KR20220023270A - Method for measuring geometric errors of vertical 5-axis machine tools - Google Patents

Abstract

The present invention provides a method for measuring geometric errors of vertical five-axis machine tools which can simply and accurately measure 11 geometric errors with constant values regardless of transport positions of five transport axes by using a measurement apparatus and a reference ball. According to one embodiment of the present invention, the method for measuring geometric errors of vertical five-axis machine tools uses a reference ball installed on a rotary table rotating around two perpendicular rotational axes of a vertical five-axis machine tool and a measurement apparatus measuring the position of the reference ball to measure geometric errors of the vertical five-axis machine tool and comprises: a reference coordinate system setting step of setting a reference coordinate system of the five-axis machine tool; an error definition step of defining a plurality of geometric errors and measurement variables of the five-axis machine tools; a modeling step of using modeling coordinate values resulting from mathematically modeling the coordinate values of the reference ball and the coordinate values of the measurement apparatus with respect to the reference coordinate system to calculate real measurement values of the reference ball including the plurality of geometric errors; and an error separation step of separating the plurality of geometric errors from the real measurement values of the reference ball measured by the measurement apparatus while rotating the two rotational axes to a plurality of positions. In the error separation step, the real measurement values are measured at a plurality of points resulting from rotating one of the two rotational axes once by a prescribed angular interval at three points resulting from rotating the other one of the two rotational axes by a prescribed angle.

Description

Method for measuring geometrical errors of vertical 5-axis machine tools {METHOD FOR MEASURING GEOMETRIC ERRORS OF VERTICAL 5-AXIS MACHINE TOOLS}

The present invention relates to a method for measuring the geometric error of a vertical 5-axis machine tool, and more particularly, to a vertical 5-axis machine tool using the center point measurement value of a reference ball measured with a measuring instrument mounted on the vertical 5-axis machine tool. It relates to a measurement method that can identify the geometric error of

In a vertical 5-axis machine tool consisting of 3 linear axes and 2 rotating axes, 11 geometric errors with constant values occur regardless of the positions of the 5 feed axes, which are the three perpendicularity errors and the angles generated by the three linear axes. It consists of two perpendicularity errors and two rotation axis errors that occur on the rotation axis.

In fact, in a 5-axis machine tool, the precision of the equipment is lowered due to these geometric errors, and the machining quality is lowered due to the relative error between the tool and the work piece. Therefore, in order to improve processing quality, it is necessary to measure and correct these geometrical errors.

Existing methods that can measure these geometric errors include a laser interferometer, a perpendicularity mirror, a double ball bar, R-Test, and a method using a processed specimen.

However, the method using the laser interferometer and the perpendicularity mirror can individually measure only the perpendicularity error of the linear axis, and there is a limit in measuring the geometrical error related to the rotation axis. Most of the methods by the double ball bar and R-Test can measure only the geometrical error related to the rotation axis, and for this, there is a limitation that several measurement setups must be performed. The method using the processed specimen is to process a number of processing patterns on a 5-axis machine tool, measure and analyze the processing error to identify the geometrical error, and requires additional work for specimen processing and measurement analysis.

Therefore, there is a need for a measurement method that can simply and accurately measure 11 geometrical errors that are constant regardless of the feed position of the axis in a vertical 5-axis machine tool.

In one aspect of the present invention, in a vertical 5-axis machine tool consisting of three linear axes and two rotational axes, 11 geometric errors having a constant value regardless of the transfer positions of the five transfer axes are measured using a measuring instrument and a reference ball. We want to provide a way to measure accurately. In addition, we intend to provide a periodic measurement method for geometrical errors of machine tools to compensate for geometrical errors during initial installation of vertical 5-axis machine tools or when the operating environment is changed.

The method for measuring geometrical error of a vertical 5-axis machine tool according to an embodiment of the present invention includes a reference ball installed on a rotary table rotating about two mutually perpendicular rotation axes of a vertical 5-axis machine tool, and the reference ball A method of measuring a geometric error of the vertical 5-axis machine tool using a measuring instrument for measuring a position, the method comprising: a reference coordinate system setting step of setting a reference coordinate system of the 5-axis machine tool; an error definition step of defining a plurality of geometric errors and measurement variables of the 5-axis machine tool; Modeling that calculates the actual measurement value of the reference ball including the plurality of geometric errors by using the modeling coordinate values that mathematically model the coordinate values of the reference ball and the coordinate values of the measuring instrument with respect to the reference coordinate system, respectively step; and an error separation step of separating the plurality of geometric errors from the actual measurement values of the reference ball measured with the instrument while rotating the two rotation axes to a plurality of positions, wherein in the error separation step, the actual measurement values is measured at three points at which one of the two rotary shafts is rotated by a predetermined angle, respectively, and at a plurality of points where the other of the two rotary shafts is rotated by one rotation at regular angular intervals.

