JP5705283B2 - Machine tool and measuring method of rotation axis of machine tool - Google Patents

Description

  The present invention relates to a machine tool and a method for measuring a rotation axis of a machine tool.

  In the prior art, a machine tool that performs processing such as cutting by moving a tool relative to a workpiece is known. In such a machine tool, a numerically controlled machine tool is known in which a tool path is designated by coordinates of a predetermined axis and the like, and machining is performed while the tool is automatically moved with respect to the workpiece. The relative position of the tool with respect to the workpiece can be changed by moving at least one of the workpiece and the tool. As a method of changing the relative position of the tool with respect to the workpiece, it is known to rotate the workpiece or the tool around the rotation axis in addition to the control of moving the workpiece or the tool along the linear motion axis.

  The rotation axis for moving the tool relative to the workpiece can be set to an arbitrary inclination angle with respect to the surface of the table to which the workpiece is attached. For example, the rotation axis can be set so as to extend in a direction perpendicular to the table surface or in a direction inclined with respect to the table surface. The angle of the rotating shaft with respect to the surface of such a table is preset at the time of design. However, the angle of the rotating shaft may slightly deviate from the angle at the time of design due to manufacturing errors that occur during the manufacture of machine tools, aging changes during use, and the like. Further, the position of the rotation axis, that is, the point through which the rotation axis passes may be slightly deviated from the design position. Patent Documents 1 to 3 disclose a method of measuring the amount of deviation of the tilt angle of the rotating shaft and the position of the rotating shaft.

  For example, Patent Document 1 discloses an error calculation method for accurately calculating a rotation axis tilt error or a position error due to an assembly error or a machining error. In this error calculation method, the work table is relatively rotated around the rotation axis with respect to the main axis to be positioned at least at three measurement positions having different rotation angles. Next, the center position of the measurement sphere disposed on the work table at each measurement position is measured by a touch sensor attached to the spindle. Next, an actual direction vector of a predetermined rotation axis is calculated based on the measured center position of the measurement sphere at each measurement position. Finally, it is disclosed that an inclination error of an actual direction vector with respect to a reference direction vector of a predetermined rotation axis is calculated.

JP 2005-61834 A JP 2006-231509 A JP 2007-44802 A

  Although the deviation of the rotating shaft due to manufacturing error, secular change at the time of use, etc. is small, it is preferable to measure the rotating shaft every predetermined period in order to maintain machining accuracy. Alternatively, it is preferable to measure the rotation axis immediately before performing processing that requires high processing accuracy.

  In the measurement of the rotation axis that is repeated every predetermined period, it is preferable that the inclination of the rotation axis and the position of the rotation axis can be measured in a short time. However, the measurement of the rotating shaft according to the conventional technique has a problem that it takes time and labor. For example, in the method described in Patent Document 1, in order to calculate the tilt error and the position error of one rotation axis, it is necessary to measure the measurement spheres at three places where the rotation angles are different from each other, which takes time. there were. In addition, there is a problem that the calculation for calculating the tilt error and the position error of the rotation axis is complicated.

  An object of the present invention is to provide a machine tool capable of measuring a rotation axis in a short time and a measurement method of the rotation axis.

The machine tool of the present invention rotates in the first rotational direction around the first axis and three linear axes composed of a first linear axis, a second linear axis, and a third linear axis that are orthogonal to each other. A movable body that supports the table and moves in the direction of the first linear motion shaft, one of the second linear motion shaft or the third linear motion shaft, and the first linear motion shaft. Adjusting means for adjusting the inclination of the moving body so that the first axis is parallel to a plane including the surface, and a measuring ball attached to the table in a state where the moving body is set to the reference state by the adjusting means Are measured at two positions rotated by 180 degrees in the first rotation direction, and based on the center positions of the two measurement balls, the first linear motion axis , the second linear motion shaft , Bei the measuring means for calculating the position of the inclination and the first axis in the coordinate system and a third linear axis That.

  In the said invention, a 1st axis line can incline with respect to each linear motion axis of a 1st linear motion shaft, a 2nd linear motion shaft, and a 3rd linear motion shaft.

In the above invention, the table is formed so as to further rotate in the second rotation direction around the second axis inclined with respect to the three linear motion axes, and the first axis is the table in the second rotation direction. The adjustment means is configured so that the first axis and the second axis when the table is at the predetermined angular position are: The measuring means is formed to be adjustable so as to be parallel to a plane including the first linear motion axis and the second linear motion shaft, and the measurement means further sets the center position of the measurement sphere attached to the table in the second rotational direction Based on the center position of the measurement sphere measured by rotating in the first rotation direction and the center position of the measurement sphere measured by rotating in the second rotation direction. first direct drive shaft of the second axis, the second direct drive shafts and third linear It can be calculated the position of the inclination and the second axis, and a relative position of the second axis with respect to the first axis at a coordinate system consisting of.

In the above-mentioned invention, the measuring means rotates at 180 degrees in the first rotation direction and measures two positions of the measurement sphere measured by rotating 180 degrees in the second rotation direction. Based on the center positions of the measurement balls measured at a total of three positions, the first linear axis , the second linear axis, and the second axis of the first axis and the second axis are made the same . the inclination of the coordinate system consisting of three linear axes and the position of the first axis and the second axis can be calculated.

