Papers by Keyword: Chatter

Abstract: Sectors such as energy, aerospace, and heavy machinery increasingly rely on the machining of large components, where boring bars can easily exceed 200 mm in diameter and reach length-to-diameter ratios of up to 14. In these operations, chatter remains the dominant limitation due to the inherently low dynamic stiffness of such long tools. While Tuned Mass Dampers (TMDs) are widely applied in small and medium-sized boring bars, but transferring this technology to large-scale tools introduces significant challenges, particularly in the selection and tuning of damper components and the difficulty of evaluating performance prior to manufacturing. Because producing large boring bars is costly, a structured and predictive design strategy is essential to avoid trial-and-error iterations. This work introduces a scaling methodology that adapts TMD-integrated boring bar designs to large dimensions, providing a systematic approach to predict dynamic behavior across different tool sizes. The methodology is demonstrated through a case study involving Ø200 mm boring bar with length of 14 times the diameter. Experimental validation with the manufactured prototype confirms that the proposed scaling strategy enables effective chatter suppression and offers a practical path for extending TMD technology to large-scale boring applications.

Abstract: This study investigated the effects of tool runout on chatter vibration taking images of a machined surface to assess the vibration strength, number of vibrations, and phase difference depending on the spindle speed and axial depth of the cut. This study obtained significant results regarding the stability pocket represented by the spindle speed. We observed that the stability limit changed depending on tool runout.

Abstract: This study presents a time domain simulation and workpiece surface generation framework for broaching operations, carried out with broaching tools of arbitrary geometry by machine tools of general dynamics. First, a three degree of freedom simulation model is formulated by considering an adequately discretized infinitely rigid tool, and a broaching machine, which is compliant in all translational spatial directions. Taking contact loss events into account, this leads to system a piecewise-smooth delay differential equations with state dependent delays, due to the allowed deviations in the speed of cutting. Through numeric integration of these equations, the dynamic displacement and cutting edge engagement of the broaching tool are evaluated, which serve as inputs for the developed surface generation routines. Then, a discretized workpiece surface is generated by finding the last active cutting edge, and its corresponding displacement for each point, allowing the numeric investigation of surface roughness and integrity through standardized techniques. Finally, to demonstrate the capabilities of the proposed framework, force and displacement signals as well as the generated surface and its virtual quality assessment are presented for a typical broaching operation.

Abstract: The occurrence of chatter during machining processes is a serious problem because of an excessive vibration that consequently dropped the quality of the machined surface. Especially on the turning process of tube shaped workpieces e.g. steel pipe that has relatively low stability limit represented by low critical depth of cut due to the naturally low dynamic stiffness of steel pipe. A cheap and simple method to increase the stability limits during the turning process of steel pipe has been developed in this research by using “Sand” as granular damper material to dissipate the elevated vibration energy. An experimental research is performed to investigate the performance of the sand damper by doing the cutting process of two different diameter the steel pipe that is filled up by sand. The result of the experiment shows that the 3 inch nominal diameter with fully filled of Sand can increase the stability limits from the critical depth of cut 0.68 mm (empty or without sand) up to 3.27 mm (full) or elevate by 4.8 times (almost fivefold). On the other hand, the 2.5 inch nominal diameter by filling with full of sand can improve stability limits from the critical depth of cut 0.95 mm (without sand) up to 3.05 mm or increase by 3.2 times. In simple words, the result of this research can be concluded that the increasing of the stability limits means also the elevated of the quantitative performance or the production rate of the turning process of Steel pipe almost up to fivefold. Keywords: Stability limits, chatter, sand damper, turning, steel pipe, vibration.

Abstract: The article discusses the issues of chatter damping during milling. The relationship between the amplitude of forced vibrations and the cutting speed has been established. The choice of the optimal values ​​of the cutting condition during end milling is proposed to ensure the minimum vibration amplitude.

