Microstructural changes during precision machining of thin substrates

This paper reports investigations in machining of thin substrates with thickness less than 100μm. The machining process induces severe plastic deformation through the thickness of the machined thin workpiece due to the high ratio of the depth of cut to workpiece thickness. The diamond face turning is used to machine thin workpieces down to a thickness less than 100μm. The microstructure of the machined sample is studied and x-ray diffraction used to observe the crystallographic orientation / texture. The microstructures of the thin machined workpieces are seen to become more random, denser, and finer with the shape of the grains less elongated as compare to the bulk and thick machined sample. The x-ray diffraction analyses indicate that machining of thin substrates changes the texture or orientation. Different deformation mechanisms may occur when machining thin workpiece especially at thicknesses below 100μm

Study on end brush deburring and sintered diamond ball deburring of micro-features milled

The presence of top burr in the micro-features produced by milling process can deteriorate and affect the surface quality of the products. Though there are some deburring methods can be used and reported successfully remove the burr in the micro scale features, however simpler and alternative method is still needed. Two of the deburring methods that can be used are end brushing and sintered diamond ball methods. Therefore the aim of this paper is to study the application of the end brush and sintered diamond ball for deburring top burrs exist on micro features produced by milling process. Slot milling experiments were conducted and subsequently deburring process using the two methods was conducted. Micro scale features were also produced using milling process followed by deburring. The deburred results were observed visually using optical microscope and Scanning Electron Microscope (SEM) and average surface roughness was measured. Experimental results show that the end brush and sintered diamond ball deburring have successfully remove the top burrs. The end brush deburring method produced better surface quality compared to the sintered diamond ball

Poly(2-hydroxyethyl methacrylate) hydrogels for contact lens applications–a review

The emerging technology in biomedical engineering requires biocompatible materials, which are also referred to as biomaterials. For a material to be considered biocompatible, it should not interact with human tissues in a harmful way, and vice versa. Various properties of biocompatible materials, such as mechanical and optical properties, have to be considered for different biomedical applications. One of the most popular applications of biomaterials is for contact lenses. Hydrogels, specifically poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels, are among the most popular ones in ophthalmologic applications, especially in soft contact lenses. This paper reviews the use of PHEMA hydrogels as one of the important biomaterials. The possible applications, properties, and manufacturing process of PHEMA hydrogels, especially in contact lens applications, are addressed. Many studies have shown that PHEMA hydrogels possess many advantages in contact lens applications and have promising development prospects. © 2021, Universitas Indonesia. All rights reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Performance Analysis of Gap Controller Using Current Sensor Module for A Small-Scale Electric Discharge Machining (EDM) Machine

Controlling the gap between the electrode and workpiece to provide sufficient space for spark ignition is one of the solutions to increase the Electric Discharge Machining (EDM) Material Removal Rates (MRR) and improve the surface finish quality. This paper proposes two contributions to the EDM machine development, i.e., the small-scale EDM prototype and the application of the current sensor and servo mechanism in the rail moving system for the gap controller. Three different capacitors (47 µF, 100 µF, and 330 µF) and two workpiece materials (aluminum alloy and steel) are used as the variable of the experiment. The application of servo mechanism in rail moving system that works based on feedback system from the current sensor is used as the technique for controlling the gap. In this paper, The EDM process was conducted using the proposed prototype, an optimum supplied current is identified, MRR is calculated, and the surface finish is evaluated using visual inspection and manual measurement. The result shows that steel workpiece needs a higher value of supplied current than aluminum to reach stable spark ignition for each capacitance value. The increasing value of capacitor is followed by the increasing value of material removal rates. However, the surface finish quality is not directly dependent on the capacitance value. It is observed that the cavity created using a 100 µF capacitor has the best surface finish for both aluminum and steel workpieces among the other capacitance value. © 2023 American Institute of Physics Inc.. All rights reserved.12 month embargo; first published 28 December 2023This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Electrochemical exfoliation of pencil graphite core by salt electrolyte

Exfoliation of pencil graphite core throughout electrolysis process is considered as one of the simple and friendly method to synthesis graphene from graphite. In this research, sodium sulphate (Na2SO4) was used as an electrolyte to investigate the effect on pencil graphite core with different grades for exfoliation process. Pencil graphite core was applied as both anode and cathode electrodes and exposed in 0.1 mol of Na2SO4 solution and followed with sonication in DMF solution. The morphology of exfoliated graphite was characterized by FESEM and TEM image. It was found that higher pencil grade produced more exfoliated powder as compared to lower grade pencil, and morphology investigation revealed that the exfoliated powder can produced graphene in nanoplatelet forms