CN102151866A - Three-ball-based multistation coordinate unifying method of processing center - Google Patents

Abstract

The invention discloses a method for unifying multi-station coordinates of a machining center based on three spheres. The method takes the relative position constant reference system established by the three spheres as a reference, and can realize the positioning of workpieces at any angle, which is equivalent to increasing the number of machining centers. The motion dimension can mainly realize accurate centering boring. First fix the workpiece on the working turntable, bore the workpiece on one side, then replace the tool with a probe, calibrate the standard ball and the workpiece machining hole, then rotate 180°, and calibrate again, using the on-machine measurement The coordinate transformation algorithm realizes the unification of the two coordinate systems, calculates the theoretical and actual angle difference, adjusts the machining direction of the spindle, and performs boring on the other side, and finally completes. Also can realize the accurate positioning of the secondary clamping of the workpiece.

Description

A method for unifying multi-station coordinates of machining center based on three-sphere

technical field

The present invention belongs to the technical fields of mechanical manufacturing and detection. Through three or more standard spheres, a space coordinate system is established, and the method of precisely locating the actual rotation angle of the turntable is realized by using the theory of coordinate transformation, so as to finally achieve precise machining, which is equivalent to adding a numerical control machining center. of dimensions.

Background technique

For the current CNC machining center, due to the large mass of the turntable, the inertia is very large, it is difficult to achieve accurate positioning of the turntable, especially difficult to achieve centering boring, and there will be low product pass rate and multiple repairs, which improves the quality of the machine. Cost, in the face of these problems, the use of laser interferometry can achieve precise positioning, but the cost is too high. The main method is offline detection and secondary repair. This greatly prolongs the production cycle and processing cost of the product, and also reduces the precision.

Contents of the invention

Aiming at the defects or deficiencies created by the above-mentioned prior art, the purpose of the present invention is to provide a method for unifying multi-position coordinates of a machining center based on three spheres, combined with the on-machine measurement function, to solve the above problems well, the method At the same time, it has the characteristics of simple mechanism, low cost and simple use.

In order to realize above-mentioned task, the present invention takes following technical solution:

Use the on-machine measurement function of the machining center to realize the centering boring of the workpiece on the turntable:

Step 1: First, clamp the workpiece to be processed on the turntable of the machining center and fix it;

Step 2, fix the fixture fastened with three standard balls on the turntable, and the three standard balls cannot be collinear;

Step 3, using the tool of the machining center to bore the workpiece;

Step 4: In the tool magazine, replace the tool with a probe, calibrate the three standard balls, measure the position of the workpiece hole at the same time, and establish the initial workpiece coordinate system through the measurement software.

Step 5: Rotate the turntable by 180°, use the probe to calibrate the three standard spheres again, establish a secondary workpiece coordinate system, and use the coordinate transformation theory to obtain the actual rotation angle.

Step 6: Replace the measuring head with a tool again, and make the tool carry out the second boring along the direction of the angle difference, and complete the centering boring.

This method borrows from the detection method and the coordinate transformation theory of using the standard ball to detect the error in the three-coordinate measuring machine, and realizes the precise positioning of the turntable. The detection error is to use the coordinate measuring machine to measure 25 points on the hemisphere of the standard sphere, use all 25 to calculate the center of the least square sphere, and calculate the maximum and minimum difference as the detection error, and in the machining center, the machining center As the body and motion mechanism of the CMM, a method of on-machine measurement realized by using the probe instead of the tool is equivalent to transplanting the entire CMM to the machining center, realizing the measurement of the centers of multiple standard balls Calibration, and then establish a reference coordinate system of the workpiece, no matter how the machining center moves, their relative positions are unchanged, combined with the coordinate transformation theory, the unity of different coordinate systems can be realized, the coordinate transformation theory has been established in the machining center It has been well applied in the field and measurement. The entire algorithm is integrated in the numerical control system or on an external PC, and realizes indirect measurement control and algorithm processing through RS232 communication.

The fixture of the standard ball must be designed reasonably, and a matrix of mounting holes is designed. According to different systems, the positional relationship of the three standard balls must be adjusted to prevent interference and achieve correct measurement.

In order to better improve the positioning accuracy, more than three standard spheres can be used to establish a coordinate system, and more redundant data can be used to improve the accuracy of the mathematical model. At the same time, a standard ball can be used to calibrate the on-machine measuring probe and perform probe radius compensation.

Using the invariance of relative position, the positioning of any corner can be realized. By using the reference coordinate system, the secondary accurate positioning of the clamping of the workpiece can be realized.

Description of drawings

Fig. 1 is a schematic diagram of centering boring of a workpiece on a working turntable.

The labels represent: 1. Y-axis of secondary workpiece coordinate system, 2. Working turntable of machining center, 3. Fixture, 4. Angle difference, 5. Rotated workpiece, 6. Y-axis of initial workpiece coordinate system, 7. Tool 8 in tool magazine, tool magazine 9, probe 10, X axis of initial workpiece coordinate system, 11, X axis of secondary workpiece coordinate system, 12, standard ball, 13, workpiece before rotation, 14, rotation The cutter before, 15, the cutter after rotation.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

Referring to Fig. 1, the application tools involved in the present invention mainly include the machining center turntable and its motion mechanism, tool magazine and three-ball positioning device. The machining center turntable refers to the working turntable 2 of the machining center. The tool magazine includes a tool holder 8, a probe 9 and a tool 7/14/15. The three-ball positioning device mainly includes a fixture 3 and three standard balls 12.

