KR20210023107A - Method and apparatus for correcting thermal deformation of machine tool spindle, machine tools using the same - Google Patents

Abstract

According to the present invention, a bearing, at least one temperature sensor installed around the bearing to detect the ambient temperature of the bearing, and a cooling passage for circulating a cooling fluid around the bearing in order to suppress heat generation of the bearing are provided inside a spindle of a machine tool. For the thermal deformation compensation of the machine tool spindle, the correction amount for the thermal deformation of spindle is calculated according to a temperature value detected by the temperature sensor, but a thermal deformation correction range is divided into a heating section and a cooling section, and different formulas for calculating the heat deformation correction amount are applied to the heating section and the cooling section, but the deviation of the heat deformation correction amount does not occur.

Description

TECHNICAL FIELD [Method and apparatus for correcting thermal deformation of machine tool spindle, machine tools using the same}

The present invention relates to a method for correcting thermal deformation of a machine tool spindle, and more particularly, to a method and apparatus for correcting thermal deformation of a spindle that tracks heat generation and cooling of the spindle.

The machine tool is formed of a metal structure, and during operation, heat deformation occurs in the structure due to heat generation of the rotating part. As shown in FIG. 1, the spindle 20 installed in the column of the machine tool 10 rotates at a high speed by the bearing 40 installed therein to process the work. At this time, the rotational force of the spindle 20 rotates a tool (not shown) mounted at its tip through the bearing 40 built into the spindle 20. At this time, heat is generated in the bearing 40 supporting the spindle 20 in a rotating state, and this heat is conducted to the main body of the spindle 20 around the bearing 40.

In addition, heat generation of the bearing 40 increases according to an increase in the rotational speed and rotation time of the spindle 20, which is transmitted to the entire spindle 20. In this way, heat generation of the bearing 40 causes thermal deformation of the spindle 20, and the thermal deformation of the spindle 20 changes the relative distance between the tool installed at the tip of the spindle 20 and the workpiece, thereby reducing the machining accuracy of the workpiece. Results.

Therefore, in the correction of thermal deformation of the spindle 20 of the machine tool 10, the amount of thermal deformation of the spindle 20 is calculated, and the position of the spindle 20 is corrected by driving the actuator 60 by the calculated amount of thermal deformation. Is to give.

In order to correct the thermal deformation of the spindle 20, at least one temperature sensor 30 is installed around the bearing 40 inside the spindle 20, and the temperature sensor 30 in the numerical control device 70 A method of acquiring a value of, calculating the amount of thermal deformation of the spindle 20, and correcting the thermal deformation of the spindle 20 based on this has been used.

However, the calculation of the amount of correction for thermal deformation using the temperature sensor 30 is performed with the cooling flow path 50 installed to circulate the cooling fluid inside the spindle 20 or change the rotation speed or stop the rotation of the spindle 20. Due to the same various factors, it is not possible to satisfactorily correct the non-linear thermal deformation characteristics.

Hereinafter, a method for correcting thermal deformation commonly used in the machine tool 10 is introduced, and further, a problem thereof is examined.

A temperature sensor 30 is installed around the inner bearing 40 of the spindle 20 of the machine tool 10, and the temperature of the spindle 20 is detected through the temperature sensor 30. Based on the detected temperature data, the amount of correction for thermal deformation of the spindle 20 for each temperature section stored in advance in the numerical control device 70 is read, and the position of the spindle 20 is corrected by reflecting it in the numerical control device 70. By doing so, the thermal deformation of the spindle 20 according to the temperature is corrected.

However, the correction of the thermal deformation of the spindle 20 using the temperature sensor 30, as disclosed in Figs. 2 and 3, a sudden change in the rotational speed of the spindle 20 or a cooling channel inside the spindle 20 (cooling). line) (50), the thermal deformation is shown in a non-linear graph shape.

Therefore, the thermal deformation of the spindle 20, which appears in the form of a nonlinear graph, is the linear equation of Equation 1 below in the section corresponding to the usage environment in order to simplify the program coding of the thermal deformation correction algorithm and improve the reliability of the correction result value. It has been used by linear fitting.

(Equation 1) y = Σa _n (t _n -T _n )

Where y = correction amount, n = temperature sensor number, a _n = temperature sensor gain, t _n = temperature sensor data, T _n = temperature sensor offset.

However, in the correction of the thermal deformation of the spindle 20 according to Equation 1, there is a cooling channel 50 between the bearing 40 and the temperature sensor 30 installed near the tip of the spindle 20. Due to the cooling action, as disclosed in FIG. 3, a heating phase in which the spindle 20 rotates at a constant speed or higher to increase the temperature of the spindle 20 and the rotation of the spindle 20 The thermal deformation characteristics are changed in a cooling phase in which the temperature of the spindle 20 is stopped or rapidly decelerated, and at the same time, the temperature of the spindle 20 is lowered by the cooling passage 50.

