Evaluation of cutting forces and temperatures in micro-milling of NiTi alloys using finite element modeling

Abstract

Today, micro-milling of NiTi alloys is used to manufacture precision mechanisms, instrumentation, space technology, micro-electro-mechanical systems, biomedical devices, and implants. It is becoming increasingly widespread. Micro-milling is the process of manufacturing high-precision small parts using microtools, and it is characterized by more difficult chip formation conditions and higher specific cutting forces than conventional milling. These adverse effects are greatly amplified when machining difficult-to-machine materials such as NiTi alloy. Poor machinability of NiTi leads to high specific cutting energy, cutting forces and temperatures, severe tool wear, and excessive burr formation. The study’s main objective was to determine the dependence of cutting forces and temperatures on machining conditions and the recommended ratios of the micro-mills’ cutting-edge radius to minimum chip thickness and scaling coefficient. To investigate forces and cutting temperatures during the micro-milling of the austenitic Ni56.5Ti43.5 alloy utilizing end micro-mills with diameters 0.2 and 0.5 mm under variable cutting conditions, finite element modeling was applied using the DEFORM-3D software. The adequacy of the developed finite element model was proven by comparing the simulation results with experimental studies of cutting forces. Changes in cutting forces and temperatures were examined depending on the feed per tooth and cutting depth. The dependencies for specific cutting forces on the scaling coefficient were also determined. This enabled the establishment of acceptable limits for the scaling coefficient and the minimum chip thickness. The results may improve micro-milling technologies and enhance the efficiency of manufacturing products with micro-elements, such as biomedical devices and implants, precision mechanisms, and micro-electro-mechanical systems.