Improvements in out-of-roundness and microhardness of inner surfaces by internal ball burnishing process

The internal surface quality plays a role in part performance. Out-of-roundness and surface microhardness of inner surfaces play an important role in the efficiency of any round mechanical part that rotates during work. Ordinary grinding of some metals and alloys such as aluminum, copper and brass is difficult. Wheel clogging on the grinding of such metal causes rapid wheel breakdown and frequent dressing of the wheel is required. In the present work, the internal machined surfaces were burnished by a simple newly designed internal ball burnishing tool. The experimental work is carried out on a CNC lathe machine to establish the effect of four internal ball burnishing parameters; namely, burnishing speed, feed rate, depth of penetration and number of passes. A significant improvement in out-of-roundness and surface microhardness in aluminum alloy 2014 workpiece has been obtained without the need for the difficult to set-up grinding equipment normally used for inner surfaces super-finishing. The proposed newly designed internal ball burnishing tool can be used to burnish the inner surfaces of many non-ferrous parts which have many industrial applications.