Tool horizontal position parameters (2) and table thickness parameters (1) After the workpiece is mounted on the workbench, it is necessary to determine the position of the workpiece in the upper platform coordinate system. This requires knowing the thickness parameter of the table. If the parameter is not accurate, it will cause the coordinates of the machining point to translate up and down as a whole. In addition, while calibrating the thickness parameter, the positional parameter of the tool in the pedestal coordinate system can be determined by the function relationship. For the convenience of calibration calculation, a process hole is processed on the upper platform of the 6-TPS type milling machine.
The horizontal position calibration of the tool is controlled by the hand wheel module to control the probes in three positions in the inner cavity of the process hole, so that the probe contacts the inner wall of the process hole, and the hand wheel module is triggered to calculate the current origin of the platform coordinate system at the base coordinates. The position on the XBYB plane is A'1, A'2, A'3. Since the point is taken on the inner wall of the process hole, the distance from the center point of the probe to the center of the process hole is constant d=Rr, and r and R are The radius of the probe and process hole. There is an error vector Δc. Therefore, the position vector of the probe center point (also the head point) on the XBYB plane in the base coordinate system: c=c'+ΔcΔc is the horizontal distance between the center of the process hole and the origin of the upper platform coordinate system. It is also the distance between the actual tool tip point and the nominal tool head point. There is no error in the 3D translation process, but when the table is processed with the attitude, an error will occur. Therefore, this parameter needs to be calibrated.
The dashed probe of the calibration process is the nominal probe position. The projection point of the axis of the dashed probe in the base coordinate system is the center of the circle, and the circumference of the radius RM is the projection circle of the motion track of the origin of the upper platform coordinate system; (PMx, PMy ) is the coordinate of the origin of the upper platform coordinate system on the projection circle; d is the horizontal distance between the actual probe and the origin of the upper platform coordinate system; H is the sum of the thickness h of the upper platform and the radius r of the probe; Δz is the horizontal trigger of the upper platform The difference between the height of the probe and the attitude-triggered probe; Δzd is the height difference caused by the distance d; α and β are the inclination direction angle and inclination angle of the upper platform; β' is the work surface edge (PMx, PMy) to (cx , cy) The tilt angle in the direction.
Control the upper platform to leave the probe, pay attention to ensure that the origin of the upper platform coordinate system moves on the projection circle, and at a certain position (determined by the angle θ), the upper platform is moved with an attitude, and the inclination angle is β, the upper platform The relationship between the amount of descent Δz and the angle θ ("+" line) is the amount of descent of the upper platform when the distance between the actual probe and the nominal probe is 0; ("O" line) is the distance between the two is not 0 At the same time, it can be found that if RM takes appropriate parameters, the amount of drop on the upper platform is approximately cosine function distribution, and the amount of decrease has maximum value Δzmax and minimum value Δzmin. After the tool is replaced, the height of the tool needs to be renewed. Make a determination: if the length of the changed tool is L'c, set the height of the new tool point to H'c, and have: H'c=Hc-(L'c-Lc). Determine the height of the tool tip point of the new tool, and do not need to re-measure each time the tool is changed.
Conclusion A new type of Cnc Milling Machine is introduced. According to the characteristics of this type of milling machine, the attitude calibration algorithm of the tool relative to the base system of the milling machine is given. The algorithm plays an important role in improving the machining accuracy of the milling machine. At present, the algorithm uses the parameter calibration module of 6-HITPKM CNC milling machine. The actual machining shows that the algorithm is effective, which plays a great role in promoting the commercialization and practicalization of parallel machine tools.
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