High-efficiency machining of large aspect-ratio rotational parts by rapid contour approaching WEDM

Abstract

This research proposes a rapid contour approaching wire electrical discharge machining (RCA-WEDM) method based on polygon sectional feeding strategy to achieve large aspect-ratio rotational parts with high efficiency. Many of the rotational parts are made of difficult-to-cut material to achieve high performance such as superalloy material used in feedback rod and wear-resistant material used in injector plunger, which make them difficult to be machined by traditional processes. In order to fabricate those parts, the RCA-WEDM method provides a new and effective feeding strategy and approach to achieve high efficiency. In RCA-WEDM, a precise auxiliary rotary axial was applied to hold and rotate the workpiece. The principle of this new feeding strategy was described and theoretical analysis was also carried out to investigate criteria for optimization of the process according to the size of the workpiece. Afterwards, a series of optimal polygons was recommended for different sizes of the workpiece based on the analysis of experimental results. Moreover, two sets of experiments were conducted to study the machining performance and to verify the criteria of recommended optimal polygons. Experiments showed a good machining effect including high MRR and good controlling of diameter size by implementing recommended optimal polygons. Also, machined workpieces were in good shape precision and high geometrical accuracy, and the achieved maximum MRR reached 26.25 mm3/min. At last, a qualified feedback rod sample was fabricated as an example of precision machining; the dimensional accuracy of the machined workpiece was controlled within 2 μm and its best surface roughness was less than 0.5 μm by adding the polishing step.