Research On Selection Of Optimal Cutting Parameters In High-speed Milling Of Thin-walled Al-alloy Workpiece

1,IntroductionAt present, the mechanism and technology of High Speed Milling (HSM) are still unsubstantial in home, which makes the bad use of HSM by slowing spindle speed of the end mill, depressing cutting parameters and wrong selecting of end mill, that causes the worse utilization and the higher cost of the machine. By researching the dry milling of Aluminum alloy, the principle of selecting optimal cutting parameters in high speed milling of thin-walled structure components are studied. The law of cutting force under different parameters should be given, so that the optimal selection can be made and the machining efficiency will be improved.2,The law of force variety with five main cutting parametersThe peripheral milling model with end mill is illustrated in Fig. 1. The main cutting parameters introduce here: radius of the end mill (R-mm), axial depth of cut (da-mm), radial depth of cut (dr-mm), spindle speed of the end mill (nt-r/min), feed rate of the end mill (Vf-mm/min),and another parameter feed rate per tooth (ft-mm/z), which given by nt and Vf indirectly.With the high speed milling machine FIDIA D165, the data of cutting force of the high-speed steel end mill on LC4 material is gathered, and the mathematic mould of predicting the cutting forces is founded successfully, with which the law of force variety is analysed systemically and worked out: using down milling style,①for cutting force of X direction, it has peak value with the augment of R, will be increased with the augment of da, dr and Vf, and will be decreased with the augment of nt;②for cutting force of Y direction, it has lowest value with the augment of Vf, will be increased with the augment of da and dr, and will be decreased with the augment of R and nt; using up milling style, for cutting force of both X and Y direction, it will be increased with the augment of da, dr and Vf, and will be decreased with the augment of R and nt.Then, get the principle of optimal selecting of cutting parameters for thin-walled structure components machining.1) enough bigger R ;2) smaller de and deeper da;3) by a certaint higher nt and concertedly faster Vf;3,Machining experimentation of thin-walled structure componentsFirstly, the static analysis of 1mm thickness 30mm depth thin-walled cavity under 1~100N focus force on the top is studying in ANSYS. Table 1 gives the stress and displacement, showing the component always has a big elastic distortion. So the conclusion can be made that the problem of the end mill missing caused by the elastic distortion will be difficult to avoid in machining of deep thin-walled component.In the attempt experiment, the problem related has happened. Other more, the quiver vibrating phenomena terribly happens in the machining, which can be reduced by down milling style and faster feed rate of the end mill.At last, the thin-walled cavity with 0.5mm thickness 12mm depth at upside and 0.8mm thickness 15mm depth at downside is machined successfully. Fig.2 is the photo of the component. From the picture, there is a distinct distortion on the right side, where is the thinnest place of the cavity for precise milling and happens quiver vibration phenomena. And with the measurement of other surfaces by three coordinate machine, knowing the plane tolerance of the upper surfaces is below 0.055mm and the uprightness to the bottom is below 0.725mm, and the lower ones'is below 0.028mm and 0.104mm. Besides, the surface roughness of them is all below 0.3μm, and the best is 0.1μm.4,ConclusionBy researching the dry milling of Aluminum alloy, the principle of optimal selecting cutting parameters in high speed milling of thin-walled structure components are established. With it, less than 1mm thickness thin-walled cavity component is machined efficiently and successfully, which can be helpful to guide the process planning of such components and generalize the application of the high-speed milling.A series of conclusions from the studying have been got:1) by researching of cutting removal efficiency, found a hidden factor which can judge the NC system's efficiency, that is in processing shape and parameters all certain situation, using the ahead function of NC system, the shorter of machining time needed the better of the NC system;2) the law of cutting force variety with the high-speed steel end mill on LC4 material is analyzed systemically and worked out: using down milling style,①for cutting force of X direction, it has peak value with the augment of R, will be increased with the augment of da, dr and Vf, and will be decreased with the augment of nt;②for cutting force of Y direction, it has lowest value with the augment of Vf, will be increased with the augment of da and dr, and will be decreased with the augment of R and nt; using up milling style, for cutting force of both X and Y direction, it will be increased with the augment of da, dr and Vf, and will be decreased with the augment of R and nt;3) for the high-speed-milling of thin-walled structure component, the thickness of the cavity left should be uniform; with smaller de and deeper da,the machining efficiency of thin-walled structure component can be improved successfully; by using down milling style and faster feed rate of the end mill, the quiver vibrating phenomena can be reduced ;4) for the high-speed-milling of open-thin-walled structure component, with the thin-walled thickness left less than 2mm, it is avoidless to occur quiver vibrating and end curling phenomena, which causes the bad surface of the component; othermore, must be care for the environment factor, which can cause the thin-walled component distortion, such as oil fog or airflow with high pressure;Otherwise, the reason of quiver vibrating phenomena should be studied deeply.