatively easily by using the time constant ratio, but when it is slow, the future data is not known, so a separate method should be provided.

For this purpose, the delayed correction value δ _d is added to the thermal displacement δ _T according to the existing temperature-thermal displacement data table to calculate the final thermal displacement prediction δ.

The above-described delay correction value δ _d may increase the accuracy of prediction by using an exponential function as shown in Equation 6 below.

Here, δ _{d, I} is the initial value of the delay correction value, and can be easily programmed by representing the difference in the following equation (7).

Here, G is change gain and has a correlation as shown in Equation 8 below, and it can be applied in actual use based on this value.

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

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

It is appropriate to use exponential smoothing as shown below, and gain K _n can also be set to a value that changes from the change of rotational speed to minimize time delay due to smoothing. 9 can be represented.

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

K _n uses a value between 0 and 1, and the closer it is to 1, the smaller the averaging effect becomes. This will be described with reference to FIG. 8.

8 illustrates 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 changed.

As a method of fluctuation, the gain is decreased exponentially with time, and the prediction error is reduced by changing the gain with time.

In addition, c is a case in which a delay correction value δ _d is added to improve transitional followability, and thermal displacement may be predicted through temperature measurement with the smallest error.

In the case of axis shift, since the phenomenon appears immediately as a constant value for the rotational speed variation, the axis shift amount according to the rotational speed is simply calculated based on the data table of FIG. 19 without applying a smoothing function.

9 is for explaining the process of calculating the thermal displacement according to the temperature fluctuation and starts by checking the state of the temperature input module for reading the temperature (S100).

Check whether there is an abnormality, and first check whether the measured temperature is a warning value of temperature abnormality (S110).

If the temperature measured in the step of checking the temperature input module state (S100) is within the normal range, the process proceeds to the next step (S120), and if an abnormality occurs in the measured temperature value, a malfunction warning (S130) is issued. Generate and exit.

Malfunction warning (S130) may be of a form that can be seen visually or hearing, and can transmit an electrical signal to the CNC control device (60).

When normal in the above-described abnormality determination step (S110), the current temperature ( T _n ) is read (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 current temperature ( T _n ) is lower than the maximum temperature range ( T _MAX ), and 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).

Thereafter, the difference temperature Δ T _n and the maximum allowable difference temperature Δ T _MAX are compared (s170), and when the difference temperature Δ T _n is high, the current measured temperature value ( T _n ) is discarded and the previous measured temperature is discarded. Substituting the value T _n-1 (S180) to the next step (S190).

In addition, when the difference temperature (Δ T _n ) and the maximum allowable difference temperature (Δ T _MAX ) are compared (s170) and the difference temperature (Δ T _n ) is low, the next measured temperature value ( T _n ) is maintained. Proceed to (S190).

At this time, it is possible to effectively remove the spike Sp of the heat displacement prediction value as shown in FIG.

Thereafter, the current temperature value T _n is searched for an index j in the temperature-heat displacement data table shown in FIG. 15 (S190).

After that, through the linear interpolation, the thermal displacement (δ _{E, n} ) with respect to the current temperature value ( T _n ) is calculated (S200) and ends.

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

First, read the spindle speed ( S _n ) (S300), compare the previous spindle speed ( S _n-1 ) with the currently measured spindle speed ( S _n ), and determine the delay correction value according to whether there is a variation (S310). Will be determined.

Number of previous main shaft rotation in the aforementioned S310 phase (S _n-1) and the number of revolutions shown in Fig. 17 when there is no change in the number of rotation the main axis of the currently measured (S _n) - δ by using a temperature time constant gain data table _d The change 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 Search for (S330).

After that, the delay correction value initial value δ _{d and I} values for the spindle speed S _n are calculated (S340).

After that, the delay correction value δ _{d, n} is initialized (S350), and the process proceeds to step S320 described above to calculate the δ _d change gain G using the rotation speed-temperature time constant gain data table shown in FIG. 17 (S320).

After that, the delay correction value δ _{d, n} by the exponential reduction equation is calculated (S360) and ends.

Figure 11 shows a flow chart of smoothing the heat displacement command value.

First, the total heat displacement δ _n is calculated (S400), and the main shaft rotation speed S _n is read (S410).

Thereafter, by comparing the currently input spindle speed ( S _n ) and the previous spindle speed ( S _n-1 ) to determine whether there is a change (S420).

If the result of the above-described main shaft rotation speed ( S _n ) fluctuation determination (S420) is changed, the process proceeds to the step of calculating (S430) the gain ( F ) of the gain ( K ) change.

If the result of the above-described main shaft rotation speed ( S _n ) fluctuation determination (S420) does not change, the smoothing gain K is initialized (S440).

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

Thereafter, the smoothing gain minimum value K _MAX for the spindle speed S _n is calculated (S460), and the gain F of the gain K change is calculated (S430).

