Yan-Cherng Lin

In the process of Electrochemical Machining (ECM), the electrolyte renewal is likely to be poor as the machining gap is too narrow, so that the machining accuracy and surface quality are influenced, especially in the electrochemical trepanning of special structures, such as the rectangular groove with inner cylinder. As the flow field in the machining gap is difficult to be uniform, the machining quality is low and the cylindrical taper angle is large. Based on the abovementioned difficulties in ECM process, this study used ECM with mask and ECM with tool sinking, as well as the methods with and without ultrasonic vibration assisted sidewall-insulated electrodes, to conduct a comparative experiment on the electrochemical trepanning of rectangular groove with inner cylindrical structure for SUS304 stainless steel cylindrical workpieces. This study also discussed the effects of different ECM trepanning processing methods on the quality characteristics, such as cylindrical taper angle and surface morphology. The research results showed that in comparison to the ECM with mask, ECM with tool sinking had a smaller cylindrical taper angle and better surface morphology. When the ultrasonic vibration assistance was used for ECM with tool sinking, the uniformity of the flow field was improved. The electrolyte pressure changed rapidly in the processing area with the ultrasonic vibration assistance, resulting in pumping effect and cavitation effect, both of which disturbed the electrolyte, and promoted the renewal of the electrolyte in the machining gap. As a result, the resistance within the machining area is reduced, a smaller cylindrical taper angle was obtained, and the flow marks at the bottom of the rectangular groove were significantly reduced. Moreover, the surface morphology and surface roughness of the rectangular groove with inner cylinder after processing were better.

The micro lens array (MLA) has played an important role in optical systems for the past few years, and the precision of pressing dies has dominated the quality of MLAs in glass molding. Few studies have covered the transcription effects on surface roughness of pressing dies for this technology. Therefore, this research utilized pressing dies to produce a sine-wave lens array on glass molding, to transform the Gauss-distributed spotlight into a uniform straight one and then characterize the transcription effects of these lenses. Pressing dies with a sine-wave shape were firstly cut by wire electrical discharge machining (WEDM), and then ultrasonic polishing using diamond abrasives was applied to finish the sine-wave surface with an original roughness of 0.2 μm Ra. Next, the sine-wave lens arrays were pressed by glass molding at the appropriate pressure and temperature, before evaluating the transcription effects of transforming the Gauss-distributed spotlight into a uniform straight one. The result showed that the sine-wave lens array stuck easily to the pressing die and then ruptured during glass molding due to the poor surface roughness of pressing tool. However, the diamond abrasive with appropriate sizes could establish good surface roughness on pressing dies via ultrasonic polishing, and the pressing die with a low surface roughness of 0.08 μm Ra was able to successfully perform MLA in the glass molding. However, only pressing dies with a surface roughness smaller than 0.023 μm Ra could produce precision glass lenses to transform the Gauss-distributed spotlight into a uniform straight one.

The main application of electrical discharge machining in ceramic processing is limited to conductive ceramics. However, the most commonly used non-conductive potteries in modern industry, such as aluminum oxide (Al₂O₃), also reveal the limitations of choosing a suitable process. In this study, Taguchi based TOPSIS coupled with AHP weight method to optimize the machining parameters of EDM on Al₂O₃ leads to better multi-performance. The results showed that the technique is suitable for tackling multi-performance machining parameter optimization. The adhesive foil had a significant impact on material removal rate, electrode wear rate, and surface roughness, according to the findings. In addition, the response graph of relative closeness is used to determine the optimal combination levels of machining parameters. A confirmation test revealed a good agreement between predicted and experimental preference values at an optimum combination of the input parameters. The suggested experimental and statistical technique is a simple, practical, and reliable methodology for optimizing EDM process parameters on Al₂O₃ ceramics. This approach might be utilized to optimize and improve additional process parameters in the future.

The goal of this study was to investigate the optimal variables settings in internal grinding for shrink fit tool holder. The effects of the main grinding variables on finishing responses were comprehensively investigated based on Taguchi method. The main process variables such as abrasive grain size (AGS), grinding wheel speed (GWS), feed rate for rough (FRR), depth for rough (DR), feed rate for finishing (FRF), depth for finishing (DF), dressing speed (DS), and workpiece rotational speed (WRS) were chosen to determine their effects on grinding performances related to roundness and surface roughness in the internal grinding of the shrink fit tool holder. The experimental response values were transferred to signal-to-noise (S/N) ratios, and then the significant process variables associated with the grinding performance were examined by analysis of variance (ANOVA). In addition, the optimal combination levels of the grinding variables were also obtained from the response graphs of S/N ratios to improve the surface quality of internal grinding. The experimental results show that the significant grinding variable affecting the roundness was FRF. In addition, the significant variables with regard to surface roughness were AGS, GWS, FRR, DR, DF, and DS. The optimal grinding variable settings were achieved. Consequently, the finishing characteristics of internal grinding could be enhanced to meet the requirements of modern manufacturing applications.

This study aims to conduct experiments to explore metal based diamond wheel dressing and truing using developed wire electrical discharge (WEDM). The experimental outputs were analyzed to evaluate the effects of machining parameters on machining removal rate (MRR) and abrasive protrusion during dressing and truing caused by WEDM. During experiments, the wear and compensation issues could be overcome induced by the traditional EDM to improve the efficiency and precision as the WEDM was adopted. The experimental results showed as expected that the wire discharge grinding wheel dressing will lead the processing base not offset. In Taguchi experiment the maximum contribution was current and pulse time, large diameter grinding wheel to remove the highest rate of 11.78 mm3/min, while maximum protrusion amount only 33.12 μm, can reach the theoretical maximum protrusion amount.

This paper aims to establish an effective mathematical model with relation to electrical discharge machining (EDM) in gas based on response surface methodology (RSM). Moreover, the optimal combination levels of machining parameters for material removal rate (MRR) and surface roughness (SR) were also explored. The experimental tasks were implemented by a specific design of experimental method named central composite design (CCD) method based on RSM to develop quadratic regression mathematical model. The significant parameters and their interactions were examined by analysis of variance (ANOVA) to evaluate the importance on MRR and SR. The essential parameters of EDM in gas such as peak current (I_p), pulse duration (T_p), air pressure (G_P) and servo reference voltage (S_v) were chosen to investigate the effects on MRR and SR. From the analysis results, the optimal set of parameter setting levels were 12 A peak current (I_p), 750 μs pulse duration (T_p), 5 kg/cm2 gas pressure (G_P) and 34 V servo reference voltage (S_v), and the optimization of MRR and SR were 1.99 mm3 and 2.43μm as the machining parameters were set at the optimal levels.

Investigating machining performance of conductive ceramics (Al₂O₃ + 30 vol% TiC) using electrical discharge machining (EDM) is the aim of this work. The EDM machining parameters such as machining polarity, peak current, auxiliary current with high voltage, pulse duration, no load voltage, and servo reference voltage were chosen to explore the effects on material removal rate (MRR), electrode wear rate (EWR), and surface roughness (SR). The L18 orthogonal array based on the Taguchi experimental method was adopted to determine EDM machining characteristics systemically, and the experimental data were statistically analyzed by analysis of variance (ANOVA). Experimental results showed EDM is a feasible process to shape conductive ceramics, and relationships between machining characteristics and parameters were examined. Moreover, machining parameter optimal combination levels in machining conductive ceramics via EDM were also determined.