Optimization method of milling feed rate for complex tool path trajectories based on a constant cutting force prediction model

Using a constant feed rate in the complex tool path machining can easily cause sudden changes in cutting force load and fluctuations, reducing the machining efficiency and machining surface quality. To address this problem, this paper proposes an offline optimization method for the milling feed rate based on the constant cutting force prediction model. Firstly, the change of two-dimensional equivalent load (effective depth of cut) in the machining process because of the complexity of the tool-path trajectory was analyzed, and the cutting force surface model comprising three parameters of effective depth of cut, feed rate and average cutting force was constructed by experiments, and the feed rate change model based on the constant cutting force was got by taking the maximum cutting force during machining at constant feed rate as the limit cutting force constraint. Based on the Z-Map model and the feed speed regulation model, the feed speed of each tool point is calculated; the feed speed is initially optimized according to the surface roughness constraints and the machine acceleration constraints, and then the feed speed is optimized in stages based on the size of the engagement angle at each tool point. Finally, the machining examples were experimentally verified. The results show that the proposed optimization method can control the cutting force fluctuation within a constant range, significantly shorten the machining time and improve the surface quality of the machined workpiece, which verifies the effectiveness of the proposed method.