KR100319115B1 - A method and an apparatus for measuring the 2-D position error of a NC machine tool - Google Patents

Abstract

The present invention relates to a method and apparatus for measuring a two-dimensional position error of an NC machine tool, and to accurately measure the spatial position of a spindle in a two-axis feed machine by measuring a moving coordinate point of the spindle in a two-dimensional plane. There is a purpose to do this.

Therefore, the reference coordinate input step of measuring the coordinates of the first reference sphere mounted on the table and inputting it to the controller, the distance between the first reference sphere and the second reference sphere and the distance between the first and second balls of the fixed holder mounted on the spindle The initial setting step of inputting the control unit to the control unit, the actual measurement step of measuring the distance of the first and second ballbars through the LVDT of the first and second ballbars by operating the spindle on a two-dimensional plane, and obtained in the above steps through the control unit Two-dimensional position proceeding to the coordinate point display step of obtaining and displaying the position coordinates of the spindle as a function of the measurement distance of the first and second ball bars, the distance between the first and second reference spheres, and the distance between the first and second balls. An error measuring method; In the two-axis feed machine tool, a fixed holder having the insertion shaft and the first and second balls, the first and second reference spheres attached to the upper surface of the table and the first and second reference balls are mounted on the upper end, and The ball is mounted on one side, characterized in that the two-dimensional position error measuring device consisting of the first and second ball bars mounted between the first and second balls and the first and second reference balls.

Description

A method and an apparatus for measuring the 2-D position error of a NC machine tool}

The present invention relates to a method and apparatus for measuring a two-dimensional position error of an NC machine tool. More specifically, the space of a spindle in a two-axis feed machine tool can be measured by measuring a moving coordinate point of the spindle on a two-dimensional plane. The present invention relates to a method and apparatus for measuring two-dimensional position error of an NC machine tool that can accurately verify phase position.

In general, the ball-bar is a kind of device that measures the position accuracy of NC machine tools (machining center, milling, etc.), 3D coordinate measuring machine, and robot. Compared to a device (laser interferometer, etc.), it is widely used and is in use. The present invention is an improvement of the above-described ball bar. First, a ball bar capable of length measurement (one-dimensional measurement) used in the related art is as follows.

6 shows a conventional ballbar for measuring length, comprising a single linear variable differential transformer (LVDT) consisting of a tube 101 and a transducer 102 mounted to an inner diameter of the tube 101; It consists of a ball (b) is mounted on the side end of the tube 101 and the transducer (102).

Therefore, in the case of using the ball bar configured as described above, as shown in FIG. 7, first, the reference sphere 103 is mounted on the upper surface of the table T, and the movable sphere 104 is mounted on the spindle S. Afterwards, the ball b fixed to one end of the LVDT 100 is mounted to the reference hole 103, and the ball b fixed to the other end is mounted to the moving hole 104.

Hereinafter, as illustrated in FIGS. 7 and 8, the measuring method in the state in which the ball bar is mounted as described above is as follows.

A reference coordinate input step (200) of first measuring the coordinates (X, Y, Z) of the reference sphere (103) and inputting them to the controller as origin coordinates (X0, Y0, Z0);

Next, the actual measuring step of measuring the distance (L1) between the balls located on both sides with the LVDT 100 while rotating the spindle (S) in the hemisphere continuously or randomly around the reference sphere (103) ( 201);

Next, after calculating the theoretical distance L1 between the reference sphere 103 and the ball b mounted on the spindle S from the coordinates displayed on the controller, the theoretical distance at the measurement distance L of the ballbar. Through the error calculation step 202 of calculating the distance error (displacement L = L-L1), which is a value obtained by subtracting (L1), the error in the distance traveled by the spindle S in space is measured.

However, when using a single ball bar as described above, by measuring only the distance (one dimension) from the reference sphere 103 to the spindle (arbitrary point), the coordinate of the tool position on the two-dimensional plane of the two-axis feed machine tool Since the measurement was impossible, there was a problem in that the position and accuracy of the spindle were not accurately verified.

In addition, since the ball bar can be rotated only in the hemispherical shape, there was also a problem that can not be measured in a space other than the sphere radius in which the ball bar is rotated about the reference sphere 103.

The present invention has been invented to solve the above-described problems, and by measuring the spindle coordinate point on a two-dimensional plane by using two ball bars and T-shaped fixed holder, the spindle of the two-axis feed machine tool It is an object of the present invention to provide a method and apparatus for measuring two-dimensional position errors of NC machine tools that can accurately verify the position and precision in space.

In addition, by adjusting the length of the LVDT, the measurement range on the two-dimensional plane can be extended.

