On the modeling and analysis of machining performance in microendmilling

In this research, the machining performance of the micro-endmilling process is studied in terms of the surface generation and the cutting forces. Due to specific limitations of existing machine tools in terms of required spindle speed and accuracy, a miniature machine tool testbed was developed to perform the experimental aspect of this investigation.; A mechanistic cutting force model for the micro-endmilling of multiple-phase materials was developed. This model explicitly considers the various phases in determining the magnitude and variation of the cutting force as well as the effects of machining with a cutting edge radius equal in magnitude or larger than the chip thickness. A new chip thickness computation algorithm is developed to include the minimum chip thickness effect. Orthogonal, microstructure-level finite element simulations are used to calibrate the parameters of the slip-line plasticity and elastic deformation force models for the primary metallurgical phases, ferrite and pearlite, of multi-phase ductile iron workpieces. The model is able to predict the magnitudes of the forces for both the ferrite and pearlite workpieces as well as for the ductile iron workpieces within 20%.; The surface generation process in the micro-endmilling of both single phase and multi-phase workpiece materials was also examined. 508 micron diameter endmills with edge radii of 2 and 5 microns were used to machine slots in ferrite, pearlite and two ductile iron materials at feedrates ranging from 0.25 to 3.0 microns/flute. A surface generation model to predict the surface roughness for the slot floor centerline is then developed based on the minimum chip thickness concept. Two phenomena were found to combine to generate an optimal feedrate for the surface generation of single phase materials, the geometric effect of the tool and process geometry and the minimum chip thickness effect. The surface roughness measurements for the ductile iron workpieces indicate that the micro-milling surface generation process for multi-phase workpiece materials is also affected by the interrupted chip formation process as the cutting edge moves between phases resulting in burrs at the phase boundaries and the associated increases in surface roughness.