Chatter Suppression in Boring Process Using Passive Damper
During machining process, chatter is an unavoidable phenomenon. Boring bars possess the cantilever shape and due to this, it is subjected to chatter. The adverse effect of chatter includes the increase in temperature which will leads to excess tool wear. To overcome these problems, in this investigation, Cartridge brass (Cu – 70% and Zn – 30%) is passively fixed on the boring bar and also clearance is provided in order to reduce the displacement, tool wear and cutting temperature. A conventional all geared lathe is attached with vibrometer and pyrometer is used to measure the displacement and temperature. The influence of input parameters such as cutting speed, depth of cut and clearance on temperature, tool wear and displacement are investigated for various cutting conditions. From the result, the optimum conditions to obtain better damping in boring process for chatter reduction is identified. Keywords—Boring, chatter, mass damping, passive damping.
Chatter Suppression in Boring Operation Using Magnetorheological Fluid Damper
This present study discusses about improvement of damping capability of boring tools and suppression of chatter using Magnetorheological (MR) damper. For the design and optimization of MR fluid damper volume constrained optimization methodology using ANSYS magnetic finite element routines were executed. Optimized design of MR damper was fabricated and its effect in boring operation has been investigated using an experimental setup. Experimental results were analyzed with the help of Auto-Regressive (ARX) models. Results show that MR damper application reduces the possibility of chatter and improves the stability of boring operation.
Identification of natural frequencies and damping ratios of machine tool structures by the dynamic data system approach
Abstract Modal parameter identification of machine tool structures is conventionally achieved by first obtaining frequency response curves from experimental data and then implementing a graphical approximation or curve fitting procedure. The principal shortcomings of this procedure originate from the inherent limitations of the Fourier Transform method, used in obtaining the frequency responses, and from the subjective judgement of the analyst attempting to obtain the modal parameters by curve fitting. As an alternative to the conventional method a direct modal parameter identification method, based on the Dynamic Data System approach, has been proposed. It utilizes data in the form of time series to develop discrete difference equations representing the dynamic properties of the machine tool structure at the points of measurement. The subsequent use of the models allows the determination of the global dynamic properties of the system such as the modal natural frequencies and damping ratios. The theoretical relationships between the continuous vibratory system and its discrete representation in the form of Autoregressive Moving Average (ARMA) models has been introduced and discussed. The proposed method has been applied to the analysis of experimental data obtained from a drilling machine. Subsequently a comparative assessment is given between these results and results obtained by the conventional Fourier Transform based method.