Research On PMC Control Method Based On Temperature Compensation

Ball screw in the feed system of CNC machine tool is an important component of precision transmission and positioning, and its character will directly affect the machining accuracy of CNC machine tool. After the machine long time continuous and high-speed running, components contracting region(ball screws, bearing et al)of ball screw feeding system generate a lot of heat. In the internal of the CNC machine tool, the heat can not send out timely, the temperature of ball screw will increase, causing the thermal deformation of ball screw, and between the tool and part position changes, so make the precision of CNC machine tool decreased. Especially for the finish machining of CNC machine tool, thermal deformation error caused by the ball screw can not be ignored. So the compensation of ball screw thermal deformation has an important significance to improve the machining precision of CNC machine tool.This subject is based on DL-20 CNC machine tool produced by Dalian Machine Tool Group feed system of ball screw as the research object, the Programmable Machine Controller of FANUC 0i system build to the core, through the PMC programming ladder diagram control machine of ball screw axial thermal deformation compensation. The main research contents of this paper are as follows:(1) The structure and working principle of the CNC machine tool feed system are introduced, and analyzes the CNC machine thermal error generation, and describes the method to reduce the thermal error.(2) Establishes a three-dimensional model of ball screw, through the analysis and calculation of the source of ball screw feed system, in the constraint conditions and thermal load are determined circumstances, the thermal load is loaded into the finite element model of ball screw, and analyses temperature field and thermal deformation of ball screws by using Simulation module, and obtain the ball screw thermal deformation image and the thermal deformation of the theoretical value.(3) Measures CNC machine tool feed system of ball screw’s thermal deformation when it is in reciprocating motion, and use MATLAB to draw graphics of measured data, and summarizes the law of ball screw’s thermal deformation.(4) Introduces the basic structure and working principle of PMC in FANUC 0i system, According to the measurement of the thermal deformation law of ball screw compiles the thermal error compensation program, and applies the compensation program in actual machining, whether parts size is within the scope of the requirements.By using PMC control program compensates ball screw thermal deformation, The error of CNC machining of parts size is in the scope of the requirements, illustrates this method can solve the problem that ball screw thermal deformation causes parts size increasing gradually.