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Micro-electrical discharge machining (μEDM) is an unconventional machining method that is suitable for machining of conductive materials including highly doped silicon (Si) wafers. This paper reports a novel method of heat-assisted μEDM machining of Si wafers by varying the temperature to increase the electrical conductivity of Si. In order to achieve this condition, a ceramic heater is used to heat the Si wafers within the temperature range of 30–250 °C. In this study, the machining performances in terms of the material removal rate, tool wear rate, surface quality, and materials characterization have been investigated accordingly. The machining performance of p-type (1–10 Ω cm) Si wafers was investigated to machine a cavity based on different temperatures with a constant discharge energy of 50 μJ and a feed rate of 50 μm/min. The results indicated that increasing the machining temperature allowed achieving a higher material removal rate, lower tool wear rate, and lower surface roughness. The highest material removal rate of 1.43 × 10−5 mm3/s and a surface roughness of 1.487 μm were achieved at 250 °C. In addition, the material removal rate increased by a factor of ~16 times compared to the results obtained at the lowest temperature, 30 °C, and the Raman spectroscopy analysis revealed that no significant changes occurred in the Si structure before and after machining.

Product miniaturisation is one of the key aspects of modern manufacturing technology. One of the ways to fabricate miniaturised product is micromachining using sophisticated computer numerically controlled (CNC) machine tools. However, conventional CNC machines are bulky, stationary, and unable to carry out parallel operations. This research aims to develop a modular robotic platform which would be able to carry out machining operation in mesoscale. Hexapod robots are legged mobile robots which are used for verities of applications. Here, we have implemented a hexapod robotic platform to support and move the cutting tool (in this case, a drilling tool). The robot was controlled from the host computer through serial communication. A graphical user interface (GUI) was designed and implemented to operate the robot and the drilling spindle. Several machining operations were carried out with the system to assess its performance. An innovative compensation algorithm has been proposed to improve the positional accuracy of the robot movement. The proposed algorithm takes into account spindle speed and linear velocity to mitigate the positional error. The positional accuracy was improved by more than 60% after implementing the error compensation scheme. In this research we managed to achieve sub-10 μm repeatability (≤ 10 μm) at the lowest spindle and point to point linear speed of 2500 RPM and 200 mm/min, respectively. The performance (in terms of positional accuracy) of the robot was also compared with that of an existing commercial micromachining system where the robot was found to be almost ~ 2× time poorer to that of the commercial machine. Finally, the machined holes’ quality was measured in terms of circularity and taperness. It was observed that at the best machining parameters circularity deviation was as low as 29.4 μm while taperness was 0.54 degree.

In this paper, metallic thermoelectric generators were studied and fabricated using copper (Cu) and cobalt (Co) as their respective positive and negative thermoelements. Thus, the chosen Cu-clad polyimide substrate alleviated the deposition of Cu and eased the microfabrication. A lateral device structure might assist in generating larger output power through its longer thermoleg length. Hence, the fabricated thick-film devices had planar and lateral structures with lateral heat flow and lateral thermopile layout. The strong correlations of electrical and thermal conductivities in metal thermoelements have resulted in lower Seebeck coefficient along with reduced thermoelectric power-generating performances. Alternatively, a thermoleg cross-sectional area ( ${A}$ ) optimization approach may optimize these disrupting correlations and improve their power-generating effectiveness, whereas a sandwiched planar structure can allow more thermopiles to be integrated without influencing the generator’s size. Both A optimization and sandwiched planar structure have rarely been applied and studied in the past works and have never been implemented using metal thermoelements. Hereafter, a Cu–Co device was enhanced through ${A}$ optimization by increasing the thickness of Co over 3.86 times the Cu thickness, and the implementations of a sandwiched planar structure. Herein, a flexible sandwiched planar thermoelectric generator was fabricated for the first time, using simpler microfabrication. This enhanced Cu–Co generator achieved a thermoelectric efficiency factor of ${6.6} \times {10}^{-{3}}\,\,\mu $ Wcm−2K−2( $12.89~\mu $ Wcm−2) at a temperature difference of 44.2 K. It remarked 3.1 times of improvement (by stacking three sets of thermopile) than its similar single Cu–Co thermopile of ten thermocouples.

