Experimental Research Of Helical Milling And Drilling For Titanium Alloy

Titanium alloys are excellent candidates for the needs of aerospace industry owingto their high strength to weight ratio and excellent corrosion resistance, maintained evenat high temperature，and it is being used as one of the main structure material in aircraftstructure. With fast development of aviation industry Titanium has been used more andmore widely. However, titanium alloys are regarded as extremely difficult cut materials，the hole-making processing of titanium alloys has been an unsolved problem. It isdifficult to meet the criteria of modern manufacturing by using conventional drillingmethod, and the invention of helical milling has provides an reasonable solution for thehole-making processing of titanium alloys. This work is focused on the study of toolwear mechanism, the cutting force and quality of machined holes of helical milling anddrilling, and analyzing the influence of cutting parameters on surface roughness ofhelical milling. It mainly includes the following aspects:Design the life experiment of helical milling and drilling. Tool wear was observedwith optical microscope, microscopic wear morphology was carried out using ascanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) allowedfurther compositional investigation in three different wear stages: initial wear, mediumwear and final wear. Tool wear location, wear pattern and wear mechanisms werestudied. The combined action of diffusion, adhesion and oxidation were observed inboth helical milling and drilling process.Design the Surface quality experiment of helical milling and drilling. By theexperiment system，the cutting force signal is collected and analyzed, and surfacequality factors such as roundness, diameter accuracy and roughness were measured. Inthe cutting forces and surface quality two aspects, the differences between helicalmilling and drilling were analyzed. Helical milling has obvious advantage in the cuttingforce, roundness and roughness comparing with drilling.Designed different combinations of cutting parameters interactively experiment ofhelical milling. Based on the artificial neural network (ANN) model developed, theeffects of the cutting parameters on the surface roughness were discussed. Three specific parameters in helical milling, namely spindle speed, feed rate, and screw pitch,were taken into consideration for the surface roughness. As the result of the experiment,the best combinations of cutting parameters is low spindle speed, high feed rate, andhigh screw pitch. It can ensure good surface roughness, but also can improve efficiencyand reduce demand for the machine.