Frictional behavior of tool-workpiece on surface quality of glow discharge polymer during micro-milling

Machining of concavities and other complex microstructures on glow discharge polymer (GDP) films is critical to its high laser power performance, especially in the inertial confinement nuclear fusion. This study mainly investigated the effect of tool-workpiece frictional mechanism on the quality of machined surface in micro-milling of GDP. A series of milling tests of micro-grooves with different spindle speeds (n) and spindle axis deflection angles (θ) were conducted using a cubic boron nitride (CBN) milling tool. The orthogonal cutting slip line model was adopted to reveal the material removal mechanism of GDP. The wear mechanism and friction coefficient of the contact area between GDP material and the CBN tool were analyzed. The chip thickness and shear stress were innovatively used to characterize the surface roughness. The regression models of milling forces, surface profiles, shear stresses and surface roughness with chip thickness were established. The tribo-performance of the CBN tool on GDP material was characterized using cutting specific energy and a friction coefficient. Research results show that θ has a significant effect on the surface quality than n. At θ of 20° and n of 30,000 rpm, the contour error of the micro-groove structure is about 0.11 μm, a reduction of 93.9% compared with at θ of 0°. Thermal softening and strain hardening are found the keys affecting surface morphology. Chip morphology such as segmental, granular, and crack chips was observed. The adhesion wear on the CBN tool surface was found critical to its machining performance.