Vertically Aligned Carbon Nanotubes array which is also sometimes labeled as carbon nanotubes forests has many applications in several engineering fields for its remarkable mechanical, electrical, optical, and thermal properties. The Vertically Aligned Carbon Nanotubes array is often employed in developing microdevices such as pressure sensor, angle sensor, switches, etc. To successfully integrate carbon nanotubes forest to the micro-electro-mechanical systems based devices, micropatterning of the carbon nanotubes forest is required. There are several methods available to realize micropatterning of Vertically Aligned Carbon Nanotubes array, from in-situ patterning during the growth process to post-patterning process. Each has its advantages and disadvantages. This paper will discuss elaborately different patterning processes of the carbon nanotubes forest and their different characteristics.

A sequential process combining laser beam micromachining(LBMM) and micro electro-discharge machining (μEDM) for the micro-drilling purpose was developed to incorporate both methods' benefits. In this sequential process, a guiding hole is produced through LBMM first, followed by μEDM applied to that same hole for more fine machining. This process facilitates a more stable, efficient machining regime with faster processing (compared to pure μEDM) and much better hole quality (compared to LBMMed holes). Studies suggest that strong correlations exist between the various input and output parameters of the sequential process. However, a mathematical model that maps and simultaneously predicts all these output parameters from the input parameters is yet to be developed. Our experimental study observed that the µEDM finishing operation's various output parameters are influenced by the morphological condition of the LBMMed holes. Hence, an artificial neural network(ANN) based dual-stage modelling method was developed to predict the sequential process's outputs. The first stage of the dual-stage model was utilized to predict various LBMM process outputs from different laser input parameters. Furthermore, in the second stage, LBMM predicted outputs (such as pilot hole entry area, exit area, recast layer, and heat affected zone) were used for the final prediction of the sequential process outputs (i.e. machining time by μEDM, machining stability during μEDM in terms of short circuit count and tool wear during μEDM). The model was evaluated based on the average RMSE (Root Mean Square Errors) values for the individual output parameters' complete set data, i.e. μEDM time, short circuit count and tool wear. The values of Average RMSE for the parameters as mentioned earlier were found to be 0.1272(87.28% accuracy), 0.1085(89.15% accuracy), 0.097 (90.3% accuracy), respectively.

Laser beam micromachining (LBMM) and micro electro-discharge machining (µEDM) based sequential micromachining technique, LBMM-µEDM has drawn significant research attention to utilizing the advantages of both methods, i.e. LBMM and µEDM. In this process, a pilot hole is machined by the LBMM and subsequently finishing operation of the hole is carried out by the µEDM. This paper presents an experimental investigation on the stainless steel (type SS304) to observe the effects of laser input parameters (namely laser power, scanning speed, and pulse frequency) on the performance of the finishing technique that is the µEDM in this case. The scope of the work is limited to 1-D machining, i.e. drilling micro holes. It was found that laser input parameters mainly scanning speed and power influenced the output performance of µEDM significantly. Our study suggests that if an increased scanning speed at a lower laser power is used for the pilot hole drilling by the LBMM process, it could result in significantly slower µEDM machining time. On the contrary, if the higher laser power is used with even the highest scanning speed for the pilot hole drilling, then µEDM processing time was faster than the previous case. Similarly, µEDM time was also quicker for LBMMed pilot holes machined at low laser power and slow scanning speed. Our study confirms that LBMM-µEDM based sequential machining technique reduces the machining time, tool wear and instability (in terms of short circuit count) by a margin of 2.5 x, 9 x and 40 x respectively in contrast to the pure µEDM process without compromising the quality of the holes.

