Papers by Author: Qing Hua Song

Abstract: Flexible parts such as turbine blade, blisk and monolithic components are widely used in the aeronautical industry, and high Speed Machining (HSM) technology is used to increase productivity and reduce production costs. Chatter is an undesirable phenomenon in high speed machining processes because of deteriorative surface finish, early cutting tool failure and unexpected machine tool damage. It can be avoided in higher speed milling processes if stability lobes is determined. In this paper, a non-linear regenerative force model is applied to a bull-nose tool geometry in order to obtain the machine operation stability lobes. An analytical-experimental method is proposed to obtain the stability lobes during high speed milling flexible parts with bull-nose end mills. The method is calculated and validated.

Abstract: Semi-discretization method is applied to construct stability chart and performance contour in the parametric space for milling processes. The method creates a mapping of the system responses in a finite dimensional state space. Based on the discipline of that, the smaller the largest absolute value (μmax) of the characteristic multipliers of the mapping is, the faster the system converges to zero, minimization of μmax leads to optimal stable limit. The optimal limits are obtained by using stability chart and performance contours. Additional, a novel analytical method for selection of optimal depth of cut (axial depth of cut) is presented. An example of 2-DOF down-milling model is employed to demonstrate the method. It is shown that the spindle speeds corresponding to the optimal depths of cut locate the left side of the resonant spindle speeds, and the optimal cutting parameters pair (spindle speed and depth of cut) can be used to offer high finishing accuracy in precision machining.

Abstract: A method for predicting the stability of thin-walled workpiece milling process is described. The proposed approach takes into account the dynamic characteristics of workpiece changing with tool positions. A dedicated thin-walled workpiece representative of a typical industrial application is designed and modeled by finite element method (FEM). The workpiece frequency response function (FRF) depending on tool positions is obtained. A specific 3D stability chart (SC) for different spindle speeds and different tool positions is then elaborated by scanning the dynamic properties of workpiece along the machined direction throughout the machining process. The dynamic optimization of cutting parameters for increasing the chatter free material removal rate and surface finish is presented through considering the chatter vibration and forced vibration. The investigations are compared and verified by high speed milling experiments with flexible workpiece.

Abstract: A new dynamics model for multi-degree of freedom high-speed milling system is proposed, which takes account of regenerative effects and the effects of the relative vibration of spindle axis in milling process. Based on the mode synthesis theory and the zeroth-order approximation of the Fourier series, an integrated stability analytical method for multiple frequencies is presented, which involves multiple orders modal characteristics and higher order excitations in high-speed milling process. The chatter stability lobes are predicted in the frequency domain using the proposed stability analytical method, and verified by milling experiments. It is shown that stability regions involving multiple natural modes are reduced contrary to the case of single natural mode.

Abstract: In this article, modal experiments were used to analysis the dynamics characteristics of the grinding machine. Static modal testing has validated the nature frequency and the critical speeds were also recognized by dynamic racing experiment. In grinding experiment, the surface roughness was investigated in different speed of workpiece spindle. The way to reduce vibration that caused to bad surface roughness of workpiece was also discussed. This experiment laid a foundation to optimize the structure parameter to improve the dynamic character of the grinding machine.