The vertical 5-axis machine tool includes three linear axes, an X-axis, a Y-axis, and a Z-axis, and the two rotation axes include an A rotation axis rotating about the X axis, and a C rotation axis rotating about the Z axis and, in the reference coordinate system setting step, the origin of the reference coordinate system is set to the intersection of the central position of the X-axis and the A rotation axis, and the reference coordinate system is the X-axis, Y-axis, and Z-axis of the vertical 5-axis machine tool can be defined based on

In the error definition step, the plurality of errors include: a perpendicularity error of the Y-axis with respect to the X-axis, a perpendicularity error of the Z-axis with respect to the Y-axis, a perpendicularity error of the Z-axis with respect to the X-axis, and the Z A perpendicularity error of the A rotation axis with respect to the axis, a perpendicularity error of the A rotation axis with respect to the Y axis, a perpendicularity error of the C rotation axis with respect to the Y axis, a perpendicularity error of the C rotation axis with respect to the X axis, an offset error of the rotation axis A with respect to the Y axis, an offset error of the rotation axis A with respect to the Z axis, an offset error of the rotation axis C with respect to the X axis, and an offset error of the rotation axis C with respect to the Y axis can do.

In the modeling step, the actual measurement value of the reference ball including the plurality of geometric errors is an abnormal measurement value in the absence of the plurality of geometric errors, and between the reference ball and the measuring instrument due to the plurality of geometric errors. It can be calculated by adding the relative displacement.

In the error separation step, the actual measured value is the position of the reference ball at three points rotated by the same predetermined angle in the (+) and (-) directions including 0 degrees around the A rotation axis, the C rotation axis 11 geometrical errors can be derived by measuring at a plurality of points rotated by 1 at regular angular intervals around the .

The measurement variable is, in the initial measurement position, the rotation radius, which is the distance in the X-axis direction from the central point of the C rotation axis to the reference ball, and the installation error that is the distance in the Y-axis direction from the center point of the C rotation axis to the position of the reference ball , and a height of the reference ball, which is a distance in the Z-axis direction from the upper surface of the rotation table of the C rotation axis to the center point of the reference ball.

In the error separation step, the rotation radius, the installation error, and the height of the reference ball may be calculated.

In the error separation step, a perpendicularity error of the X-axis, the Y-axis, the Z-axis, the A rotation axis, and the B rotation axis among the plurality of geometric errors may be calculated using the rotation radius and the installation error.

In the error separation step, an offset error of the rotation axis A and the rotation axis C among the plurality of geometric errors may be calculated using the height of the reference ball.

According to an embodiment of the present invention, 11 geometrical errors of the linear axis and the rotary axis can be simultaneously separated by three measurement patterns in a vertical 5-axis machine tool.

In addition, since it uses a measuring instrument and a reference ball, it is inexpensive compared to other measuring equipment, and the measurement setup is simple.

In addition, since the geometric error is separated by the center point measurement value of the reference ball measured at three positions about one rotation axis, it is possible to accurately measure the geometric error for the entire area of the vertical 5-axis machine tool, and without changing the measurement setup. Since all geometric errors can be separated in a short time, when a change in equipment installation and use environment occurs, the measurement method of this embodiment can be used for periodic measurement and correction of geometric errors to maintain the precision of equipment at a constant level.

