ENHANCEMENT OF PRODUCTIVITY BY INTELLIGENT PROGRAMMING OF FEED RATE IN 3-AXIS MILLING

An optimized feed scheduling strategy (OFSS) is proposed in this paper to maximize the metal removal rate in 3-axis milling while guaranteeing the machining accuracy. This strategy integrates the feed drive dynamics, described by the acceleration/deceleration (Acc/Dec) profile, with the minimum-time trajectory planning in order to achieve the desired feed rate at the appropriate position. An optimum use of the feed drive capabilities is considered to track the changes in the cutting geometry along the tool path. Therefore, this strategy combines different constraints and various criteria in modifying the feed rate to maintain near-constant cutting force resulting in highly non-linear problem. The constraints include the cutting force, the feed rate boundaries, the contour error and the characteristics of the (Acc/Dec) profile. The criteria are the maximum production rate, the machining accuracy and safety. The performance of the OFSS in terms of these criteria, is compared to two end milling operations where the trajectory planning disregards the feed drive dynamics. The first is based on a feed scheduling strategy using control points (FSCP). The second is a milling operation with nominal feed rate. By increasing the feed rates, the OFSS improves the machining accuracy, reduces the machining time, and allows a better regulation of the cutting force.