Abstract: In order to improve the cutting stability of high-efficiency micro turn-milling machine tools, avoid the chattering problem during the cutting process. In this paper, the chatter problem in the cutting process is studied based on the stable lobes. By analyzing the high-efficiency turn-milling machine tool mechanism and the turn-milling model, the micro turn-milling dynamic dynamic vibration model and the mathematical model of turn-milling chatter are obtained. Then, based on the hammer test method, the transfer function of the tool-workpiece system is obtained, and the turn-milling stable lobes of the high-efficiency micro turn-milling machine tool is constructed. Finally, the research on the stable zone of the turning main spindle parts, the turning back spindle parts and the high-frequency milling part are completed. The experimental research results guide and optimize the selection of cutting parameters for turn-milling process.

Abstract: Based on the dynamic model of 1/4 vehicle suspension, an active control system is designed using the fractional order exponential reaching law of model following variable structure control strategy. An active suspension with linear quadratic optimal control is used as the reference model. The sliding mode switching surface parameters is designed by pole placement method to ensure the stability of the system. At the same time, combined with the index reaching law proposed by Professor Gao Wei Bing and the definition and properties of fractional index, constructs a similar fractional order exponent reaching law to improve the dynamic quality of sliding mode motion. And in MATLAB, system modeling and controller design are implemented. By setting up experiments, the different suspensions are compared. The results show that compared with the passive suspension, the performance of the vehicle can be improved better, and the performance of the tracking reference model has good tracking performance. Moreover, compared with the integral exponential reaching law, the chattering can be more effectively weakened. Finally, before and after the change of vehicle parameters in the simulation, the results show that the system has good robustness.

Abstract: This paper deals with a natural frequency distribution of a six-axis industrial robot in order to analyze chatter vibrations in upcoming milling processes. Since the dynamic vibration behavior of the robotic system can be manipulated by changing the robot’s joint configuration, experimental modal analysis is performed to determine the natural frequencies in the entire workspace. In this study, methods of design of experiments are used to derivate a mathematical model that predicts the natural frequencies of the robotic structure for any joint configuration within the considered workspace.

Abstract: Machine tool vibrations cause uncomfortable noise, may damage the edges of cutting tools or certain parts of machine tools, but most importantly, they always have negative effect on the quality of the machined surface of workpieces. These vibrations are especially intricate in case of milling processes where complex tool geometries are used, like helical, serrated, non-uniform pitch angles, and so on. During the milling process, the arising vibrations include free, forced, self-excited, and even parametrically forced vibrations together with their different combinations. Regarding surface quality, the most harmful is the self-excited one called chatter, which is related to the regenerative effect of the cutting process. Its relation to machined surface quality is demonstrated in an industrial case study. The modelling and the corresponding cutting stability are presented in case of a helical tool applied for milling with large axial immersions. The extremely rich spectrum of the measured vibration signals are analyzed by means of model-based predictions, and the results are compared with the spectral properties of the corresponding machined surfaces. The conclusions open the way for new kinds of chatter identification.

Abstract: The first step to predict the milling stability is to identify the dynamic characteristics of cutting process. And the mass loading effects of removal material play an important role on the dynamic characteristics of milling process for thin-walled parts, such as impeller, turbine blades and automobile components, which is changing with cutting time or tool position. Therefore, how to identify the instantaneous dynamic characteristics of milling process is one of the most significant problems. In the paper, a structural dynamic modification method with variable mass to predict the instantaneous dynamic characteristics of multi-axis milling thin-walled workpiece with complex curved surface is proposed. The proposed method takes into account the variations of dynamics characteristics of workpiece with the tool position and material removal. And the material cutting process is regarded as the structural dynamic modifications of cutting system, the instantaneous dynamic characteristics of which can be estimated by the extended Sherman-Morrison-Woodbury formula to obtain the corrected frequency response function (FRF). Experiments were carried out to obtain the instantaneous dynamics of a thin-walled workpiece and the results were verified by finite element method (FEM).