Chatter Stability of Metal Cutting and Grinding Y. Altintas 1 (1), M. Weck 2 (1) 1 Manufacturing Automation Laboratory, Department of Mechanical Engineering The University of British Columbia, Vancouver, Canada 2 Laboratory of Machine Tools and Production Engineering, Aachen, Germany. Abstract This paper reviews fundamental modeling of chatter vibrations in metal cutting and grinding processes. The avoidance of chatter vibrations in industry is also presented. The fundamentals of orthogonal chatter stability law and lobes are reviewed for single point machining operations where the process is one dimensional and time invariant. The application of orthogonal stability to turning and boring operations is presented while discussing the process nonlinearities that make the solution difficult in frequency domain. Modeling of drilling vibrations is discussed. The dynamic modeling and chatter stability of milling is presented. Various stability models are compared against experimentally validated time domain simulation model results. The dynamic time domain model of transverse and plunge grinding operations is presented with experimental results. Off-line and real-time chatter suppression techniques are summarized along with their practical applications and limitations in industry. The paper presents a series of research topics, which have yet to be studied for effective use of chatter prediction and suppression techniques in industry. Keywords: Cutting, grinding, chatter 1 INTRODUCTION Dynamics of metal cutting and grinding processes have been a focus area of manufacturing research since the establishment of CIRP. This article is dedicated to the memory of Professor J. Tlusty who contributed significantly to the understanding and engineering of dynamic cutting, stability and avoidance of chatter vibrations in machine tools. This article is compiled to review the current state of the knowledge in dynamic cutting, grinding and the existing research challenges in modelling and avoiding machine tool vibrations. Tlusty presented the overview of dynamic cutting in the last CIRP key note paper dealing with the topic in 1978 [102]. He focused extensively on the modelling and measurement of dynamic cutting coefficients, and their influence on the chatter stability in single point metal cutting processes. Peters et al. surveyed the grinding process models in 1984 [75], and Inasaki and Karpuschewski [47] recently compiled the state of the research on grinding chatter in a CIRP key note article. They focused on the modelling of grinding process dynamics, chatter stability and monitoring. Rivin presented a CIRP key note paper on tool-spindle interface dynamics [82]. He discussed the influence of structural interfaces on the dynamic stiffness of the machines in detail along with comparison of various design solutions. Weck reviewed the structural dynamics of recent Parallel Kinematic machine tool structures, and their comparison with Cartesian machine tools [119]. He summarized the assessment of the dynamic stiffness and performance of the PKM machine tools. Van Lutterwelt et al [108] and Byrne et al [18] reviewed the machining research studied over the years, and outlined most common metal cutting mechanics models used in predicting the cutting forces. While Finite Element based metal cutting simulation models are most common in analysing the plastic deformation trends at the cutting edge, orthogonal to oblique cutting transformation and mechanistic models are mainly used in predicting cutting forces exciting machine tool vibrations [2]. The CIRP key note articles listed above provide in detail and state of knowledge in cutting process mechanics [18], dynamic cutting force coefficients [102], dynamics of grinding [47], machine tool design [119] and tool – spindle interfaces [82] which are most related to machine tool vibrations overviewed in this article. These authors provided a significant review of literature in the related areas, which will not be repeated here. However, there has been significant research progress in developing more advanced models in representing the dynamics of various cutting operations. With the advances in computer, sensor and high-speed machine tool technology, there have been new methods in predicting and avoiding chatter vibrations on the production floor. This article reviews the mathematical models of dynamic cutting and grinding, prediction of chatter stability for various operations, and off-line and on-line chatter avoidance techniques successfully used in the laboratories and industry. The article is organized as follows. The pioneering chatter stability theories of Tlusty [104] and Tobias [106] are presented in Section 2. Their theories provide fundamental understanding of dynamic cutting and chatter stability lobes. The application of orthogonal cutting chatter stability to single point machining operations, such as turning and boring is presented in Section 3. The current unsolved issues, such as dynamic cutting force coefficients and process damping, as well as the non-linearities in the stability models are discussed as research challenges. Section 4 reviews the dynamics and research challenges in predicting both forced and self- excited, chatter vibrations in drilling operations. The mathematical model of dynamic milling is presented in section 5. Past and recent stability theories in milling are reviewed, and the stability lobes predicted by various approaches are compared against exact, time domain, numerical solutions. Time domain modelling of dynamic grinding processes is presented in Section 6. Section 7 covers the review of on-line and off-line chatter vibration suppression techniques. A brief overview of challenging research tasks in dynamic cutting are listed in section 8, followed by a summary of the current state of knowledge in the field of dynamic cutting and grinding in section 9.