In accordance with an aspect of the present invention, a reference coordinate input step of measuring coordinates of a first reference sphere mounted on a table and inputting the same to a controller, and a distance between the first reference sphere and a second reference sphere and mounted on a spindle Initial setting step of inputting the distance between the first and second balls of the fixed holder to the control unit, the actual measurement step of measuring the distance of the first and second ballbars through the LVDT of the first and second ballbars by operating the spindle on a two-dimensional plane And the position coordinates of the spindle as a function of the measurement distance of the first and second ballbars obtained in the above step, the distance between the first and second reference spheres, and the distance between the first and second balls through the control unit. Characterized in that the two-dimensional position error measuring method proceeds to the coordinate point display step; In the two-axis feed machine tool, a fixed holder having the insertion shaft and the first and second balls, the first and second reference spheres attached to the upper surface of the table and the first and second reference balls are mounted on the upper end, and The ball is mounted on one side, characterized in that the two-dimensional position error measuring device consisting of the first and second ball bars mounted between the first and second balls and the first and second reference balls.

1 is a perspective view showing a two-dimensional position error measuring apparatus of the present invention.

2 is a cross-sectional view taken along the line A-A of FIG.

3 is an enlarged cross-sectional view taken along the line B-B in FIG.

4 is a schematic view for explaining the measuring method of the present invention.

5 is a process chart showing the measuring method of the present invention.

6 is a schematic view showing a conventional ballbar for length measurement.

7 is a schematic view for explaining a conventional measuring method.

8 is a process chart showing a conventional measuring method.

Explanation of symbols for main parts of the drawings

1: fixed holder

b11: first ball, b12: second ball

11: insertion axis

21,22: 1st and 2nd reference district

b21: first reference ball, b22: second reference ball

3: first ballbar

31: LVDT (Electronic Micrometer)

311: tube, 312: transducer

32: upper socket

33: lower socket

4: second ball bar

41: LVDT (Electronic Micrometer)

411: tube, 412: transducer

42: upper socket

43: lower socket

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows a two-dimensional position error measuring apparatus of the present invention, Figure 2 is a cross-sectional view taken along the line A-A of Figure 1, the configuration thereof is as follows.

A two-axis feed machine tool having a spindle (S) moved in the Z axis and a table (T) moved in the X axis;

Insertion shafts 11 fixed to the spindle S are formed in the upper center, and fixing the first and second balls b11 and b12 mounted on both sides of the lower side with the insertion shaft 11 as a boundary. A holder 1;

First and second reference spheres 21 and 22 attached to an upper surface of the table T and having first and second reference balls b21 and b22 mounted thereon;

Upper and lower sockets 32, 42, 33 and 43 are mounted on both sides, and the first and second balls b11 and b12 and the first and second reference balls b21 and b22 are respectively mounted. It is characterized by consisting of two ball bars (3, 4, 5).

As shown in FIG. 3, the first and second ballbars 3 and 4 include a single LVDT 31 and 41 (electron micrometers) including the tubes 311 and 411 and the transducers 312 and 412, and the tubes 311 and 411. Lower sockets 33 and 43 fixed to one end of the upper socket and upper sockets mounted to one end of the transducers 312 and 412 to which the first and second balls b11 and b12 of the fixing holder 1 are mounted. 32, 42, 52).

In particular, the tubes 311 and 411 may include a first tube 311a and 411a on which the lower sockets 33 and 43 are mounted, and a second tube 311c and 411c to which the transducers 312 and 412 are inserted. Spiral shafts 311b and 411b are fixed to the ends of the tubes 311a and 411a, while tapped holes 311d and 411d are fastened to the ends of the second tubes 311c and 411c. Is formed. Thus, the length of the first and second ballbars 3 and 4 can be adjusted during use.

And the inclined groove inclined from the outside to the center is formed in the front of the upper and lower sockets, the magnet (M) is fitted in the center, the plurality of balls are mounted to the socket through the line contact.

Therefore, when using the ball bar configured as described above, as shown in Figure 4, first, the first and second reference spheres (21, 22) are mounted on the upper surface of the table (T), and fixed to the spindle (S) Mount the holder (1). Thereafter, the first and second reference balls b21 and b22 mounted on the first and second reference spheres 21 and 22 are mounted on the lower sockets 33 and 43 of the first and second ball bars 3 and 4. The upper sockets 32 and 42 of the first and second ball bars 3 and 4 are mounted to the first and second balls b11 and b12 of the fixed holder 1.

Hereinafter, the two-dimensional position measuring method in the state in which the fixed holder 1, the first and second reference spheres 21 and 22, and the first and second ball bars 3 and 4 are mounted as follows. .

4 and 5, a reference coordinate input step 51 of first measuring the coordinates (x1, y1) of the first reference sphere 21 and inputting the same to the controller;

Next, a distance A between the first reference sphere 21 and the second reference sphere 22 and a distance B between the first and second balls b11 and b12 of the fixed holder 1 are input to the controller. An initial setting step 52;

Next, by operating the spindle S on which the fixed holder 1 is mounted on a two-dimensional plane, the distances L1 and L2 are measured through the LVDTs 31 and 41 of the first and second ballbars 3 and 4. Real measurement step 53;

The distance A between the measurement distances L1 and L2 of the first and second ballbars 3 and 4 and the first and second reference spheres 21 and 22 obtained through the control unit and the first, 2 Measuring the position coordinate point of the spindle in two-dimensional space through the coordinate point display step 54 of obtaining and displaying the position coordinates Px and Py of the spindle as a function of the distance B of the balls b11 and b12. will be.