Therefore, in the case where the heat distortion characteristics are different in the heating section and the cooling section as described above, different thermal distortion correction amount characteristic equations are applied in the heating section and the cooling section as shown in the following equation.

Heat distortion correction amount (Y)=G x H x C _heat

Cooling section heat distortion correction amount (Y)=G x H x C _cool

Here, G = gain value, H = temperature sensor value, C _heat = spindle heat deformation in the heating phase and the characteristic equation between the temperature sensor, C _cool = spindle heat deformation in the cooling phase and This is the characteristic equation between temperature sensors.

As described above, by applying different thermal deformation correction amount characteristic equations to the heating section and the cooling section, as shown in Figs. 4 and 5, the correction of the thermal deformation of the spindle 20 is performed at the beginning of the machine tool operation, the spindle ( 20) In the heating section where this rotation continues, the thermal deformation correction amount characteristic equation calculates the thermal deformation correction amount of the spindle 20 close to the exponential function, and based on this, the position of the spindle 20 (more precisely, it is installed at the tip of the spindle. By correcting the position of the old tool), it is possible to relatively accurately correct the spindle 20 to the original position where thermal deformation has not occurred.

However, as shown in FIG. 5, when the spindle 20 suddenly stops rotating in the heating section or changes to a cooling section in which the rotational speed is rapidly decelerating below a certain speed, the cooling section thermal deformation correction amount characteristic equation is applied, Since this cooling section thermal deformation correction amount characteristic equation differs from the heating region thermal deformation correction characteristic equation and a time constant, the calculated correction amount has a thermal deformation correction amount and a deviation (AB) of the heating region. That is, when changing from the heating section to the cooling section, the amount of correction for thermal deformation is suddenly changed as much as the deviation, and the spindle moves, resulting in a problem that the machining precision of the workpiece is deteriorated.

Similarly, when switching to the heating section by increasing the rotational speed of the spindle 20 again after the cooling section is applied, the thermal deformation correction amount in the heating section with a different time constant is changed to the characteristic equation, so that the thermal deformation correction amount Deviation occurs, which causes the problem of deteriorating the machining precision of the workpiece again.

As the heating section and the cooling section are repeatedly switched, the correction amount of the thermal deformation of the spindle 20 amplifies the error, and thus, the machining precision of the workpiece becomes worse and worse.

An object of the present invention for solving the above problems is a method or apparatus for calculating a correction amount for thermal deformation of a machine tool spindle, when the spindle switches between a heating phase and a cooling phase. The purpose of this is to improve the machining precision of the workpiece by preventing the correction of the thermal deformation from becoming inaccurate due to the deviation of the thermal deformation correction amount, calculating a more accurate thermal deformation correction amount, and correcting the thermal deformation of the spindle based on this.

The solution of the present invention for achieving the above object is to extract a higher-order characteristic equation of a curve fitting in order to mathematically more accurately express the correlation between the nonlinear thermal deformation of the machine tool spindle and the temperature sensor, and , This is converted into a discrete equation and implanted in a machine tool numerical control device (NC) to compensate for thermal deformation.

A more detailed solution of the present invention is a method for correcting thermal deformation of a machine tool spindle, comprising: a bearing, at least one temperature sensor installed around the bearing to detect an ambient temperature of the bearing, and heat generation of the bearing. In order to correct the thermal deformation of the machine tool spindle having a cooling flow path through which a cooling fluid flows around the bearing to suppress it, the thermal deformation correction amount of the spindle is calculated according to the temperature value detected from the temperature sensor, and the calculated In the thermal deformation correction method of a machine tool for correcting the thermal deformation of the spindle according to the thermal deformation correction amount,

Detecting a temperature value around the spindle from the temperature sensor,

Based on the temperature value detected by the temperature sensor, the primary thermal deformation correction amount of the heating section presupposes that the heating state continues as the spindle rotates, and the spindle decelerates or stops rotating below a predetermined speed range. As a result, the correction amount of the primary thermal deformation of the cooling section is calculated, assuming that the cooling state is maintained, respectively,

Calculate a offset gain value according to the difference between the first heat distortion correction amount in the heating section and the first heat distortion correction amount in the cooling section,

Determine whether the spindle is a heating section or a cooling section,

When the spindle is a heating section, the first thermal distortion correction amount of the heating section is multiplied by the offset gain value to calculate the final thermal distortion correction amount of the spindle, and when the spindle is a cooling section, the primary thermal distortion correction amount of the cooling section Multiplied by the offset gain value and calculated as the final thermal deformation correction amount of the spindle,

The final thermal deformation correction amount of the spindle is reflected in the thermal deformation correction program of the numerical control device (NC) of the machine tool, and the thermal deformation correction of the spindle is controlled to execute, thereby implementing a method for correcting the thermal deformation of the machine tool spindle.