1 is a diagram illustrating the configuration of a reference ball and a measuring instrument for a method of measuring a geometric error of a vertical 5-axis machine tool according to an embodiment of the present invention.
Figure 2 is a flow chart showing the overall geometrical error measurement method of the vertical 5-axis machine tool according to an embodiment of the present invention.
3 is a view showing the configuration and reference coordinate system of each axis in the vertical 5-axis machine tool.
4 is a view showing a perpendicularity error between three linear axes in a vertical 5-axis machine tool.
5 and 6 are diagrams showing geometrical errors with respect to two rotation axes in a vertical 5-axis machine tool.
7 is a view showing 11 geometrical errors in a vertical 5-axis machine tool.
8 and 9 are diagrams illustrating a process of defining a measurement variable in a method for measuring a geometric error of a vertical 5-axis machine tool according to an embodiment of the present invention.
10 is a diagram illustrating kinematic modeling for coordinates of a reference ball and a measuring instrument with respect to a reference coordinate system.
11 is a view showing the rotation angle of the axis of rotation A in the vertical 5-axis machine tool according to an embodiment of the present invention.
12 is a view showing a measurement position for a constant rotation angle of the C rotation axis in a vertical 5-axis machine tool according to an embodiment of the present invention.
13 is a flowchart showing a subdivided error separation step among the overall sequence of a method for measuring geometrical errors of a vertical 5-axis machine tool according to an embodiment of the present invention.
14 is a diagram illustrating a process of separating seven perpendicularity errors of a linear axis and a rotation axis among geometric errors of a vertical 5-axis machine tool according to an embodiment of the present invention.
15 is a diagram illustrating a process of separating four offset errors of a rotation axis among geometric errors of a vertical 5-axis machine tool according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

In addition, since the size and thickness of each component shown in the drawings are arbitrarily indicated for convenience of description, the present invention is not necessarily limited to the illustrated bar.

Throughout the specification, when a part is "connected" to another part, it includes not only the case where it is "directly connected" but also the case where it is "indirectly connected" with another member interposed therebetween. In addition, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

1 is a diagram illustrating the configuration of a reference ball and a measuring instrument for a method of measuring a geometric error of a vertical 5-axis machine tool according to an embodiment of the present invention.

Referring to Figure 1, the geometrical error measuring method of the vertical 5-axis machine tool according to an embodiment of the present invention, the reference ball 110 installed on the rotary table 100 of the vertical 5-axis machine tool, the reference ball A geometrical error is measured using a measuring instrument 200 capable of measuring the position of 110 .

The rotary table 100 rotates about two rotation axes A and C (see FIG. 3 ), and may have a flat plate shape. The reference ball 110 is installed on the rotary table 100 . The measuring instrument 200 is configured to measure the position of the reference ball 110 , and may measure the position of the center point of the reference ball 110 by contacting the reference ball 110 . In this specification, the position of the reference ball 110 means the center point of the reference ball 110 . The reference ball 110 may be installed on the rotary table 100 in a form connected to a bar-shaped support to have a height H that is a distance from the reference plane of the rotary table 100 .

Hereinafter, a method of measuring the geometrical error of a vertical 5-axis machine tool using the reference ball 110 and the measuring instrument 200 will be described. In this description, a case of measuring the position of the reference ball 110 using a touch trigger probe as an example of the instrument 200 is described, but the present invention is not limited thereto, and the position of the reference ball can be measured The instrument may also include other instrumentation such as a position inspector (Trinity probe). In addition, although the description is based on the structure of a typical vertical 5-axis machine tool in this description, the same method may be applied to a vertical 5-axis machine tool having a different feed axis configuration.

Figure 2 is a flowchart showing the overall geometrical error measurement method of the vertical 5-axis machine tool according to an embodiment of the present invention, Figure 3 is a view showing the configuration and reference coordinate system of each axis in the vertical 5-axis machine tool.

Referring to Figure 2, the geometrical error measuring method of the vertical 5-axis machine tool according to an embodiment of the present invention, the reference coordinate system setting step (S100), the error definition step (S200), the modeling step (S300), and the error Separation step (S400) is included.

In the reference coordinate system setting step S100, a reference coordinate system is set. In a vertical 5-axis machine tool, if the center line of the two rotation axes (A, C) is set as the average line of the rotational feed of each rotation axis, the origin of the reference coordinate system (Ref., see Fig. 3) is the intersection of the center position of the X axis and the axis of rotation A can be set to Set the distance from the origin of the reference coordinate system (Ref.) to the center point of the upper surface of the rotation table of the rotation axis C as O _X , O _Y , O _Z according to each linear axis direction. The reference coordinate system is defined by matching the actual X axis of the vertical 5-axis machine tool with the X axis of the reference coordinate system at the origin of the reference coordinate system, and defining the axis perpendicular to the reference coordinate system X axis as the Y axis of the reference coordinate system, Set the Z-axis of the reference coordinate system in the direction of the right-handed coordinate system with respect to the plane. When the reference coordinate system is set in this way, a geometric error may be defined accordingly.

