TWI592252B - Angular error correction device and method for machine tools - Google Patents

Description

Tool machine rotating shaft positioning accuracy detecting device and method

The invention relates to a detecting device, in particular to a detecting device for detecting and correcting the positioning accuracy of a rotating shaft of a multi-axis machine tool.

In recent years, the processing dimensions of many traditional machine tools have been upgraded from the original three-axis to multi-axis, composite design, and even to the high-precision, long-stroke gantry machine. In the above-mentioned machine tool, multi-axis machine tool There are a plurality of rotating parts, ranging from one to two, and more than six. The application of more and more rotating components to mechanical equipment is an industrial trend, so the positioning accuracy of the rotating shaft of the rotating element will be in the future. The precision machining equipment will play a very important role.

Regarding the accuracy of the rotating element of the machine tool, in the draft specification of the International Organization for Standardization (ISO), the standard for bidirectional positioning accuracy of the rotating element of the five-axis machine tool must be within 16 arc seconds (arc-sec). In order to meet the requirements of this standard, the detection and correction of the accuracy of the rotating components of the tooling machine is the most effective and direct way to improve the quality of the product to meet international standards.

The system of measuring machine tools has been developed for a long time. The following describes the techniques commonly used in the current five-axis machining machine to detect the rotational error of the rotating platform, and the problems existing in the prior art:

1. Measuring tool for measuring the yaw angle or tilting axis of the machining center (API angle splitter Swivel check) is to use the level meter to erect on the upper turntable. The upper turntable is mounted on the tilting axis of the machine tool, and the machine tool rotates at an angle. The turntable is reversed at the same angle, and the error value of the measuring level is the tilting angle of the machine tool. This detection technique is only applicable to the tilting axis.

2. The wireless rotary axis correcting instrument uses an external high-precision rotating platform with a laser interferometer as a measurement reference to detect the error of the rotating shaft of the upper turntable and the lower machine tool, and the external rotating platform is mounted on the rotating shaft of the machine tool. When a forward rotation signal is input on the rotating shaft, an external reverse rotation signal is input by the external high-precision rotating platform, and the relative error of the two rotating shafts is detected by the external interferometer, because the external rotating shaft is used as a contrast, Only energy measures the optical encoder or linear optical scale error between the two rotating axes.

3, the automatic collimator with 12 or 24 faces, using the measurement of the light source through the multi-faceted reflection of the resulting small angle principle, can detect the angular error of the index plate and the turntable, but because of 12 or 24 faces The flaw of the relative angle of each surface exists in the 稜鏡 itself, and the center of the 12-sided or 24-sided 和 and the indexing disc and the center of the turntable shaft need to be matched, otherwise a sine wave error will be caused.

In summary, it can be known that the existing rotation angle detecting device for the multi-axis machine tool mainly detects the angle error by an external special instrument, or calculates the result by relative comparison of the inner and outer rotating shafts, and the erection time is too long. How to measure and compensate the error of the rotating platform of the multi-axis machine tool is the key technology that needs to be improved at present.

In view of the existing device for detecting the rotating shaft of the multi-axis machine tool, the instrument that needs to be installed outside the machine tool needs a wide measuring environment, and the erection time is long. After continuous experiment and research, the invention finally develops an improvement. There are currently missing inventions.

The present invention is mainly directed to providing a machine tool rotating shaft positioning accuracy detecting device, which is disposed in a machine tool, the machine tool is provided with a linear optical scale, and includes: a sensing module, the sensing module is provided with a suspension seat a connecting rod is arranged on the top of the suspension seat, and the connecting rod is coupled to the machine tool, and two sensors are installed on the suspension seat, and the sensing directions of the two sensors are staggered, and the sensing direction is The staggered area is set as a sphere measuring area; a ball fixed group, the ball fixing group is provided with a magnetic seat, and the magnetic seat is disposed on the machine tool, and the magnetic seat is combined with an extension rod at the extension rod The free end is combined with a ball to extend the ball into the sphere measuring area of the sensing module; and a computer electrically connecting the machine tool and the sensing module, receiving the two sensors and the The data of the machine tool is used for program operation.