Meanwhile, the first heat distortion correction amount of the heating section is calculated by substituting the temperature value detected from the temperature sensor into a discrete equation of the heat distortion characteristics of the heating section, and the first heat distortion correction amount of the cooling section is the temperature detected from the temperature sensor. It is characterized in that it is calculated by substituting the value into a discrete equation for the thermal deformation characteristic of the cooling section.

In addition, the correction amount of the first thermal deformation of the heating section and the cooling section is calculated as shown in Equations 2 and 3 below,

(Equation 2) Correction amount for the first heat distortion in the heating section (Y) = G x H x C _heat

(Equation 3) Cooling section 1st heat distortion correction amount (Y) = G x H x C _cool

The calculation of the final heat distortion correction amount is calculated as shown in Equation 5 below by reflecting the offset gain value according to the difference in the first heat distortion correction amount between the heating section and the cooling section in Equations 2 and 3, respectively,

(Equation 5) Final thermal distortion correction (Y) = G _i H _i Σ(a _ni z ^-n ) / Σ(b _ni z ^-n )

In Equation 5, the relationship between the temperature sensor value (H) and the thermal distortion correction amount (Y) is modeled as a seventh-order discrete equation as shown in Equation 6 below,

(Equation 6) Y(z)/H(z) = G{a ₇ z ^-7 + ... + a ₀ } / {b ₇ z ^-7 + ... + 1}

Expressing Equation 6 as a discrete equation for the amount of heat distortion correction as shown in Equation 7 below,

(Equation 7) y(k) = G{a ₇ h(k-7)+a ₆ h(k-6)...+a ₁ h(k-1)+a ₀ h(k)}-b ₇ y(k-7)- b ₆ y(k-6)...-b ₁ y(k-1)

In the above equations, Y=heat distortion correction amount, G=gain value, H=temperature sensor value,

C _heat = characteristic equation between the spindle thermal deformation and the temperature sensor in the heating phase,

C _cool = characteristic equation between spindle thermal deformation and temperature sensor in the cooling phase

y(k) = current thermal distortion correction amount, i = sensor number, n = an integer greater than or equal to 0,

a _n = coefficient of the nth delay data of the temperature sensor, b _n = coefficient of the nth delay data of the correction amount,

z ^-1 = 1st time delay, z ^-n = nth time delay.

The equation 7 is implanted in a machine tool numerical control device (NC) to correct thermal deformation of the spindle.

In addition, the offset gain value is determined whether the machine tool is the first operation after calculating the first thermal deformation correction amount between the heating section and the cooling section, and when the machine tool is the first operation, the offset gain value is 1 And, when the machine tool is not operated for the first time, a ratio of the first heat distortion correction amount between the heating section and the cooling section is calculated as a offset gain value.

In addition, when the machine tool is not the first operation, the offset gain value is the first heat distortion correction amount (B) for the heating section to be applied in the future or the first heat distortion correction amount for the cooling section to be applied in the current heating section first heat distortion correction amount (A). It is calculated by dividing (B).

In addition, the first heat distortion correction amount in the heating section and the first heat distortion correction amount in the cooling section are always calculated.

In an embodiment according to the present invention, the apparatus for correcting thermal deformation of a machine tool spindle includes a bearing, at least one temperature sensor installed around the bearing to detect an ambient temperature of the bearing, and suppresses heat generation of the bearing. A machine tool spindle having a cooling flow path for circulating a cooling fluid around the bearing in order to do so,

Based on the temperature value detected by the temperature sensor, the primary thermal deformation correction amount of the heating section presupposes that the heating state continues as the spindle rotates, and the spindle decelerates or stops rotating below a predetermined speed range. As a result, the primary heat distortion correction amount of the cooling section is calculated on the premise that the cooling state is maintained, and the offset gain value according to the difference between the primary heat distortion correction amount in the heating section and the primary heat distortion correction amount in the cooling section is calculated. It calculates, determines whether the spindle is a heating section or a cooling section, and if the spindle is a heating section, multiplying the first thermal deformation correction amount of the heating section by the offset gain value is calculated as the final thermal deformation correction amount of the spindle. , When the spindle is a cooling section, it is calculated as the final thermal distortion correction amount of the spindle by multiplying the offset gain value by the primary thermal distortion correction amount of the cooling section, and reflecting the final thermal distortion correction amount of the spindle in the thermal distortion correction program. A numerical control device (NC) for controlling the spindle to perform thermal deformation correction,

And an actuator that receives the thermal distortion correction control signal of the spindle from the numerical control device and moves the position of the spindle by the correction amount.

