Stability Modeling And Analysis For Orthogonal Turn-milling Of Shaft Parts

With the rapid development of modern industry, more and more shaft parts withcomplicated structure and shape are needed. Such as landing gears, automobile enginecrankshafts are typical shaft parts. The shape and working surfaces of these parts areconstituted by complex surface. By ordinary machine method such as turning, milling andother conventional methods, it’s difficult to obtain desired accuracy, even it is impossible tomachine. Due to the high safety performance and long service life, some parts are made ofhigh strength steel or titanium alloy material for example. These materials are difficult tomachine. The material removal rate of some parts are up to90%. Long machine cyclespresents very big challenge to us. Strong cutting force will generate when machiningdifficult materials. Because of the overhang of the tool and other factors, the rigidity ofmachining system is weak. It’s prone to chatter. The chatter of machine tool will makemachining process instable, resulting in decreased surface quality and low metal cutting rates,even damage the machine tool. Therefore, one of the main obstacles to improve machiningcapabilities is chatter.Compared to the traditional machining methods, such as milling, turning and boring,the machining condition of orthogonal turn-milling is more complex with the instantaneousvariable cutting depth and thickness. In this paper, we considered the kinematicscharacteristics of orthogonal turn-milling, and deduced the cutting force model of orthogonalturn-milling and established stability model of orthogonal turn-milling. Then, we obtainedthe stability Lobe diagrams, and analyzed the influence of mode coupling effect on thestability of orthogonal turn milling. The accuracy of the stability model was verified on aturn-milling compound machining center. After that, the difference of stability modelbetween the orthogonal turn-milling and ordinary milling was analyzed. The result showsthat in the case of no chatter the orthogonal turn-milling could take a bigger cutting depthcompared to milling. Then, we analyzed the influence of the cutting depth and the axialfeeding on the stable region. It is found that with different diameter ratio between theworkpiece and the cutter, the influence of variable cutting depth on the stability model is different. The influence of machine parameters such as axial feed rate, the eccentric amountand the workpiece-tool diameter ratio in stability of orthogonal turn milling were analyzedby single-factor method. Under stable condition, the maximum machine efficiency withdifferent parameters was also analyzed. The analysis provides a theoretical basis inoptimizing the orthogonal turn-milling parameters, and guaranteeing the efficiency of shaftparts machine.