Double-sided milling of thin-walled parts by dual collaborative parallel kinematic machines

Thin-walled parts with double-sided features are widely used in many industrial sectors but their machining is particularly time consuming and challenging. Collaborative machining is a new paradigm in the development of industrial 4.0. It can potentially revolutionize the existing thin-walled part machining methods, leading to higher productivity, flexibility and sustainability. For this end, this paper introduces a novel concept with dual parallel kinematic machines (PKMs) collaboratively performing synchronized and asynchronized cutting and support from both sides of a thin-walled part, without changeover/re-clamping of the workpiece. Compared to the conventional single-sided machining, this study shows that static and dynamic performances of the workpiece are significantly improved under the dual PKM collaborative operation. A case study of milling a thin-walled part with double-sided features was conducted by PKMs under three comparative strategies, namely, double-sided synchronized milling, alternative single-sided milling, and sequential single-sided milling. Experimental results show that the novel double-sided synchronized milling strategy by dual collaborative PKMs produced the best dimensional accuracy and satisfactory surface quality due to the improved static stiffness and dynamic performance, and balanced deflections. More importantly, a two-fold greater productivity has been achieved as the novel strategy doubles the material removal rate while eliminating the cumbersome in-process steps used in conventional single-sided machining.
Keywords: collaborative machining, thin-walled part, parallel kinematic machine (PKM), double-sided milling, productivity