Further, the machine tool of the present invention comprises a spindle, a rotating platform, and a controller, wherein the sensing module is fixed to the bottom end of the spindle by the connecting rod, the ball fixing group The magnetic base is magnetically fixed to the rotating platform, the controller is electrically connected to the linear optical scale, and the computer is electrically connected to the controller.

Further, the suspension seat of the present invention is provided with a top plate, four cantilevers are formed around the top plate, two adjacent cantilevers are provided with an instrument bracket, and the other two cantilevers are respectively provided with a light source bracket, the connection The rod is coupled to the center of the top plate, and the sensor is coupled to each instrument bracket, and the sensing directions of the two sensors are staggered at right angles, and a light source is coupled to each light source bracket.

Preferably, the computer of the present invention wirelessly receives data of the two sensors and the machine tool.

Preferably, the sphere of the present invention is a rigid body or a glass sphere.

When the present invention is applied, it is a method for detecting the positioning accuracy of the rotating axis of the machine tool, and the part involved in the calculation is calculated using a computer. Firstly, the rotating platform is rotated to rotate the ball to any three points, and the tool module is used to drive the sensing module to detect the position of the ball, read the coordinates of any three points, and then use the least square method to obtain the rotating platform. The coordinate of the reference axis is calculated from the coordinate of the reference axis and the coordinate of the position of the ball, and the coordinate formula of any position to be tested is calculated, and the path of the tool machine is generated by using the coordinate formula.

The tool machine drives the ball to move along the infeed path, and selects more than three points to be tested in the moving path, and the sensing module respectively measures the ball at each point to be measured, and the tool The data of the machine is added to the data of the sensing module detecting the offset of the ball, and the actual coordinates of all the points to be measured are obtained, and the actual rotation center is calculated by the least square method; finally, the formula of the cosine theorem is used, The coordinate of the actual rotation center, and the coordinate value of the starting point and the end point before and after the machine tool rotates the ball to the original angle, calculate the actual angle of rotation, and subtract the original angle from the actual angle to obtain the rotation. The angular error amount of the rotating shaft of the platform, thus completing the detecting operation of the present invention.

The invention has no special requirements for the erection environment, and does not need to be erected outside the machine table, and can reach: 1. avoid accidental collision, and 2, do not need a wide working environment, and calculate the axis of the sensor by any three points. Position and take the path to avoid the manual adjustment of the axis, thus effectively reducing the effectiveness of the erection time.

10‧‧‧Tool machine

11‧‧‧ Spindle

12‧‧‧Rotating platform

13‧‧‧Linear optical ruler

20‧‧‧Sensor module

21‧‧‧suspension

211‧‧‧ top board

212‧‧‧cantilever

213‧‧‧ instrument holder

214‧‧‧Light source bracket

22‧‧‧ Connecting rod

23‧‧‧ Sensors

24‧‧‧Light source

A‧‧‧ sphere measurement area

30‧‧‧sphere fixed group

31‧‧‧Magnetic seat

32‧‧‧Extension rod

33‧‧‧ sphere

40‧‧‧ computer

‧‧‧‧Axis

B‧‧‧00

B’‧‧‧Points to be tested

Ω‧‧‧ The angle between the zero point and the X axis

θ‧‧‧An angle between the point to be measured and the zero point

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a preferred embodiment of the apparatus of the present invention.

2 is a perspective view of a sensing module in accordance with a preferred embodiment of the present invention.

Figure 3 is a perspective view of a ball set in accordance with a preferred embodiment of the present invention.

4 is a flow chart showing the steps of a method in accordance with a preferred embodiment of the present invention.

Figure 5 is a schematic illustration of the operation of the method of the preferred embodiment of the present invention.

Figure 6 is a graph showing the path calculation formula of the method of the preferred embodiment of the present invention.

