Stability Analysis And Parameter Optimization Of Thin-walled Parts Milling

In order to reduce the weight of aircraft or spacecraft as much as possible,and to meet the requirements of performance and structural strength,various kinds of thin-walled parts are widely used in aerospace instruments.These thin-walled parts of the machining accuracy and surface quality requirements are usually relatively high,mostly by CNC milling processing.However,thin-walled parts generally have the characteristics of large space size,complex structure shape,high material removal rate,poor wall stiffness,and many difficult materials,etc.,so that the milling process of such parts is very poor,prone to milling chatter and other phenomena,so it is often necessary to predict the milling stability before processing.In this paper,thin-walled parts milling as the research object,by means of structural dynamics,numerical simulation,experimental modal analysis,finite element modal analysis,cutting test and other methods,the milling flutter stability of aluminum thin-walled parts milling was studied,and the milling process parameters were optimized.The main work contents and results of this paper are as follows:(1)The dynamic milling thickness model and dynamic milling force model of thin-walled parts were established,and the single-point contact dynamic model of thin-walled parts was established.Based on the structural dynamics method,a multi-point contact dynamic model for thin-walled parts milling was established,which was used to predict the side milling stability of thin-walled parts.In this method,the change of tool and workpiece dynamic parameters along the tool axis is considered.Firstly,the dynamic equations are established in each direction of the milling system coordinate system,and then the model established at each point is transformed into the whole multi-point contact milling dynamic model by using the structural dynamic method.(2)In order to verify the accuracy of the established multi-point contact dynamic model for thin-walled parts milling,the milling flutter stability of a set of workpieces was predicted.By comparing with the cutting test results,it is concluded that the stability prediction results of the multi-point contact milling dynamic model are more accurate.And the three-dimensional milling stability leaflet diagram with spindle speed,axial cutting depth and radial cutting depth as coordinate axes is drawn.(3)Using genetic algorithm,the milling parameters were optimized for side milling of 7075 aluminum alloy thin-wall parts.The objective of optimization was to maximize material removal rate and minimize surface roughness,and the limitations of milling chatter stability on the selection of milling parameters were considered.The results show that,compared with the optimization results based on the single-point contact dynamics model,the optimization results based on the multi-point contact dynamics model can ensure the machining accuracy and have higher efficiency.