An experimental study on the machining characteristics in ductile-mode milling of BK-7 glass

Abstract

Glass is considered as one of the most challenging materials to machine because of its high hardness coupled with high brittleness. The challenge, in machining such a brittle material, lies in achieving the material removal through plastic deformation rather than characteristic brittle fracture. It has already been established that every brittle material, no matter how brittle it is, can be machined in ductile mode under certain critical conditions. The critical conditions are material specific, and hence, every material tends to show unique behavior in terms of critical conditions during machining process. This paper outlines the results of an experimental study to determine the critical chip thickness for ductile-brittle transition, chip morphology, and the effect of cutting speed on the critical conditions in peripheral milling process of BK-7 glass. It is established experimentally that the cutting speed affects the chip morphology, machined surface quality, and critical conditions due to possible thermal effects in such a way that ductile-brittle transition phenomenon is facilitated at high cutting speeds.

On the theoretical foundation for the microcutting of calcium fluoride single crystals at elevated temperatures

“…The state-of-the-art research on ductile-regime cutting of brittle materials seeks solutions to several critical problems including the following: (1) crack formation and subsurface damage; 2,3 (2) determination of critical undeformed chip thickness 4 using different experimental techniques such as plunge cutting, 5 fly cutting, 6 scratching, 7 and diamond turning; 8 (3) theoretical solutions through modelling and simulation using analytical model, 9 molecular dynamics simulation, 3,9 and finite element method; 8 (4) material anisotropy effect on machining; 8–10 and (5) machining-induced amorphous layer such as in single-crystal Si and SiC. 11,12 Although ductile cutting of various brittle materials can be achieved under properly adjusted machining parameters, the unsolved problem of subsurface damages, such as the formation of an amorphous layer in Si/SiC and microstructural changes in CaF 2 , 8 is still observable to affect the optical properties of the final product.…”

Precision and mirror micro-grinding of micro-lens array on macro-freeform glass substrate for micro-photovoltaic performances

“…It has been known that the ductile-mode mirror cutting of brittle materials may be realized by decreasing the cutting depth to nanometer-scale [5]. However, it brought out inefficiency due to nanometer-scale depth of cut due to rapid wear of single-point diamond tool in process.…”