KR20190102442A - Method for measuring geometric errors of 4-axis machine tools - Google Patents

Abstract

Disclosed is a method for measuring a geometric error of a four-axis machine tool. According to one embodiment of the present invention, the method for measuring the geometric error of the four-axis machine tool comprises: a step of constructing a reference coordinate system; a step of defining an error; a step of calculating a first actual encoder value and a step of calculating a second actual encoder value including a standard ball coordinate calculation process, a measurement part coordinate calculation process, an ideal encoder value calculation process, an encoder value calculation process according to an error amount, and an actual encoder value calculation process, and calculating the actual encoder value of the first reference ball and the second reference ball by performing the processes with respect to the first reference ball and the second reference ball respectively; and an error separation step of separating a plurality of error components from the actual encoder value for the first reference ball and the second reference ball calculated from the actual encoder value calculating step.

Description

Method for measuring geometric errors of 4-axis machine tools

The present invention relates to a geometric error measuring method of a four-axis machine tool, and more particularly, geometric error of a four-axis machine tool that can measure a constant seven errors regardless of the position by using the coordinates of the center of the two reference balls It relates to a measuring method.

In a four-axis machine tool consisting of three linear axes and one rotary axis, a constant geometric error is defined as seven regardless of position, which means that the linearity error (3) and the perpendicularity error (2) of the rotary axis between the linear axes It means offset error (2).

In the case of a real machine tool, such a geometric error lowers the precision of the equipment and generates a relative error between the tool and the workpiece, resulting in a machining error. Therefore, in order to reduce the machining error, such geometric error must be measured and corrected.

Conventional methods for measuring geometric errors include rectangular mirrors, laser interferometers, double ballbars, R-tests, and specimens.

The rectangular mirror method requires a rectangular mirror and a displacement sensor, and it is cumbersome to measure the rectangular error separately. The method using a laser interferometer also requires expensive equipment, and can measure only one squareness error at a time, and the laser alignment for the squareness measurement is very difficult. All of these methods can only measure the squareness error, not the geometric errors related to the axis of rotation.

Double ballbar, R-Test, and machining specimens can measure several geometric errors at once, but not all of the seven geometric errors defined above. In the error measurement using the double ball bar, one ball is installed on the spindle side and the other ball is installed on the table side using the double ball bar, and the distance between the two ball centers is changed by the geometric error of the equipment, so the error is separated and measured. However, there are limitations to the measurement distance and several measurement setups are required to isolate all errors.

Republic of Korea Patent Publication No. 10-2011-0085210

The present invention has been made to solve the above-mentioned conventional problems, the object of the present invention is as follows.

First, the present invention is to provide an error measuring method capable of simultaneously measuring and separating a certain geometric error regardless of position in a four-axis machine tool consisting of three linear axes and one rotation axis.

Second, the present invention is to provide a geometric error measuring method of a four-axis machine tool that can reduce the measurement error.

Third, the present invention is to provide a method for periodically measuring the geometric error of the equipment for error correction when the initial installation of the equipment or when the use environment is changed.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention provides a method of measuring the geometric error of a four-axis machine tool using a first reference ball, a second reference ball and two measuring balls having different heights. Provided are a geometric error measuring method of a four-axis machine tool including a step, an error definition step, a first real encoder value calculation step, a second real encoder value calculation step, and an error separation step.

In the step of configuring the reference coordinate system, a reference coordinate system is configured.

In the error definition step, a certain geometric error is defined for the 4-axis equipment regardless of the position.

The first actual encoder value calculation step and the second actual encoder value calculation step, respectively, the reference ball coordinate calculation process for obtaining the coordinate value of the reference ball for the reference coordinate system, the measurement unit coordinates for obtaining the coordinate value of the measurement unit for the reference coordinate system Calculation process, the process of calculating the ideal encoder value when there is no error, the relative value of the reference ball center to the measurement unit by comparing the coordinate value of the reference ball for the reference coordinate system with the coordinate value of the measurement unit for the reference coordinate system Calculating an encoder value according to an error amount to obtain an encoder value according to an error amount, and calculating an actual encoder value by adding an encoder value according to the error amount to the ideal encoder value to obtain an actual encoder value. The ball of the first reference ball and the second reference ball by executing the ball and the second reference ball respectively The encoder value is calculated.

