Error Compensation Technology For CNC Machine Tool And Its Application

Error compensation technology for CNC machine tool is an economic and efficientmethod to improve the precision of CNC machine tool and its machining precision. Thispaper discusses the causes of CNC machine tool error, the measurement mode, the advancederror compensation technologies such as modeling and real-time compensation etc., as well astheir application.Major research tasks completed are shown as follows:(1) With regard to the deflection error due to force of gravity when square ram of theheavy-duty NC floor type boring&milling machine extends, propose the measurementscheme which makes use of dial gage, straight edge and HEIDENHAIN absolute linearencoder; establish the mathematical curve model for the deflection error corresponding to theextension elongation of the ram; and apply the method of PLC controlled point-by-pointhydraulic compensation for real-time compensation, which achieves the good results and hasbeen successfully used in Series TK products.(2) In connection with the low-efficiency of manual adjustment after tool wear in case offinish machining of the linear boring cutter, recommend to add the automatic cutter diametercompensation function on the special-purpose crankshaft processing machinery. The generaldesign concept is to make the special-purpose crankshaft machinery realize the real-timesupervision for precision of the machined parts through adding the automatic measurementand servo adjustment modules. The automatic cutter adjustment procedure will be initiatedonce the machining error exceeding the setting range and the servomotor will accuratelyadjust the fine boring cutter, to realize the automatic cutter diameter compensation.(3) Discuss and analyze the correlation between positioning error of the heavy-duty floortype boring&milling machine tool spindle and temperature variation; measure thetemperature of various parts of the spindle through PT100temperature sensor; measure theerror of axis W of the boring rod under different temperature conditions; obtain the curve ofaxis-W position error versus temperature variation; establish the “temperature VS deformation”mathematical model; and realize the real-time compensation for thermal deformation error ofthe heavy-duty NC machine tool in combination with the temperature compensation ofSIEMENS840D NC system.This comprehensive domestic CNC machine error compensation technology status, forthree representative case studies CNC machine error, error solutions such that the currentshortcomings and difficulties, design new solutions to better improve the error compensationtechnology, and applied to actual production, get a good error compensation precision and economic efficiency.