In order to understand the technical features and practical effects of the present invention in detail, and in accordance with the contents of the specification, the following is further described in detail with reference to the preferred embodiments shown in the drawings, as shown in FIG. 1 to FIG. The machine tool rotating shaft positioning accuracy detecting device of the present invention is to install a sensing module 20, a ball fixing group 30, and a computer 40 in the machine tool 10, wherein the machine tool 10 is a numerically controlled multi-axis tool. The machine includes a main shaft 11, a rotating platform 12, a linear optical scale 13, and a controller (not shown); the main shaft 11 is movable up and down along the Z axis, and the rotating platform 12 is rotatable and Moving in the XY plane, the linear optical scale 13 can measure the position of the machine tool 10 moving along the X-axis, the Y-axis or the Z-axis. The controller is electrically connected to the linear optical scale 13 and can control the spindle 10 of the machine tool 10 and rotate. The action of platform 12.

As shown in FIG. 2, the sensing module 20 is provided with a suspension seat 21, and the suspension base 21 is provided with a top plate 211. The top plate 211 is a cross-shaped and horizontally disposed plate body, and four sides are formed around the top plate 211. a cantilever 212, in which a bottom surface of the two adjacent cantilevers 212 is coupled to an instrument bracket 213, and a light source bracket 214 is respectively coupled to the bottom surface of the other two cantilevers 212, and a connecting rod 22 is coupled to the top of the center of the top plate 211. The sensing module 20 is fixed to the bottom end of the main shaft 11 by the connecting rod 22, and a sensor 23 is respectively mounted on the two instrument holders 213. The sensor 23 can be a PSD (position sensing detector) and a CCD (charge coupled). a sensor, a CMOS (Complementary Metal Oxide Semiconductor Device), a two-dimensional sensor, or the like that senses an object position signal, and is defined by the sensors 23 to be fixed to the captured image The image capturing center of the center of the face is calculated, and the distance between the center of the image object and the image capturing center is calculated. The sensing directions of the two sensors 23 are parallel to the X-axis direction of the machine tool 10 and the Y-axis direction of the machine tool 10, respectively. The sensing directions of the two sensors 23 are staggered into a right angle, and the area where the sensing directions of the two sensors 23 are staggered is set as a sphere measuring area A, and a light source 24 is respectively mounted on the two light source brackets 214, and each light source 24 is installed. The light rays are respectively irradiated toward the sensor 23 in the opposite direction, and each of the sensors 23 is provided with sufficient light for image capturing.

Referring to FIG. 3, the ball fixing group 30 is provided with a magnetic base 31. The magnetic base 31 is magnetically fixed to the rotating platform 12 of the power tool 10. The top of the magnetic base 31 is coupled to extend upward. The extending rod 32 is coupled to a ball 33 at the free end of the extending rod 32. The ball 33 can be a rigid body or a glass ball. The ball 33 can extend into the spherical measuring area A of the sensing module 20. The ball 33 is sensed by the two sensors 23, it is judged whether the center of the ball 33 is located at the sensing center of the sensor 23, or the distance of the center of the ball 33 from the sensing center of the sensor 23 is calculated; In the present invention, the image is compared and calculated in the manner of sensing the ball 33. Since there is no difference between the images before and after the rotation of the sphere, only the image when the position is moved changes, so that the image of the sensing sphere 33 is used before, The comparison calculation of the post-image does not have the problem of angular deviation, which can reduce the occurrence of errors.

The computer 40 is electrically connected to the controller, and the computer 40 receives data of the two sensors 23 in a wireless or wired manner, data of the position coordinates of the machine tool 10 measured by the linear optical scale 13, and the The data of the rotation angle of the rotating platform 12 is programmed in accordance with the program loaded in the computer 40, and the result of the program operation is provided to provide the controller with compensation for the rotation axis angle of the machine tool 10.

The invention also provides a method for detecting the positioning accuracy of the rotating shaft of the machine tool, which is a method for detecting the positioning accuracy of the rotating shaft of the machine tool by using the device of the invention mentioned above, mainly using a machine tool 10 The internal linear optical scale 13 cooperates with the external module composed of the sensing module 20 and the ball fixing group 30, and measures the three-dimensional coordinates of the machine tool 10, and utilizes the axis and the zero point of the rotating shaft in the same plane (with the axis The three points at which the heart begins to rotate and the point to be measured (the point at which the axis is rotated by an angle from the starting point) can be used to calculate the angle of rotation using the cosine theorem and calculate the angle; for example, The three points on the YZ plane can measure the rotation angle of each point to be measured on the A-axis. The rotation angle of each point to be measured on the B-axis can be measured from three points on the XZ plane, and the three points on the XY plane can be measured. The rotation angle of each point to be measured on the C axis is measured.

