Minimisation of micro-wall deformation through variable feed rate technique in micro-milling operations

This study examines the minimization of micro-wall deformation in micro-milling operations by implementing variable feed rate techniques. Micro thin walls, typically characterized by a thickness below 100 mu m and a heightto-thickness ratio >10, pose significant machining challenges due to their low stiffness and susceptibility to deformation under cutting forces. The study advocates for the application of variable feed rates to mitigate deformation, particularly at the entry and exit points of the cutting tool. Using Al6061-T6 as the workpiece material and carbide cutting tools, the minimum uncut chip thickness was determined, followed by an assessment of the effects of cutting strategy and direction on wall deformation. Experiments considering the minimum uncut chip thickness were conducted to evaluate the impact of different variable feed rates on wall deformation. The findings indicate that jump-to-jump milling yielded the most favorable results in minimizing deformation, whereas in-line milling demonstrated superior performance in reducing burr formation. Additionally, wall deformation was observed to be most pronounced during up-up or down-down milling. However, the up-down cutting method exhibited the potential to reduce deformation by approximately tenfold. Overall, the variable feed rate technique resulted in a reduction of deformation by up to 62 %, with the minimum deformation measured at approximately 2.5-3 mu m, compared to 22 mu m in the worst-case scenario. Furthermore, the optimal feed rate range was found to improve surface roughness values by up to 30 %, supporting the overall improvement in machining quality.