In this study, a knowledge-based system has been developed for selection of non-conventional machining processes using a hybrid multi-criteria decision making Method. This approach is a combination ofDEMATEL(Decision Making Trial and Evaluation Laboratory),ANP(Analytic Network Process) andVIKOR(VlseKriterijumska Optimizacija I Kompromisno Resenje, in Serbian, meaning Multi-criteria Optimization and Compromise Solution) methods which evaluates different types of quantitative and qualitative measures of performance and economic factors, and ultimately provides a set of capable processes in order of priority. Twelve machining processes, eight group of workpiece material and eighteen shape features have been investigated in this study. What separates this approach from others is that, this hybrid method considers the influence of factors in the network relation map as well as their relative importance. Moreover, unlike other popular ranking methods such as TOPSIS (Technique for Order Preference by Similarity to the Ideal Solution), it is not just based on two reference points, namely ideal and inferior points; instead, it proposes a compromise solution and not just a single ranking score. Observations have shown that the developed system works satisfactorily, yields acceptable results and makes accurate decisions as well. It also provides a comparative study among the alternative processes by utilizing graphical features for better analysis and judgment of acceptable alternatives.

In recent years, the need for Silicon carbide (SiC) ceramic arises due to several industrial applications. However, the cost of machining such components is very high. Electrical discharge machining (EDM) serves as the most viable machining technique. In this study, optimum setting of sinking-EDM parameters and mathematical model of siliconized silicon carbide (SiSiC) using aluminum powder mixed dielectric fluid has been developed. Analysis of variance shows that, material removal rate (MRR) increases with high discharge current and low servo voltage, whereas tool wear ratio (TWR) and surface roughness (Ra) decreases with low current and pulse-on time. The effects of design parameters on the machining characteristics were investigated using fractional factorial (resolution V) technique. Confirmatory test was then carried out to validate the models developed.

In recent years, researchers have demonstrated increases interest in studies involving silicon carbide (SiC) materials due to several industrial applications. Extreme hardness and high brittleness properties of SiC make the machining of such material very difficult, time consuming and costly. Electrical discharge machining (EDM) has been regarded as the most viable method for the machining of SiC. The mechanism of EDM process is complex. Researchers have acknowledged a challenge in generating a model that accurately describes the correlation between the input parameters and the responses. This paper reports the study on parametric optimization of siliconized silicon carbide (SiSiC) for the following quality responses; material removal rate (MRR), tool wear ratio (TWR) and surface roughness (Ra). The experiments were planned using Face centered central composite design. The models which related MRR, TWR and Ra with the most significant factors such as discharge current (Ip), pulse-on time (Ton), and servo voltage (Sv) were developed. In order to develop, improve and optimize the models response surface methodology (RSM) was used. Non-linear models were proposed for MRR and Ra while linear model was proposed for TWR. The margin of error between predicted and experimental values of MRR, TWR and Ra are found within 6.7, 5.6 and 2.5% respectively. Thus, the excellent reproducibility of this experimental study is confirmed, and the models developed for MRR, TWR and Ra are justified to be valid by the confirmation tests.

Proses etching atau punaran melibatkan pelbagai tindak balas kimia dan sangat penting dalam menentukan kualiti wafer silikon. Projek ini menyelesaikan masalah utama wafer ketika proses punaran, iaitu keserakan data pembuangan sisa wafer di sepanjang dram punaran. Cecair punaran yang digunakan dalam projek ini terdiri daripada komposisi asid HNO3, HF, and CH3COOH. Dram punaran telah diubahsuai untuk menyelesaikan masalah pembuangan sisa wafer yang rendah di setiap wafer pertama dan terakhir dalam sesuatu kompatmen dram. Tujuan utamanya adalah untuk mengurangkan jurang perbezaan variasi dalam pembuangan sisa wafer, di mana nilai pembuangan silicon adalah rendah berbanding pembuangan silicon wafer di tengah kompatmen. Antara cadangan tersebut adalah menambahkan "kepingan wafer PVC tahan asid" di sebelah wafer pertama dan terakhir dalam setiap kompatmen. Selepas memperoleh keputusan yang memberangsangkan, kepingan PVC tersebut dikekalkan dalam rekabentuk dram yang baru. Sifat wafer pertama dan terakhir dinilaikan untuk memastikan tiada kualiti yang terjejas berbanding wafer-wafer di tengah kompatmen. Morfologi permukaan dan kekasaran wafer (purata kekasaran;Ra dan kekasaran "skewness";Rms) menggunakan mikroskop tujahan atom (AFM) dianalisis untuk dibandingkan dengan dram lama. Keseragaman pembuangan wafer tanpa masalah pembuangan rendah di hujung kompatmen telah diperhatikan. Kata kunci: Proses punaran, permukaan "Micromachining", wafer silicon, pembuangan silicon wafer, kekasaran permukaan wafer silikon Etching process involves various chemical reactions and reflects significantly on the silicon wafer quality. The paper addresses the major problem on wafers during etching that is wafer removal distribution throughout etching drum compartment. The etchant used in this study were the composition of HNO3, HF, and CH3COOH. The etching drum has been redesigned to overcome the lower removal problem at the end of each compartment and to reduce the big disparity in wafer removal distribution. The proposed idea is to install a piece of "circumferential acid resistant PVC wafer" for the remaining empty slot (empty area without wafers) at each end of a compartment. The permanent PVC piece with certain gap at each end is then fabricated for the new drum design. The characteristics of the end wafers are compared with other wafers in the compartment to study the etching difference that leads to this problem. Surface morphology and surface roughness parameters (arithmetic roughness mean; Ra and surface skewness [roughness root mean square]; Rms) using atomic force microscopy (AFM) comparison between old drum design (big wafer gap) and new drum design (smaller gap with additional PVC chip) had been analyzed. The uniformity without lower removal problem at the end compartment is observed in removal distribution graph. Key words: Etching process; surface micromachining; silicon wafer; etching removal; silicon wafer surface roughness

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