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Modeling and compensation technology for the comprehensive errors of fixture system

Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixture. How to reduce the position and orientation deviation of workpiece has become a technical problem of improving the processing quality of workpiece. In order to increase machining accuracy, an implementation scheme of fixture system comprehensive errors (FSCE) compensation is proposed. A FSCE parameter model is established by analyzing the influence of contact points on the position and orientation of workpiece. Meanwhile, a parameter identification method for FSCE parameter model is presented by using the 3-2-1 deterministic positioning fixture, which determines the model parameters. Moreover, a FSCE compensation model is formulated to study the compensation value of the cutting position. By using RenishawOMP60 Probe and combining vertical machining centre (SKVH850) equipment with SKY2001 Open CNC System, on-machine verification system (OMVS) is built to measure FSCE successfully. The processing error can be reduced by analyzing the cutting position of the tool with the homogeneous transformation of space coordinate system. Finally, the compensation experiment of real time errors is conducted, and the cylindricality and perpendicularity errors of hole surface are reduced by 30.77% and 28.57%, respectively. This paper provides a new way of realizing the compensation of FCSE, which can improve the machining accuracy of workpiece largely.