Since the method of the present invention applied to the three rotating shafts of A, B or C of the machine tool 10 can be analogous, the preferred embodiment of the present invention only takes the rotating shaft of the C-axis as an example, and the other two rotating shaft methods are similar. Referring to the step flow chart of FIG. 4, the method steps of the preferred embodiment of the present invention will be described with reference to the configurations shown in FIG. 1 to FIG.

Mounting device: The connecting rod 22 is fixed to the bottom end of the main shaft 11 of the machine tool 10, the sensing module 20 is mounted on the main shaft 11 of the machine tool 10, and the magnetic seat 31 of the ball fixing group 30 is magnetically fixed to the rotating platform. 12, the ball 33 is located between the sensing module 20 and the magnetic base 31, the computer 40 and the sensing module 20 are electrically connected, and the computer 40 is electrically connected to the controller of the machine tool 10.

Calculating the reference rotation center: Referring to FIG. 1 to FIG. 3 and FIG. 5, the initial position of the ball 33 is any first point, and the sensing module 20 is driven by the main shaft 11 of the machine tool 10 to make the ball 33 enter the sphere. In the measurement area A, after the sensing center of the two sensors 23 coincides with the center of the ball 33, the computer 40 is connected to the machine tool 10 through the library of the controller, and the ball 33 detected by the linear optical scale 13 is read. The coordinates (X ₁ , Y ₁ , Z ₁ ), then the spindle 11 drives the sensing module 20 to move away, and the rotating platform 12 rotates at any angle to rotate the ball 33 to any second point, and then the spindle 11 is driven. The measuring module 20 repeats the foregoing measurement method to read the coordinates (X ₂ , Y ₂ , Z ₂ ) of the sphere 33 detected by the linear optical scale 13 , and finally the spindle 11 drives the sensing module 20 to move away and rotate. The platform 12 is rotated at any angle, and then the ball 33 is rotated to any third point. Then, the sensing module 20 is driven by the machine tool 10, and the measurement is repeated to read the ball detected by the linear optical scale 13. 33, coordinates _{(X 3, Y 3, Z} 3); the above-described ball 33 is located at any of the three linear optical scale 13 to detect the coordinates of the minimal square , Determined with reference to the axis of the rotary platform 12 via the computer 40 calculating the coordinates.

Generate the infeed path code for measurement: Please refer to Figure 6. On the plane of the rotation axis of the C axis, as shown in the figure, the coordinate of the reference axis α is (0, 0), and the coordinate of the zero point b is ( X ₀ , Y ₀ ), the angle between the zero point b and the X axis is ω, the angle between the point b′ to be measured and the zero point b is θ, and the coordinate formula of the point b′ to be measured is calculated as follows: the coordinates of the zero point b are

The coordinates of the point to be measured b' are

Therefore, the point to be measured b'=(X ₀ cos θ-Y ₀ sin θ, X ₀ sin θ+Y ₀ cos θ)

Substituting the coordinate formula of the point to be tested b' into the computer 40 to generate an infeed path of the machine tool 10 written by the digital control code (NC-code), causing the rotating platform 12 to move the ball 33 to the XY plane to be tested. point.

Obtaining the actual coordinates of the point to be measured: firstly, the spindle 11 is raised along the Z axis in the feeding path of the machine tool 10, so as to avoid the collision between the sensing module 20 and the extension rod 32 connecting the balls 33, and then the circle After the ball 33 moves to the first point to be measured (X _p and Y _p ), the spindle 11 directly descends to the original position along the Z axis, so that the ball 33 enters the sphere measurement area A, and then the two sensors 23 detect The center of the ball 33 is displaced from the sensing center of the sensor 23 by the X-axis direction and the Y-axis direction X _e and Y _e , and the coordinates of the linear optical scale 13 recorded inside the machine tool 10 are added to the ball 33. The displacement amount can be used to obtain the actual position, so the actual coordinates (X _r , Y _r ) of the first point to be measured = (X _p +X _e , Y _p +Y _e ), and then repeat the aforementioned measurement method measurement Move to the second point to be measured and the other ball 33 to be measured, and the actual coordinates of the second point to be measured and the actual coordinates of other points to be measured are obtained.

