Prediction of cutting forces in micromilling process of reentrant microchannels with micro serrated pin fins

Microchannel heat sinks with reentrant microchannels with micro serrated pin fins (RMSPF) show their favorable merits to improve heat dissipation performance for cooling applications. Micromilling with micro staggered multi-edge ball-end milling tools (SMBMT) provides a high-efficiency strategy to produce the RMSPF. Accurate prediction of cutting forces by models is essential for the micromilling process of RMSPF, and is also helpful for the design of micro cutters. Nevertheless, there is no knowledge of the prediction of cutting forces in micromilling process with discrete cutting edges. To this aim, a prediction model of cutting forces has been developed for the micromilling of RMSPF in oxygen-free pure copper plates by the SMBMT in this study. The discrete cutting edge geometry, size effects in the micromilling process, and staggered engagement between the tool teeth of SMBMT and workpiece were considered and incorporated, which differed from other cutting force models significantly. Based on minimum chip thickness criteria, the cutting force was modeled in two distinct regimes, i.e., shearing-dominant and ploughing-dominant regimes. The predicted cutting forces were compared to experimental measurements, and the accuracy of the cutting force model was validated for the micromilling of RMSPF by the SMBMT. The cutting force model with the incorporation of size effect showed much better agreement with experimental results and induced more accurate predictions. Moreover, the mechanism of cutting force oscillations during tool rotation in micromilling of RMSPF was also discussed.