HIGH-SPEED END MILLING USING A FEEDFORWARD CONTROL ARCHITECTURE

Experiments are performed for end milling aluminum at 15,000 RPM spind le speed (1,508 m/min cutting speed) and up to 3 m/min table feedrate using an experimental machine tool control system. A digital feedforwa rd controller for feed drive control incorporates the Zero Phase Error Tracking Controller (ZPETC) and feedforward friction compensation. Th e controller achieves near-perfect (+/-3 mu m) tracking over a 26 mm t rajectory with a maximum speed of 2 m/min. The maximum contouring erro r for a 26 mm diameter circle at this speed is less than 4 mu m. Track ing and contouring experiments are conducted for table feedrates as hi gh as 10 m/min. Frequency domain analysis demonstrates that the feedfo rward controller achieves a bandwidth of 10 Hz without phase distortio n. In a direct comparison of accuracy, the machining errors in specime ns produced by the experimental controller were Icp to 20 times smalle r than the errors in specimens machined by an industrial CNC.