In the error separation step, a plurality of error components are separated from actual encoder values for the first reference ball and the second reference ball calculated from the actual encoder value calculating step.

In the error separation step, a right angle error with respect to the X axis of the C axis, a right angle error with respect to the Y axis of the C axis, and a right angle error between the X axis and the Y axis may be calculated from the actual encoder value of the first reference ball.

The perpendicularity error with respect to the X axis of the C axis, the perpendicularity error with respect to the Y axis of the C axis, and the perpendicularity error between the X axis and the Y axis are respectively calculated with respect to the first reference ball and the second reference ball. It can be the average of the values.

In the error separation step, the offset error in the X direction of the C axis, the offset error in the Y direction of the C axis, the perpendicularity of the X axis and the Z axis from the actual encoder value calculated from the first reference ball and the second reference ball. Error and the squareness error of the Y-axis and the Z-axis can be calculated.

If the moving distance of the Z-axis in which the measurement unit is installed is longer than the preset value, the actual encoder value is measured at various points by changing the height of the second reference ball, and then the geometric error is calculated and averaged to use for the squareness error. It can improve the measurement accuracy.

The offset error in the X direction of the C axis is offset in the X direction of the C axis calculated from the actual encoder value of the first reference ball and the offset in the X direction of the C axis calculated from the actual encoder value of the second reference ball. It can be the mean value of the errors.

The offset error in the Y direction of the C axis is offset in the Y direction of the C axis calculated from the actual encoder value of the first reference ball and the offset in the Y direction of the C axis calculated from the actual encoder value of the second reference ball. It can be the mean value of the errors.

The installation radius, the installation height, and the Y-direction installation error of the first and second reference balls required to obtain the plurality of error components may be obtained from actual encoder values.

The plurality of error components may be measured from various points of the first reference ball and the second reference ball, and averaged to calculate a final error component to minimize the measurement error.

The first reference ball and the second reference ball may not be used at the same time, but only the first reference ball may be used, but the height may be sequentially measured using the second reference ball by changing the height.

Referring to the effects of the present invention configured as described above are as follows.

First, according to the method for measuring the geometric error of a four-axis machine tool according to an embodiment of the present invention, a single geometric error may be simultaneously measured and separated regardless of the position of the four-axis machine tool by one measurement.

Second, according to the geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention can calculate the geometric error from the average of the measured value to reduce the measurement error.

Third, according to the method for measuring the geometric error of a four-axis machine tool according to an embodiment of the present invention, the reference ball and the measuring part have a low price, a short measuring time, and are easy to measure even by non-professionals. In this case, by using the measurement method of the present embodiment periodically by using the geometric error in the measurement and correction it is possible to maintain the precision of the equipment to the initial level.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

The above summary as well as the detailed description of the preferred embodiments of the present application described below will be better understood when read in connection with the accompanying drawings. Preferred embodiments are shown in the drawings for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown.
1 is a view showing the configuration of the first reference ball, the second reference ball and the measuring unit for the geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention;
2 is a flow chart generally showing a geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention;
3 is a diagram illustrating a reference coordinate system configuration and an axis configuration of a four-axis machine tool;
4 is a view showing the perpendicularity error between three straight axes of a four-axis machine tool according to an embodiment of the present invention;
5 is a view showing a geometric error associated with a rotation axis of a four-axis machine tool according to an embodiment of the present invention;
6 is a view showing seven errors of the method for measuring the geometric error of a four-axis machine tool according to an embodiment of the present invention;
7 is a flowchart illustrating a step of calculating an actual encoder value in a geometric error measuring method of a four-axis machine tool according to an exemplary embodiment of the present invention;
8 is a view showing the principle of the geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention;
9 is a view showing the installation error in the Y direction of the first reference ball in the geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention;
10 is a view showing a measuring position of the spherical reference when the rotation axis rotates by a predetermined angle in the method for measuring the geometric error of a four-axis machine tool according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the accompanying drawings are only described in order to more easily disclose the contents of the present invention, but the scope of the present invention is not limited to the scope of the accompanying drawings that will be readily available to those of ordinary skill in the art. You will know.

In describing the embodiments of the present invention, the same components and the same reference numerals are used for the components having the same functions, and are not completely identical to the components of the prior art.

