Micro-grooving of brittle materials using textured diamond grinding wheels shaped by an integrated nanosecond laser system

The freeform surfaces including both the aspherical and prismatic concave/convex have been widely utilized in optical, electronical, and biomedical areas. Most recently, it is reported that grinding with structured wheels provides new possibility to generate patterns on hard and brittle materials. This paper reports the latest research progress on micro-grooving glass ceramic using laser structured bronze bond diamond grinding wheels. A nanosecond pulse laser is firstly integrated into an ultra-precision machine tool and used for the in-line conditioning of super abrasive grinding wheels, i.e. truing, dressing, and profiling/texturing. Meanwhile, an offset compensation method, considering the shifting depth of focus (DoF) at different laser irradiation position, is proposed to accurately generate various profiles on the periphery of the grinding wheels. Three types of patterns (riblets, grooves, and pillars) are successfully fabricated on the ceramic substrate using the laser textured grinding wheels. The results indicate that the integrated laser system offers high flexibility and accuracy in shaping super abrasive grinding wheels, and the grinding using textured grinding wheels provide a promising solution to generate functional structures on hard and brittle materials.

Fundamental Investigation of Diamond Cutting of Micro V-Shaped Grooves on a Polycrystalline Soft-Brittle Material

Fabricating micro-structures on optical materials has received great interest in recent years. In this work, micro-grooving experiments were performed on polycrystalline zinc selenide (ZnSe) to investigate the feasibility of surface micro-structuring on polycrystalline soft-brittle material by diamond turning. A photosensitive resin was coated on the workpiece before cutting, and it was found that the coating was effective in suppressing brittle fractures at the edges of the grooves. The effect of tool feed rate in groove depth direction was examined. Results showed that the defect morphology on the groove surface was affected by the tool feed rate. The crystallographic orientation of grains around the groove was characterized by electron backscatter diffraction (EBSD), and it was found that the formation of defects was strongly dependent on the angle of groove surface with respect to the cleavage plane of grain. The stress distribution of the micro-grooving process was investigated by the finite element method. Results showed that the location of tensile stresses in the coated workpiece was farther from the edge of the groove compared with that in the uncoated workpiece, verifying the experimental result that brittle fractures were suppressed by the resin coating.

Effects of Abrasive Particle Type, Load and Sliding Distance on Micro-Abrasion Resistance of High Speed Steel Coated with AlCrN or AlTiN

High Speed Steel (HSS) specimen surfaces were coated with AlCrN and AlTiN via Physical Vapor Deposition (PVD) method. Then, the wear performances of the film coatings so produced were investigated by using different abrasive types with different particle sizes. During the micro-abrasion wear tests, 0.5, 1 and 1.5 N loads were applied for periods of 60 and 180 seconds. During the wear tests, wear loss increased with increasing SiC and Al2O3 abrasive particle size. Micro-grooving and micro-rolling wear were observed when F800 and F1200 abrasive slurry were used, respectively. It was determined that the volume losses formed by SiC abrasive particles on AlTiN and AlCrN coatings to be higher than Al2O3 abrasive particles. Volume losses increased with the increase in the applied load and the number of cycles. The AlCrN coatings exhibited better wear resistance than the AlTiN coatings. The applied test load had a significant effect on the wear mechanisms observed.