The measuring method of the rotation axis of the machine tool according to the present invention includes three linear motion axes composed of a first linear motion shaft, a second linear motion shaft, and a third linear motion shaft that are orthogonal to each other, and around the first axis A measuring method of a rotation axis of a machine tool comprising a table rotating in a first rotation direction and a moving body that supports the table and moves in the direction of a first linear movement axis, wherein the first axis is a second linear movement Adjusting the tilt of the moving body to be parallel to a plane including one of the shaft or the third linear motion shaft and the first linear motion shaft, and a measurement attached to the table by a sensor mounted on the spindle of the machine tool measuring a center position of the sphere at two positions of the table is rotated 180 degrees in a first rotational direction, the first direct drive shaft of the first axis based on the center position of the two positions of the measuring ball, the second straight a step of calculating the position of the inclination and the first axis in the coordinate system consisting of shaft and the third linear axis No.

  ADVANTAGE OF THE INVENTION According to this invention, the measuring tool of a machine tool and a rotating shaft which can implement the measurement of a rotating shaft in a short time can be provided.

1 is a schematic perspective view of a machine tool in an embodiment. It is a schematic side view of the part of the machine tool bed, the moving body, and the spindle head in the embodiment. It is a schematic perspective view of the Y-axis movement device in an embodiment. It is an expansion perspective view of the part of the carriage in an embodiment. It is a schematic diagram explaining adjustment of the inclination of a moving body. It is the schematic explaining the relationship between the axis line of B axis in the embodiment, and the axis line of C axis. It is a flowchart of the measurement control which measures the rotating shaft in embodiment. It is a schematic perspective view of the part of the table of the state which has arrange | positioned the table in the measurement start position. It is a schematic perspective view of the part of the table of the state which rotated the table 180 degrees in the C-axis direction from the measurement start position. It is a schematic perspective view of the part of the table of the state which rotated the table 180 degrees in the B-axis direction from the measurement start position. It is a block diagram of the machine tool in an embodiment.

  With reference to FIGS. 1 to 11, a machine tool and a method for measuring a rotation axis of the machine tool in the embodiment will be described. In the present embodiment, a numerically controlled machine tool will be described as an example.

  FIG. 1 is a schematic perspective view of a machine tool in the present embodiment. FIG. 2 is a schematic side view of portions of a machine tool bed, a movable body, and a spindle head. With reference to FIGS. 1 and 2, the machine tool 11 includes a bed 13 serving as a base and a column 15 erected on the upper surface of the bed 13. A moving body 27 is arranged on the upper surface of the bed 13. The moving body 27 supports a table 35 that rotates the workpiece 1 via an inclined swivel base 28. The workpiece 1 is fixed to the upper surface of the table 35.

  A saddle 17 is disposed on the front surface of the column 15. Further, a spindle head 21 is disposed on the front surface of the saddle 17. A main shaft 25 is attached to the main shaft head 21. A tool 41 for machining the workpiece 1 is attached to the main shaft 25. The tool 41 processes the workpiece 1 while rotating together with the spindle 25.

  The machine tool 11 in the present embodiment includes a moving device that changes the relative position between the tool 41 and the workpiece 1. In the present embodiment, a machine coordinate system with a predetermined position on the machine tool as the origin is set. An X axis, a Y axis, and a Z axis that are orthogonal to each other in the machine coordinate system are determined in advance. When designing the machine tool, the direction in which the axis of the main shaft 25 extends (the vertical direction in FIG. 1) is referred to as the Z-axis. An axis extending in the horizontal direction along which the moving body 27 moves is referred to as a Y axis. An axis extending in the horizontal direction in which the saddle 17 moves, that is, a direction perpendicular to the Z axis and the Y axis is referred to as an X axis.

  The moving device can relatively move the tool 41 and the workpiece 1 in the X-axis direction, the Y-axis direction, and the Z-axis direction. Further, the moving device can rotate and move the workpiece 1 relative to the tool 41 in the B-axis direction around the axis 52 of the tilt turntable 28 and the C-axis direction around the axis 53 of the table 35. .

  The moving device includes an X-axis moving device that moves the tool 41 relative to the workpiece 1 in the X-axis direction. The X-axis moving device includes a pair of X-axis rails 19 a and 19 b formed on the front surface of the column 15. The saddle 17 is formed so as to be able to reciprocate along the X-axis rails 19a and 19b. The X-axis moving device moves the saddle 17 by a ball screw mechanism. The X-axis moving device includes an X-axis servo motor 20 that rotates the screw shaft of the ball screw mechanism. The X-axis moving device moves the saddle 17 by driving the X-axis servomotor 20. The spindle head 21 and the tool 41 move in the X-axis direction together with the saddle 17.

  The moving device includes a Z-axis moving device that moves the tool 41 relative to the workpiece 1 in the Z-axis direction. The Z-axis moving device includes a pair of Z-axis rails 23 a and 23 b formed on the front surface of the saddle 17. The spindle head 21 is formed so as to be capable of reciprocating along the Z-axis rails 23a and 23b. The Z-axis moving device moves the spindle head 21 by a ball screw mechanism. The Z-axis moving device includes a Z-axis servomotor 24 that rotates the screw shaft of the ball screw mechanism. The Z-axis moving device moves the spindle head 21 by driving the Z-axis servo motor 24. The tool 41 moves in the Z-axis direction together with the spindle head 21. Further, a drive motor that rotates the main shaft 25 around the axis is disposed inside the main shaft head 21.

  FIG. 3 is a schematic perspective view of the Y-axis moving device in the embodiment. Referring to FIGS. 1 to 3, the moving device includes a Y-axis moving device that moves tool 41 relative to work 1 in the Y-axis direction. The Y-axis moving device includes a pair of Y-axis rails 29 a and 29 b arranged on the upper surface of the bed 13. The moving body 27 is formed so as to be capable of reciprocating along the Y-axis rails 29a and 29b. The column 15 is formed with a hollow portion 15a so that the movable body 27 can move in the Y-axis direction.

