| The numerical control processing capability of large-scale structural parts of aircraft reflects the overall manufacturing level of a national aviation.TC18 frame parts are important structural parts of the aircraft.The structure of these parts is very complicated and the machining process is difficult.During the cutting process,the relative vibration between the tool and the workpiece will produce vibration marks on the surface of the part.In addition,the milling cutter continues to process on the surface of the part with vibration marks,and the cycle is repeated,which may cause the reduced vibration ripple and the entire machined surface to form regenerative chatter.At the same time,the thermal conductivity of titanium alloy is very low,so that the heat is concentrated on the cutting edge of the tool,which greatly hinders the heat loss,causing the cutting temperature to rise rapidly,resulting in deterioration of the surface quality and rapid wear of the tool.In this paper,the machining efficiency,process flutter stability and cutting parameters optimization are studied from the aspects of process optimization,machining flutter stability and cutting process optimization in the process of NC machining.The previous processing process of frame parts is not synchronous,so it is difficult to unify the production specifications.This paper first analyzes the processing technology and processing difficulties of frame-type structural parts,and studies the standardized technology of frame-type parts,so as to prepare for the standardization of cutting parameters,tooling and cutting tools.The stability prediction of high speed end milling cutter for TC18 frame parts was studied.Firstly,in order to obtain the accurate flutter stability domain graph,the milling force coefficient identification experiment and modal analysis hammer experiment were carried out on the selected cutter-workpiece system to obtain the milling force coefficient and modal parameters required for the flutter stability domain respectively.Then the average cutting force is determined by single factor cutting force experiment.The dynamic characteristics of the cutter and the workpiece subsystem directly affect the milling stability.On the basis of establishing the milling dynamics model of the whole process system,the flutter stability region of the process is calculated analytically by semi-discrete method based on the regenerative flutter theory in machining.Then,on the basis of dynamic simulation,the limit stability region is further established.Aiming at the cutting difficulty of titanium alloy TC18,orthogonal experiment and single factor experiment on the surface roughness of high-speed cutting of titanium alloy TC18 were carried out to study the influence of feed amount,cutting depth and rotation speed of each tooth on the surface roughness.According to the result of orthogonal experiment,the surface roughness prediction model is established and the significance of the model is tested.The optimization model of cutting parameters based on the machining stability of the process system is proposed.Multiple influence factors,considering the process to determine the cutting parameters optimization of multiple constraints,constraints,the scope,objective function and design variables,established by rotation,each tooth feed,cutting depth and cutting width for the variables of the biggest production efficiency of the objective function,and finally by milling experiments prove that after stable milling parameter optimization of the workpiece surface processing precision is improved,the optimized material removal rate is 8.1 cm3/min,about 0.7 times of removal rate before optimization.Optimized to improve the efficiency of the machining,the cost of the production process control to achieve parts.It can be seen that the process parameter optimization based on the dynamic analysis of the milling process of structural parts is more scientific and effective. |
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