Study on Surface Dimensional Errors in Peripheral Milling of Thin-walled Workpieces Using Static and Dynamic Finite Element Models

• Main Author: 蔡哲雄
• Other Authors: 廖 崇 禮
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/43526909707195551131

博士 === 國立臺灣科技大學 === 機械工程系 === 88 === ABSTRACT A dynamic finite element model and a static finite element model together with an adequate end milling cutting force model are developed, respectively, in this study to analyze the surface errors in peripheral milling of thin-walled workpieces. The modeling of cutting system includes two parts, one is the spindle-bearing-tool system and the other is the workpiece. The helical fluted end mill is modeled with the pretwisted Timoshenko-beam element which can more accurately simulate the specific geometry of the cutter. The workpiece is modeled with a 3-D isoparametric 12-node element which takes into account the geometry and thickness variations of workpiece during peripheral milling. The present dynamic and static finite element models are developed first. The static model neglects the dynamic effect during milling and assumes that the tool and the workpiece deform to their static equilibrium positions at any milling instant, which are found iteratively by the modified Newton-Raphson method. The dynamic model includes the dynamic effect during milling and the resulting finite element equations of motion of cutting system are solved by the Newmark integration method. The cutting force models of helical fluted end mill are then described. Both the static and dynamic analysis procedures of peripheral milling are also given. After the deflections of tool and workpiece are obtained, the surface dimensional error of workpiece at the corresponding grid point can be easily computed. The present simulation models are experimentally verified. Finally, the approach to reduce the surface errors in peripheral milling is presented. From the present study it is found that the cutting conditions, tool selection and workpiece thickness will affect the surface dimensional errors. Also the installed offset of end mill has serious effect on the cutting force variations and machined surface roughness.