Research And Design On CNC System Of Three Dimensional Numerical Control Engraving Machine Based On The Curve Synthetic Interpolation Theory

With the rapid development of numerical control technology,the degree of automation of mechanical manufacturing process is continuously improved.In recent years,the numerical control technology has been widely applied to engraving processing.Now widely used CNC engraving machine control systems are limited to straight line and circular arc interpolations.With the increasing needs of society,these linetypes can not meet our needs anymore.Zibo Zhiheng Industry&Trade Co.,Ltd requested us to develope a CNC system for engraving machine.This system can interpolate as many linetypes as possible and has the function of tool radius compensation.So,in this paper,research and design on CNC system of three dimensional numerical control engraving machine based on the curve synthetic interpolation theory is proposed.This system has been running and debugging on the engraving machine in the laboratory.Details are as follows:It is determined that the control system is an open CNC system based on industrial control computer.The electrocircuit based on Advantech PCI-1750 has been designed that can realize the movement of three axis and speed control of electric spindle.The engraving machine numerical control system is developed by using the advanced programming tool of VC6.0.This system contains many functional modules.It can meet the requirements of CNC engraving machines.Interpolation and the function of tool radius compensation are important modules of NC system which determine the machining accuracy and qual ity of CNC system.In this paper,differential interpolation theory is used to interpolate line,circular arc,ellipse,hyperbolic and parabolic in plane.Digital differential analyzer is used to interpolate lines in space.Line and circular arc's equidistan ce curves still are line and circular.So the traditional method is used to realize the function of tool radius compensation for lines and circular arcs.But ellipse,hyperbolic and parabolic's equidistance curves no longer are ellipse,hyperbolic or parabol ic.It is difficult to directly obtain their equidistance curves.Synthetic interpolation theory is used to interpolate ellipse,hyperbolic and parabolic's equidistance curves.The transition of all linetypes is solved by the sharp corner and internal corne r theory based on synthetic interpolation theory.C-function cutter radius compensation is realized in CNC engraving machines.The difference interpolation theory is used to interpolate quadratic curves.And Synthetic interpolation theory is used to realize the function of cutter radius compensation for these linetypes.So the curve fitting process is omitted.This can reduce the CAD / CAM geometric error of curves and improve the machining precision of the system.In this paper,the screen displaying of the numerical control processing graphics is studied.Three-view drawing and isometric drawing of numerical control processing graphics are obtained through the projection transformation,the plane scaling,translation of spatial points.They can display in the middle of the display area in maximum size.It is beneficial to check the e rror of NC processing code and display the processing track in real time.It can advance the grade of the system.