Thereafter, the gain K _n is calculated by the exponential reduction equation (S470).

The gain K _n calculated by the above-described exponential reduction _formula and the gain minimum value K _MAX are compared and determined (S480).

If the gain K _n calculated by the exponential reduction _formula is smaller than the gain minimum value K _{MAX in the} above-described comparison judgment (S480), the gain K _n by the exponential reduction _formula is calculated (S500) and ends. .

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) Calculate the gain ( K _n ) by (S500) and ends.

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

When the rotation speed is changed, the gain is initialized and the lower limit of the gain is determined according to the rotation speed-smoothing gain minimum value data table shown in FIG.

In determining the gain F , the rotation speed-temperature time constant gain data table of FIG. 17 may be used.

The gain K _n is calculated using the exponential reduction equation, and then the smoothed thermal displacement prediction value δ _{E, n} is finally obtained using the exponential reduction equation.

FIG. 12 is a flowchart illustrating an algorithm for calculating axis shift, and data values required for calculating the axis shift include linear interpolation using the rotation-axis shift data table of FIG. 19. Through the calculation of the axis shift correction amount δ _A at a specific rotation speed.

The above-described calculation of axis shift will be described in more detail with reference to FIG. 12.

First, the spindle speed S _n is read (S600), and the index j is searched (S610) in the data table to which the spindle speed S _n belongs.

Subsequently, the axis shift correction amount δ _A with respect to the spindle speed S _n due to linear interpolation is calculated (S620).

As described above, the thermal displacement prediction value δ _{E, n} and the axial movement correction value δ _A are calculated, and the actual correction command is made based on the final result value calculated as described above. It demonstrates with reference.

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

Thermal displacement, unlike Axis shift, occurs during continuous surface machining and is characterized by an increase or decrease with time.

Accordingly, when the calculated thermal displacement prediction values δ _{E and n} are simultaneously corrected in the same manner as Axis Shift, scratches may occur on the processed surface.

As an example, if a sudden transfer of 2 占 퐉 occurs in the direction of the main axis of the axis, a stripe-shaped flaw that is clearly visible to the naked eye occurs.

In order to minimize this phenomenon, in the case of thermal displacement correction, a time dispersion correction should be used as shown in FIG. 13 and the correction unit should be reduced.

The time variance correction refers to correcting the unit correction amount at a certain period of time.

For example, if the thermal displacement correction value is estimated to be 10 μm, the unit correction amount is 1 μm, and the correction period is 1 second, a total of 10 corrections are performed by 1 μm per second.

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

The calibration period should be determined to sufficiently follow the thermal displacements generated at high speeds, and the unit compensation should be the minimum that the machine can respond to.

Referring to FIG. 14, a procedure of performing actual correction will be described.

First, the smoothed thermal displacement correction value (δ _{E, n} ) and the axis shift correction value (δ _A ) are read (S700) (S710), and the previous thermal displacement origin correction amount ( Z _{th, n-1} ) is read. Read (S720).

Next, the above-described thermal displacement origin correction amount Z _{th, n-1} and the new correction value δ _{E, n} are compared and judged (S730).

If there is no change in the thermal displacement origin correction amount Z _{th, n-1} and the new correction value δ _{E, n in the} above-described comparison determination step S730, the final origin correction value Z _n is calculated (S740). do.

If the thermal displacement origin correction amount Z _{th, n-1} and the new correction value δ _{E, n} vary in the above-described comparison determination step S730, the thermal displacement origin correction amount Z _{th, n-1} ) And the new correction value δ _{E, n} to determine which value is larger (S750).

If the thermal displacement origin correction amount Z _{th, n-1} is greater than the new correction value δ _{E, n in the} above-described step of comparison determination S750, the smoothing gain K is initialized (S760) to obtain the final zero correction value ( 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) Increase (S770) and then calculate the final zero correction value ( Z _n ) (S740).

As described above, after the final zero point correction value Z _n is calculated (S740), the zero point correction function is performed (S780).

Therefore, the final zero point correction value ( Z _n ) is the final command value input to the CNC zero shift function and is in integer units. Accordingly, the servo motor 50 receives a command to move the feed system, and the zero shift value Z _n is the thermal displacement. It consists of the sum of the shift value Z _th by and the shift value δ _A by the axis shift.

In addition, as shown in FIG. 13, the shift value Z _th by the thermal displacement performs time-dispersion correction, and the axis shift is the immediate correction.

As described above, the surface of the workpiece is smoothly processed as shown in FIG. 25 when correction is performed by the spindle head displacement correction method of the machine tool according to an embodiment of the present invention.

On the other hand, as shown in the accompanying drawings as a measure of the axis movement of the machine tool, the data is shown in Table 1 as shown in Table 1.

On the other hand, Figure 21 is measured while changing the spindle speed in steps of 10,000rpm, 20,000rpm, 30,000rpm (between 1,000rpm) before the axis shift compensation (black) and after the axis shift correction (gray) The result is.