  The Y-axis moving device moves the moving body 27 by the ball screw mechanism 30. The Y-axis moving device includes a Y-axis servo motor 32 that rotates the screw shaft of the ball screw mechanism. The Y-axis moving device moves the moving body 27 by driving the Y-axis servomotor 32. The tilt turntable 28 and the table 35 move in the Y axis direction together with the moving body 27.

  The moving device includes a B-axis rotation moving device that rotates the tool 41 relative to the workpiece 1 in the B-axis direction. The axis 52 of the B axis in the present embodiment is not parallel to any of the X axis, the Y axis, and the Z axis. That is, the B-axis axis 52 is inclined with respect to each of the three linear motion axes. The B-axis rotational movement device includes an inclined swivel base 28. Inside the moving body 27, a servo motor for rotating the tilt turntable 28 is disposed. By driving the servo motor of the tilt turntable 28, the tilt turntable 28 rotates around the axis 52 of the B axis. The work 1 rotates in the B-axis direction together with the tilt turntable 28 and the table 35.

  The moving device in the present embodiment includes a C-axis rotation moving device that rotates the tool 41 relative to the workpiece 1 in the C-axis direction. When the tilt turntable 28 is at a predetermined angular position in the B-axis direction, the C-axis axis 53 is designed to be parallel to the Z-axis. The C-axis rotational movement device includes a table 35. A servo motor is disposed inside the tilt turntable 28. By driving the servo motor, the table 35 rotates around the axis 53 of the C axis. The workpiece 1 rotates with the table 35 in the C-axis direction.

  Thus, the machine tool 11 has three linear motion axes on which the main shaft 25 moves relative to the workpiece 1. That is, the machine tool 11 has an X axis, a Y axis, and a Z axis as linear motion axes. In the present embodiment, the first linear motion axis will be described as the Y axis, the second linear motion shaft as the Z axis, and the third linear motion shaft as the X axis. Further, the machine tool 11 has two rotating shafts on which the main shaft 25 rotates relative to the workpiece 1. That is, the machine tool 11 has a B-axis axis 52 and a C-axis axis 53 as rotation axes. In the present embodiment, the first rotation direction will be described as the C-axis direction, and the second rotation direction will be described as the B-axis direction. The first axis is referred to as a C-axis axis 53, and the second axis is referred to as a B-axis axis 52.

  The machine tool in the present embodiment includes a control device 70. The control device 70 is connected to a servo motor and a drive motor of the moving device. The control device 70 can move the tool 41 relative to the workpiece 1 by controlling the servo motor of the moving device.

  Referring to FIGS. 1 and 2, machine tool 11 is a plane in which the surface of table 35 includes the X axis and the Y axis of the machine coordinate system when the rotation angle with respect to each rotation axis is 0 °, that is, the XY plane. And the B axis axis 52 and the C axis axis 53 preferably cross each other. However, the surface of the table 35 may be slightly tilted or the axis 52 and the axis 53 may be slightly separated due to manufacturing errors or aging.

  The machine tool 11 includes an angle adjustment device as an adjustment unit that adjusts the inclination of the moving body 27. In the present embodiment, the inclination of the moving body 27 is adjusted so that the B-axis axis 52 and the C-axis axis 53 extend parallel to the YZ plane over the Y-axis stroke of the moving body 27. In the present embodiment, a state in which the B-axis axis 52 and the C-axis axis 53 extend in parallel to the YZ plane while the moving body 27 is moving in the Y-axis direction is referred to as a reference state. .

  Referring to FIG. 3, the angle adjusting device includes a plurality of carriages 31 that engage with Y-axis rails 29a and 29b and move along Y-axis rails 29a and 29b. The moving body 27 is supported by the Y-axis rails 29a and 29b via the carriage 31.

  FIG. 4 is an enlarged perspective view of the carriage according to the present embodiment. A flat edge locator 36 is disposed on the side surface of the carriage 31. A plurality of push bolts 33 are attached to the edge locator 36. An adjustment washer 34 is disposed on the surface of the carriage 31. A plurality of adjustment washers 34 having different thicknesses are prepared in advance. The adjustment washer 34 is formed to be replaceable. The adjustment washer 34 is fixed to the carriage 31.

  The carriage 31 has a bolt insertion hole 31 a into which a fixing bolt for fixing the moving body 27 to the carriage 31 is inserted. Further, the adjustment washer 34 is formed with a hole 34a through which the fixing bolt is passed. The moving body 27 is fixed to the carriage 31 by disposing the moving body 27 on the surface of the adjustment washer 34 and fixing the fixing bolt to the bolt insertion hole 31a. Referring to FIG. 3, in the present embodiment, carriages 31 to which push bolts 33 and adjustment washers 34 are attached are arranged at four locations. The plurality of carriages 31 are arranged so as to support the end portions on both sides of the moving body 27 in the moving direction.

  FIG. 5 shows a schematic diagram when the inclination of the moving body is adjusted by the angle adjusting device of the present embodiment. In FIG. 5, the moving body 27 is schematically shown in a flat plate shape. The angle adjusting device can adjust the height at which the movable body 27 is supported from the bottom by changing the thickness of the adjustment washer 34. The inclination of the moving body 27 in the thickness direction indicated by the arrow 102 when the moving body 27 is moved in the Y-axis direction, that is, the inclination (roll) around the axis 92 parallel to the Y-axis is adjusted. The inclination around the shaft 92 is such that the thickness of the adjustment washer 34 disposed on the carriage 31 engaged with one Y-axis rail 29a and the adjustment washer 34 disposed on the carriage 31 engaged with the other Y-axis rail 29b. The thickness can be adjusted by changing the thickness.