In addition, the reference coordinate system can be defined based on the linear axis of the vertical 5-axis machine tool at the origin of the reference coordinate system.

Here, the set reference coordinate system also sets the reference coordinate system by matching the actual X-axis of the vertical 5-axis machine tool with the X-axis of the reference coordinate system. When the reference coordinate system is set in this way, a geometric error may be defined accordingly.

Referring to FIG. 3 , the vertical 5-axis machine tool includes an X axis, a Y axis, and a Z axis perpendicular to each other, an A axis rotating about the X axis, and a C axis rotating about the Z axis. Accordingly, the reference ball 110 installed on the upper surface of the rotary table 100 may change the position according to the rotation angles of the two rotary shafts A and C.

In the error definition step S200 , a total of 11 errors may be defined with respect to the previously set reference coordinate system.

4 is a view showing a perpendicularity error between three linear axes in a vertical 5-axis machine tool.

_ZX, Y축을 기준으로 Z축의 직각도 오차를 α_ZY, X축을 기준으로 Y축의 직각도 오차를 γ_YX 로 정의할 수 있다. 즉, 3개의 직선축(X, Y, Z)에 대한 3개의 직각도 오차를 정의할 수 있다.Referring to FIG. 4 , the perpendicularity error of the Z-axis with respect to the X-axis is calculated.

_ZX , the perpendicularity error of the Z axis with respect to the Y axis can be defined as α _ZY , and the perpendicularity error of the Y axis with respect to the X axis can be defined as γ _YX . That is, three perpendicularity errors with respect to three linear axes (X, Y, Z) can be defined.

5 and 6 are diagrams showing geometrical errors with respect to two rotation axes in a vertical 5-axis machine tool. In relation to the two rotation axes A and B, in addition to the above-described perpendicularity error, an offset error occurs. The geometric error of the rotation axis is caused by a parallel relationship with the linear axis and a difference in center point.

_AZ, Y축을 기준으로 A 회전축의 직각도 오차를 γ_AY 로 정의할 수 있다. 또한, Z축을 기준으로 A 회전축의 오프셋 오차를 δ_AZ, Y축을 기준으로 A 회전축의 오프셋 오차를 δ_AY 로 정의할 수 있다.Referring to FIG. 5 , the perpendicularity error of the A rotation axis with respect to the Z axis is calculated.

The perpendicularity error of the A rotation axis with respect to the _AZ and Y axes can be defined as γ _AY . In addition, the offset error of the A rotation axis with respect to the Z axis may be defined as δ _AZ , and the offset error of the A rotation axis with respect to the Y axis may be defined as δ _AY .

_CX 로 정의할 수 있다. 또한, Y축을 기준으로 C 회전축의 오프셋 오차를 δ_CY, X축을 기준으로 C 회전축의 오프셋 오차를 δ_CX 로 정의할 수 있다.Referring to FIG. 6 , the perpendicularity error of the B rotation axis with respect to the Y axis is α _CY , and the perpendicularity error of the C rotation axis with respect to the X axis is obtained.

It can be defined as _CX . In addition, the offset error of the C rotation axis with respect to the Y axis may be defined as δ _CY , and the offset error of the C rotation axis with respect to the X axis may be defined as δ _CX .

7 is a view showing 11 geometrical errors in a vertical 5-axis machine tool.

Referring to Figure 7, a vertical 5-axis machine tool consisting of three linear axes (X, Y, Z) and two rotation axes (A, B) can be defined a total of 11 geometric errors.

In addition, in the error definition step ( S200 ), a measurement variable may be defined.

8 and 9 are diagrams illustrating a process of defining a measurement variable in a method for measuring a geometric error of a vertical 5-axis machine tool according to an embodiment of the present invention.

Referring to FIG. 8 , the distance from the center point of the rotation table 100 , that is, the rotation axis C to the center point of the reference ball 110 in the X-axis direction is defined as a 'rotation radius (R)'. In addition, the distance from the center point of the rotation axis C to the center point of the reference ball 110 in the Y-axis direction from the initial position of measurement is defined as 'installation error (Δw _Y )'. At this time, since it can be assumed that the installation error of the reference ball 110 in the X-axis direction is included in the rotation radius R, only the installation error Δw _Y of the reference ball in the Y-axis direction can be considered. In addition, referring to FIG. 9 , the distance in the Z-axis direction from the top surface of the rotation table of the rotation axis C to the center point of the reference ball is defined as 'height (H)'. As such, in the error definition step S200, three measurement variables may be defined.

