Tool Path Optimization Of Trochoidal Milling For Cavities Based On Dynamic Characteristics

The cavities are commonly seen in landing gear struts, especially in the landing gear inwhere double eccentric sleeves exist. At that condition, the machining area is narrow and thedemands need to be strictly met. In the actual process of high speed machining aiming atlanding gears, the time for cavities machining accounts for the high proportion of the overallprocessing time. Sometimes, the proportion is even as high as30%. Therefore, improvingthe efficiency of cavities processing for landing gear struts is of great significance. As known,cutting depth is large at the corner and the engaging angles increase with the increase ofspindle speed and feed rate. The cutting forces change drastically in the above area. Hence,the conservative machining parameter is adopted when applying toolpath to machiningcavities. On the other hand, the shape of landing gears with large L/D ratio is complex andthe worse rigidity appears in the support at both ends. The cutters are susceptible to vibrateat the processing situation. In order to figure out the machining problems, the followingaspects are studied:The mid-axis theory is referred to generate the centerline of the cavity boundary contour.According to the proposed single side topological traverse rules, the inscribed circles onmedial axis and corresponding common tangents are constructed. Furthermore, the singletrochoidal milling and double trochoidal milling method are carried out. Surely, thetrochoidal milling methods are applied to the cavities machiningAfterwards, an approach to predict cutting force of trochoidal milling is proposed basedon radial depth of cut. The tool entry angle and exit angle can be easily obtained by definingthe radial depth of cut. In addition, the prediction model aims precisely at the movementcycle of trochoidal milling instead of cycles of tool teeth to describe the overall load appliedto the tool in trochoidal milling. For a higher precision, the more accurate formula forcalculation of chip thickness is put into use for the force prediction of trochoidal millingaiming at its particularity.Subsequently, the research for dynamics of trochoidal milling is conducted on the basisof the proposed cutting force model. Unlike previous milling dynamics modeling, this paper explores the relationship among the radial cutting depth, cutter rotation speed and stability oftrochoidal milling method. Thus, the dynamics model of trochoidal milling based on theradial cutting depth is put forward. According to this model, the maximum radial cuttingdepth can be determined in the actual processing conditions. Further, the optimal step lengthof trochoidal toolpath trajectory is obtained. Under the premise that machining stability isguaranteed, the maximum cavity machining efficiency is naturally ensured. Simulationscoincide with experiment results perfectly, which shows the effectiveness of the proposedoptimization strategy.Experiments and simulation are applied to valid the effectiveness of proposed cuttingforce model, dynamic model and optimization strategy for trochoidal milling.