Also, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, a geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a view showing the configuration of the first reference ball, the second reference ball and the measuring unit for the geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention.

As shown in Figure 1, the geometric error measuring method according to an embodiment of the present invention is the center of the first reference ball 110, the second reference ball 120 and the reference ball, which are two reference balls different in height It is a method of measuring the geometric error using the measurement unit 200 that can measure the.

Hereinafter, a method of measuring an error using the first reference ball 110 and the second reference ball 120 will be described. However, the present invention is not limited thereto, and the first measured value is first measured at a predetermined height using one reference ball. You can also obtain the second measurement by changing the height and measuring again.

Since 4-axis machine is composed of X-Y-Z-C axis, there is no way to change the height of the reference ball installed on C axis by simply driving the axis. Therefore, two balls of different heights must be used to obtain the squareness error of the Z-axis and the X-axis, the squareness error of the Z-axis and the Y-axis, the offset error of the C-axis in the X direction, and the offset error of the C-axis in the Y direction.

Therefore, in order to measure the error, the first reference ball 110 and the second reference ball 120 are installed on the rotating plate 100. Here, the first reference ball 110 and the second reference ball 120 are installed in different heights. The first reference ball 110 and the second reference ball 120 may be installed at intervals of 180 degrees. Here, the first reference ball 110 may be installed at 0 degrees, and the second reference ball 120 may be installed at 180 degrees. Then, the error calculation is made around the first reference ball 110, the second reference ball 120 can be used for error induction and offset error calculation using the height difference.

In the present exemplary embodiment, the first reference ball 110 and the second reference ball 120 are installed at intervals of 180 degrees for the convenience of error measurement, but the first reference ball 110 and the second reference ball ( The angle between 120 is not necessarily 180 degrees, and may be installed at any angle if the height of the first reference ball 110 and the second reference ball 120 is different. Here, the axis of rotation of the flat plate 100 may be a C axis, and the three axes of linear movement may be X, Y, and Z axes, respectively.

In addition, in the present embodiment, the first reference ball 110 and the second reference ball 120 are installed, and the flat plate 100 rotating around the C axis is provided to be movable in the Y direction, and the first reference ball 110 is provided. ) And a measurement unit 200 for measuring the position of the center point of the second reference ball 120 is movable in the X and Z directions. As the measuring unit 200, a touch probe or a position probe (MT-check) may be applied. The touch probe can calculate the center point coordinates by measuring the sphere surface of the reference ball at various positions, and the Position INSPECTOR can measure the center point coordinates at once because three displacement sensors are configured in the form of Trinity.

 2 is a flow chart generally showing a geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention.

As shown in Figure 2, the geometric error measuring method according to an embodiment of the present invention comprises the step of configuring the reference coordinate system (S110), the error definition step (S120), the first actual encoder value calculation step (S130), the second actual An encoder value calculating step S140 and an error separation step S150 are included.

3 is a view showing a reference coordinate system configuration of a four-axis machine tool according to an embodiment of the present invention, Figure 4 is a view showing the perpendicularity error between the three straight axes of the four-axis machine tool according to an embodiment of the present invention 5 is a view showing a geometric error related to the axis of rotation of a four-axis machine tool according to an embodiment of the present invention.

In the reference coordinate system configuration step S110, a reference coordinate system is configured. Here, as shown in FIG. 4, γ _XY , which is a perpendicularity error with respect to the Y axis of the X axis, may be used to represent the linear feed axis X based on the linear feed axis Y. In addition, the linear feed axis Z can be modeled using the squareness errors β _ZX and α _ZY . That is, the basic plane may be configured using the linear feed axes X and Y, and the reference coordinate system may be configured by indicating the direction of the linear feed axes Z. In this embodiment, in order to simplify the coordinate system, as shown in FIG. 3, the reference coordinate system may be placed at the center point of the upper surface of the C-axis (rotation axis) table in the initial state.

FIG. 6 is a view illustrating seven errors of a geometric error measuring method of a four-axis machine tool according to an exemplary embodiment of the present invention. FIG.