  The angle adjusting device can adjust the position at which the movable body 27 is supported from the side by adjusting the insertion depth of the push bolt 33. The pushing bolts 33 attached to each of the four carriages 31 can individually adjust the pushing amount. The inclination of the moving body 27 indicated by the arrow 101 when the moving body 27 is moved in the Y-axis direction, that is, the inclination (yaw) around the axis 91 parallel to the Z-axis can be adjusted.

  In adjusting the inclination of the moving body 27, for example, a dial indicator is attached to the main shaft 25. A stretch (straight gauge) is placed on the surface of the table 35. While the dial indicator is in contact with the stretch, the moving body 27 is moved in the Y-axis direction with the maximum stroke. The moving amount of the moving body 27 at this time is not limited to the maximum stroke, and may be reduced to a frequently used moving range.

  The value of the dial indicator during the movement period of the moving body 27 is detected, and the thickness of the adjustment washer 34 is adjusted so that the error of rotating around the shaft 92 is minimized. Further, the push-in amount of the push bolt 33 is adjusted so that the error of rotating around the shaft 91 is minimized. In this way, the inclination of the moving body 27 is set to be minimal, and the moving body 27 is set to the reference state. When the adjustment of the inclination of the moving body 27 is completed, the moving body 27 is fixed to the carriage 31 with fixing bolts. The adjustment washer 34 is not prepared with various thicknesses, and the thickness of one adjustment washer 34 may be adjusted by grinding little by little.

  By adjusting the inclination of the moving body 27 by the angle adjusting device, the inclination of the moving body 27 around the axis 91 parallel to the Z axis and the inclination around the axis 92 parallel to the Y axis can be regarded as substantially zero. . That is, the rolling operation and yawing operation of the moving body 27 can be ignored. As a result, the moving body 27 performs only the pitching operation. Further, the B-axis axis 52 and the C-axis axis 53 of the machine tool extend in parallel to the YZ plane. In other words, the first axis and the second axis extend in parallel to a plane including the first linear movement axis and the second linear movement axis.

  FIG. 6 is a schematic diagram for explaining the axis of the B axis and the axis of the C axis in the machine tool. The first plane 61 is a plane including the B-axis axis 52, and the second plane 62 is a plane including the C-axis axis 53. By adjusting the inclination of the moving body 27 by the angle adjusting device, the first plane 61 and the second plane 62 are parallel to the YZ plane. The third plane 66 is a plane parallel to the XY plane including the X axis and the Y axis.

  The angle α of the B-axis axis 52 with respect to the third plane 66 and the angle β of the C-axis axis 53 with respect to the third plane 66 are predetermined by design values. However, the angles α and β may deviate slightly from the design values. For example, the angle β is designed at 90 °, but is slightly deviated from 90 ° in an actual machine tool.

  Further, in the design of the machine tool, the B-axis axis 52 and the C-axis axis 53 intersect. However, the B-axis axis 52 and the C-axis axis 53 may be slightly separated due to manufacturing errors or the like. In this case, the B-axis axis 52 and the C-axis axis 53 are in a torsional relationship.

  The machine tool 11 according to the present embodiment includes a measuring device as a measuring unit that measures the center position of the measurement sphere and calculates the inclination and position of the rotation axis based on the measured position of the measurement sphere. The measuring apparatus according to the present embodiment measures the inclination and position of the axis 53 of the C axis. Further, the inclination and position of the axis 52 of the B axis are measured. Further, the relative position of the B-axis axis 52 with respect to the C-axis axis 53 is calculated. As described above, the measuring apparatus according to the present embodiment measures the two rotation axes.

  FIG. 7 shows a flowchart of measurement control for measuring the rotation axis in the machine tool of the present embodiment. The measurement control of the present embodiment can be performed at a predetermined period during manufacturing or in use. Alternatively, it can be performed immediately before processing requiring high dimensional accuracy. As described above, the inclination of the moving body 27 is adjusted in advance to obtain the reference state.

  In step 111, the center position of the measurement sphere 44 when the table 35 is rotated using the measurement sphere 44 is measured. In the present embodiment, the center positions P1, P2, and P3 of the measurement sphere 44 are measured when the table 35 is rotated in the C-axis direction and the B-axis direction. That is, the measurement of the center positions of the three measurement balls is performed.

  FIG. 8 shows a schematic perspective view of a portion of the table when measuring the first center position P1 of the measurement sphere. The measurement start position of the table 35 for starting the measurement of the center position of the measurement sphere 44 is set in advance. FIG. 8 shows a state in which the table 35 is arranged at the measurement start position. In each of the C-axis direction and the B-axis direction, a reference angle position at which the rotation angle is 0 ° is determined in advance. At the measurement start position, for example, the rotation angle in the C-axis direction is 0 °, the rotation angle in the B-axis direction is 0 °, and the surface of the table 35 is substantially parallel to the XY plane. .

  The measurement sphere 44 is disposed at the end of the surface of the table 35. The height and diameter of the measuring sphere 44 from the surface of the table 35 are accurately known. By measuring using the measurement sphere 44, it is possible to measure a precise position with high accuracy. A touch sensor 42 is attached to the main shaft 25. A probe 43 is attached to the touch sensor 42. An output signal of the touch sensor 42 is input to the control device 70. The measuring tool is not limited to the touch sensor 42, and may be a displacement measuring device or a non-contact sensor using a laser.

