The Research And Development Of CNC System For High Speed Camshaft Grinder

Camshaft is the key component of an automobile engine. Its machining quality is an important determinant for the performance of engine. Camshafts productions require high machining efficiency and machining precision. The conventional method of camshafts grinding has several defects, such as long preparation period, low grinding accuracy and surface quality, so it can't meet the needs of new productions. This thesis sets the high-speed and high-precision CBN grinding as objective, and studies the key theories and techniques for camshafts grinding systematically. The main contents of this thesis are listed as follows:According to the features of cam grinding, the two-axis simultaneous machining model was established, and motion equations for the workpiece rotation (C-axis) and the linear motor moving (X-axis) were deduced, which provided theoretical foundation for the two-axis motion control.As the profile of cam was complicated, cubic B-spline algorithm was used to complete all the data processing in this thesis, such as fitting the curve of cam profile, calculating the angle and the displacement increment data of C-axis and X-axis in every CNC interpolation cycles. Then the velocity and acceleration of the two axes were further analyzed, and the movement process was also optimized to improve the dynamic response and motion control precision of the servo system.Linear servo card is the core control equipment for X-axis linear motion, the thesis researched PCI device driver development technology on Linux platform, and provided the corresponding driver module to complete R/W operation between the CNC and the card, and thereby the X-axis linear motion can be controlled by CNC.The FIPO (Feed Interpolation) module was developed to control the speed-changing rotation of C-axis, which could be activated by M Code, and automatically processed the pre-planned speed curve table of C-axis. FIPO can complete the acceleration, deceleration, and circular motion, making the motion control of C-axis could be more flexible.With the above theoretical study, the camshaft grinding application program was developed based on the IPC and HNC-32 NC system. The modules of G code automatic programming, cyclical camshaft grinding and automatic wheel dressing were embedded, and the wheel wear was dynamically compensated. In addition, the thesis researched HMI interaction technology, and provided a good user interface.Finally, the bulit-in PLC in NC system was introduced, and the ladder diagram was programmed to achieve sequence control for all I/O signals of CNC and machine tools, new custom M code was also developed to perform other auxiliary functions.