In the error definition step S120, a total of seven errors are defined with respect to the reference coordinate system. As shown in FIG. 6, the seven errors are offset errors (δ _CX ) in the X direction of the C axis, offset errors (δ _CY ) in the Y direction of the C axis, and right angle errors (β) with respect to the X axis of the C axis, respectively. _CX ), orthogonality error with respect to Y axis of C axis (α _CY ), orthogonality error with respect to X axis of Z axis (β _ZX ), orthogonality error with respect to Y axis of X axis (γ _XY ), Y axis of Z axis Can be defined as the squareness error α _ZY .

_CX로 정의될 수 있다.The center position of the axis of rotation is defined by the center offset error δ _CX , δ _CY between the center of the reference coordinate system and the center of the axis of rotation between the linear axis (Y axis) on which the axis of rotation (C) is mounted and the axis of rotation. The attitude of the axis of rotation (C axis) relative to Y and X is two squareness error α _CY ,

Can be defined as _CX .

7 is a flowchart illustrating a step of calculating an actual encoder value in a geometric error measuring method of a four-axis machine tool according to an embodiment of the present invention, and FIG. 8 is a geometric error measurement of a four-axis machine tool according to an embodiment of the present invention. A diagram showing the principle of the method.

As shown in FIG. 7, the first actual encoder value calculating step S130 of FIG. 2 includes a reference ball coordinate calculation process P131, a measurement unit coordinate calculation process P133, an ideal encoder value calculation process P135, and an error amount. The encoder value calculation process (P137) according to, and the actual encoder value calculation process (P139).

In addition, as shown in FIG. 8, a reference coordinate system (Ref.) Is set at the center of the upper surface of the plate 100 rotating around the C axis in the initial measurement state, and the measurement unit 200 is installed on the plate 100. When measuring the coordinate of the center of the ball 110, the position of the center point of the first reference ball 110 and the measurement unit 200 from the reference coordinate system (Ref.) Using a homogeneous transformation matrix (Homogeneous Transformation Maxtrix) I can express it. In the reference ball coordinate calculation process P131 of FIG. 7, a coordinate value of the first reference ball 110 with respect to the reference coordinate system may be obtained. The coordinate value of the first reference ball 110 is as shown in Equation 1 below.

At this time, since the C axis is installed on the moving Y axis, the origin of the reference coordinate system should be set and fixed as the center of the C axis in the initial state. When constructing the XY plane of the reference coordinate system, only the perpendicular error γ _XY is determined based on the Y axis. It can be configured using. In the vector representing the position of the first reference ball 110 with respect to the C-axis, H ₁ is the height of the first reference ball 110, Δw _Y1 is the installation direction of the first reference ball 110 in the Y direction (Fig. 9). R ₁ is an installation radius of the first reference ball 110. Since the installation error Δw _X1 in the X direction is included in the radius R ₁ , no error is separately defined.

9 is a view showing the Y-axis installation error of the first reference ball 110 in the geometric error measurement method of a four-axis machine tool according to an embodiment of the present invention.

In addition, in the measurement unit coordinate calculation process P133, the coordinate value of the measurement unit 200 with respect to the reference coordinate system may be obtained.

10 is a view showing the measurement position of the reference ball when the rotation axis rotates by a predetermined angle in the method for measuring the geometric error of a four-axis machine tool according to an embodiment of the present invention.

As shown in FIG. When the flat plate 100 on which the first reference ball 110 is installed rotates by a predetermined angle, the center of the first reference ball 110 may be measured by the measurement unit 200 at each measurement position.

The coordinate value of the measurement unit 200 may be calculated as shown in Equation 2 below.

Similarly in the measurement unit coordinate calculation process (P133), since the C axis is installed on the moving Y axis, the origin of the reference coordinate system should be set and fixed to the center of the C axis in the initial state, and when the XY plane of the reference coordinate system is configured, Can be configured using only the squareness error γ _XY . In addition, (t _X , t _Y , t _Z ) is a coordinate point of the measurement unit 200 with respect to the Z axis, and all coordinate axes and the measurement unit are matched with the reference coordinate system at the center of the C axis.

Hereinafter, the encoder values of the X, Y, and Z axes may be derived by using the coordinates of the first reference ball 110 and the coordinates of the measurement unit 200 calculated as described above. Here, the encoder value may mean the movement amount of each axis required for the measurement unit 200 to touch the first reference ball 110.