  In the measurement of the center position of the measurement sphere 44, for example, the probe 43 is brought into contact with a plurality of positions around the measurement sphere 44. The position of the machine coordinate system when the probe 43 comes into contact with the measurement ball 44 is detected by a position reading device provided on each of the X axis, the Y axis, and the Z axis. Based on a plurality of positions when the probe 43 comes into contact with the measurement sphere 44, the center position of the measurement sphere 44 can be calculated. In the present embodiment, the first center position P1 of the measurement sphere 44 is detected at the measurement start position. Next, as shown by the arrow 103, the table 35 is rotated 180 ° in the C-axis direction.

  FIG. 9 is a schematic perspective view of the table portion when measuring the second center position P2 of the measurement sphere. By rotating the table 35 by 180 ° in the C-axis direction from the measurement start position, the measurement ball 44 is also arranged at a position rotated by 180 ° in the C-axis direction. In this state, the second center position P2 is measured. Referring to FIG. 8, next, as shown by an arrow 104, the tilted turntable 28 is rotated 180 ° in the B-axis direction from the measurement start position.

  FIG. 10 shows a schematic perspective view of a portion of the table when measuring the third center position P3 of the measurement sphere. By rotating the tilt turntable 28 by 180 ° in the B-axis direction from the measurement start position, the table 35 and the measurement ball 44 are also arranged at a position rotated by 180 ° in the B-axis direction. In this state, the third center position P3 is measured. In this manner, the first center position P1, the second center position P2, and the third center position P3 are measured. The respective center positions P1, P2, and P3 are expressed by the following equations in the coordinates of the machine coordinate system.

  Referring to FIG. 7, next, in step 112, the direction vector of the axis 53 of the C axis is calculated. In step 113, a straight line expression when the C-axis axis 53 is projected onto the YZ plane is calculated. With reference to FIGS. 6, 8, and 9, the perpendicular bisector between the first center position P <b> 1 and the second center position P <b> 2 becomes the axis 53 of the C axis. A midpoint Cc through which the axis 53 of the C axis passes is calculated. The midpoint Cc is a point where the distance from the first center position P1 is equal to the distance from the second center position P2. When the coordinates of the midpoint Cc are represented by (Xcc, Ycc, Zcc), the midpoint Cc is expressed by the following equation.

  Next, a vector P1P2 from the first center position P1 to the second center position P2 is calculated. When the vector P1P2 is represented by (P1P2x, P1P2y, P1P2z), the vector P1P2 can be calculated as follows.

  Here, if a rotation matrix rotated 90 ° around the X axis is a matrix Rx, the matrix Rx can be expressed as follows.

  Here, a direction perpendicular to the surface of the table 35 is defined as a direction in which the axis 53 of the C axis extends. When the rotation angle in the C-axis direction is 0 ° and the rotation angle in the B-axis direction is 0 ° (see FIG. 8), the direction vector of the axis 53 of the C-axis is the second from the first center position P1. Is a vector obtained by rotating the vector P1P2 toward the center position P2 by 90 ° around the X axis. If the direction vector VC of the C-axis axis 53 is (VCx, VCy, VCz), the direction vector VC can be expressed as follows.

  In this way, the direction vector VC of the C-axis axis 53 can be calculated. Further, the equation of the straight line 55 when the C-axis axis 53 is projected onto the YZ plane can be expressed by the following equation based on the midpoint Cc and the direction vector VC.

  Next, referring to FIG. 7, the same calculation is performed for the axis 52 of the B axis. In step 114, the direction vector of the axis 52 of the B axis is calculated. In step 115, an equation of a straight line obtained by projecting the axis 52 of the B axis on the YZ plane is calculated. With reference to FIGS. 6, 8, and 10, the perpendicular bisector between the first center position P <b> 1 and the third center position P <b> 3 becomes the axis 52 of the B axis. A midpoint Bc passing through the axis 52 of the B axis is calculated. The midpoint Bc is a point where the distance from the first center position P1 is equal to the distance from the third center position P3. When the coordinates of the midpoint Bc are represented by (Xbc, Ybc, Zbc), the midpoint Bc is expressed by the following equation.

  Next, the direction vector of the axis 52 of the B axis is calculated. The direction vector of the axis 52 of the B axis is a vector obtained by rotating the direction vector from the first center position P1 to the third center position P3 by 90 ° around the X axis. When the vector P1P3 from the first center position P1 to the third center position P3 is represented by (P1P3x, P1P3y, P1P3z), the vector P1P3 can be represented by the following equation.

  Further, the vector P1P3 is rotated by 90 ° using the matrix Rx rotated by 90 ° around the X axis. The direction in which the axis 52 of the B-axis extends is defined as a direction perpendicular to the rotation surface on which the tilted turntable 28 of the moving body 27 rotates. When the direction vector VB of the axis 52 of the B axis is expressed by (VBx, VBy, VBz), the direction vector VB can be expressed as follows.

  A straight line 54 when the axis 52 of the B axis is projected on the YZ plane can be expressed by the following expression based on the midpoint Bc and the direction vector VB.

  Referring to FIG. 7, next, in step 116, a B-axis center indicating the position of the B-axis axis 52 and a C-axis center indicating the position of the C-axis axis 53 are calculated. Here, the B-axis center and the C-axis center are the intersections of the B-axis axis 52 and the C-axis axis 53 in the design of the machine tool, and both of them coincide with each other. However, as described above, the B-axis axis 52 and the C-axis axis 53 are usually in a torsional relationship. In this case, the B-axis axis 52 and the C-axis axis 53 are closest to each other. Are the B-axis center and C-axis center. In step 117, the distance between the B-axis axis 52 and the C-axis axis 53 is calculated. Referring to FIG. 6, each of B-axis center Q and C-axis center R is set at a position at which B-axis axis 52 and C-axis axis 53 are closest to each other. The distance between the B-axis axis 52 and the C-axis axis 53 corresponds to the distance between the B-axis center Q and the C-axis center R.