Therefore, it is possible to measure the error of the machine tool through the coordinate point (Px, Py) of the spindle (S) moved in the space.

Therefore, the following formula is applied to the coordinate points Px and Py obtained in the coordinate point display step.

(Mathematical formula)

Where Px = X-axis coordinate point of the spindle,

Py = Y-axis coordinate point of the spindle,

L1 = distance between the balls on both sides of the first ballbar,

L2 = distance between two balls of the second ballbar,

x1 = X-axis coordinate value of the first reference sphere,

A = distance between the first and second reference spheres,

B = distance between the first and second sockets.

On the other hand, in the actual measuring step 53, the moving range of the spindle (S), the first ball bar 3 is to be the center of the first reference ball (b21) of the first reference sphere (21) As shown in FIG. 4, the two-dimensional movement range and the second ball bar 4 become a portion where the two-dimensional movement range centered on the second reference ball b22 of the second reference sphere 22 coincides. As described above, the movement range of the spindle S is to form a rhombus shape.

As described above, the present invention has the effect of accurately verifying the spatial position of the spindle in a two-axis feed machine tool by allowing the spindle coordinate points to be measured on a two-dimensional plane using two ballbars. .

In addition, by adjusting the length of the LVDT, it is possible to extend the measurement range on the two-dimensional plane.

Claims (7)

A reference coordinate input step 51 of measuring coordinates (x1, y1) of the first reference sphere mounted on the table and inputting the coordinates to the controller; An initial setting step 52 of inputting a distance A between the first reference sphere and the second reference sphere A and a distance B between the first and second balls of the fixed holder mounted on the spindle to the controller; A thread measuring step 53 of operating the spindle on which the fixed holder is mounted on a two-dimensional plane to measure distances L1 and L2 of the first and second ballbars through the LVDTs of the first and second ballbars; Through the control unit, the measurement distances L1 and L2 of the first and second ballbars obtained in the above steps, the distance A between the first and second reference spheres, and the distance B between the first and second balls are functions. The method of measuring the two-dimensional position error of the NC machine tool, characterized in that proceeds to the coordinate point display step 54 to obtain and display the position coordinates (Px, Py) of the spindle. The coordinate point (Px, Py) obtained in the coordinate point display step 54, Method for measuring the two-dimensional position error of the NC machine tool, characterized in that obtained by such a formula. According to claim 1, wherein the moving range of the spindle in the measuring step 53, the first ball bar is a two-dimensional movement range and the second ball bar is centered around the first reference ball of the first reference sphere 2, the two-dimensional movement range around the reference ball of the reference sphere, the two-dimensional position error measuring method of the NC machine tool, characterized in that to form a rhombus. A two-axis feed machine tool having a spindle (S) moved in the Z axis and a table (T) moved in the X axis; Insertion shafts 11 fixed to the spindle S are formed at the upper center, and fixing the first and second balls b12 and b13 are mounted at both sides of the lower sides with the insertion shaft 11 as a boundary. A holder 1; First and second reference spheres 21 and 22 attached to an upper surface of the table T and having first and second reference balls b21 and b22 mounted thereon; Upper and lower sockets 32, 42, 33, and 43 are mounted on both sides, and the first and second sockets are mounted between the first and second balls b11 and b12 and the first and second reference balls b21 and b22. Two-dimensional position error measuring device of NC machine tool, characterized by consisting of ball bars (3, 4, 5). The method according to claim 4, wherein the first and second ballbars (3,4), a single LVDT (31,41; electron micrometer) consisting of the tubes (311, 411) and the transducers (312, 412) and the tube (311, 411) of the The lower socket (33,43) fixed to one side and the upper socket (32,42) fixed to one end of the transducer (312,412) of the two-dimensional position error measuring apparatus of the NC machine tool. 6. The tube (311, 411c) according to claim 5, wherein the tubes (311, 411) comprise a first tube (311a, 411a) on which the lower sockets (33, 43) are mounted, and a second tube (311c, 411c) on which the transducers (312, 412) are inserted. Tapped holes for fixing the spiral shafts (311b, 411b) to the end of the first tube (311a, 411a), and the spiral shafts (311b, 411b) to the end of the second tube (311c, 411c) ( 311d, 411d) is a two-dimensional position error measuring apparatus of the NC machine tool. The NC machine according to claim 5, wherein inclined grooves inclined from the outside to the center are formed in front of the upper and lower sockets (32, 42, 33, 43), and a magnet (M) is inserted in the center thereof. Two-dimensional position error measurement device of the machine.