First, in the ideal encoder value calculation process (P135), the encoder value when no error exists is obtained. In an ideal case, that is, when there is no error, the position of the first reference ball 110 and the position of the measurement unit 200 should match. [Equation 3] and [Equation 4] are the position of the first reference ball 110 and the measurement unit 200 with respect to the reference coordinate system, respectively.

If there are no errors, these two values must match. That is, ^R P _{bc, 1} = ^R P _probe must be established. Therefore, ^probe P _{bc, 1, which} is a relative position of the measurement unit 200 with respect to the first reference ball 110, is expressed by Equation 5 below.

Therefore, the ideal amount of movement of each axis required to match the measurement unit 200 to the first reference ball 110 is as shown in [Equation 6].

Approaching this from the perspective of the error vector, ^probe P _{bc, 1, which} is a relative position of the measurement unit 200 with respect to the first reference ball 110, is expressed by Equation 7 below.

In an ideal case, that is, when there is no error _{, the} value of ^probe P _{bc, 1} should be 0, so that Equation 5 and Equation 6 can be derived as a result of approaching from the viewpoint of the error vector.

However, since an error actually exists, the encoder value calculation process according to the error amount (P137) compares the coordinate value of the first reference ball 110 with respect to the reference coordinate system and the coordinate value of the measurement unit 200 with respect to the reference coordinate system. An encoder value according to a relative error amount of the center of the first reference ball 110 with respect to the measurement unit 200 may be obtained.

Even if there is an error, in order to obtain the actual encoder value, the measurement unit 200 must touch the first reference ball 110, and therefore, the positions of the first reference ball 110 and the measurement unit 200 with respect to the reference coordinate system must be the same. . That is, ^R P _{bc, 1} = ^R P _probe . Referring to [Equation 7], it is expressed as Equation 8 below. Here, x ₁ , y ₁ , z ₁ may be regarded as the movement amount of each axis, that is, the encoder value required for the measurement unit 200 to touch the first reference ball 110.

In another approach, if there is an error, the ^probe P _{bc, 1,} which is a relative error amount of the first reference ball 110 with respect to the measurement unit 200, is obtained, and then additionally moved by this value to calculate the movement amount of each axis. have. Referring to [Equation 7], it is expressed as Equation 9 below.

^Probe P _{bc, 1} in [Equation 9] refers to the relative error amount of the center of the first reference ball 110 with respect to the measurement unit 200, ideally this value is 0, but in practice due to the geometric error An additional amount of error may occur by this value. That is, the measurement unit 200 needs to move additionally by this value to touch the first reference ball 110.

In the actual encoder value calculation process (P139), the actual encoder value may be obtained by adding the encoder value according to the error amount to the ideal encoder value. In other words, when the ideal encoder value is m _{ideal, 1} and the value that each axis needs to move additionally by geometric error is Δm ₁ , and the real encoder value is m _{real, 1} , m _{real, 1} = m _{ideal, 1} + Δm ₁ . m _{ideal, 1,} Δm _{1 ,} m _{real, 1} may be represented by Equation 10, Equation 11, and Equation 12.

However, when obtaining a value that each axis should be further moved by the geometric error, it should be considered in which axis the first reference ball 110 and the measuring unit 200 is installed. When the measurement unit 200 can move only in the X and Z directions as shown in FIG. 3, the reference ball installed in the C axis, rather than the measurement unit 200, must move to move in the Y direction. Therefore, when Δm ₁ , which is the value that the measurement unit 200 needs to move in the Y direction, is − ^probe P _{bc, 1, y} should be used.

The value calculated in [Equation 12] is defined for the reference coordinate system and is the encoder value of the X, Y, and Z axes that the measurement unit must move to measure the first reference ball 110. All seven geometrical components are included.

Hereinafter, the actual encoder value may be calculated by performing the second actual encoder value calculating step S140 in the same manner as the actual encoder value of the first reference ball 110 is obtained for the second reference ball 120. Since the process of obtaining the actual encoder value of the second reference ball 120 is the same as that of obtaining the encoder value of the first reference ball 110, a detailed calculation thereof is omitted.

The actual encoder value for the second reference ball 120 is as shown in [Equation 13] below.