  B axis center Q and C axis center R are calculated. The X-coordinate of the C-axis center R is the X-coordinate Xcc shown in the above equation (2-1). Further, the X coordinate of the B-axis center is the X coordinate Xbc shown in the above equation (7-1). The Y and Z coordinates of the B-axis center Q and the C-axis center R become the Y and Z coordinates of the intersection 56 of the two straight lines when the B-axis axis 52 and the C-axis axis 53 are projected onto the YZ plane. . The intersection point 56 is calculated from the equation (6-1) for the axis 53 of the C axis and the equation (10-1) for the axis 52 of the B axis. The Y coordinate Yi and Z coordinate Zi of the B axis center Q and the C axis center R are expressed by the following equations.

  Here, the constant AA, the constant BB, and the constant CC are as follows.

  A distance ΔBCx from the B-axis center Q to the C-axis center R is a distance in the X-axis direction between the B-axis center Q and the C-axis center R. The distance ΔBCx is expressed by the following equation.

  Referring to FIG. 7, next, in step 118, the inclination of the B-axis axis 52 and the inclination of the C-axis axis 53 are calculated. Here, the angle formed between the axis 52 of the B axis and the axis 53 of the C axis and the XY plane is obtained. An angle represented by the inner product of the unit vector (1, 0) in the Y direction on the YZ plane and the direction vector VB of the axis 52 of the B axis is defined as an angle θb. In addition, an angle represented by an inner product of the unit vector (1,0) in the Y direction on the YZ plane and the direction vector VC of the axis 53 of the C axis is defined as an angle θc. The angle θb and the angle θc can be expressed by the following equations.

  From the above equations (14-1) and (14-2), the angle θb and the angle θc are as follows.

  Here, the angle θb corresponds to the inclination angle α of the axis 52 of the B axis, and the angle θc corresponds to the angle β of the inclination of the axis 53 of the C axis. Thus, in the machine tool 11 of this Embodiment, the position of each rotating shaft is computable. Further, the inclination of the rotation axis can be calculated. More specifically, for the B-axis axis 52, the position of the B-axis center Q and the angle α can be calculated. For the C-axis axis 53, the position of the C-axis center R and the angle β can be calculated. Further, a distance ΔBCx between the B-axis axis 52 and the C-axis axis 53 can be calculated. That is, the relative position of the C-axis axis 53 with respect to the B-axis axis 52 can be calculated. By using these values, the position of the intersection of the surface of the table 35 and the axis 53 of the C axis at an arbitrary angular position of the B axis can also be obtained.

  FIG. 11 shows a block diagram of the machine tool in the present embodiment. The machine tool 11 is formed so as to be able to perform measurement control for measuring the rotation axis. Further, the machine tool 11 is configured to be able to perform machining control for machining the workpiece 1 based on the result of measurement control of the rotation axis.

  The user creates an input program 71 for machining control. The input program 71 receives a machining control program and other input information. Other input information includes machine parameters such as tool information. In the present embodiment, an input program for measurement control is created in advance and stored in the control device 70. Note that the measurement control program may be created by the user and input to the input program 71.

  The machine tool 11 includes a control device 70. The control device 70 includes a reading interpretation unit 72, an interpolation calculation unit 73, and a servo motor control unit 74. The reading / interpretation unit 72 reads the input program 71 and sends the programmed movement command to the interpolation calculation unit 73. The interpolation calculation unit 73 calculates a position command value for each interpolation cycle and sends the position command value to the servo motor control unit 74. For example, the interpolation calculation unit 73 calculates a movement amount for each time interval set based on the movement command. The servo motor control unit 74 drives each axis servo motor 75 based on the position command value.

  In the machine tool 11, when measuring the rotation axis, the table 35 is moved to the measurement start position manually or as shown in FIG. Further, the main shaft 25 and the moving body 27 are moved so that the probe 43 is disposed above the measurement sphere 44.

  Next, the inclination and position of the rotating shaft are automatically measured by measurement control. The user instructs the machine tool to start measurement control. The reading interpretation unit 72 reads an input program 71 for performing measurement control. The probe 43 and the table 35 are arranged at predetermined positions by the functions of the interpolation calculation unit 73 and the servo motor control unit 74. The probe 43 moves to a position where it contacts the surface of the measurement sphere 44. The touch sensor 42 sends a signal that the probe 43 has contacted the measurement ball 44 to the rotation axis calculation unit 76. The rotation axis calculation unit 76 detects the coordinates when the probe 43 contacts the measurement sphere 44 and calculates the center position of the measurement sphere 44.

  The rotation axis calculation unit 76 has a first center position P1 and a second center position in a state where the table is in the measurement start position, a state where the table is rotated in the C-axis direction, and a state where the table is rotated in the B-axis direction. P2 and the third center position P3 are calculated. Based on the first center position P1, the second center position P2, and the third center position P3, the rotation axis calculator 76 determines the inclination and position of the B-axis axis 52 and the inclination of the C-axis axis 53. And calculate the position. These calculated measurement results of the rotation axis are stored in the storage unit 77.