10 to 12 are views illustrating some processes of a method for measuring geometrical errors of a vertical 5-axis machine tool according to an embodiment of the present invention, and FIG. It is a diagram illustrating modeling, and FIG. 11 is a view showing the rotation angle of the axis A in a vertical 5-axis machine tool according to an embodiment of the present invention, and FIG. 12 is a vertical 5-axis according to an embodiment of the present invention. It is a diagram showing the measurement position for a constant rotation angle of the C axis of rotation in a machine tool.

In the modeling step (S300), the coordinate values of the reference ball 110 with respect to the reference coordinate system and the coordinate values of the measuring instrument 200 with respect to the reference coordinate system by using the 11 geometric errors and three measurement variables defined above, respectively It can be modeled mathematically.

In more detail, values obtained by mathematically modeling the coordinate values of the reference ball 110 and the coordinate values of the measuring instrument 200 with respect to the reference coordinate system are defined as modeling coordinate values. Referring to FIG. 10 , mathematical modeling may be performed using a homogeneous transformation matrix as a path from the origin Ref. of the reference coordinate system to the center point of the reference ball 110 . Here, T denotes a homogeneous transformation matrix, and P denotes a position vector. For example, the homogeneous transformation matrix ^R T _X is a homogeneous transformation matrix of the X-axis with respect to the reference coordinate system (Ref.), and ^C P _bc is a vector indicating the position of the reference ball with respect to the C rotation axis. The coordinate value of the reference ball 110 with respect to the reference coordinate system calculated through this mathematical modeling becomes the modeling coordinate value of the reference ball 110 . The modeling coordinate value of the reference ball 110 may be calculated as shown in (Equation 1) below. Here, a denotes the rotation angle of the A rotation axis, and c denotes the rotation angle of the C rotation axis.

(Formula 1)

Also, referring to FIG. 10 , a path from the origin Ref. of the reference coordinate system to the measuring instrument 200 may also be mathematically modeled using a homogeneous transformation matrix. The coordinate value of the measuring instrument 200 with respect to the reference coordinate system calculated through such mathematical modeling becomes the modeling coordinate value of the measuring instrument 200 . The modeling coordinate value of the measuring instrument 200 may be calculated as shown in (Equation 2) below.

(Equation 2)

On the other hand, the touch trigger probe 200 is fed to measure the reference ball 110 for the measurement value of the reference ball 110 when there is no geometric error in the 5-axis machine tool, that is, the reference coordinate system origin (Ref.). If the encoder value of each feed axis to be performed is defined as an ideal measured value (m _ideal ), the ideal measured value is a value in which the center point of the reference ball 110 and the position of the measuring instrument 200 exactly match. This can be calculated as (Equation 3) below.

(Equation 3)

On the other hand, the encoder of each feed axis required for the measuring instrument 200 to measure the reference ball 110 with respect to the measurement value of the reference ball when there is a geometric error in the 5-axis machine tool, that is, the reference coordinate system origin (Ref.) If the value is defined as an actual measured value (m _real ), the actual measured value is a value obtained by adding the relative displacement ( ^probe P _bc ) due to an error between the reference ball 110 and the measuring instrument 200 to the abnormal measured value. That is, the actual measured value may be calculated by adding the coordinate value Δm due to the relative displacement to the ideal measured value. The formula for the actual coordinate value can be calculated as (Equation 4) below. However, in the case of a vertical 5-axis machine tool, such as a structure in which the two rotation axes are mounted on a linear axis, the reference ball 110 must be transferred in the direction of the touch trigger probe 200 in the direction of the linear axis in the opposite direction, so the relative displacement must be added as the opposite sign.

(Equation 4)

Accordingly, the actual measured value m _real of the reference ball 110 using the measuring instrument 200 may be calculated as shown in (Equation 5) below.

(Equation 5)

Therefore, it can be confirmed that the actual measurement value (m _real ) of the reference ball considering the geometrical error is changed by the rotation angles (a, c) of the two rotation axes (A, C).

In the error separation step ( S400 ), a plurality of errors are separated into actual measurement values measured while rotating the A rotation axis and the C rotation axis to transfer the position of the reference ball.

