Study On Dynamics In Helical Milling Of Difficult-To-Cut Materials

In order to meet the requirements of high precision, high efficiency and highreliability of aviation products, more and more new materials have been widely used,the quality and efficiency problems have become increasingly prominent in thehole-making process. This dissertation aims at the hole-making problem abouttypically difficult-to-cut materials for aviation manufacturing field, and studies thehelical milling dynamics about titanium alloy and carbon fiber reinforced composites(CFRP). The follwing contributions have been made as follows.Cutting force model is established in helical milling of titanium alloy process.Considering the un-deformed chip thickness, the effect of the side edges and bottomedges of the cutting tool and the change of the cutting parameters, analytical cuttingforces model is set up in the helical milling process. The cutting experiments arecarried out about titanium alloy (Ti-6Al-4V), cutting force coefficients are identifiedbased on the average cutting force method according to the single-factor test, and thecoefficients are corrected taking into account the different cutting parameters. Thecorrectness of the analytical model of cutting force in helical milling of titanium alloyis ultimately validated.The cutting parameters are optimized in the helical milling of titanium alloy.Considering the tool life, cutting efficiency and the surface roughness, the cuttingparameters in helical milling of titanium alloy under the coolant conditions areoptimized based on the Pareto Genetic Algorithm. The cutting experiments are carriedout according to the cutting parameters after optimized. The results show that thesurface roughness of the holes can meet the quality requirements in the aviationsystem.The cutting forces are analyzed and the effects of cutting forces on the machiningquality are studied in the helical milling of CFRP. The influences of cutting parameterand tool wear etc. related parameters on the cutting forces are analyzed based on theexperimental results. The analytical model of cutting force in helical milling of CFRPis improved, the cutting forces coefficients are identified and corrected, and thecorrectness of the theoretical model is verified. The changes of the diameter error,roundness error and the surface roughness of the holes are analyzed in the whole. The relationships between the cutting forces and the delamination in the entrance of thehole and the surface roughness in the inner wall are discussed in detail.The cutting force and the hole-making quality about CFRP/titanium laminatedmaterial are analyzed. The helical milling experiments are carried out forCFRP/titanium alloy laminated materials. The diameter error, the entrance and exitquality of the holes, tool wear state and the changes of cutting force are all discussed,respectively. The results show that the tool wear, chip removal and cooling issues arethe key problems affecting the quality of the hole-making in the laminated materials.The above research achievements enrich the relative research progress to thehelical milling technology, and have important practical significance in the promotingits early application to the aviation industry.