Place the workpiece 13 before rotation near the center of the turntable 2 of the machining center and fix it, while the three-ball positioning device can be fixed at the same time, or the tool can be replaced with a probe and then fixed. The three standard balls can be fixed according to the specific platform. Adjust the position of the standard sphere to realize the distribution of more measuring points on the standard sphere and improve the accuracy of the established coordinate system.

The turntable 2 of the machining center is a mechanism that can be rotated by a motor and has an encoder. The encoder is a reading device that uses grating counting and has a sensor processing circuit to achieve relative or absolute position detection. .

Among them, the Y-axis 6 of the initial workpiece coordinate system and the X-axis 10 of the initial workpiece coordinate system are the coordinate systems before rotation, and the Y-axis 1 of the secondary workpiece coordinate system and the X-axis 11 of the secondary workpiece coordinate system are the actual coordinate system after rotation. In the coordinate system, the clamp 3 after the turntable is rotated is an ordinary iron plate. The three-ball positioning device is the basis for realizing the unification of coordinates. According to the relative invariance of their positions, the unification of the coordinate systems can be realized through the rotation and translation of the two coordinate systems. The theoretical and actual angle difference 4 can be obtained by calculation, and then the rotation The previous workpiece 13 is mapped to the secondary coordinate system composed of the Y-axis 1 of the secondary workpiece coordinate system and the X-axis 11 of the secondary workpiece coordinate system, and the starting point of machining is calculated, and finally the tool is moved along the theoretical and actual angle difference 4 vector directions, start machining from the starting point of machining, and finally realize precise boring. It can be seen that this method is very convenient to realize the coordinate unification and positioning of multiple stations.

By using this method, the precision of the boring of the machining center can be improved, the efficiency and quality of machining can be improved, the rate of defective products can be reduced, the cost of off-line detection and the use of additional equipment can be reduced, and the secondary clamping and positioning can be realized conveniently.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. Under the circumstances, some simple deduction or replacement can also be made, all of which should be regarded as belonging to the scope of patent protection determined by the submitted claims of the present invention.

Claims (9)

1. machining center multistation coordinate unified approach based on three balls, it is characterized in that: this method comprises the following steps:

Step 1, the workpiece 13 before at first will rotating is installed on the machining center Work turning table 2, and fixes;

Step 2 is fixed on the anchor clamps 3 that are fastened with three standard ball 12 on the machining center Work turning table 2, and three standard ball 12 can not conllinear;

Step 3 utilizes the preceding workpiece 13 of the preceding 14 pairs of rotations of cutter of rotation to carry out bore hole;

Step 4 in tool magazine 8, changes the cutter 14 before the rotation into gauge head 10, and three standard ball 12 are demarcated, and measures the position in preceding workpiece 13 holes of rotation simultaneously, sets up initial workpiece coordinate system by Survey Software; Described initial workpiece coordinate system is exactly the coordinate system that utilizes the centre of sphere foundation of three standard ball 12;

Step 5, with machining center turntable 2 Rotate 180s °, described 180 ° is the angle that machining center Work turning table 2 will rotate in theory, utilize gauge head 10 once more three standard ball 12 to be demarcated, set up the secondary workpiece coordinate system, utilize the coordinate transform theory, obtain differential seat angle 4; Described secondary workpiece coordinate system is the coordinate system that utilizes the centre of sphere of three standard ball 12 to set up behind work in-process heart turntable 2 Rotate 180s ° once more;

Step 6 changes gauge head 10 into postrotational cutter 15 once more, makes cutter carry out the bore hole second time along the direction of differential seat angle 4, has finished heart bore hole.

2. the method for claim 1 is characterized in that, described machining center comprises that directions X, Y direction, Z direction rectilinear motion and W direction turntable rotate, and be horizontal Machining centers, cutter is parallel with Work turning table, and each axle all is equipped with high-precision encoder, has the on-machine measurement function.

3. the method for claim 1 is characterized in that, described standard ball 12 is steel balls, and what select for use is that diameter is that 10mm, the highest circularity are that 0.08um, dimensional accuracy are 0.5um and the steel ball that has fixed bar.

4. the method for claim 1 is characterized in that, has the matrix form screw above the described anchor clamps 3 and is used for fixing standard ball, also has clamping screw to be used for fixing with the working face of turntable below the anchor clamps 3.

5. the method for claim 1 is characterized in that, described bore hole is to through hole of 13 processing of the workpiece before rotating.

6. the method for claim 1 is characterized in that, described gauge head 10 is that mechanical type triggers gauge head, is used for contact type measurement.

7. the method for claim 1 is characterized in that, described Survey Software is based on the software with measurement and error assessment function of PC, also can be the measurement module that increases in the digital control system, can set up workpiece coordinate system according to measuring point.

8. the method for claim 1 is characterized in that, described coordinate transform theory is exactly by matrix operation, utilizes translation and rotation transformation algorithm to realize the conversion of a coordinate system to another coordinate system.

9. the method for claim 1 is characterized in that, described differential seat angle 4 is exactly the poor of the angle of theoretical rotation and angle that Practical Calculation obtains.

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