Eliminating the inclination angle of the point to be measured: In the foregoing step of determining the actual coordinate of the point to be measured, since the rotating platform 12 has the possibility of tilting, the actual coordinates of the respective points to be measured need to be homogeneously converted, and the Tilted coordinate position, homogeneous coordinate formula: If the two coordinate systems are rotated, the homogeneous rotation transformation matrix of the original coordinate system around the X-axis, Y-axis or Z-axis rotation angle θ angle (that is, the inclination angle) is :

The θ angle described above is obtained by rotating the ball 33 from 0 degrees to 180 degrees by the rotating platform 12, moving the sensing module 20 with the spindle 11 to move to the center and the two sensing of the ball 33. When the sensing centers of the device 23 are coincident, the value of the linear optical scale 13 of the power tool 10 is read, and the position of the ball 33 on the X-axis at two points (0 degrees and 180 degrees) is measured. Since the value of the Y coordinate is the same, the influence on the tilt angle of the Y-axis 17 can be ignored first, and then the coordinates of 0 degrees, the coordinates of 180 degrees, and the coordinates of the position where the sphere 33 should ideally be 180 degrees, Using computer 40 Substituting the formula of the cosine theorem, the angle θ can be obtained. After the actual coordinates of all the points to be measured are converted by the computer 40 through the aforementioned homogeneous rotation transformation matrix, the actual coordinates of the elimination tilt angle can be obtained; however, if the rotating platform 12 does not have Tilting, the method of the present invention can skip the step of eliminating the tilt angle of the point to be measured, and directly use the actual coordinates of all the points to be measured as subsequent calculations.

The actual center of rotation is calculated: using the minimum area circle method, three actual coordinates are substituted into the computer 40 to calculate the coordinates (i, j) of the actual center of rotation of the rotating platform 12.

Calculating the angular error value: in the XYZ rectangular coordinate system, the coordinates of the actual rotation center are (i, j), and the rotating platform 12 drives the ball 33 to rotate by an original angle, before and after the rotation of the ball 33 and the actual rotation center The length between the two is b and c. The distance between the starting point and the ending point before and after the rotation of the ball 33 is a, which is calculated by the computer 40 and substituted into the formula of the following cosine theorem: It can be obtained that the actual angle is Ω, and the angle error of the rotation axis of the C axis can be obtained by subtracting the Ω from the original angle, and the angular error amount is input into the controller through the computer 40 to correct the angular position of the rotating shaft of the machine tool 10. Error compensation value.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any one of ordinary skill in the art can use the present invention without departing from the scope of the present invention. Equivalent embodiments of the invention may be made without departing from the technical scope of the present invention.

10‧‧‧Tool machine

11‧‧‧ Spindle

12‧‧‧Rotating platform

13‧‧‧Linear optical ruler

20‧‧‧Sensor module

30‧‧‧sphere fixed group

40‧‧‧ computer

Claims (9)