In one embodiment according to the present invention, the machine tool of the present invention comprises a thermal deformation correction device of the machine tool spindle.

The present invention uses different equations for calculating the amount of thermal deformation in the heating section according to the rotation of the machine tool spindle and the cooling section according to the rotation stop or rapid deceleration of the spindle, while the deviation of the thermal deformation correction amount when the heating section and the cooling section are switched. It does not occur, and by more accurately following the thermal deformation of the spindle, there is an effect of eliminating the correction deviation according to the thermal deformation correction, and further improving the machining precision of the workpiece through the accurate correction of the thermal deformation of the spindle.

1 is a perspective view of a machine tool having a spindle in which thermal deformation occurs as an embodiment of the prior art.
2 is a graph conceptually showing thermal distortion correction by linear fitting as an embodiment of the prior art.
3 is a graph showing thermal distortion correction as an embodiment of the prior art.
4 is a graph showing the correction of thermal deformation of a spindle when switching from a heating section to a cooling section as an embodiment of the prior art.
5 is a graph showing a variation of the amount of correction for thermal deformation of a spindle when switching from a heating section to a cooling section as an embodiment of the prior art.
6 is an embodiment of the present invention, a flow chart for correcting the thermal deformation of the spindle.
7 is a graph conceptually showing thermal deformation correction by curve fitting as an embodiment of the present invention.
8 is a graph showing variations in the amount of correction for thermal deformation of a spindle when switching from a heating section to a cooling section as an embodiment of the present invention.

A preferred embodiment of the present invention will be described with reference to the accompanying drawings.

First, the machine tool 10 to which the present thermal distortion correction method is applied includes a bearing 40 inside the spindle 20, and at least one installed around the bearing 40 to detect the ambient temperature of the bearing 40. The above temperature sensor 30 is provided with a cooling flow path 50 through which a cooling fluid flows around the bearing 40 in order to suppress heat generation of the bearing 40.

The thermal distortion correction of the spindle 20 of the machine tool 10 includes a numerical control device 70 for calculating the thermal distortion correction amount of the spindle 20 according to the temperature value detected from the temperature sensor 30, and the numerical value. In accordance with the thermal distortion correction amount signal applied from the control device 70, the actuator 60 is driven to move the spindle 20, thereby performing thermal distortion correction of the spindle 20.

Hereinafter, an embodiment of the present invention, a method for correcting thermal deformation of the spindle 20 of the machine tool 10 will be described with reference to FIGS. 6 to 8.

When the machine tool 10 is in the operating state, the numerical control device 70 is in a ready state to perform thermal deformation correction of the spindle 20, and the thermal deformation correction of the spindle 20 is performed by the following operation. .

A temperature value around the spindle 20 is detected from the temperature sensor 30 of the spindle 20.

Subsequently, the first heat distortion correction amount is calculated using the temperature value detected from the temperature sensor 30. Here, the calculation of the primary thermal deformation correction amount is a heating phase based on the premise that the heating state continues as the spindle 20 rotates, and the spindle 20 decelerates or stops rotation below a predetermined speed range. As a result, it is calculated independently for each cooling phase assuming that the cooling state continues.

Meanwhile, the first heat distortion correction amount of the heating section is calculated by substituting the temperature value detected from the temperature sensor 30 into a discrete equation of the heat distortion characteristics of the heating section, and the first heat distortion correction amount of the cooling section is the temperature sensor ( Calculate the temperature value detected from 30) by substituting it into the discrete equation for the thermal deformation characteristics of the cooling section.

That is, it can be expressed as a characteristic equation transfer function between the temperature sensor value and the thermal distortion correction amount (Y) = the gain value ⅹ the temperature sensor value ⅹ the temperature sensor value and the heat distortion correction amount (Y).

This can be expressed as an equation of the first-order thermal deformation correction amount between the heating section and the cooling section as shown in Equations 2 and 3 below.

(Equation 2) Correction amount for the first heat distortion in the heating section (Y) = G x H x C _heat

(Equation 3) Cooling section 1st heat distortion correction amount (Y) = G x H x C _cool

Where G = gain value, H = temperature sensor value, C _heat = characteristic equation between spindle thermal deformation and temperature sensor in heating phase, C _cool = spindle thermal deformation and temperature in cooling phase It is a characteristic equation between sensors.

On the other hand, the characteristic equation for calculating the first thermal distortion correction amount is corrected in a curved form in order to mathematically more accurately express the correlation between the nonlinear thermal deformation of the spindle 20 and the temperature sensor 30 as shown in FIG. 7. It is a high-order characteristic equation of (curve fitting).

