The positioning accuracy compensation of turning milling machine tool
Whether the turning milling compound machining machine tool can meet the requirements of machining accuracy, in addition to geometric accuracy testing, it is also necessary to test the positioning accuracy of the machine tool. The main reason for the formation of the positioning error of the machine tool is the screw error and reverse clearance of the CNC machine tool. The screw pitch error compensation is mainly to compensate the system error, which can improve the positioning accuracy of the machine tool, the repetitive positioning accuracy and the reverse error of the drive screw movement.
The movement and positioning accuracy of the main components before the reconfigurable machine tool configuration meet the requirements of design and processing. In order to meet the accuracy requirements after the reconfigurable machine tool configuration, it is necessary to measure the reverse clearance and repeated positioning accuracy of the reconfigurable machine tool to obtain the accuracy data after the reconfigurable machine tool configuration, so as to compensate it. Based on the above idea, the laser interferometer is used to measure the motion axis error, For the results of positioning accuracy detection, such as reverse clearance and complex positioning accuracy, the CNC machine tool is compensated for accuracy through the pitch error and reverse clearance compensation function of the retractable configuration machine tool controller, so that the positioning taper is significantly improved.
For turning milling compound machining machine tools equipped with Y-axis components, the inspection items to be carried out mainly include: Z-axis positioning accuracy and dare to repeat positioning accuracy detection, X-axis positioning accuracy and repeat positioning accuracy detection, Y-axis positioning accuracy and coin duplicate positioning accuracy detection, etc. Because the Z-axis stiffness is large, or the new configuration will not cause a large change in the positioning tip, the positioning accuracy detection of the Z-axis can be stopped after the configuration, so only the accuracy change caused by the reconfigurable positioning accuracy of the X-axis and Y-axis is studied.
The basic principle of software compensation for micro turning milling compound machine tool is that in the machine coordinate system, without compensation, the measuring stroke is divided into several equal segments within the axis measuring stroke, the average position deviation of each target position is measured, and the average position deviation is inversely superimposed on the interpolation command of the digital control system.
The pitch error compensation includes unidirectional compensation and bidirectional compensation. The unidirectional compensation uses the same data compensation for the forward and reverse movement of the feed axis, and the bidirectional compensation uses different data compensation for the forward and reverse movement of the feed axis. The CNC system of turning milling compound machining center adopts one-way skimming error compensation. In the numerical control system, the reverse clearance is compensated mainly by setting the parameters of the reverse clearance. The reverse clearance compensation is effective when the coordinate axis is in any mode. After the compensation of the screw pitch error of the lead screw, measure the maximum positioning error, and then analyze the positioning error, repeated positioning error, position dispersion and other accuracy indicators. If they exceed the standard, continue to modify the compensation data, and finally make the extruding degree meet the standard. The error measurement and compensation steps are as follows:
(l) Installation and commissioning of high-precision displacement measurement device;
(2) According to the national standard, the measuring program shall be prepared. During the whole journey, the measuring points shall be positioned at evenly spaced locations;
(3) Record the actual accurate position of the operation to these points;
(4) Mark the errors at each point to form an error table in different command bit basins;
(5) Input the error table into the CNC system and compensate according to the error table.