Study On Technology And Simulation For High-speed Milling Of Thin-walled Workpiece

Thin-walled workpiece is mentioned light weight structural workpiece which is composed of thin boards and finnings. It has prominent advantages of light weight, high intensity, beautiful sculpt and so on and its engineering application becomes broad increasingly. But thin-walled structure is very difficult for manufacturing because the problems of deformation, destabilization and vibration are easily occurred in the process of manufacturing. Thin-walled workpiece manufacture is an international recognized complex manufacturing technics.High-speed cutting is a fast developed high and new technology in manufacturing in the world nowadays. In industry developed country, high-speed cutting is recognized as a new cutting machining conception by more and more mechanical engineers. Compared with other processing methods in cutting thin-walled workpiece with low stiffness, high-speed processing has obvious advantages. Because it has the characteristics of small cutting force, low cutting thermal deformation, high cutting speed, high material removal rate, high machining precision and so on. A mass of cutting heat was gone with high-speed chip, even in no-cooling condition, the thermal distortion and compressive distortion of workpiece and cutter are slight. We can get not only high cutting efficiency, but also high cutting precision. While machining long and low rigidity thin-walled workpiece, we can also acquire satisfied machining effect.In this paper, we analyze the influencing factors of machining precision in high-speed milling of thin-walled workpiece firstly. The influencing factors depend mainly on the geometrical error of technological system making up of machine tool, clamp, cutter and workpiece, thermal distortion under force and error generated by workpiece's innerstress. We analysis the reason and characteristic of machining distortion, and draw the conclusion that cutting force and rigidity of frame member are crucial influencing factors of processing quality. The inevitable cutting vibration in process of machining deteriorates the finished surface quality of workpiece, reduces the life span of machine tool and cutter, generates noise and even makes that it is impossible for cutting. We put forward several technological approaches to improve machining precision of thin-walled workpiece.Based on the study of the influencing factors of machining precision in high-speed milling of thin-walled workpiece, we make use of the methods of theory analysis, computer analog simulation and machining experiment, arrange processing technics and optimize cutting parameters, ensure machining precision, and improve machining quality and efficiency.Then found an improved theoretical dynamic milling force model, which includes the influences of undeformed chip thickness, effective rake angle and chip flow angle. The simulation results indicate that the distribution of milling force has a significant influence on the dimensional precision of the finished part in the cut-in process. Suggestions about how to select the cutters and the milling parameters are given in order to gain an ideal milling force distribution.Modal analysis is a technology which is used to confirm the vibration characteristics of structure. It is the basic content in all dynamic analysises. Harmony analysis is mainly used to analyze the periodic response which is produced by persistent periodic body load in structural system, and ascertain the modal response while linear organization is bearing body load which varies according to sinusoidal rule as the time varies. Through modal and harmony analysis of thin-walled workpiece with ANSYS software, we get the inherent parameters of system vibration and supply a theoretical basis for avoiding occurring sympathetic vibration and improving machining precision.After the high-speed milling experiment of thin-walled workpiece, we use the milling force which is collected in the experiment to correct milling force model and verify the reliability of milling force model.The regularity for the influence of high-speed milling parameters on workpiece dimensional precision, surface quality and milling force is reached through high-speed milling orthogonal test of aluminum alloy thin-walled workpiece and analyzing the measurement results of dimensional precision, shape precision and surface roughness. The preferred principle for machining parameters is obtained, and the high-speed milling parameters for thin-walled workpiece are optimized.