Method for Online Control of the Cutting Process Stability

2014

Nowadays techniques for online controlling the cutting process stability are based on the use of a sensor, in order to identify the occurrence of self-excited relative vibration between tool and part. A disadvantage of these techniques is that dynamic stability control system reacts only after passing over the stability limit, and the self-excited vibrations have already appeared. Hence, any reaction to the instability occurrence is delayed. This paper presents a novel technique for dynamic stability online control in cutting processes. According to it, the current operating point of the machining system is not only permanently brought into the stability domain, for maintaining the process stable, but also kept near the stability limit, for reaching the maximum level of productivity. The new technique has the following advantages: (i) provides to permanently use the entire processing capacity of the machining system, in optimal terms of dynamic stability; (ii) in the designing stage...

John Wiley & Sons, Ltd eBooks, 2013

Cutting Dynamics and Machining Instability Material removal-as the most significant operation in manufacturing industry-is facing the ever-increasing challenge of increasing proficiency at the micro and nano scale levels of high-speed manufacturing. Fabrication of submicron size three-dimensional features and freeform surfaces demands unprecedented performance in accuracy, precision, and productivity. Meeting the requirements for significantly improved quality and efficiency, however, are contingent upon the optimal design of the machine-tools on which machining is performed. Modern day precision machine-tool configurations are in general an integration of several essential components including process measurement and control, power and drive, tooling and fixture, and the structural frame that provides stiffness and stability. As dynamic instability is inherently prominent and particularly damaging in high-speed precision cutting, design for dynamics is favored for the design of precision machine tool systems [1]. This approach employs computer-based analysis and design tools to optimize the dynamic performance of machine-tool design at the system level. It is largely driven by a critical piece of informationthe vibration of the machine-tool. Due to the large set of parameters that affect cutting vibrations, such as regenerative effects, tool nonlinearity, cutting intermittency, discontinuous frictional excitation, and environmental noise, among many others, the effectiveness of the approach commands that the dynamics of machining be completely established throughout the entire process. This book explores the fundamentals of cutting dynamics to the formulation and development of an innovative control methodology. The coupling, interaction, and evolution of different cutting states are studied so as to identify the underlying critical parameters that can be controlled to negate machining instability and enable better machine-tool design for precision micro and nano manufacturing. The main features that contribute to the robust control of cutting instability are: (1) comprehension of the underlying dynamics of cutting and interruptions in cutting motions, (2) operation of the machine-tool system over a broad range of operating conditions with

2011

Research of machining dynamics have long history i n manufacturing processes with consideration of cutting interruption, intermittenc y and coupled interaction between the tool and workpiece. It gives better understanding of the und erlying physics of material removal. The complex motions in cutting dynamics are mainly caus ed by discontinuities, including chip and tool-workpiece seizure as well as complex stick–sli p motion. Through the application of discontinuous system theory, a comprehensive unders tanding of the grazing phenomena is induced by the boundary of frictional-velocity and the loss of contact between the tool and workpiece are discussed. Significant insights are t o control machine-tool vibration and to develop tool wear free machine-tool concept. The ex periment on the stainless steel machining is presented in the paper and generation of machine to ol vibrations and the associated cutting dynamics is considered.

2011

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Materials, 2021

Machining processes through cutting are accompanied by dynamic phenomena that influence the quality of the processed surfaces. Thus, this research aimed to design, make, and use a tool with optimal functional geometry, which allowed a reduction of the dynamic phenomena that occur in the cutting process. In order to carry out the research, the process of cutting by front turning with transversal advance was taken into account. Additionally, semi-finished products with a diameter of Ø = 150 mm made of C45 steel were chosen for processing (1.0503). The manufacturing processes were performed with the help of two tools: a cutting tool, the classic construction version, and another that was the improved construction version. In the first stage of the research, an analysis was made of the vibrations that appear in the cutting process when using the two types of tools. Vibration analysis considered the following: use of the Fast Fourier Transform (FFT) method, application of the Short-Time ...

Journal of dynamic systems, measurement, and …, 1993

This paper reviews the important recent research contributions for control of machining processes {e.g., turning, milling, drilling, and grinding). The major research accomplishments are reviewed from the perspective of a hierarchical control system structure which considers servo, process, and supervisory control levels. The use and benefits of advanced control methods (e.g., optimal control, adaptive control) are highlighted and illustrated with examples from research work conducted by the authors. Also included are observations on how significant the research to date has been in terms of industrial impact, and speculations on how this research area will develop in the coming decade.

2009

It is already accepted by most of the researchers working in this domain, that cutting process dynamics is nonlinear and, more than that, there are proves to sustain the appearance, under certain conditions, of chaos. There are also suggestions of non-linear and chaotic models to characterize the dynamic behaviour of the cutting process. This paper aims to be a first step made in order to conceive a system to control the machining process stability, based on a chaotic approach; this purpose requires, first of all, the existence of a reliable method to evaluate the position of the manufacturing system operating point relative to its stability limit, which can be done by monitoring cutting process characteristic parameters.

IFAC-PapersOnLine, 2015

The identification of the stability lobes for machine-tool vibrations is presented for interrupted turning processes with round inserts. An analytic cutting force model for round inserts is derived, where the directional factors depend nonlinear and non-homogeneous on the depth of cut. Furthermore, the effect of vibrations in the cutting speed direction on the chip thickness modulation is taken into account, which leads to a state-dependent delay. A multifrequency solution is presented for the stability analysis of metal cutting processes, where the cutting force is characterized by periodic coefficients and state-dependent delays.

2008

The motivation of the work is to simulate the cutting tool dynamics, the piezoelectric actuators using the finite element method (FEM); Also, developing of a custom made FORTRAN program that is executed in series with the steady-state analysis subroutine in ABAQUS™ to be able to implement positive position feedback (PPF) control law to suppress the vibrations generated during the cutting

IAEME Publication, 2021

Machining and measuring operations are invariably accompanied by relative vibration between work piece and tool. The effect of vibration is excessive stresses, undesirable noise, looseness of part and partial or complete failure of parts. In this work the cutting tool vibration will be measured by using digital Vibrometer, which can measure displacement velocity, acceleration and frequency. The sensor will be attached with the tool post for sensing the vibration tool during turning operation. Vibration also increases in the cutting tool due to whiling of the job mounted between two stocks of lathe machine. With the increasing feed rate, the surface roughness of work will increase. The feed rate can be considered as a main cutting factor in the machining operation. The mildsteel material will be used for collecting data at various cutting parameters like depth of cut, speed, feed rate etc. on the completion of experimental work data will be analysing using MATLAB. By doing the same we will be able to predict behaviour for the system under any operating cutting parameters.