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High Speed Milling Process Planning of Free Form Surface and Autonomous Decision Technology

Author: ZhangZhongSong
Tutor: WangYiQiang
School: Jilin University
Course: Mechanical Manufacturing and Automation
Keywords: HSM Cutting parameter Free-form surface Autonomous decision Ball end mill
CLC: TG54
Type: PhD thesis
Year: 2011
Downloads: 68
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Abstract

HSM(High Speed Milling)has been wildly used in many fields after decades years of development. It is more and more important to enterprise and has irreplaceable function on some product manufacturing, such as dies and aviation products.Workpieces have more and more free form surfaces. The quality and efficiency of workpieces is reguired more and more highly.The operation experience of HSM is relatively less.The research on theory of HSM process is a relative shortage.The intelligent decision technology of HSM process is not high.Its process planning depends on experiences and is limited by working environment. Therefore, it is necessary to study on HSM process planning of free-form furface and autonomous decision technology.The research on HSM parameters is a precondition and of HSM process planning .The decision theorires and methods are essential conditions. On the base of analysis on research status and development of HSM process planning and autonomous decision, this paper has further researched on the HSM process and autonomous decision technology .The main research contents and methods include:(1) On the basis of tests of HSM typical materials, this paper researched on the relationship between milling parameters and surface roughness. Using the different test methods to fit different milling conditions.By using test datas, the milling parameters were made regression analysis, some formulas were got, the influence of single parameters on surface roughness was discussed, and the influence of interaction items on surface roughness was analysised.The influence law of ball end mill pitch angle was researched. The test indicated that the influence of ball end mill pitch angle on roughness is obvious in test. The influence law is that the roughness largen quckly at first,then becomes smaller quickly in the range of pitch angle from 0 degree to 25 degree.The forming reason of the poorest pitch angle was discussed and formula was determined. (2)The HSM parameters were planned, and the relative constraints of HSM free form surface were discussed in this paper. The relationship between the axis force,aixis acceleration and feed velocity was analysised.The S curve feed velocity was planned under the axis constraints.The sufficient milling conditions of ball end mill were derivated according to the sufficient milling conditions of ring mill cutter. By using equicalent arc to fit the curve on workpiece surface, the radial feed formulas were got which three axis constant scallop height milling free form surface with ball end mill.According to the offset curve vector equation and the geometry relationship between the workpiece surface and tool path, this paper has given a more precise method which getting the radial feed when using equivalent arc is not suitable. For instance, there are some corners or curves with rapid currage change.(3)The tool life was determined in HSM. On the basis of having known the tool and load is similar with another, this paper determinded the tool life according to the relative Miner theory. In the condition of lack of tool life datas, it could avoid tool changing during cutting, increase the use efficiency, decrease the times of tool life test,and is practical.The similarity between tools was evaluated according to the material attributes and shape characteristics of tools. To fill or forsake the missing datas could decrease the unfavorable influence by using tolerance relation of rough set theory.A discrete method of continous attributes of workpiece material was proposed. This paper analysis the interval of data discretization about the grey absolute incidence degree ,give a determinding method of banlance of contimuous data interval with grey entropy and propose a dynamic multi-stage discrete method of continuous attributes based on absolute degree of grey incidence and balance degree of grey entropy. It can keep the classification ability.With the theorem of grey absolute incidence degree, the incomplete attributes are reduced, and the result is unique.(4)This paper researched on the autonomous decision of HSM parameters,and has proposed three methods to meet different conditions of HSM free form surface.In the condition of several given process plan optimal selection,AHP is a good decision method.According to machining laws of HSM, a new method of measuring weights was given,and has good effect. In the condition of known cutting formula,the cutting parameters is optimized by using mathematical programming.In the condition of unknown cutting formula, similarity which is about materials machinability and tool spectfication was calculate firstly considering cutting environment. Then the similar case was get, At last the process decision was done based on CBR by using LS-SVM.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal cutting and machine tools > Milling and milling machine
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