High removal rate grinding of transmission components using CBN wheels

Abstract

Higher productivity and improved part quality requirements are increasingly being demanded of material removal processes. While these demands impose significant challenges, in some cases they also present opportunities to consider grinding as a viable alternative to processes such as turning, milling, and broaching. This has been made possible through advances in various aspects of grinding technology including abrasives, wheel design, coolant, and its application as well as machine tool technology. The current paper discusses grinding of a nodular cast iron transmission yoke component on a dual spindle grinder as opposed to the current processes of milling and broaching. High contact length in this application presented significant problems to supply coolant to the grinding zone and had an adverse effect on wheel life. An electroplated cubic boron nitride wheel was designed with special arrangements to supply coolant to the grinding zone. This design facilitated grinding the yokes at a specific removal rate of 200mm3/mms and a cutting speed of 80 m/s while maintaining yoke parallelism of less than 5 μm. Grinding tests were conducted using water-soluble oil coolant. Both grinding power and part parallelism were monitored in a pilot run to evaluate the wheel life. The approach was demonstrated to provide lower total operating cost while providing superior part quality.