Design of experiment for the optimization of micro-milling of polymethylmethacrylate (PMMA)
Liow, John Yuh Han
Date of Issue2010
School of Mechanical and Aerospace Engineering
Singapore-MIT Alliance Programme
In recent years, there has been a considerable amount of research on microfluidics for the creation of highly-miniature parts for use in both chemical and biological analyses. Through the various manufacturing methods, microfluidic devices offer an attractive alternative to large complicated instruments since they are compact and sometimes reusable. Among the many techniques available, micromilling has the potential as a rapid prototyping technique for the production of channel features in polymer substrates. In this study, the micromachining of Polymethylmethacrylate (PMMA), a common material for microfluidic applications, is studied. A design of experiments (DOE) that varied three factors (the step-over ratio, feed rate, and spindle speed) during the micromilling process was conducted to determine a set of optimized parameters that minimizes the responses for surface roughness and step height deviation. Four different end mill diameters (Ø 0.2, 0.5, 1.0, 4.0 mm) were investigated with each of the three input factors varied at three test-levels. For each of the two responses for a chosen end mill diameter, regression was performed to fit the data from measurements with a quadratic model. Results of analysis for all the end mills indicated that a better fit for the surface roughness response model than for the step height deviation response model. Furthermore, input values that minimize the surface roughness and the deviation in step height were computed using an optimization routine in DESIGN EXPERT. These optimized values provide good estimates on the machine parameter settings for the micromachining of PMMA microchannels.