Tool compensation proposed :     End mill machining a workpiece on a CNC machine , it is clear that moving rail gauge tool center does not coincide with the workpiece contour , this is because the contour milling cutter motion envelope is formed . Knife sites Mills center called tool ( 4,5 coordinates CNC machine tool position called vector) , the movement of the knife sites track gauge which represents the trajectory of the tool. In NC machining , is prepared in accordance with the size of the workpiece contour program , or by programmed trajectory size knife sites , which should be handled according to specific circumstances .          CNC end milling machine     In the full-function CNC machine tools , CNC tool compensation system , according to the dimensions of the workpiece contour programming, establish , after performing tool compensation , the CNC system automatically calculates the knife sites to automatically adjust the tool trajectory. Direct use of the preparation and processing procedures workpiece size , tool wear , replace the machining program unchanged, so the use of simple and convenient.     Economical CNC machine tools simple structure , low price , there is a certain amount of production owned enterprises . In the economical CNC system, if no tool compensation function, can only knife sites trajectory size processing establishment , which requires first calculate the trajectory of sites based on the size of the knife the size and contour cutter diameter. So large computation , complex, and tool wear , replace the need to recalculate the size of the knife track sites , re- processing establishment .