The Research On Cutting Force In High Speed Milling Process Of Difficult-to-Machine Materials

There are many characteristics in the machining of difficult-to-machine materials, such as high cutting force, high cutting temperature, work hardening, cutting abration of tools, and so on. These characteristics, which make the machining of difficult-to-machine materials a difficulty in cutting machining, not only cause low efficiency, but also reduce tools' life. As high speed machining can improve the machinable performance of difficult-to-machine materials, the research on the technology of high speed machining difficult-to-machine materials becomes increasingly important. The purpose of this research is to study the cutting force in the high speed milling process of difficult-to-machine materials. This is relative with the optimization of the cutting parameters, which is an important part of the task which is named "research on high effective CNC machining system of landing gear".In this thesis, we lay our emphasis on the model of cutting force of difficult-to-machine materials, especially high strengh materials, in the high speed milling process. Following the introduction of the characteristics and cutting mechanism of high speed machining, we educe the feasibility of the high speed machining difficult-to-machine materials. We summarize common models of cutting force and the means of establishing a cutting force model, then choose the appropriate one for our research based on the analysis of the advantage and disadvantage of each method.An analytic model of cutting force in the case of high speed milling of difficult-to-machine materials is established. The cutting force is forecasted from the relationship between the cutting parameters and cutting force coefficients. The comparison between cutting force results from this model and that from the experiment validates the veracity and practicability of the cutting force model established. The prediction of cutting force, based on the analytic model we, is precise in the trend on variation of cutting force. It also shows accurate in the value of cutting force, especialy the radial and tangent cutting force. And the error results mainly from the regression calculation in the progress of establishing cutting force model.After the experiment of high-speed milling 300M ultra-high-strength steel, we present an empirical cutting force model to estimate the influence of milling parameters on milling forces in the case of high-speed milling of difficult-to-machine materials. The empirical relationship between the cutting force and the cutting parameters is given, as theoretical foundation of the optimization and selection of cutting parameters. The last but not the lease, using the empirical cutting force model as restriction, we optimize the cutting parameters in the milling process of one typical part of landing gear. The result shows that the empirical model of cutting force established reflects characteristics of cutting force in the case of high speed machining difficult-to-cut materials, especialy the ultra-high-strengh ones. Compared with the conventional formula, involving less influencing parameters, this empirical model is more convenient in controlling cutting force.