Combined effects of tool surface texturing, cutting parameters and minimum quantity lubrication (MQL) pressure on micro-grinding of BK7 glass

Abstract

Capability of sintered micro-grinding tool is limited by low chip space, ineffective lubrication access and premature loading which results in high cutting forces and brittle mode fractures on the work surfaces. Usage of textured tool is one of the methods to avoid aforesaid phenomena and to achieve high cutting performance. On machine fabrication of textured micro-tools and correlating their cutting mechanism with texture dimension are some of the primary challenges. A new electric discharge texturing method for on-machine fabrication of textured tools is devised and the tools with optimum intermittent ratio but varying texture dimensions are fabricated. Micro-grinding experiments are carried out on BK7 glass to establish the correlation between cutting performance with texture dimension, cutting parameters and MQL (minimum quantity lubrication) pressure. It is concluded that tool with small size and large number of texture units reduced the cutting forces, surface roughness and edge chipping by 25–35 % of those obtained by a tool without texture at depth of cut 10 μm and feed rate 5 mm/min. The amount of reductions of these two process parameters even reached to 50–60 % at high depth of cut 40 μm and feed rate 11 mm/min. The reduction in output parameters is supported by the observation of effective migration of chips in the passive areas. It is also established in this study that MQL spray droplet size should be very close to the texture dimension to ensure maximum cutting fluid access in the machining zone. Analytical derivation of penetration depth for textured tools indicated delayed chances of ductile to brittle transition when the tools with small size texture units are used in place of the tools with large size texture units.