Abstract
Ultra-precision diamond cutting (UPDC) is a promising machining technology to generate precise components with optical grade surface. However, a tool rake angle turns to be negative when the tool radius is significantly larger than cutting depth during UPDC. The resulted plowing motion, which is the well-known size effect, causes undeformed and uncut materials remaining on the machined surface and thus affects the surface integrity of final components. In this study, the tribology behavior of tool/workpiece was altered in order to resolve the problematic size effect. A magnetic field was superimposed into titanium alloys during UPDC to increase the friction coefficient at the tool/workpiece interface in order to minimize the size effect and reduce minimum chip thickness (MCT) in UPDC. The experimental results showed the friction coefficient at the tool/workpiece interface increased under the magnetic field influence and a better surface quality was achieved in the presence of magnetic field. MCT of titanium alloys was reduced to 1μm by utilizing the proposed machining technology which the reduction percentage reached to 50%. A lower MCT value means the feasibility of machining under smaller depth of cut and thus enhances the existing precise level of components fabricated in ultra-precision machining.
Highlights
Ultra-precision diamond cutting (UPDC) is a widely used machining technology to produce precise components with high geometric complexity and accuracy
The friction coefficient at the tool/workpiece interface was calculated by dividing the tangential force with the normal force
A magnetic field is firstly applied into ultra-precision machining area to take an effect on minimum chip thickness (MCT), which is a simple and economic method without needing complicated equipment
Summary
Ultra-precision diamond cutting (UPDC) is a widely used machining technology to produce precise components with high geometric complexity and accuracy. A machined surface is generated by the tool with highly negative rake angle, which the ploughing effect is introduced in UPDC. For the condition of undeformed chip thickness less than the critical value in UPDC, the workpiece surface undergoes both elastic and plastic deformations, which a diamond tool burnishes or ploughs. The chip is not generated unless undeformed chip thickness is larger than critical thickness, which the above phenomenon is named as size effect. De Oliveira et al [1] stated that the cutting forces generated in micro-cutting was capable to use for determining certain characteristic chip thickness, and they confirmed that minimum uncut chip thickness was changed in micro-cutting, regardless of workpiece materials and tool geometry. Liu et al [2] investigated the critical factors for MCT in micro-cutting using steel and aluminum alloys as the workpieces, they found that the model of MCT should consider the effects of thermal softening and cutting velocity
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