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TL;DR: In this paper, a specific cutting test has been designed to specifically measure and control the dynamics of the part and the cutting conditions of a finishing toolpath, and the influences of the cutting speed and damping coefficient on the chatter occurrence are discussed.
Abstract: The numerical simulation of machining process is a key factor in the control of parts machining process. Its development aims at improving the process reliability and reduces the time spent during the process planning stage. In this context, we use a specific time domain simulation allowing modeling the dynamics of a thin wall part turning operation. After having introduced the basics of the proposed approach we present a specific cutting test that has been designed to specifically measure and control the dynamics of the part and the cutting conditions of a finishing toolpath. The influences of the cutting speed and damping coefficient on the chatter occurrence are discussed. In order to better control the simulation uses, an analysis of the simulation parameters influences on the simulated results is proposed.
19 citations
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TL;DR: In this article, the stability behavior with a time-varying spindle speed is connected to the stability behaviour with constant spindle speeds, and strategies for tuning the parameters of the speed variation for an optimal stabilization are developed.
Abstract: In the present paper the chatter instability of variable speed machining is studied. Though, there exist numerical methods for the computation of the stability lobes for variable speed machining, especially in turning processes the potential of an active spindle speed variation for chatter suppression is mostly unexploited. In the case of a slowly time-varying spindle speed, which is practicable on a real machine tool, the stability behavior with a time-varying spindle speed is connected to the stability behavior with constant spindle speeds. This so-called frozen time approximation helps to understand the stabilizing mechanism of turning with spindle speed variation. Strategies for tuning the parameters of the speed variation for an optimal stabilization are developed. The results presented here are useful for a practical implementation of variable speed machining to increase the productivity without any negative effect due to the variation of the spindle speed.
78 citations
TL;DR: In this paper, a cutting force model based on the instantaneous chip thickness is proposed to optimize the cutting parameters and the geometry of the cutting tool in order to control the loading on the tool and thus the final quality of the borehole.
Abstract: Orbital drilling is a highly complex machining operation. Due to the tool helical trajectory, the chip thickness is highly variable along the cutting edges and during the tool revolution. This can be made even more difficult by the cutting tool geometry, which can be also very complex. This explains why cutting forces are very difficult to model and to estimate for different cutting tool geometries. The aim of this study is to develop a cutting forces model depending on the tool geometry and cutting conditions in order to control the final quality of the machined borehole. First, the geometry of the chip is modelled taking into account the parameters defining the trajectory and the tool geometry. A cutting force model, based on the instantaneous chip thickness, is then set up. An experimental study validates the modelling through measurements of cutting forces made during orbital drilling tests. From this modelling, it is possible to optimise the cutting parameters and the geometry of the cutting tool in order to control the loading on the tool and thus the final quality of the borehole.
52 citations
TL;DR: In this article, a robust stability analysis of turning is presented for flexible workpiece by modeling the varying dynamic properties due to the material removal process by means of finite element method, where the frequency response function is traced along tool position.
44 citations
TL;DR: In this article, an experimental case of turning a steel thin-walled tube featuring intense vibrations with variable parameters was studied. And a stability analysis was carried out for several states of this evolutive system in order to gather insight into the steady cutting conditions.
22 citations
TL;DR: The present study could provide an in-depth understanding of the dynamic behavior of flexible workpieces in turning operations and produce more accurate modal parameters estimation and chatter onset location prediction than the simplified model.
Abstract: Chatter happens frequently in turning of flexible parts, jeopardizing the dynamic stability of the operation. The chatter stability prediction is dependent on the accurate estimation of the structural parameters of the cutting system. This paper aims to quantify the influence of the support conditions on dynamics of the flexible parts in straight turning. Given the time-varying cutting tool position during machining, first, the chatter stability of the cutting system along the cutting path is analyzed, and the critical stiffness expression for chatter onset prediction is deduced. Then, two models of the spindle-workpiece-tailstock system using analytical and numerical methods are constructed and compared. The simulation results showed that increasing the spindle bearing or tailstock support stiffness cannot effectively improve the stiffness distribution and the eigenfrequency of the machined rod, whereas the frequency of the system tends to be increased evidently with the chuck size decreased. In comparison with the experimental results, it has been shown that the model involving the effect of spindle bearing and center support enables to produce more accurate modal parameters estimation and chatter onset location prediction than the simplified model. Besides, the measured displacement signals demonstrate a good mapping relation with the theoretical analysis results. The present study could provide an in-depth understanding of the dynamic behavior of flexible workpieces in turning operations.
14 citations