Milling-grinding of sapphire domes with brazed diamond tools force modelling and wear mechanisms

Abstract In this study, sapphire crystal rods were precisely milled-ground into hemispherical domes using brazed diamond tools, and a corresponding mechanical model was developed to delineate the theoretical relationship between milling-grinding force and speed ratio. To validate the model, a series of hemispherical dome forming experiments were conducted, wherein variations in milling-grinding force under different tool and workpiece rotational speeds were analyzed. The results exhibited strong agreement with the proposed force model, thereby providing a theoretical basis for guiding future process optimization. The average time required to form a single dome is approximately 40 min, resulting in a post-processed surface roughness (Ra) of less than 2.5 μm. Following the milling-grinding process, brazed diamond tools demonstrate minimal wear, predominantly governed by a combination of friction-induced abrasion, abrasive particle fracture, and grain detachment.