A new velocity profile generation for high efficiency CNC machining application

Abstract

Computer Numerical Control has been widely applied within the manufacturing industry due to its great productivity and relatively low cost. A challenging problem that needs to be addressed is that when increasing the motion speed to improve productivity, the CNC motion accuracy may also degrade. This thesis presents the latest effort in improving the motion planning by employing a new velocity profile to save operation time and thus enhance working efficiency, while maintaining good motion accuracy. In traditional motion planning, S- or T-curve velocity profile is generally utilized in the design of successive movements, and the next movement starts only after the previous movement stops. In this thesis, a new velocity profile with improved S-curve is proposed, by which the next movement starts without waiting for the previous movement to stop, and thereby the operation time is saved and efficiency is improved. Two methods without jerk control and with jerk control are developed to generate this new velocity profile. The significance of the new approach lies in the reduction of machining time without degrading motion accuracy. Experiments are finally performed in a real CNC machine application to compare the new velocity profile and the traditional velocity profile. Experimental results show that the new velocity profile without jerk control requires the shortest operation time but slightly increases of the position and contour errors when compared to the traditional velocity profile. The new velocity profile with jerk control requires less operation time and exhibits compatible motion accuracy that is an improvement against the traditional velocity profile.