Precision Micromachining Channels in Highly Elastic Polymers for Applications in Tissue Engineering

The aim of this research is to investigate the effect of elastic recovery on the ability to precisely control depth of cut when micromachining channels in poly(methyl methacrylate) (PMMA). Both a standard and impact resistant PMMA were machined using an orthogonal micro-slitting arrangement. While holding speed and cutting edge radius constant, the intended depth of cut was varied from 10 μm to 85 μm in order to determine the actual depth of cut due to chip formation and the fraction of material that was ploughed and then elastically recovered. Elastic recovery was determined by using a profilometer to measure step height after machining a partial groove. Results show that intended depth of cut and actual depth of cut are a function of material properties, with greater ploughing occurring in the PMMA material with lower tensile strength and higher strain to yield. When cutting resulted in a permanent trench being formed, actual depth of cut was related in a linear manner to the intended depth of cut. At lower intended depths of cut, the majority of material was ploughed beneath the cutting edge with little evidence of chip formation. In addition, at lower depths of cut a size effect was observed, where thrust force exceeded cutting force. Greater cutting and thrust forces were evident from the PMMA material with higher tensile strength. Resultant forces for both samples were related in a linear manner to the final trench depth. In general, the results indicate that orthogonal micro-slitting experiments may be used to generate process maps to accurately predict the depth of cut achieved when micromachining channels in highly elastic polymers.