Referring to FIG. 11 , the position of the reference ball 110 may be measured at 0 degrees and three points rotated at the same predetermined angle in the (+) direction and the (-) direction about the A rotation axis.

12, the reference ball at a plurality of points (j = 1, 2, 3, ??, N) rotated once at a constant angular interval about the C rotation axis at each position of the three points of the rotation axis A of FIG. The position of (110) can be measured.

In more detail, referring to FIGS. 11 and 12 , three points rotated about the A rotation axis, for example, a 0 degree position ((a) of FIG. 1), a position of a ((b) of FIG. 11), and -a degree position (Fig. 11(c)), respectively, the position of the reference ball at a plurality of points where the rotation table 100 on which the reference ball 110 is installed is rotated by one rotation at regular angular intervals about the C rotation axis. can be measured

The actual measured value of the reference ball is expressed as m _real (0, c) at a plurality of points rotated at a constant angular interval about the C axis of rotation at 0 degrees about the axis of rotation A (c in parentheses is the rotation angle), the actual measured value of the reference ball at a degree position around the A axis of rotation is expressed as m _real (a, c), and the actual measured value of the reference ball at -a degree around the A axis of rotation is expressed as m When expressed as _real (-a, c), it can be calculated as (Equation 6), (Equation 7), and (Equation 8) below, respectively.

(Equation 6)

(Equation 7)

(Equation 8)

13 is a flowchart showing the subdivided error separation step (S400) of the overall procedure of the geometrical error measurement method of the vertical 5-axis machine tool of FIG. 2 .

13, by applying the trigonometric one-turn formula as shown in (Equation 9) below to the actual measurement value of the reference ball calculated from (Equation 6) to (Equation 8), the previously defined vertical 5-axis machine tool A separation equation for all geometric errors (7 squareness errors and 4 offset errors) can be derived.

(Equation 9)

14, in order to calculate the 7 squareness errors of the 5-axis machine tool, the turning radius (R) and the installation error (Δw _y ) can be calculated as shown in (Equation 10) and (Equation 11) below. there is.

(Equation 10)

(Equation 11)

Using the rotation radius (R) and the installation error (Δw _y ) calculated in this way, the perpendicularity error of the linear axis and the rotation axis can be calculated from the reference ball measurement value measured at the position where the rotation axis A is 0 degrees as shown in (Equation 12). there is.

(Equation 12)

In addition, using the rotation radius (R) and the installation error (Δw _y ), the linear axis and the perpendicularity error of the rotation axis as shown in (Equation 13) from the reference ball measurement value measured at the +a and -a degrees of the A rotation axis. can be calculated.

(Equation 13)

Therefore, the error term composed of the two squareness errors in (Equation 12) and (Equation 13) can be independently calculated using the previously calculated squareness error as shown in (Equation 14) below.

(Equation 14)

)과 기 산출된 직각도 오차로부터 산출한다. 오프셋 오차는 기준볼의 높이(H)와 연관되어 있으므로 아래의 (수식 15)와 같이 높이(H) 값을 먼저 산출한다.Referring to FIG. 13, the four offset errors related to the two rotation axes of the vertical 5-axis machine tool are the one rotation average value (

) and the calculated squareness error. Since the offset error is related to the height (H) of the reference ball, the height (H) value is calculated first as shown in (Equation 15) below.

(Equation 15)

Referring to FIG. 15, when the offset error term is calculated using the height (H) value of the reference ball calculated by (Equation 15) and the one-turn average value of the actual measured value, it is as shown in (Equation 16) below.

(Equation 16)

The error term composed of the two offset errors in (Equation 16) is calculated using the previously calculated offset error as shown in (Equation 17) below.

(Equation 17)

In this way, using the geometrical error measurement method of a vertical 5-axis machine tool according to an embodiment of the present invention, 11 geometrical errors of a vertical 5-axis machine tool consisting of a perpendicularity error of a linear axis and a perpendicularity and an offset error of a rotation axis The error and three measurement variables can be isolated simultaneously. In addition, for 11 geometrical errors, a total of 3 measurements were performed while rotating the C axis of rotation once at regular intervals at the 0 degree position around the A axis and at three positions rotated at the same predetermined angle in the (+) and (-) directions. Measured values can be calculated mathematically.

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings. It goes without saying that it falls within the scope of the invention.

