Moon-Chul Yoon

Measurement of Droplet Size and Distribution for Minimum Quantity Lubrication (MQL)

Cutting fluid in machining is important due to their role in reducing tool wear and improving surface finish. However, controlling the usage is imperative due to the ecological and/or economical and reasons. Minimum quantity lubrication (MQL) has recently emerged as a viable option to minimize the amount of fluid used in machining without sacrificing its lubrication and cooling in machining. This paper presents our effort to understand the parameters in the MQL process in order to expand its effectiveness in cutting operations. Although some literature regarding the influence of flow rates and nozzle directions is available, this information is insufficient. This paper studies three new parameters in the MQL process, namely the droplet size, the droplet size distribution, and the wetting angle. Confocal laser scanning microscopy (CSLM), wavelet filtering, and image processing algorithms were used to calculate the droplet geometry and distribution for various commercially available MQL oils. The wetting angles of the oils were measured by depositing oil droplets onto TiSiN and TiAIN coated inserts. The parameters studied are important to estimate the comparative performance of lubricant-coating pairs.

Spectral analysis of malfunction mode in endmilling

For the investigation of the chatter modes, the power spectrum of the parametric time series model was adopted and analyzed at several mixed conditions of different revolution. This paper describes a methodology for an application of several time series such asAR (forward-backward, burg, least square, Yule Walker, geometric lattice, instrumental variable),ARX (least square, instrumental variable),ARMAX, ARMA, Box Jenkins, Output Error. To estimate the chatter mode using their spectral analysis their results were compared with one another. As a result, it was proven that several time series methods can be used for chatter mode estimation. Among them, theARX, ARMAX and instrumental variable methods (iv4) are more desirable and reliable than the other algorithm for the exact calculation of the chatter mode in endmilling. Among three cutting forces, the z direction cutting force,Fz, has more powerful characteristics of chatter occurring than the cutting forces,Fx andFy, in the sense that weak mode is calculated exactly and there is no shifted or pseudo mode in the estimated power spectra of endmilling forces.

Monitoring of Tooth Passing and Chatter Properties in End-Milling

The purpose of this study is to develop a reliable machining condition monitoring system (MCMS) of end-milling for practicing engineers, which is a monitoring system with time series recursive algorithm. The suggested MCMS can analyze end-milling force signals using power spectrum analysis (PSA) and frequency response function analysis (FRFA) with recursive parametric model. Comparing with other non-parametric technique of time series, the suggested PSA and FRFA are using recursive parametric techniques. It is applied to practical application for monitoring of tooth passing which is closely related to spindle speed and chatter vibration. In order to detect several independent physical components such as tooth passing and chatter, it is presented in the frequency domain. This analysis provides an effective method in monitoring. The proposed MCMS is an efficient and reliable method for detecting spindle speed and malfunction behavior. In PSA and FRFA analysis, the recursive extended instrument variable(REIV) is used for on-line identification and mode detection in end-milling. The objective of MCMS in this work also includes a comparison of chatter and tooth passing with recursive algorithm.