Comparing and combining off-line feedrate rescheduling strategies in free-form surface machining with feedrate acceleration and deceleration

Abstract

Off-line rescheduling feedrates based on changing surface geometry in free-form surface machining could reduce machining time, increase tool life, and improve surface finish quality. Various feedrate rescheduling strategies have different feedrate rescheduling control parameters. These parameters could be chip thickness, metal removal rate (MRR), or resultant forces. The paper compares these feedrate rescheduling strategies in machining time and feedrate changes. Machining time could be reduced significantly if appropriate values are set for those control parameters. Further, various strategies are combined for better results in two ways: the minimum and the maximum feedrate combination. Machining time could be reduced with both feedrate combinations. The minimum feedrate combination could protect machining against excessive chip thickness, MRR, resultant force, or other conditions that may occur using only one of these rescheduling strategies. The maximum feedrate combination could further reduce machining time with a loose control on those conditions. The paper also points out that advantages of feedrate rescheduling may not been in real if distances between neighboring cutting locations are too small for the machine to arrive at rescheduled feedrates in sharply changing cutting directions and feedrates. The method to calculate real feedrates and machining time is provided in consideration with feedrate ac/deceleration.