100 turn table
110 reference ball
200 instruments

Claims (9)

Measuring the geometrical error of the vertical 5-axis machine tool using a reference ball installed on a rotary table rotating around two mutually perpendicular rotation axes of the vertical 5-axis machine tool, and a measuring instrument that measures the position of the reference ball As a method,
a reference coordinate system setting step of setting a reference coordinate system of the 5-axis machine tool;
an error definition step of defining a plurality of geometric errors and measurement variables of the 5-axis machine tool;
Modeling that calculates the actual measurement value of the reference ball including the plurality of geometric errors by using the modeling coordinate values that mathematically model the coordinate values of the reference ball and the coordinate values of the measuring instrument with respect to the reference coordinate system, respectively step; and
an error separation step of separating the plurality of geometric errors from the actual measurement value of the reference ball measured by the measuring device while rotating the two rotation shafts to a plurality of positions;
includes,
In the error separation step,
The actual measurement value is measured at a plurality of points where one of the two rotation axes is rotated by a predetermined angle at three points, the other one of the two rotation axes is rotated by one rotation at a constant angular interval, respectively, of a vertical 5-axis machine tool A method of measuring geometrical errors. The method of claim 1,
The vertical 5-axis machine tool includes three linear axes, an X-axis, a Y-axis, and a Z-axis,
The two rotation axes include an A rotation axis that rotates about the X axis, and a C rotation axis that rotates about the Z axis,
In the reference coordinate system setting step, the origin of the reference coordinate system is set as the intersection of the central position of the X-axis and the A rotation axis, and the reference coordinate system is based on the X-axis, Y-axis, and Z-axis of the vertical 5-axis machine tool. Defining method for measuring geometrical errors of vertical 5-axis machine tools. 3. The method of claim 2,
In the error definition step,
The plurality of errors may include a perpendicularity error of the Y axis with respect to the X axis, a perpendicularity error of the Z axis with respect to the Y axis, a perpendicularity error of the Z axis with respect to the X axis, and the A rotation axis with respect to the Z axis. a squareness error of the A rotation axis with respect to the Y axis, a perpendicularity error of the rotation axis C with respect to the Y axis, a perpendicularity error of the axis C with respect to the X axis, a perpendicularity error of the axis A with respect to the Y axis Vertical 5-axis, including an offset error of the A rotation axis, an offset error of the A rotation axis with respect to the Z axis, an offset error of the C rotation axis with respect to the X axis, and an offset error of the C rotation axis with respect to the Y axis A method of measuring geometrical errors of machine tools. The method of claim 1,
In the modeling step,
The actual measurement value of the reference ball including the plurality of geometric errors is calculated by adding an abnormal measurement value in the absence of the plurality of geometric errors and the relative displacement between the reference ball and the measuring instrument due to the plurality of geometric errors A method of measuring geometrical errors of vertical 5-axis machine tools. 3. The method of claim 2,
In the error separation step,
The actual measured value is the position of the reference ball at three points rotated by the same predetermined angle in the (+) and (-) directions, including 0 degrees around the A rotation axis, at a constant angular interval around the C rotation axis A method of measuring geometrical errors of a vertical 5-axis machine tool that derives 11 geometrical errors by measuring at multiple points rotated by a . 6. The method of claim 5,
The measurement variable is
In the initial measurement position, the rotation radius, which is the distance in the X-axis direction from the central point of the C rotation axis to the reference ball, an installation error that is the distance in the Y-axis direction from the center point of the C rotation axis to the position of the reference ball, and the C rotation axis Including the height of the reference ball, which is the distance in the Z-axis direction from the upper surface of the rotary table to the center point of the reference ball, the geometrical error measuring method of a vertical 5-axis machine tool. 7. The method of claim 6,
In the error separation step,
A geometrical error measuring method of a vertical 5-axis machine tool for calculating the rotation radius, the installation error, and the height of the reference ball. 8. The method of claim 7,
In the error separation step,
Using the rotation radius and the installation error to calculate the perpendicularity error of the X-axis, Y-axis, Z-axis, A rotation axis, and B rotation axis among the plurality of geometric errors, geometrical error measurement of a vertical 5-axis machine tool method. 8. The method of claim 7,
In the error separation step,
Using the height of the reference ball to calculate the offset error of the A rotation axis and the C rotation axis among the plurality of geometric errors, a geometrical error measuring method of a vertical 5-axis machine tool.

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