Meanwhile, the first heat distortion correction amount for the heating section and the heat distortion correction amount for one cooling section are always calculated from the moment when the machine tool 10 is turned on until the machine tool 10 is turned off. do. In other words, it is always calculated from the moment when the numerical control device 70 of the machine tool 10 is turned on until it is turned off.

Next, it is determined whether the machine tool 10 is the first operation (a state in which the operation is started by turning on the power). More precisely, when the numerical control device 70 of the machine tool 10 is turned on and is within a predetermined time range, it is determined as the first operation of the machine tool 10.

As a result of the determination, when the machine tool 10 is the first operation, the offset gain value according to the difference between the primary thermal deformation correction amount (A) in the heating section and the primary thermal deformation correction amount (B) in the cooling section is set to 1. .

If, as a result of the determination, the machine tool 10 is not the first operation, it is determined whether the spindle 20 is in a rotating state by reading the rotational speed of the spindle 20 of the machine tool 10.

As a result of determining the rotational state of the spindle 20, when the spindle 20 is not in the rotating state, it returns to an initial state in which a temperature value is read from the temperature sensor 30. As a result of the determination, if the spindle 20 is determined to be in a rotating state, the first heat distortion correction amount (B) for the heating section to be applied in the future or the first heat distortion correction amount in the cooling section ( By dividing B), the offset gain value according to the difference in the first-order thermal distortion correction amount is calculated.

If this is expressed as a more specific formula, it can be expressed as in Equation 4 below.

(Equation 4) Offset gain (A/B) = GHΣ(a _n z ^-n )/Σ(b _n z ^-n )

In addition, when there are several temperature sensors 30, Equation 4 can be expressed as Equation 5 below.

(Equation 5) Offset gain (A/B) = G _i H _i Σ(a _ni z ^-n ) / Σ(b _ni z ^-n )

In Equations 4 to 5, G=gain value, H=temperature sensor value, i=sensor number, n=an integer greater than or equal to 0, a _n = coefficient of nth delay data of temperature sensor, b _n = nth delay of correction amount Data coefficient, z ^-1 = 1st time delay, z ^-n = nth time delay.

In the next step, it is determined whether the spindle 20 is a heating section or a cooling section.

As a result of the determination, when the spindle 20 is a heat generation section, the first heat distortion correction amount in the heat generation section is multiplied by the offset gain value to be calculated as the final heat distortion correction amount of the spindle 20, and the spindle 20 is a cooling section. In the case of, it is calculated as the final thermal distortion correction amount of the spindle 20 by multiplying the first thermal distortion correction amount in the cooling section by the offset gain value.

The calculation of the final thermal distortion correction amount reflects the offset gain value according to the difference in the primary thermal distortion correction amount between the heating section and the cooling section in Equations 2 and 3, respectively, and can be expressed as Equation 6 below. The relationship between the temperature sensor value (H) and the thermal distortion correction amount (Y) is modeled using a 7th-order discrete equation.

(Equation 6) Y(z)/H(z) = G{a ₇ z ^-7 + ... + a ₀ } / {b ₇ z ^-7 + ... + 1}

In addition, Equation 6 is expressed as a discrete equation for the amount of heat distortion correction as in Equation 7 below.

(Equation 7) y(k) = G{a ₇ h(k-7)+a ₆ h(k-6)...+a ₁ h(k-1)+a ₀ h(k)}-b ₇ y(k-7)- b ₆ y(k-6)...-b ₁ y(k-1)

In Equations 6 to 7, Y=heat distortion correction amount, G=gain value, H=temperature sensor value,

y(k) = current thermal distortion correction amount, i = sensor number, n = an integer greater than or equal to 0,

a _n = coefficient of the nth delay data of the temperature sensor, b _n = coefficient of the nth delay data of the correction amount,

z ^-1 = 1st time delay, z ^-n = nth time delay.

Next, the thermal deformation correction of the spindle 20 is performed by reflecting Equation 7 as the final thermal deformation correction amount of the spindle 20 to the thermal deformation correction program of the numerical control device 70 of the machine tool 10. .

As described above, the method of correcting thermal deformation of the spindle 20 of the machine tool 10 of the present invention includes a heating section according to the rotation of the spindle 20 of the machine tool 10 and the rotation stop or rapid deceleration of the spindle 20. While using different equations for calculating the amount of heat distortion correction in the cooling section, the difference in the amount of heat distortion correction does not occur when the heating section and the cooling section are switched, so that the thermal deformation of the spindle 20 is more accurately followed, thereby correcting according to the thermal distortion correction. There is an effect of improving the machining precision of the workpiece by eliminating the deviation and further correcting the thermal deformation of the spindle 20 accurately.