Product miniaturization is the key factor for success in the field of microelectro-mechanical system, optics, biomedical engineering, aerospace, automobile, and many others. One of the ways to achieve product miniaturization is microfabrication by micromachining. Micromachining can be broadly classified into two categories, namely tool based and beam based. Some of the tool-based micromachining techniques are micromilling, microdrilling, microturning, microelectro discharge machining, electrochemical micromachining (EMM), etc. Beam-based micromachining includes laser beam micromachining, electron beam micromachining, photo lithography, etc. EMM has emerged as one of the pivotal technologies in the fields of microfabrication and nanofabrication. The basic setup for EMM consists of pulsed DC voltage supplied to the electrodes; in this case, the workpiece and the tool. The reverse image of the tool profile is generated on the workpiece in this procedure. High material removal rate, greater control over the process, and flexibility of machine setup are some of the advantages that EMM offers. Even though the process offers so many diverse applications, it is limited by some inherent process flaws like formation of oxide layer, deposition of metal on tool, low machining time, etc. To overcome these limitations, many hybrid micromachining techniques have been developed with state-of-the-art process control scheme and advancement in microtool fabrication for EMM. Due to its flexibility and favorable conditions, EMM will lead other micromachining technologies in various industrial applications in the near future. This chapters aims to shed light on the various aspects of EMM.

Currently, two manufacturing methods, namely CNC (Computer Numerical Control) machining and rapid prototyping (RP), are widely used to produce final products and prototypes. Both the processes have their own advantages. CNC machining such as milling and grinding (subtractive method) can fabricate parts with higher precision and accuracy. On the other hand, RP (additive method), can manufacture parts with complicated 3-D (three dimensional) features, which ensures effective material usage. However, RP produced parts lack accuracy and smooth surface finish. In this research, we are aiming to achieve on-machine mechanical post-processing of 3-D printed (using Fused Deposition Modelling, a kind of RP process) parts to achieve higher dimensional accuracy and better surface roughness. To achieve the goal, we developed a new hybrid system to assimilate both of these processes. There are, however, two vital considerations needed to be taken into account for integrating the two processes. The first concern is the integration of dissimilar control systems for two processes and the second aspect is maintaining the tools’ (milling spindle and the heat extruder) setup accuracy during the changeover step. The developed hybrid machine has been tested with experimentations and the result showed that the dimensional accuracy was improved by 71% to 99% when the FDM part was compared with the final part after abrasive milling operation. At the same time, average surface roughness (Ra) was improved up to 91.3%. Further, we found that low layer thickness improves the product quality. The proposed system could push the conventional FDM system to the next level to attain better quality of final products. ABSTRAK: Dua kaedah terkini proses pembuatan, dinamakan mesin Kawalan Komputer Bernombor (CNC) dan prototaip langsung (RP) telah digunakan secara meluas bagi menghasilkan produk dan prototaip. Kedua-dua proses mempunyai keistimewaan tersendiri. Mesin CNC seperti mesin penghasil permukaan dan mesin penebuk lubang (melalui kaedah pengurangan) dapat menghasilkan sesuatu bahagian dengan ketepatan tinggi. Pada sudut lain, RP (melalui kaedah penambahan), dapat menghasilkan bahagian dengan kaedah 3D (tiga dimensi) yang rumit tetapi berkesan dalam memaksimakan penggunaan material. Walau bagaimanapun, penghasilan bahagian melalui kaedah RP mempunyai kekurangan pada ketepatan dan kekurangan pada kekemasan permukaan akhir. Kajian ini bertujuan meraih ketepatan dimensi yang lebih tinggi dan kekemasan permukaan yang lebih bagus pada proses terakhir pada bahagian cetakan mesin mekanikal 3D (menggunakan Model Deposit Fuse iaitu salah satu proses RP). Bagi mencapai tujuan ini, kami menghasilkan sistem hibrid terbaru untuk mengasimulasi kedua-dua proses. Walau bagaimanapun, terdapat dua perkara penting perlu diambil kira untuk diintegrasi bersama kedua-dua proses. Penilaian pertama adalah pada sistem kawalan tidak serupa, dan kedua pada aspek pengekalan alat (gelendung pemutar dan kepanasan pembentuk) ketepatan penyediaan semasa peringkat perubahan. Mesin hibrid yang dicipta telah diuji melalui eksperimentasi dan keputusan menunjukkan ketepatan dimensi telah bertambah daripada 71% kepada 99% semasa bahagian FDM dibandingkan dengan bahagian akhir selepas operasi putaran kasar. Pada masa sama, purata permukaan kasar (Ra) telah bertambah kepada 91.3%. Kami juga mendapati ketebalan lapisan bawah telah menambah baik kualiti produk. Sistem yang dicadangkan dapat mengubah sistem FDM konvensional kepada peringkat lebih tinggi bagi memperolehi kualiti terbaik pada produk akhir.

