Stability Analysis For Micro-Milling Nickel-base Superalloy Process

Nowadays there is strong demand for micro parts and components which are able to function properly at high temperature in the fields of aerospace, biomedical, energy and power. Nickel-base superalloy with good overall thermal performance is well fit for the requirement of micro parts and components. Micro milling is a novel processing technology for machining micro and high-precision parts with high temperature resistance and it can be applied to nickel-base superalloy micro parts. Nickel-base superalloy is a kind of typical difficult-to-process material and chatter tends to occur during its micro-milling process.Chatter is severely vibration between tool and workpiece during the machining process. It results in poor surface quality and low processing efficiency. There is little research on the micro-milling nickel-base superalloy process now around the world. Therefore, it is necessary to research on stability during micro-milling process on nickel-base superalloy. Considering the influences of multiple regenerative effect, minimum cutting thickness and recovery of processed surface, simulation model of micro-milling process on nickel-base superalloy is built and chatter stability is analyzed. With the graph of stability lobes, optimization of cutting parameters for chatter avoidance can be realized. The study can provide guidance for the machining parameters optimization of micro-milling nickel-base superalloy micro parts. The study is also valuable for the promotion of micro-milling technology and improvement of manufacturing capability of micro parts and components with good thermo-stability. The method of the study is a good reference for the study on micro milling of difficult-to-process material. The main contents are as following:Firstly, considering the influences of multiple regenerative effect, minimum cutting thickness and recovery of processed surface, instantaneous cutting thickness model is established. Cutting force model of the micro milling on nickel-base superalloy established earlier is revised for the stability analysis in time domain.Secondly, by means of receptance coupling method, beam theory and modal experiments, frequency response function of tool point is calculated. Modal parameters are identified and transformed into physical parameters.Thirdly, combining micro-milling force model, instantaneous cutting thickness model and kinetic equation by Matlab programming language, simulation model of micro-milling process on nickel-base superalloy is established. Adopting the ratio between maximum cutting thickness of rigid cutting system and that of flexible cutting system as chatter as the chatter criterion, chatter stability is analyzed in time domain.Finally, a number of points on the graph of stability lobes which presents spindle speed and axial depth of cut in the corresponding stability status is chosen for verifying experiments. By combining machined surface quality scan by SEM inspection and power spectrum analysis of the micro-milling force signal, it is possible to judge the stability status of micro-milling on nickel-base superalloy. By the comparison of experiments’ results and stability analysis, the reliability of stability analysis for the micro-milling nickel-base superalloy process is proved.