Study On Some Key Technologies In Fixture System Comprehensive Errors Compensation

No matter in traditional manufacturing systems or in modern manufacturing systems, fixtures are absolutely important. Inevitably, installation error and manufacturing error of the fixtures as well as manufacturing error of the locating surfaces of the workpiece, will lead to the position and orientation deviation of workpiece, having a direct impact upon machining accuracy. In the process, how to reduce the position and orientation deviation of workpiece has become a technical problem in manufacturing industry. Error detection, modeling and compensation technique, as an effective method, finally comes into being. After designing a technique route of compensating the FSCE (fixture system comprehensive errors), following tasks have been accomplished in this paper:Firstly, by using homogeneous coordinate transformation and Taylor Formula, a FSCE parameter model was established to quantitatively determine the relationship between FSCE and the position and orientation deviation of workpiece. The concrete process from measuring the fixture errors to ensuring the position and orientation deviation of workpiece was provided by using the 3-2-1 deterministic positioning fixture. The extraction module of the position and orientation deviation of workpiece was developed on the basis of Visual C++ platform. Moreover, a FSCE compensation model was formulated to determine the compensation value of the cutting position. Based on the Least Square Fitting theory and the spatial coordinate's vector method, a new method was proposed to determine the orientation deviation of workpiece. Moreover, the impact of it on typical geometric accuracy was quantitatively determined.Then, based on PMAC multi-axis motion controller, the G183, G184, G185 and other testing code were edited. A general design scheme of the embedded comprehensive error compensation system was provided. Moreover, an unaided embedded module of comprehensive error compensation was developed. Research was made on communication technology between open CNC system SKY2003 and error compensation module. Based on IPC bus technology, communication interface standard of real-time information exchange and data communication protocol were construct. TCP/IP data packet structure was defined, and processing flows of data sending and receiving were provided between CNC system and error compensation module. Based on VB platform, software of real-time error compensation was developed by using Winsock network communication mode.Finally, On-machine verification experiment platform was built on SKVH850 machine center. Probe's calibration and extraction of the position and orientation deviation of workpiece experiment were carried out to get the effective radius of the probe and the position and orientation deviation of workpiece. Pre- and after-compensation experiment were carried out by using the software of real-time error compensation. Moreover, the correctness and reliability of the model and the software developed in this paper were verified.