Vertically Aligned Carbon Nanotube arrays (also termed as VACNTs or CNT forest) have recently found to be transformable to a reflective mirror from a naturally black absorber. The feature of improved reflectance can be attained by the controllable tip bending process using the bottom surface of a rotated cylindrical tool (the process called micro-mechanical bending (M2B)). In this paper, the polarized light reflectance of bent and compacted region of the CNT forest using M2B method has been investigated. We observed that reflectance from the processed CNT zone was highly dependent on the angle of incidence and polarization state of the incident laser. For the first time, the refractive index of the tip bent CNT forests by M2B method was investigated and found to be in a range of ?1.8. This work was supported by MOHE ( PRGS16-008-0039 ). The authors are grateful to IIUM, UPSI, UiTM, and MIMOS for providing machining and testing facilities to carry out the experiments and all their valuable support to carry out this research work. Scopus

The bulk appearance of arrays of vertically aligned carbon nanotubes (VACNT arrays or CNT forests) is dark as they absorb most of the incident light. In this paper, two postprocessing techniques have been described where the CNT forest can be patterned by selective bending of the tips of the nanotubes using a rigid cylindrical tool. A tungsten tool was used to bend the vertical structure of CNTs with predefined parameters in two different ways as stated above: bending using the bottom surface of the tool (micromechanical bending (M2B)) and rolling using the side of the tool (micromechanical rolling (M2R)). The processed zone was investigated using a Field Emission Scanning Electron Microscope (FESEM) and optical setup to reveal the surface morphology and optical characteristics of the patterned CNTs on the substrate. Interestingly, the polarized optical reflection from the micromechanical rolled (M2R) sample was found to be significantly influenced by the rotation of the sample. It was observed that, if the polarization of the light is parallel to the alignment of the CNTs, the reflectance is at least 2 x higher than for the perpendicular direction. Furthermore, the reflectance varied almost linearly with good repeatability (~10%) as the processed CNT forest sample was rotated from 0° to 90°.[Figure not available: see fulltext.].

This file provides the details in auasi-solution for the associated linear problem, deriation of a priori bound on the eigenvalues, proof of Lemma 5.4 and checking condition for Theorem 5.1 in the main text.

Electrolytic In-Process Grinding (ELID) is an advanced grinding process that carries out in situ dressing of the grinding wheel using an electrochemical reaction, i.e. anodic dissolution. This process is targeted to achieve the final finished product by eliminating subsequent finishing processes such as polishing and lapping. The process mainly aims for hard and brittle materials to achieve ductile mode cutting with the best cutting parameters, and by doing so to achieve the nano-level surface finish. The typical grinding particle size of the ELID grinding wheel varies from 1 to 5 µm. A characteristic ELID wheel is metal bonded which is used as an anode. There is another electrode which usually used as the cathode, and a liquid is flown between the anode and the cathode, which functions both as grinding fluid and electrolyte. A DC pulsed power supply is generally used as the power source for the electrolytic in-process dressing of the grinding wheel. This chapter will shed light on the history, fundamental and the current status of the ELID grinding related researches.