As shown in FIG. 21, it can be seen that the state after the correction is smoothed over time as the state after the correction is smoother than the state before the correction, and at this time, when the number of lines changes in the black graph before correction, the component shifts suddenly. The component that gradually changes in the gray graph after calibration is the thermal displacement component.

After the axis shift is corrected and the spindle speed is changed as shown in FIG. 22, the temperature and displacement graphs are shown by measuring the temperature and the displacement.

In FIG. 23, the slope value may be a temperature-thermal displacement data table as shown in Table 2 below.

24 is a graph before and after correction according to the main axis rotation cycle of FIG. 22.

After the correction, the thermal displacement shows a small value, thereby obtaining a smooth surface as shown in FIG. 25.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. will be.

Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is represented by the following detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

The spindle head displacement correction method of the machine tool according to an embodiment of the present invention may be applied to a machine tool in which the spindle axis is disposed in the vertical direction. In particular, a parameter such as a spike may be generated to abruptly compensate for the surface of the workpiece. 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 main shaft head.

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

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

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

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

7 is a graph for explaining an error according to a time constant difference.

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

9 is a flowchart illustrating a thermal displacement calculation according to the temperature variation to which the present invention is applied.

10 is a flowchart illustrating a delay correction value calculation to which the present invention is applied.

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

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

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

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.

20 is a graph for explaining a displacement amount axially moved according to the rotation speed to which the present invention is applied.

21 is a graph for explaining axis 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 a 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.

FIG. 25 is a photograph substituted for the drawing showing the surface of the workpiece to which the present invention is applied. FIG.

(Explanation of symbols for the main parts of the drawing)

10: Bed 11: Bed temperature sensor

20: column 30: table

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

43: head body 44: bearing

45: spindle 46: motor rotor

47: motor stator 50: servo motor

60: CNC controller

Claims (4)

In the method of correcting the spindle head displacement of a machine tool by calculating the final zero point correction value ( Z _n ) by the sum of the shift value Z _th and the shift value δ _A due to the thermal displacement. In An input step S120 of receiving a current temperature T _n from the first and second spindle temperature sensors 41 and 42 installed in the spindle head 40; A calculation step (S160) of calculating a difference temperature ΔT _n between the current temperature T _n and the previous temperature T _n-1 ; A determination step (S170) of comparing and determining the difference temperature ΔT _n and the maximum allowable difference temperature ΔT _MAX ; A substitution step (S180) of replacing the current measured temperature value ( T _n ) with a previous measured temperature value ( T _n-1 ) if the difference temperature (Δ T _n ) is high in the determination step (S170); A data retrieval step of retrieving the index j in the data table to which the temperature value T _n currently measured after the difference temperature ΔT _n is low or after the replacement step S180 in the determination step S170. (S190); And A thermal displacement calculation step (S200) of calculating a thermal displacement (δ _{E, n} ) with respect to the temperature value T _n by the linear interpolation; And the movement value ( Z _th ) is calculated based on the thermal displacement (δ _{E, n} ), including to correct the spindle head displacement of the machine tool. The method of claim 1, The calculation of the shift value δ _A by the axis shift is Measuring and reading fluctuating spindle speed ( S _n ) of the spindle (S600); A data retrieval step (S610) of retrieving an index ( j ) from a data table to which the measured spindle speed ( S _n ) value belongs; And Calculating a shift value δ _A of the axis shift with respect to the spindle speed S _n (S170); The movement value Z _th is calculated based on the movement value δ _A and the thermal displacement δ _{E, n} obtained by the axis shift. Displacement correction method for spindle head of machine tool to compensate displacement. The method of claim 2, Compensating the spindle head displacement, Step to the thermal displacement (δ _{E, n)} calculated by reading the thermal displacement correction values obtained (δ _{E, n)} from (S700); Reading an axis shift correction value obtained by calculating from the shift value δ _A by the axis shift (S710); Reading the previous thermal displacement origin correction amount Z _{th, n-1} (S720); Comparing and determining the thermal displacement origin correction amount Z _{th, n-1} and the thermal displacement correction value δ _{E, n} (S730); Calculating a final zero point correction value ( Z _n ) if the thermal displacement zero point correction amount ( Z _{th, n-1} ) and the new correction value (δ _{E, n} ) do not change; And Performing a zero point correction function from the final zero point correction value ( Z _n ) (S780); Spindle head displacement correction method of the machine tool for correcting the spindle head displacement of the machine tool, including. The method of claim 3, wherein If the thermal displacement origin correction amount Z _{th, n-1} and the new correction value δ _{E, n} change in the comparison determination step S730, the thermal displacement origin correction amount Z _{th, n-1} and the 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 increasing by one correction unit (S750 to S770) if small; Spindle head displacement correction method for a machine tool for correcting the spindle head displacement of the machine tool further comprising.

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