  When the machine tool performs machining control, the reading / interpretation unit 72 reads the inclination and position of the rotating shaft stored in the storage unit 77 in addition to the input program 71. The reading interpretation unit 72 creates a position command based on the tilt and position of the rotation axis, and sends the position command to the interpolation calculation unit 73. In the present embodiment, the reading / interpreting unit 72 rotates the tilt swivel 28 around the B-axis axis 52 passing through the B-axis center Q and around the B-axis axis 52 at the angle α, and passes through the C-axis center R along the C-axis axis at the angle β. A position command is calculated on the assumption that the table 35 rotates around 53. In this way, by controlling the movement of each axis using the actual inclination of the rotation axis and the center of the rotation axis different from the design value, the workpiece can be accurately processed.

  In the present embodiment, the rotation axis has been described in which the C axis is placed on the B axis having an inclined axis, but the normal rotation axis in which the axis of the B axis and the axis of the C axis are orthogonal to each other can also be used. Similarly, the position and inclination of the two rotation axes can be calculated. The combination of the two rotation axes may be an A axis and a B axis, or an A axis and a C axis. A machine tool may have a vertical or horizontal main spindle, and is not limited to a machining center, but has a rotary axis on a table such as a milling machine, boring machine, grinding machine, electric discharge machine, etc., and the table is an X axis, Y axis or Z axis. The present invention can be applied as long as it moves along any one of the shafts.

  The machining control of the present embodiment can be applied to the control of a machine tool that changes the relative position of the tool with respect to the workpiece with at least one rotation axis. As such machining control, tool tip point control can be exemplified. In tool tip point control, a predetermined position of the workpiece is used as an origin, and a coordinate system indicating the position of the tool tip with respect to this origin is used. The user inputs tool information such as the tool length and the relative position of the tool with respect to the origin on the workpiece as an input program. For example, the user inputs the inclination of the tool with respect to the workpiece and the position of the tip of the tool with respect to the workpiece. The control device calculates the movement amount of each axis based on the input program and drives each axis servo motor. In tool tip point control, the user does not need to input the position of the table or spindle in the machine coordinate system, and an input program can be easily created.

  In order to perform the tool tip point control, the rotation axis center and inclination are required. In the present embodiment, tool tip point control can be performed using the rotation axis center and inclination calculated in measurement control. Since the information on the actually detected rotation axis is used, high-precision machining can be performed. Further, as other machining control, an inclined surface machining command, a cutting point command, and the like can be exemplified.

  In the present embodiment, the position command for driving each axis servo motor is calculated by directly using the rotation axis center and inclination, but the present invention is not limited to this mode, and the rotation axis center at the time of design is calculated. An error with respect to the inclination may be calculated, and a position command sent to the interpolation calculation unit may be calculated based on the calculated error.

  In the present embodiment, a machine tool having two rotating shafts has been described as an example. However, the present invention is not limited to this embodiment, and the present invention can also be applied to a machine tool having one rotating shaft. For example, when the rotation axis is one axis of the C-axis axis 53, after adjusting the moving body 27 to the reference state, the center positions of the two measurement balls 44 rotated 180 ° in the C-axis direction are measured. . Based on the measured center position of the measuring sphere 44, the inclination and position of the C-axis axis 53 may be calculated. The position at this time is usually the intersection of the surface of the table 35 and the axis 53 of the C axis. The rotation axis is not limited to the C axis, and may be an A axis or a B axis.

  Alternatively, the present invention can also be applied to a machine tool whose axis of rotation is one axis of the B-axis axis 52. That is, the B-axis axis 52 can be adopted as the first axis. In this case, the first axis is inclined without being parallel to the respective linear motion axes of the first linear motion shaft, the second linear motion shaft, and the third linear motion shaft. Even if the B-axis axis 52 is adopted as the first axis, the inclination and the position of the B-axis axis 52 can be calculated by the same control. The position at this time is the intersection of the surface of the table that rotates in the B-axis direction and the axis 52 of the B-axis. The rotation axis may be an inclined A axis or B axis.

  In the machine tool of the present embodiment, it is assumed that the axis of the rotation axis exists on a plane parallel to the YZ plane using the angle adjusting device, and the inclination of the moving body is adjusted to such an extent that the error from this plane can be regarded as zero. Is going. And when measuring the inclination and position of one rotating shaft, it is only necessary to measure the center position of two measurement balls, and the rotating shaft can be measured easily and in a short time. In the case of a machine tool having two rotation axes as in the present embodiment, the first center position of the measurement sphere is measured at the measurement start position. The table is rotated 180 ° in the first rotation direction from the measurement start position, and the second center position of the measurement sphere is measured. Further, the third center position of the measurement sphere is measured by rotating 180 ° in the second rotation direction from the measurement start position. The center position of the measurement sphere at the measurement start position can be shared for the measurement of the two rotation axes. For this reason, the positions and inclinations of the two rotation axes can be calculated based on the measured values of the center position three times. Note that what is shared is not limited to the first center position of the measurement sphere, but may be the second center position or the third center position.

  In the present embodiment, the inclination of the moving body is adjusted so that the axis of the B axis extends in parallel with the YZ plane. However, the present invention is not limited to this configuration, and the state of extending in parallel with the XY plane including the Y axis and the X axis is used. The reference state may be used. That is, you may adjust to the inclination of a mobile body so that a 1st axis line may extend in parallel with the plane containing a 3rd linear motion axis and a 1st linear motion axis.

  In the measuring method of the rotation axis in the present embodiment, the moving body is tilted so that the first axis extends parallel to a plane including one of the second or third linear movement axis and the first linear movement axis. A step of adjusting. It includes a step of measuring the center position of the measurement sphere attached to the table with a probe attached to the spindle of the machine tool at two locations rotated 180 degrees in the first rotation direction. Further, the method includes a step of calculating the inclination and position of the first axis based on the two central positions of the measurement sphere. By this method, the rotation axis can be measured easily and in a short time. For this reason, the time of measurement control performed before processing control can be shortened.

