The Study On The Milling Characteristic For Titanium Alloy In Additive/Subtractive Hybrid Manufacturing

Additive/Subtractive Hybrid Manufacturing(A/SHM)combines the advantages of both additive manufacturing,which could fabricate complex parts,and subtractive manufacturing process,which could obtain high precision and quality.This emerging technology could improve the dimensional and surface quality,as well as remove material defects.A/SHM could machine internal surface of complex structures that provides a new method to fabricate high-performance complex parts.This thesis studies on A/SHM process for titanium alloy.A milling force prediction model,considering the geometric characteristic and residual heat induced by additive manufacturing is developed.A milling experiment platform is set up to simulate the A/SHM environment and milling experiments are carried out to verify the accuracy of the model.The milling characteristic is analysed based on the predition model and experiments.The main research contents are as follows:(1)The surface and end profile of Ti-6Al-4V parts fabricated by Direct Metal Deposition(DMD)are studied,and the end profile milling force model is developed based on differential method,considering the influence of the end profile,helix angle of the cutter and engagement of multiple cutting edges;(2)The milling force coefficients of DMDed parts are calibrated by a series of slot milling experiments.Predicted milling forces of half-slot milling and end profile milling are compared with experiments,and the changes of milling forces are investigated through the milling force model.This model offers a monitoring method for the end profile milling process in A/SHM;(3)The temperature build-up of Ti-6Al-4V part in DMD process is measured,and a preheating milling platform is designed to simulate the environment of milling process in A/SHM.The influence of temperature on milling operation of DMDed Ti-6Al-4V parts is investigated.A predicted milling force model is proposed considering the influence of temperature on material property,tool flank wear and plastic deformed layer of machined surface.The milling force changes are studied by the model and preheating milling experiments.The surface roughness and profile of machined surface at different temperatures are also investigated.