Research On Modeling And Control Strategy Of Errors From Tool And Workpiece In Five-axis NC Machining

Five-axis CNC machining technology has become one of the core technologies of advanced manufacturing technology and intelligent equipment.Along the main line of the development of high-speed and high-precision CNC technology,the control strategy of five-axis machining error is studied in this thesis.Based on the analysis of the sources and the classification of five-axis machining error,summed up the development and the lack of error control method,and cleared the research direction and content of the control of machining error system in CNC system.The dynamic compensation of five-axis space tools error is the key technology of the error control derived from the the tool.By modeling and analyzing the tool wear when machining in five-axis,this thesis proposes a dynamic compensation strategy for tool wear of efficient tool management technology based on open CNC system,and given the strategies for dynamic calculation,prediction and detection of tool error.Simulation results show that the tool dynamic compensation technology can greatly reduce the error caused by the tool wear in five-axis machining.The combination of space cutter compensation and five-axis NURBS machining technology is a challenge of improving the accuracy and speed of five-axis machining.By studying space tool compensation techniques in five-axis machining,this thesis presents a described method of triple NURBS curve model appliying to five-axis machining.The position and orientation of cutting tool and the contact position can be described completely by this method,which can effectively achieve space tool compensation in five-axis.Experimental results show that this method can effectively solve space tool compensation in five-axis NURBS machining.The workpiece model adjustment based on-machine testing is a more general and direct error control strategy.This thesis proposes a controllable method for workpiece model error correction on the basis of the machine detection technology.It achieves the control of the workpiece errors through the optimal selection of the machine detection point calculation of reconstruction points and the refit of the workpiece surface.Experiment shows that the method has a significant effect on the control of the workpiece errors when machining batch of workpiece with good rigidity.On-machine measurement and real-time control of errors are the difficulties of high-precision and efficient machining,and the trajectory planning is the key starting point to solve this problem.This thesis presents a complete trajectory planning strategy for the real-time control of five-axis CNC machining error by increasing the track re-planning module to overcome the shortcomings of the macro program,which can not execute forward planning in real-time compensation.And the whole working process of the trajectory planning module was given at last.Precision and Speed in five-axis machining is a traditional contradiction.This thesis optimizes the planning method of processing speed in the complete trajectory planning stage.And propose an intelligent S-type acceleration and deceleration control method which select according to the type of path.And this method can make five-axis machining smoother.Simulation shows,the method of adaptive S-type acceleration and deceleration control and technology of variable interpolation cycle for precise interpolation can improve the processing speed in the premise of ensuring the accuracy of processing.For the actual verification of the error control strategy of errors in five-axis NC machining proposed in this thesis,two kinds of five-axis CNC system prototype are produced based on the traditional five-axis CNC system software and hardware structure.And the experimental verification shows that the five-axis CNC system based on the error control strategy in the thesis can significantly improve the accuracy and processing speed of the five-axis machining.