Research Of A Multi-process Control System For Crystal Grinding And Polishing Machine Based On Motion Controller

The high efficiency,high precision and compound machining are the major trends and developments of the NC machine.China is a huge market potential for crystal machining and trading.The quality of grinding and polishing immediately influences precision,roughness and transparency of workpiece,which is the key for improving production efficiency.This paper presents a research and development of a multi-process control system for crystal machining to improve production efficiency and precision to solve the problems in current equipment under the support of a horizontal cooperate projects.The main works and achievements have been done as followed:(1)The requirements and qualifications of the multi-process control system were proposed based on the disadvantages of current equipments and the mechanism of the crystal grinding and polishing compound machine,which has four stations.Personal computer combined with Turbo PMAC was adopted to be the core controller,according to the comprision and analysis among the mainstream control frameworks.(2)ACC-24PCI and ACC-34AA were used to improve the ability to control more servo motors and extend the input and output interfaces.The hardware architecture was set up,which has the capability to control thirteen motors.Velocity control mode was dopted in driver,posion loop was closed in Turbo PMAC.The control circuit,servo system circuit,I/O circuit and main circuit was designed.(3)The kinematic analysis model of the NC machine head was presented by Denavit-Hartenberg method.The relationship between joint control parameters and geometrical parameters of crystal was derived by face center distance and normal vector or face point and normal vector.The machining plan of crystal ball,round brilliant and elipse were designed based on the relationship and processing technology of cyrstal.(4)The upper and lower programmes were designed.The lower programmes includes transposition programs,machining programmesm,PLC programs,etc.The coordinate system in No.1 NC machine head was used to assign maching tasks for the other NC machine heads.The framework for synchronous maching was set up in Turbo PMAC.The software for the machine was designed and developed by VC++ in modular way based on Windows7 operating system.On the basis of the above research,the PID parameters were adjusted and positioning error of Z axis was measured on the physical prototype.A method of using software compensation was used to reduce positioning error from 43.4?m to 9.9?m to achieve the qualification.The experiment of machining the cutting style of 64-facets elliptical crystal was made,the finished workpiece has a high surface quality of 0.0692[im and a good dimension tolerance.The results show the validity and reliability of both the control system and algorithm.The method of this paper has reference value for developing multi-process system for compound NC machine,the result and application are significant to improve the level and innovation ability of cystal products,in addition to enhance the kernel competive in the international crystal market.