Papers by Author: Han Ming Chow

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Authors: Yao Jang Lin, Yan Cherng Lin, A Cheng Wang, Der An Wang, Han Ming Chow
Abstract: This study investigates the feasibility of EDM for processing ZrO2 and Al2O3 of non-conductive ceramics, which were covered by an assisted conductive material, an adherent copper foil, on the workpiece surface. The conductive material adhered on the surface of the non-conductive ceramics would induce a series of electrical discharges between the tool electrode and the workpiece in the initial stage of the EDM process. Thus, the pyrolytic carbon that cracked from kerosene was formed and deposited on the machined surface to maintain the progress of EDM. In this work, the essential EDM machining parameters were varied to determine the effects on material removal rate (MRR), electrode wear rate (EWR), and surface roughness. The stability of EDM progress and the surface integrities of ZrO2 and Al2O3 machined by EDM were also investigated. The aim of this study is to explore the feasibility and development of an applicable process for processing non-conductive ceramics through EDM. Moreover, the exploitation of this work can be applied to industrial applications and used to develop machining techniques for non-conductive ceramics.
Authors: Yao Jang Lin, Yan Cherng Lin, A Cheng Wang, Yuan Feng Chen, Han Ming Chow
Abstract: The aim of this study is to construct a diverse process of electrical discharge machining (EDM) in gas media, and then the new developed machining approach was used to investigate the effects of machining parameters on machining characteristics. Firstly, the feasibility of the EDM in gas media was established with consecutive electrical sparks generated within the machining gap. Moreover, the main machining parameters such as peak current, pulse duration, machining polarity, and gas media supply conditions like air compressed pressure were varied to evaluate the effects on machining characteristics of SKD 61 mold steel in the developed EDM process. The surface morphology of machined surface was observed by a scanning electronic microscope (SEM) to determine the influences of EDM discharge energy on surface integrities. From the result shown in experiments, the material removal rate (MRR) increased with peak current, pulse duration, and air pressure. In addition, the electrode wear rate (EWR) went up with peak current at first, and then attained a peak value with extending the pulse duration and the air pressure, but the EWR declined with further increasing of the pulse duration and the air pressure. Furthermore, the integrities of the machined surface revealed dramatically rough features when the peak current was set at high value. While the pulse duration was further extending, the surface integrities of the machined surface exhibited a smoothened trend obtained by EDM in gas media. Consequently, the developed technique of EDM in gas media possesses the potential of promoting machining performance, reducing environment impact, and extending the EDM applications.
Authors: Lieh Dai Yang, Wei Liang Ku, Han Ming Chow, Der An Wang, Yan Cherng Lin
Abstract: One of the difficulties for Ni-based superalloys application is its manufacturability。Traditional manufacturing process can obtain high strength due to the material characteristic with high strength at high temperature, others like low heat conducting coefficient and process hardening, therefore it could be thought of as a difficult processing material, simultaneously, high temperature drilling could also be resulted in tool wear and broken rapidly, and lead to high process cost。 This study used three Ni-based superalloys such as Mar-M247, Haynes-230 and Inconel-718,applying thermal friction drilling to conduct experiments on the CNC machine using spindle speed and feed rate as process parameters employing Taguchi methods to explore the bush length and internal hole of drilled surface roughness。The results showed that it can generate the longest bush length and best surface roughness for Haynes-230;however Inconel-718 has the largest axial force and worse bush length and surface roughness。
Authors: Der An Wang, Yan Cherng Lin, Han Ming Chow, Shih Feng Fan, A Cheng Wang
Abstract: The aim of this study is to investigate the machining characteristics of gas media used in electrical discharge machining (EDM). The process parameters were designed based on Taguchi method to manage the experimental work. The main process parameters such as machining polarity, gas pressure, peak current, pulse duration, type of gas media, and servo reference voltage were adopted to explore their effects on machining performance in terms of material removal rate (MRR) and surface roughness (SR) for SKD 61 tool steel. The experimental observed values were transferred to signal-to-noise (S/N) ratios, and then the significant machining parameters affecting obviously the machining performance were determined by analysis of variance (ANOVA). The optimal combination level of machining parameter for each machining characteristic was obtained by the S/N ratio analysis according to Taguchi methodology.
Authors: Wei Liang Ku, Han Ming Chow, Jiang Long Lin, Kun Ling Wu, Tsong Shin Sheu
Abstract: This article presents an approach which first combines grey relational grade and weighted quality loss function to convert the values of multiple responses obtained from each of the Taguchi orthogonal designed experiments into a single performance evaluation value. Then the analysis of variance (ANOVA) and the SN ratio based Taguchi analysis are conducted to find out respectively the relative importance of the process parameters and a set of near optimal parameter settings. A validation experiment is then conducted to confirm the finding. A case of multi-response turning process optimization is used to illustrate the proposed approach. Two sets of weights for the total quality loss were applied and the results were compared. The effectiveness of this approach was demonstrated by the improvement of turning performance in the both weight settings.
Authors: Wei Liang Ku, Han Ming Chow, Yao Jang Lin, Der An Wang, Lieh Dai Yang
Abstract: The main purpose of this research is to study the optimal machining parameters for a novel process of thermal friction drilling on SUS 304 stainless steel. The experiments were conducted according to an L9 orthogonal array based on Taguchi experimental designs method, and the multiple performance characteristics correlated with surface roughness (SR) and bush length (BL) was investigated by grey relational analysis systematically and comprehensively. Moreover, the significant machining parameters that most intensively affected the multiple performance characteristic and the optimal combination levels of machining parameters associated with the thermal friction drilling on SUS 304 stainless steel were determined through the analysis of variance (ANOVA) and the response graph of grey relational grade. The main machining parameters of the thermal friction drilling such as friction angle, friction contact area ratio, feed rate, and drilling speed were selected to evaluate the effects on SR and BL. The experimental results show that the thermal friction drilling revealed beneficial effects on SR and BL for drilling processes. Moreover, the optimal machining parameters for multiple performance characteristics associated with SR and BL were attained. The developed thermal friction drilling avoids serious tool wears, enhances the surface quality of the machined hole, and prolongs the tool life significantly.
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