“…In UPM, surface roughness is influenced by many factors, including cutting conditions [3], material pile-up [4], material swelling and recovery [5,6], crystal orientation [7,8], material properties [9,10], relative vibration between tool and workpiece [11,12], tool vibration [13], and spindle vibration [14]. A plethora of research has been conducted on the machinability of non-ferrous materials, such as copper and aluminum, and on chip formation with shear angle in UPM [15][16][17][18][19].…”