In the error separation step S150, seven error components are separated from actual encoder values of the first reference ball 110 and the second reference ball 120 calculated by Equations 12 and 13. I can do it.

First, the squareness error (γ _XY ) of the X-axis to the Y-axis can be calculated as shown in [Equation 15] by applying a trigonometric formula such as [Equation 14] to [Equation 12].

Here, c ₁ is the rotation angle, n is the number of measurements (= 360 / c ₁ ), R ₁ is the installation radius of the first reference ball 110, Δw _Y1 is the Y-axis installation error of the first reference ball 110 Indicates. R ₁ and Δw _Y1 are similarly calculated as in [Equation 16] by applying the trigonometric formula to [Equation 12]. R ₁ can be obtained from the encoder value for the X axis and the encoder value for the Y axis, respectively, and can be used by averaging both.

_CX)는 [수학식 17] 로부터 산출될 수 있다.Also, the right angle error (α _CY ) with respect to the Y axis of the C axis and the right angle error with respect to the X axis of the C axis (

_CX ) can be calculated from Equation 17.

_CX)는 같은 방법을 이용하여 제 2 기준볼(120)을 이용하여 구할 수도 있으며, 제 1 기준볼(110)과 제 2 기준볼(120)에 대해 구해진 값을 평균하여 사용할 수도 있다. In addition, the right angle error (γ _XY ) of the X axis of the Y axis, the right angle error of the C axis of the Y axis (α _CY ) and the right angle error of the C axis of the X axis (

_CX ) may be obtained using the second reference ball 120 using the same method, or may be used by averaging the values obtained for the first reference ball 110 and the second reference ball 120.

_ZX), Z축의 Y축에 대한 직각도 오차(α_ZY), C축의 X 방향으로의 오프셋 오차(δ_CX), C축의 Y 방향으로의 오프셋 오차(δ_CY)를 산출할 수 있다.On the other hand, by using the values measured from the first reference ball 110 and the second reference ball 120 at the same time, the squareness error with respect to the X axis of the Z axis (

_ZX ), the squareness error α _ZY of the Z-axis, the offset error δ _CX of the C-axis in the X direction, and the offset error δ _CY of the C-axis in the Y direction can be calculated.

First, Equation 18 may be derived from m _{real, 1} and m _{real, 2} values of Equations 12 and 13.

_ZX), Z축의 Y축에 대한 직각도 오차(α_ZY)가 계산될 수 있다. Z축의 X축에 대한 직각도 오차(

_ZX), Z축의 Y축에 대한 직각도 오차(α_ZY)는 [수학식 19]와 같이 제 1 기준볼(110)과 제 2 기준볼(120)의 높이차로부터 구할 수 있다.And, from [Equation 18], the squareness error with respect to the X axis of the Z axis (

_ZX ), the squareness error α _ZY with respect to the Y-axis of the Z-axis may be calculated. Squareness error with respect to the X axis of the Z axis (

_ZX ), the squareness error (α _ZY ) with respect to the Y-axis of the Z-axis can be obtained from the height difference between the first reference ball 110 and the second reference ball 120 as shown in [Equation 19].

As shown in [Equation 19], the perpendicular error (β _ZX ) with respect to the X axis of the Z axis and the perpendicular error (α _ZY ) with respect to the Y axis of the Z axis can be measured using two reference balls having different heights. If the feed distance of the vertical (Z) axis is longer than the preset value, change the height of the reference ball p times as shown in [Equation 20], measure the actual encoder value at various points, calculate the geometric error, and average In order to improve the measurement accuracy of the squareness error.

In addition, the offset error (δ _CX ) in the X direction of the C axis and the offset error (δ _CY ) in the Y direction of the C axis are measured from the first reference ball 110 and the second reference ball 120. Each value can be calculated using the value, or averaged to reduce the measurement error. First, the offset error δ _CX in the X direction of the C axis measured from the first reference ball 110 and the offset error δ _CY in the Y direction of the C axis are shown in Equation 21. The offset error δ _CX in the X direction of the C axis obtained from the ball 120 and the offset error δ _CY in the Y direction of the C axis are also calculated in the same manner.

The offset error (δ _CX ) in the X direction of the C axis and the offset error (δ _CY ) in the Y direction of the C axis are finally calculated from the first reference ball 110 and the second reference ball 120. Equation 22 can be used as an average.

