Mechanism And Process In High Speed Milling Hardened Steel With Micro-End Mill

As an important supporting technology for advanced manufacturing, high speed machining has an application in aerospace, automobile and mould industries. Due to deficiency of optimum processing strategy' support and thorough investigations into mechanism of high speed milling, problems occur in practical machining, especially for hardened steel milling with micro-milling tool.In this paper, hardened steel (HRC51) milling at high speed with coated carbide micro-end mill (4>2mm) has been investigated. Comprehensive and systematic theoretical and experimental researches have been made in issues related to mechanism and process of high-speed end milling such as cutting force, vibration, tool wear, chip morphology, optimization of machining parameters, Which have not only a theory value for the development of high speed milling, but also an important practical meanings for every industry department to choice appropriate process parameter and reduce production cost in the course of high speed milling hardened steel.The cutting force and vibration of different machining conditions have been studied. The results show that effect of cutting speed on cutting force and vibration is more unremarkable than feed per tooth and cutting depth.In high speed milling of hardened steel with micro-end mill, the main failure patterns include coating drop-off, adhesion wear, diffusion wear, tool tip breakage and abrade wear. The wear on the tool flank is badly than on the tool face. The main wear patterns of coated tool at early age of tool wear are coating drop-off and tool tip breakage.The experimental results indicate that the chip is mostly C or helix shapein hardened steel milling with micro-end mill, and the chip morphology shows that there is apparent cut slippage, which has a relation with cutting force, wear, angle and extended length of milling tool.Some technical studies have been made in issues including down milling and up milling, coating material, angle and extended length of milling tool. The studies show that up milling and down milling have little effect on cutting force, and when increasing cutting speed or feed per tooth, the vibration of climb milling is weaker than up milling, the contrary result occurs when increasing cutting depth. The lower cutting force, weaker vibration and higher tool life can be obtained in high speed milling hardened steel with AlTiN coated end-mill, which is be suited to high speed milling. The appropriate milling angles are the rake angle between -5 and 0 degree for slotting, the rake angle between 0 and 4 degree for side milling. The clearance rake should be between 10 and 15 degree, the helix angle is available for near 30 degree. With the increasing of the extended length of milling tool, the cutting force will increase firstly, but after the extended length is above a given value, the cutting force will reduce. The excited frequency in high speed milling is more higher, it is available for increasing extended length of milling tool to avoid sympathetic or quiver vibration because increasing the extended length may reduce the natural frequency of milling tool.Finally, the orthogonal experiment researches on machining parameters under different extended length of tool have been carried put. The recommended technical parameters for slotting and side milling obtained with lower cutting force, and estabilishing the experiential exponential formula of milling forces for slotting.