On the other hand, as an embodiment according to the present invention, the thermal deformation correction method may be implemented as a thermal deformation correction apparatus of a machine tool spindle 20.

The invention of such a thermal deformation correction device includes the bearing 40, at least one temperature sensor 30 installed around the bearing 40 to detect the ambient temperature of the bearing 40, and the bearing 40 It includes a machine tool spindle 20 having a cooling flow path 50 for circulating a cooling fluid around the bearing 40 in order to suppress heat generation of ),

Based on the temperature value detected by the temperature sensor 30, as the spindle 20 rotates, the amount of correction for the primary thermal deformation of the heating section is assumed to be maintained, and the spindle 20 is determined in advance. Calculate the correction amount of the first thermal deformation of the cooling section, assuming that the cooling state continues as the speed decreases below the speed range or stops the rotation, and calculates the correction amount of the first thermal deformation of the heating section and the first thermal deformation of the cooling section. The offset gain value according to the difference in the correction amount is calculated, it is determined whether the spindle 20 is a heating section or a cooling section, and when the spindle 20 is a heating section, the first thermal deformation correction amount of the heating section is calculated. The spindle 20 is multiplied by the offset gain value to calculate the final thermal distortion correction amount of the spindle 20, and when the spindle 20 is a cooling period, the primary thermal distortion compensation amount of the cooling period is multiplied by the offset gain value. A numerical control device 70 that calculates as a final thermal deformation correction amount of and controls the thermal deformation correction of the spindle 20 by reflecting the final thermal deformation correction amount of the spindle 20 in a thermal deformation correction program, and

It comprises an actuator (60) for correcting the position of the spindle (20) by receiving the thermal distortion correction signal of the spindle from the numerical control device (70).

On the other hand, the actuator 60 for correcting the position of the spindle 20 in the above embodiment is mainly used a thermomotor, such a servomotor directly moving the spindle 20, or the spindle 20 is fixed column or It is arranged to move the frame precisely.

In addition, as an embodiment of the present invention, by applying the thermal distortion correction device of the machine tool spindle 20 to a machine tool, a machine tool to which the thermal distortion correction device is applied can be implemented.

On the other hand, in the above embodiment, the method of correcting the thermal deformation of the spindle 20 of the machine tool 10 has been mainly described, but the machine tool 10 has a heating section and a cooling section, and can be applied extremely easily to all parts where thermal deformation occurs. I can. For example, if the method or apparatus for correcting thermal deformation of the present invention is applied to a column or frame of the machine tool 10, the temperature sensor 30 is placed on the column or frame of the machine tool 10 where heat is most severe. It is installed to detect temperature, and in the above embodiment, heat generation in a column or frame is calculated by dividing the heating section and the cooling section according to whether the machine tool 10 is operated or not and the rotational state of the spindle 20. An operation that can be a reference between the section and the cooling section, for example, calculates the amount of thermal deformation correction between the heating section and the cooling section based on whether or not the workpiece has started processing or whether the workpiece table has been moved, and this is applied to the numerical control device 70. It should be reflected and corrected for thermal deformation.

Therefore, the present invention is not limited to the above-described embodiments, and those of ordinary skill in the art to which the present invention pertains, various modifications and variations within the scope of the technical idea of the present invention and the scope of the claims set forth below. This would be possible, which would fall within the scope of the present invention.

10 machine tools
20 spindle
30 Temperature sensor
40 bearing
50 cooling flow path
60 actuator
70 Numerical control device

Claims (15)