  The scene for carrying out the method for measuring the rotational axis of the machine tool of the present invention is during the manufacture of the machine tool, during periodic inspections at the site where the machine tool is used, or during overhaul. At this time, after adjusting the inclination accompanying the movement of the movable body in the linear axis direction using the adjusting means, the inclination and position of the axis of the rotating shaft are calculated using the measuring means. Since the inclination of the moving body is adjusted, it is possible to easily measure the rotation axis in a short time by simply measuring the center positions of the measurement balls at two locations where the table is rotated 180 degrees with respect to one rotation axis. it can. The measured value is used for position correction of the feed axis in the machining process, and contributes to increasing the machining accuracy of the workpiece. In principle, it is preferable that the machine tool does not rely on correction of the geometric error, but adjusts as much as possible so that the geometric error is reduced in the manufacturing process, and does not perform correction. The adjustment of the inclination of the moving body by the adjusting means of the present invention not only facilitates the measurement of the rotation axis in a short time, but also contributes to reducing correction items as much as possible.

  The values of the inclination and the position of the axis of the rotating shaft measured by the measuring method of the rotating shaft of the present invention are set as initial values in the parameters of the storage unit 77 of the control device 70 at the time of shipment of the machine tool. Before performing high-precision machining at the site where the machine tool is used, the tilt adjustment of the moving body has already been performed by the adjusting means, so the measurement process of the measuring ball and the calculation process of the tilt and position of the axis of the rotation axis It is enough to do. The parameters may be rewritten based on the measurement result of the inclination and position of the axis of the rotation axis thus obtained.

  The angle adjusting device as the adjusting means in the present embodiment uses an adjustment washer and a push bolt. However, the present invention is not limited to this configuration, and any device that can adjust the inclination of the moving body can be employed.

  In each of the above-described controls, the order of the steps can be appropriately changed within a range where the function and the action are not changed. In the respective drawings described above, the same or equivalent parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. Further, in the embodiment, changes in the form shown in the claims are included.

DESCRIPTION OF SYMBOLS 1 Work 11 Machine tool 25 Main axis 27 Moving body 28 Inclined swivel base 31 Carriage 33 Push bolt 34 Adjusting washer 35 Table 36 Edge locator 41 Tool 43 Probe 44 Measuring ball 52 B-axis axis 53 C-axis axis 70 Controller 72 Reading interpretation Unit 76 Rotation axis calculation unit 77 Storage unit

Claims (5)

A machine tool having three linear motion shafts composed of a first linear motion shaft, a second linear motion shaft, and a third linear motion shaft that are orthogonal to each other, and a table that rotates in a first rotational direction around the first axis. In
A movable body that supports the table and moves in the direction of the first linear movement shaft;
The inclination of the movable body is set so that the first axis is parallel to a plane including one of the second linear motion shaft or the third linear motion shaft and the first linear motion shaft. Adjusting means for adjusting;
In the state where the moving body is in the reference state by the adjusting means, the center position of the measurement sphere attached to the table is measured at two positions rotated by 180 degrees in the first rotation direction. Measurement for calculating the inclination of the first axis , the second axis and the third axis in the coordinate system composed of the first axis and the position of the first axis based on the center position of the measurement sphere And a machine tool.   2. The machine tool according to claim 1, wherein the first axis is inclined with respect to the linear motion axes of the first linear motion shaft, the second linear motion shaft, and the third linear motion shaft. The table is formed to further rotate in a second rotation direction around a second axis inclined with respect to the three linear motion axes,
The first axis is formed to be parallel to the second linear movement shaft at a predetermined angular position of the table in the second rotation direction,
The adjusting means is configured so that the first axis and the second axis when the table is at the predetermined angular position are in a plane including the first linear movement axis and the second linear movement axis. It is formed to be adjustable to be parallel,
The measuring means further measures the measurement by measuring the center position of the measurement sphere attached to the table at two positions rotated by 180 degrees in the second rotation direction and rotating in the first rotation direction. Based on the center position of the sphere and the center position of the measurement sphere measured by rotating in the second rotation direction, the first linear motion axis, the second linear motion shaft, and the third linear motion axis of the second axis. 2. The machine tool according to claim 1, wherein an inclination in a coordinate system including a moving axis, a position of the second axis, and a relative position of the second axis with respect to the first axis are calculated. The measuring means rotates at 180 degrees in the first rotation direction and measures two positions of the measurement sphere that are measured by rotating 180 degrees in the second rotation direction. by the same with any of the positions of the total was measured at three points of position based on the center position of the measuring ball, the first direct drive shaft of the first axis and the second axis, the second calculating a slope of the coordinate system consisting of linear axis and the third linear axis, and a position of the first axis and the second axis, the machine tool according to claim 3. Three linear motion shafts composed of a first linear motion shaft, a second linear motion shaft and a third linear motion shaft orthogonal to each other, a table rotating in a first rotational direction around the first axis, and the table A measuring method of a rotating shaft of a machine tool comprising a moving body that supports and moves in the direction of the first linear motion axis,
Adjusting the inclination of the movable body so that the first axis is parallel to a plane including one of the second linear motion shaft or the third linear motion shaft and the first linear motion shaft;
Measuring a center position of a measuring ball attached to the table by a sensor attached to a spindle of the machine tool at two locations obtained by rotating the table by 180 degrees in the first rotation direction;
The inclination of the first axis in the coordinate system consisting of the first linear movement axis, the second linear movement axis, and the third linear movement axis based on the center positions of the two positions of the measurement sphere, and the position of the first axis A method for measuring the rotational axis of a machine tool, comprising:

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