A tool machine rotating shaft positioning accuracy detecting device is disposed on a machine tool, and the machine tool is provided with a linear optical scale, and includes: a sensing module, the sensing module is provided with a suspension seat, the suspension seat There is a top plate, four cantilevers are formed around the top plate, two adjacent cantilevers are provided with an instrument bracket, and two other cantilever arms are respectively provided with a light source bracket, and a connecting rod is arranged on the top of the suspension seat. The connecting rod is coupled to the center of the top plate, and the connecting rod is coupled to the machine tool. Two sensors are mounted on the hanging seat, and the sensors are combined in each instrument bracket, and a light source is coupled to each light source bracket. The sensing directions of the two sensors are staggered, the sensing directions of the two sensors are staggered into a right angle, and the area in which the sensing directions are staggered is set as a sphere measuring area; a ball fixed group, the ball fixed group is provided with a a magnetic base is disposed on the machine tool, the magnetic base is coupled with an extension rod, and a ball is coupled to the free end of the extension rod to measure the sphere of the ball into the sensing module District; and a computer The computer is electrically connected to the tool and the sensor module, the sensor, and a data receiving two tool performs the program operation. The machine tool rotating shaft positioning accuracy detecting device according to claim 1, wherein the machine tool comprises a spindle, a rotating platform, and a controller, wherein the sensing module is fixed by the connecting rod The bottom end of the main shaft, the ball fixing group is magnetically fixed to the rotating platform by the magnetic seat, the controller is electrically connected to the linear optical scale, and the computer is electrically connected to the controller. The machine tool rotating shaft positioning accuracy detecting device according to claim 1 or 2, wherein the computer receives the data of the two sensors and the machine tool in a wireless manner. The machine tool rotating shaft positioning accuracy detecting device according to claim 3, wherein the ball is a rigid body or a glass ball. A method for detecting the positioning accuracy of a rotating shaft of a machine tool comprises the following steps: installing a device: mounting a sensing module on a spindle of the machine tool, and combining a ball fixing group on a rotating platform of the machine tool, the ball fixing group is provided with a The suspended ball, the machine tool is a numerical control tool machine; the reference rotation center is calculated: the rotating platform is rotated to rotate the ball to any three points, and the tool module is used to drive the sensing module to detect the position of the ball, and read Taking the coordinates of any three points and using the least square method to obtain the coordinates of the reference axis of the rotating platform; generating the infeed path code for the measurement: calculating the coordinates of the reference axis and the coordinates of the ball position The coordinate formula of any position to be tested is generated, and the path of the tool machine is generated by using the coordinate formula; the actual coordinate of the point to be measured is obtained: the tool machine drives the ball to move along the path of the infeed, and moves the path Selecting more than three points to be tested, the sensing module located in the in-situ path of the infeed path respectively measures the spheres at the points to be measured, and detects the data of the machine tool and the sensing module. The ball The shifted data is added to obtain the actual coordinates of all the points to be measured; the actual rotation center is calculated: using the minimum area circle method, the coordinates of the actual rotation center of the rotating platform are calculated with the actual coordinates of all the points to be measured; and the angle is calculated. Error value: Calculate the rotation by using the formula of the cosine theorem with the XYZ right angle coordinate system, the coordinates of the actual rotation center and the coordinates of the starting point and the end point before and after the machine tool rotates the ball to the original angle. The actual angle of the actual angle minus the original angle gives the angular error of the axis of rotation of the rotating platform. The method of detecting a rotational axis positioning accuracy of the machine tool according to claim 5, wherein in the step of calculating an angular error value, the angular error amount is input to a controller of the machine tool, and the rotating axis of the machine tool is corrected. Angle positioning error compensation value. The method for detecting a positioning accuracy of a machine tool rotating shaft according to claim 6, wherein between the step of determining the actual coordinates of the point to be measured and the step of calculating the actual center of rotation, eliminating the inclination angle of the point to be measured The steps are as follows: obtaining the inclination θ angle of the rotating platform, and converting the actual coordinates of all the points to be measured and the θ angle through the homogeneous rotation transformation matrix, and obtaining the actual coordinates of all the points to be measured after eliminating the inclination angle, thereby The actual coordinates perform the step of calculating the actual center of rotation. The method for detecting the positioning accuracy of the rotating machine axis of the machine tool according to claim 7, wherein in the step of eliminating the inclination angle of the point to be measured, the ball is rotated from 0 to 180 degrees by the rotating platform. The tooling device drives the sensing module to detect the coordinate position of the ball at 0 degrees and 180 degrees, and then uses the cosine theorem to coordinate the position of the ball at 0 degrees, 180 degrees, and ideally 180 degrees. The formula calculates the angle θ. The method for detecting the accuracy of the positioning of the rotating shaft of the machine tool according to any one of claims 5 to 8, wherein the sensing module is provided with two sensors, and the sensing directions of the two sensors are staggered at right angles. In the step of calculating the reference rotation center, when the coordinates of the sphere are read, the sphere is sensed by two sensors to determine whether the center of the sphere is located at the sensing center of the sensor, and if so, read Take the data of the machine tool and get the coordinate position of the ball.