A machine tool spindle having a bearing, at least one temperature sensor installed around the bearing to detect the ambient temperature of the bearing, and a cooling passage through which a cooling fluid flows around the bearing to suppress heat generation of the bearing. In order to correct the thermal deformation of the machine tool, the thermal deformation correction amount of the spindle is calculated according to the temperature value detected from the temperature sensor, and the thermal deformation of the spindle is corrected according to the calculated thermal deformation correction amount. In,
Detecting a temperature value around the spindle from the temperature sensor,
Based on the temperature value detected by the temperature sensor, the primary thermal deformation correction amount of the heating section presupposes that the heating state continues as the spindle rotates, and the spindle decelerates or stops rotating below a predetermined speed range. As a result, the correction amount of the primary thermal deformation of the cooling section is calculated, assuming that the cooling state is maintained, respectively,
Calculate a offset gain value according to the difference between the first heat distortion correction amount in the heating section and the first heat distortion correction amount in the cooling section,
Determine whether the spindle is a heating section or a cooling section,
When the spindle is a heating section, the first thermal distortion correction amount of the heating section is multiplied by the offset gain value to calculate the final thermal distortion correction amount of the spindle, and when the spindle is a cooling section, the primary thermal distortion correction amount of the cooling section Multiplied by the offset gain value and calculated as the final thermal deformation correction amount of the spindle,
A method for correcting thermal deformation of a machine tool spindle by reflecting the final thermal deformation correction amount of the spindle to a thermal deformation correction program of a numerical control device (NC) of a machine tool to perform thermal deformation correction of the spindle. The method of claim 1, wherein the first heat distortion correction amount of the heating section is calculated by substituting a temperature value detected from the temperature sensor into a discrete equation of the heat distortion characteristic of the heating section, and the first heat distortion correction amount of the cooling section is the temperature sensor. A method for correcting thermal deformation of a machine tool spindle, characterized in that the temperature value detected from is substituted into a discrete equation for thermal deformation characteristics of the cooling section and calculated. The method of claim 2, wherein the discrete equation for thermal deformation properties for calculating the first-order thermal deformation correction amount is a higher-order characteristic equation for correcting the correlation between the nonlinear thermal deformation of the spindle and the temperature sensor in a curved form. How to compensate for thermal deformation of machine tool spindles. The method of claim 2,
The correction amount of the first heat distortion of the heating section and the cooling section is calculated as shown in Equations 2 and 3 below,
(Equation 2) Correction amount for the first heat distortion in the heating section (Y) = G x H x C _heat
(Equation 3) Cooling section 1st heat distortion correction amount (Y) = G x H x C _cool
The calculation of the final heat distortion correction amount is calculated as shown in Equation 5 below by reflecting the offset gain value according to the difference in the first heat distortion correction amount between the heating section and the cooling section in Equations 2 and 3, respectively,
(Equation 5) Final thermal distortion correction (Y) = G _i H _i Σ(a _ni z ^-n ) / Σ(b _ni z ^-n )
In Equation 5, the relationship between the temperature sensor value (H) and the thermal distortion correction amount (Y) is modeled as a seventh-order discrete equation as shown in Equation 6 below,
(Equation 6) Y(z)/H(z) = G{a ₇ z ^-7 + ... + a ₀ } / {b ₇ z ^-7 + ... + 1}
Expressing Equation 6 as a discrete equation for the amount of heat distortion correction as shown in Equation 7 below,
(Equation 7) y(k) = G{a ₇ h(k-7)+a ₆ h(k-6)...+a ₁ h(k-1)+a ₀ h(k)}-b ₇ y(k-7)- b ₆ y(k-6)...-b ₁ y(k-1)
Where Y=heat distortion correction amount, G=gain value, H=temperature sensor value,
C _heat = characteristic equation between the spindle thermal deformation and the temperature sensor in the heating phase,
C _cool = characteristic equation between spindle thermal deformation and temperature sensor in the cooling phase
y(k) = current thermal distortion correction amount, i = sensor number, n = an integer greater than or equal to 0,
a _n = coefficient of the nth delay data of the temperature sensor, b _n = coefficient of the nth delay data of the correction amount,
z ^-1 = 1st time delay, z ^-n = nth time delay
A method for correcting thermal deformation of a machine tool spindle, characterized in that the Equation 7 is implanted into a machine tool numerical control device (NC). The method of claim 1, wherein the offset gain value is determined whether the machine tool is the first operation after calculating the first thermal deformation correction amount between the heating section and the cooling section, and when the machine tool is the first operation, the offset gain The value is set to 1, and when the machine tool is not operated for the first time, the ratio of the first heat distortion correction amount between the heating section and the cooling section is calculated as a offset gain value. . The method of claim 5, wherein, when the machine tool is not the first operation, the offset gain value is the first heat distortion correction amount (B) or cooling section 1 in the heat generation section to be applied in the future to the current heat generation section first heat distortion correction amount (A). A method for correcting thermal deformation of a machine tool spindle, characterized in that calculated by dividing the differential thermal deformation correction amount (B). The method of claim 1, wherein the first heat distortion correction amount for the heating section and the first heat distortion correction amount for the cooling section are calculated at all times. A machine tool spindle having a bearing, at least one temperature sensor installed around the bearing to detect the ambient temperature of the bearing, and a cooling passage through which a cooling fluid flows around the bearing to suppress heat generation of the bearing. and,
