Fabrication And Cutting Performance Of Micro-textured Drills

Micro-textured twists were designed and developed in order to solve the problem of higher temperature and serious wear in drilling process. The paper analyses the influence of micro-texture on twist drill Mises stress distribution using the Finite Element Method (FEM). Laser machining method was chosen to prepare micro-textured twists. The influence of micro-textured twist drill on drilling performance was analyzed through drilling tests.Five micro-textured models were proposed based on the FEM. They are micro texture paralleling to main cutting edge (T-PX), twill micro texture with the angle of 45 degrees between the texture and main cutting edge (T-XW), micro-texture perpendicular to main cutting edge (T-CZ), micro-texture of elliptical shape (T-TY), and micro-texture of microporous shape (T-WK). By analyzing and calculating the tip Mises stress value of micro-textured twist drills, the T-TY,T-XW and T-XW twist drills’stress concentration is smaller. The appropriate micro-texture structural parameters were put forward:the T-TY twist drill has three rounds oval-shaped micro-texture,80 um groove width; the groove width of T-XW twist drill is 100 um; the groove width of T-WK twist drill is 50 um. The micro-texture spacing is 200 um, with 80 um groove depth and apart from the main cutting edge 300 um.Laser machining method was adopted to prepare micro-textured twist drills. During the preparation of micro-textured twist drills, the laser machining parameters (laser power, laser frequency, laser scanning times and laser scanning times) have impact on micro texture size and surface ablation. The reasonable processing parameters were put forward of T-TY,T-XW,T-WK twist drills. Tests showed that the groove depth of micro texture increases with the increase of laser power, decreases with the increase of laser scanning speed, first increase then decrease with the times increasing of laser scanning. The groove width of micro texture increases with the increase of laser power, but presents little change with the increase of scanning speed, laser frequency and scanning times. Considering the size and surface topography, choose the reasonable processing parameters of T-XW micro-texture to be:scanning speed 120mm/s, laser power 12W,scanning times l,scanning frequency 30Hz;The reasonable processing parameters of T-WK micro-texture are:scanning speed 12mm/s, laser power 9W,scanning times 1,scanning frequency 30Hz;The reasonable processing parameters of T-TY micro-texture are:scanning speed 100mm/s, laser power 15W,scanning times 3,scanning frequency 40Hz.Drilling tests were carried out with micro-textured twist drills and traditional twist drills. Texts showed that micro-texture can reduce the drilling force, drilling temperature and wear of twist drill significantly and decrease the length of drilling cuttings at a certain extent. Among them, T-XW twist drill performed the best drilling property, reduced drilling force about 17%-31%, decreased the drilling temperature about 19% to 21%, reduced bit wear about 38%.Micro-textured twist drill can reduce cohesive wear effectively. Surface micro-texture has an effect of anti-friction and chip breaker during the whole drilling process. Analysis suggests that the existence of micro-texture hindered the chip flow and made the twice deformation of chips that is contributed to the break of chips, which can reduce the friction and wear in the drilling process effectively; Chip is more advantageous to discharge after being broken and take away cutting heat. Furthermore, the existence of micro-texture increases the knife-chip heat dissipation area, which is helpful to decrease the drilling temperature.