Research On Thermal Error Dectection, Modeling And Compensation Of Planner-type Five-Axis CNC Milling Machine

In the process of five-axis CNC machining, under the influence of inside and outside heat sources,the machine parts and components generate non-uniform thermal deformation, destroys the correct position between the tool and the workpiece on the machine, reducing the accuracy of machining. The investigation shows that in the process of high-precision machining, the error caused by thermal deformation hold40%-70%of the total error, so reduce the thermal error become an important research to improve the machining accuracy.Research on the status of thermal error detection,modeling and compensation techniques for CNC machine tool, a rapid thermal error detection method is raised combined with the specific structure of the planner-type five-axis CNC milling machine. At the same time, a single thermal error element model and a comprehensive model are established based on the experimental data, through the space decoupling of five-axis machine tool thermal error model, a thermal error compensation function based on the origin offset is presented. The main research results obtained are as follows:(1)In order to realize the thermal error detection quickly and efficiently, completes the thermal error detection by high precision instruments-laser interferometer and ballbar to ensure the measurement accuracy, at the same time greatly simplifies the measurement process.(2)Due to the characteristics of BP network easily falling into local extreme points, establishs a GA-BP model combine genetic algorithm and neural network,which has the better accuracy and robustness. Based on Matlab graphical user interface, a error modeling and simulation prediction system is developed to achieve the visualization.(3)Based on the multi-body theory and homogeneous coordinate transformation, propose a universal method for establishment of comprehensive thermal error model. Take planner-type five-axis CNC milling machine as an example,discusses the main heat source and thermal error elements in depth, calculates to get the comprehensive thermal error model.(4)Based on the comprehensive thermal error model and differential transformation theory, analyzes the relationship between machine error movement and compensation movement, completes thermal error model space decoupling, establishs a decoupling model which achieves space error compensation calculation. Also, use origin offset of840D CNC system propose a thermal error compensation technique based on PLC, discusses the compensation theory and processes in detail.