Based on the temperature value detected by the temperature sensor, the primary thermal deformation correction amount of the heating section presupposes that the heating state continues as the spindle rotates, and the spindle decelerates or stops rotating below a predetermined speed range. As a result, the correction amount of the primary thermal deformation of the cooling section is calculated, assuming that the cooling state is maintained, respectively,
Calculate a offset gain value according to the difference between the first heat distortion correction amount in the heating section and the first heat distortion correction amount in the cooling section,
Determine whether the spindle is a heating section or a cooling section,
When the spindle is a heating section, the first thermal distortion correction amount of the heating section is multiplied by the offset gain value to calculate the final thermal distortion correction amount of the spindle, and when the spindle is a cooling section, the primary thermal distortion correction amount of the cooling section Multiplied by the offset gain value and calculated as the final thermal deformation correction amount of the spindle,
A numerical control device (NC) for controlling the spindle to perform thermal deformation correction by reflecting the final thermal deformation correction amount of the spindle in a thermal deformation correction program, and
A thermal deformation correction device of a machine tool spindle comprising an actuator for moving a position of the spindle by receiving a thermal deformation control signal of the spindle from the numerical control device. The method of claim 8, wherein the numerical control unit (NC) calculates the first heat distortion correction amount for the heating section by substituting the temperature value detected from the temperature sensor into a discrete equation for the heat distortion characteristic in the heating section, and calculating 1 in the cooling section. The differential thermal deformation correction amount is calculated by substituting the temperature value detected from the temperature sensor into a discrete equation for thermal deformation characteristics of the cooling section. The method of claim 9, wherein the numerical control device (NC) is a thermal deformation characteristic discrete equation for calculating the primary thermal deformation correction amount to correct the correlation between the thermal deformation of the nonlinear spindle and the temperature sensor in a curved form (curve fitting). ) Of the high-order characteristic equation of the machine tool spindle, characterized in that the thermal deformation correction device. The method of claim 9, wherein the numerical control device (NC) calculates the correction amount of the first thermal deformation of the heating section and the cooling section as shown in Equations 2 and 3 below,
(Equation 2) Correction amount for the first heat distortion in the heating section (Y) = G x H x C _heat
(Equation 3) Cooling section 1st heat distortion correction amount (Y) = G x H x C _cool
The calculation of the final heat distortion correction amount is calculated as shown in Equation 5 below by reflecting the offset gain value according to the difference in the first heat distortion correction amount between the heating section and the cooling section in Equations 2 and 3, respectively,
(Equation 5) Final thermal distortion correction (Y) = G _i H _i Σ(a _ni z ^-n ) / Σ(b _ni z ^-n )
In Equation 5, the relationship between the temperature sensor value (H) and the thermal distortion correction amount (Y) is modeled as a seventh-order discrete equation as shown in Equation 6 below,
(Equation 6) Y(z)/H(z) = G{a ₇ z ^-7 + ... + a ₀ } / {b ₇ z ^-7 + ... + 1}
Expressing Equation 6 as a discrete equation for the amount of heat distortion correction as shown in Equation 7 below,
(Equation 7) y(k) = G{a ₇ h(k-7)+a ₆ h(k-6)...+a ₁ h(k-1)+a ₀ h(k)}-b ₇ y(k-7)- b ₆ y(k-6)...-b ₁ y(k-1)
Where Y=heat distortion correction amount, G=gain value, H=temperature sensor value,
C _heat = characteristic equation between the spindle thermal deformation and the temperature sensor in the heating phase,
C _cool = characteristic equation between spindle thermal deformation and temperature sensor in the cooling phase
y(k) = current thermal distortion correction amount, i = sensor number, n = an integer greater than or equal to 0,
a _n = coefficient of the nth delay data of the temperature sensor, b _n = coefficient of the nth delay data of the correction amount,
z ^-1 = 1st time delay, z ^-n = nth time delay
A device for correcting thermal deformation of a machine tool spindle, characterized in that the Equation 7 is implanted into a machine tool numerical control device (NC). The method according to claim 8, wherein the numerical control device (NC) determines whether the machine tool is the first operation of the machine tool after calculating the first thermal distortion correction amount between the heating section and the cooling section, and the offset gain value is In the case of the first operation, the offset gain value is set to 1, and when the machine tool is not the first operation, the ratio of the primary heat distortion correction amount between the heating section and the cooling section is calculated as the offset gain value. A device for compensating thermal deformation of machine tool spindles. The method of claim 12, wherein, when the machine tool is not the first operation, the offset gain value is the first heat deformation of the heat generation section to be applied in the future to the first heat distortion correction amount (A) of the current heat generation section. A thermal deformation correction device of a machine tool spindle, characterized in that calculated by dividing the correction amount (B) or the primary thermal deformation correction amount (B) in the cooling section. [10] The apparatus of claim 8, wherein the numerical control device (NC) calculates the first heat distortion correction amount for the heating section and the first heat distortion correction amount for the cooling section at all times. A machine tool comprising the device for correcting thermal deformation of the machine tool spindle of claim 8.

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