Electrochemical grinding

Abstract: The electrical discharge machining (EDM) process produces the recast layer with or without cracks on the surface that requires a remedial post-treatment in the manufacture of critical or highly stressed surfaces. One of the frequently used post-treatment processes is also the abrasive electrochemical grinding (AECG) and it has been widely used in the precision machining of difficult-to-cut materials due to an enhanced surface integrity and productivity. The aim of this study is to investigate improvability of surface integrity in terms of machining voltage, electrolyte flow rate and table feed rate parameters of AECG in EDMed Ti6Al4V alloy. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and surface roughness measurement were performed to study the surface characteristics of the machined samples. Experimental results indicate that the AECG process effectively improves the surface roughness and eliminates the EDM damages completely by setting suitable grinding parameters.

Abstract: Brief design and manufacture considerations are detailed for a hybrid electrochemical grinding unit adapted from a vertical machining centre using a 40,000 rpm spindle and 500 A DC generator. Subsequently, experimental work is presented on the influence of tool bond systems, superabrasive grit type and electrical parameters when simultaneous ECM/grinding Udimet 720 using 10–15 mm diameter plain points. Single layer electroplated CBN tools produced G -ratios and maximum normal cutting forces of ∼451 and ∼45 N, respectively, compared to ∼128 and 557 N for equivalent diamond wheels. Data on workpiece roughness and overcut are also presented as are initial results for a fir tree shaped tool.

Abstract: We have carried out the electrical discharge machining (EDM) of submicron holes using ultrasmall-diameter electrodes. Two types of electrode were used: tungsten electrodes fabricated by the combination of wire electrodischarge grinding and electrochemical machining, and silicon electrodes originally designed as probes for scanning probe microscopes. The diameters of the former and latter were 1 μm or less, and less than 0.15 μm, respectively. Holes were drilled using a relaxation-type pulse generator at an open-circuit voltage of less than or equal to 20 V with the machine's stray capacitance as the only capacitance. Using tungsten electrodes, holes of less than 1 μm in diameter and more than 1 μm in depth were successfully drilled. A 1.3-μm-wide slot was also fabricated by drilling many holes with a small pitch. It was possible to drill holes of approximately 0.5 μm diameter using silicon electrodes because the electrode diameter was less than those of the tungsten electrodes. These holes have the smallest reported diameter for holes drilled by EDM, indicating the possibility of submicron- and nanoscale machining by EDM.

Abstract: We here report a method for the facile and large scale preparation of lithium-ion battery anodes based on α-Fe2O3 (hematite) nanorods with different textural characteristics and surface composition. The method combines electrostatically driven self-assembly approaches with specific adsorption and magnetically easy to disrupt soft aggregates. Special emphasis has been set to correlate the textural characteristics (porosity) and surface composition (core, core–nanoshell and core–double nanoshells) of nanorods with their electrochemical response. Thus, we have shown that nanorods present a nanophase whose specific capacity strongly depends on the lithium transport distances (nanorods with slit-shape mesopores running along their long axis vs. non-porous or surface blocked nanorods). We have also shown that the capacity retention of this nanophase after several charge–discharge processes depends on maintaining the structural integrity of the nanorods. Essential for the success of this latter study has been the use of nanorods that offer a simple tool (oriented X-ray line broadening) to follow their electrochemical grinding. Our data suggest that α-Fe2O3 mesoporous nanorods could both operate at a voltage and retain a capacity similar to that of nanostructured lithium titanates anodes if actions are taken to prevent electrochemical grinding.

Abstract: Electrochemical grinding (ECG) is a variation of electrochemical machining (ECM), in which material is removed from the workpiece by simultaneous electrochemical reaction and mechanically abrasive action. It offers a number of advantages over conventional grinding, such as low induced stress, large depths of cut, and increased wheel life. It has been reported that ECG was employed in machining stainless steel 304, metal-ceramic hard alloy of WC-Co groups, and Tungsten carbide. Inconel 718 is used extensively in aerospace because of their excellent combination of high specific strength (strength-to-weight ratio) which is maintained their fracture resistant characteristics, and their exceptional resistance to corrosion at elevated temperature. The machinability of Inconel 718 is generally considered to be poor owing to several inherent properties of the materials. Poor thermal conductivity, chemically reactivity and low elastic modulus are the common problems. In this paper, ECG is employed to process Inconel 718. To prolong the wheel life, the brazed diamond wheel is introduced to be a tool instead of the electrodeposited diamond wheel. Experiments illustrated that the tool durability has been improved from 15 hours to 50 hours when a brazed diamond wheel was employed to replace an electrodeposited diamond wheel. In addition, a proper high applied voltage and electrolyte temperature was verified to be conductive to improve the maximum electrode feed rate and material removal rate. A electrode feed rate of 6.6 mm min-1 was obtained at 30 V and 36 °C, respectively.