As described above, the method of measuring the geometric error of the four-axis machine tool using the first reference ball 110, the second reference ball 120, and the measurement unit 200 has been described.

In addition to the embodiments described above, the fact that the present invention can be embodied in other specific forms without departing from the spirit or scope will be apparent to those skilled in the art. Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive, and thus, the present invention is not limited to the above description and may be modified within the scope of the appended claims and their equivalents.

100: reputation
110: first reference ball
120: second reference ball
200: measurement unit

Claims (10)

In the method of measuring the geometric error of a four-axis machine tool using a first reference ball, a second reference ball and the measuring unit, two reference balls of different heights,
A step of constructing a reference coordinate system constituting the reference coordinate system;
An error definition step of defining a plurality of errors for four-axis equipment;
A reference ball coordinate calculation process for obtaining a coordinate value of the reference ball with respect to the reference coordinate system, a measurement unit coordinate calculation process for obtaining a coordinate value of the measurement unit with respect to the reference coordinate system, an ideal encoder value calculation process for obtaining an ideal encoder value when there is no error A process of calculating an encoder value according to an error amount by comparing the coordinate value of the reference ball with respect to the reference coordinate system and the coordinate value of the measurement unit with respect to the reference coordinate system to obtain an encoder value according to the relative error amount of the reference ball center with respect to the measurement unit. And calculating an actual encoder value by adding an encoder value according to the error amount to an ideal encoder value, and performing the first encoder ball and the second reference ball, respectively, to calculate the actual encoder value. A first actual encoder value calculating step of calculating an actual encoder value of the second reference ball and a second actual encoder value Output stage; And
An error separation step of separating a plurality of error components from actual encoder values for the first reference ball and the second reference ball calculated from the actual encoder value calculating step;
Geometric error measurement method of a four-axis machine tool comprising a. The method of claim 1,
In the error separation step,
Geometric error measurement method of a four-axis machine tool to calculate the right angle error with respect to the X axis of the C axis, the right angle error with respect to the Y axis of the C axis, the right angle error between the X axis and the Y axis from the actual encoder value of the first reference ball . The method of claim 2,
The perpendicularity error with respect to the X axis of the C axis, the perpendicularity error with respect to the Y axis of the C axis, and the perpendicularity error of the X axis and the Y axis are each calculated from the values calculated for the first reference ball and the second reference ball. Method of measuring the geometric error of an average 4-axis machine tool. The method of claim 2,
In the error separation step,
Offset error in the X direction of the C axis, offset error in the Y direction of the C axis, orthogonality error of the X and Z axes, and Y and Z axes of the actual encoder values calculated from the first and second reference balls. Method of measuring geometric error of 4-axis machine tool for calculating squareness error. The method of claim 4, wherein
The perpendicularity error between the X-axis and the Z-axis and the perpendicularity error between the Y-axis and the Z-axis are calculated using the height difference between the first reference ball and the second reference ball. The method of claim 5,
If the moving distance of the Z-axis in which the measuring unit is installed is longer than a preset value, the four-axis machining is performed by changing the height of the reference ball to measure the actual encoder value at various points, calculating the geometrical error, and averaging it to minimize the measurement error. Method of measuring geometrical error of the machine. The method of claim 4, wherein
The offset error in the X direction of the C axis is offset in the X direction of the C axis calculated from the actual encoder value of the first reference ball and the offset in the X direction of the C axis calculated from the actual encoder value of the second reference ball. Method of measuring the geometric error of a four-axis machine tool, which is the average value of the errors. The method of claim 4, wherein
The offset error in the Y direction of the C axis is offset in the Y direction of the C axis calculated from the actual encoder value of the first reference ball and the offset in the Y direction of the C axis calculated from the actual encoder value of the second reference ball. Method of measuring the geometric error of a four-axis machine tool, which is the average value of the errors. The method of claim 1,
And a mounting radius, mounting height, and Y-direction mounting error of the first and second reference balls required to obtain the plurality of error components are calculated from actual encoder values. The method of claim 1,
The plurality of error components are measured from several points of the first reference ball and the second reference ball, the average error is calculated to calculate the final error component to minimize the measurement error geometric error method of a four-axis machine tool.

Images