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Micro channels are widely used in microfluidics, and medical science for the extraction of DNA, electrophoresis, and blood protein analysis. In the current work, the wire electrical discharge machining (WEDM) process was used to fabricate micro channels on the stainless steel 316 (SS316) substrate. To check the feasibility of fabricating high-quality micro channels and thereafter micro-scale structures with the WEDM process the effect of different process parameters such as pulse-off time, pulse-on time, servo gap reference voltage and wire feed rate were investigated. The quality attributes taken were namely surface roughness of the channel base, overcut, micro channel depth, and material removal rate (MRR). The pulse-on time significantly affects surface roughness and MRR. The servo gap reference voltage is the key process parameter affecting the overcut and micro channel depth. It was observed from the parametric study that 15 µs pulse-on time, 35 µs pulse-off time, 17 v servo gap reference voltage, and 8 m/min wire feed rate are the optimum levels for getting high MRR, low surface roughness, less overcut and high micro channel depth. Additionally, the topographical, morphological, surface, and sub-surface characterization were also carried out to assess the surface integrity and extent of thermal damage caused by the WEDM process. With the optimum combination of process parameters a 6 × 6 micro needle array was successfully fabricated on the same substrate using micro channels as a basis of the fabrication process for the first time using the WEDM process. [ABSTRACT FROM AUTHOR]

Super finishing of oxygen-free high thermal conductivity (OFHC) copper disks is of great interest as copper is widely used material for high power rated mirrors in laser and other optical systems. It is difficult to super finish copper using traditional finishing processes as it is soft and can be scratched easily. Flexible tools that conform to component shape and maintain low as well as uniform pressure are needed for finishing of soft materials. In this work, open-cell porous flexible abrasive tools are developed using solvent casting method with polyurethane as the base polymer and SiC particles as abrasives. The open-cell porous tools are saturated with deionized water before use. The tools are self-replenishing as the abrasives are uniformly dispersed in the tool and the fluid trapped in pores acts as coolant as well as lubricant. The viscoelastic behavior of the fabricated tools with different abrasive concentrations is characterized using a dynamic mechanical analyzer (DMA). Spot finishing experiments are carried out to optimize the tool RPM, tool compression, and abrasive concentration for better surface finish. The average areal surface roughness (Sa) of copper disk reduced to 54 nm from 946 nm. [ABSTRACT FROM AUTHOR]

PMMA/graphene/Bentonite and PVC/graphene/Bentonite hybrid composites were prepared by solution casting method. Thermal stability, electrical conductivity and EMI shielding effectiveness in X-band were studied in detail. PVC composite with 5 wt.% Bentonite exhibited an enormous improvement in the thermal stability compared to the PVC/graphene counterpart. However, increase in Bentonite content in the hybrid composites reduced their electrical conductivity and resulted in lower overall shielding effectiveness in X band. The hybrid nanocomposites were found to have a significantly stronger influence of absorption in the overall shielding effectiveness when compared with respective polymer/graphene composites. The detailed microstructural/mechanical characterization elucidates the underlying mechanisms. [ABSTRACT FROM AUTHOR]

Micro-milling is a fast, cheap and controlled process compared to other micro-fabrication processes such as lithography, laser/electron/ion beam machining, etc. However, scarcity of cutting tools of very small dimensions often results in limited application of micro-milling. In the present study, electro discharge machining (EDM) is used for fabrication of micro-end mill tool. To ensure high dimensional accuracy of the tool, a parametric study is conducted by replicating the a tungsten carbide block to a tungsten carbide (WC) block. The relationships between the drilled cavities on the block and the features on the micro-tool are established. The influence of machining parameters (voltage, capacitance and spindle speed) on the response variables (entrance diameter, hole depth, material removal rate (MRR) and surface roughness) is reported. Capacitance is found more dominant as compared to other selected process parameters. Using optimized parameters from the parametric study, a WC micro-end mill tool of 100 µm diameter is fabricated. Channel of around 110 µm width, 40 µm depth and surface roughness of 70 nm is successfully fabricated on aluminum. The performance of the fabricated tool is compared with a commercial end mill tool by milling micro channels on stainless steel. [ABSTRACT FROM AUTHOR]

Prototyping through incremental sheet forming is emerging as a latest trend in the manufacturing industries for fabricating personalized components according to customer requirement. In this study, a laboratory scale single-point incremental forming test setup was designed and fabricated to deform AA6061 sheet metal plastically. In addition, response surface methodology with Box–Behnken design technique was used to establish different regression models correlating input process parameters with mechanical responses such as angle of failure, part depth per unit time and surface roughness. Correspondingly, the regression models were implemented to optimize the input process parameters, and the predicted responses were successfully validated at the optimal conditions. It was observed that the predicted absolute error for angle of failure, part depth per unit time and surface roughness responses was approximately 0.9%, 4.4% and 6.3%, respectively, for the optimum parametric combination. Furthermore, the post-deformation responses from an optimized single point incremental forming truncated cone were correlated with microstructural evolution. It was observed that the peak hardness and highest areal surface roughness of 158 ± 9 HV and 1.943 μm, respectively, were found near to the pole of single-point incremental forming truncated cone, and the highest major plastic strain at this region was 0.80. During incremental forming, a significant increase in microhardness occurred due to grain refinement, whereas a substantial increase in the Brass and S texture component was responsible for the increase in the surface roughness. [ABSTRACT FROM AUTHOR]

High material removal rate, high resolution and reproducibility of micromilling make it a suitable process for making microfeatures on different materials. However, existence of unwanted protrusions or surface irregularities on the machined surface known as burrs demands some post-processing to make it qualify for end use. In addition, clogging of materials on the flute surface increases the effective edge radius and tool loading during polymer machining. In the present work, a new strategy is demonstrated for simultaneous deburring of microchannel and cleaning of cutting tool during micromilling of polymethyl methacrylate. The performance of the process has been further evaluated by milling of microchannels in oxygen-free high conductivity copper workpiece. Burr formation, surface roughness and tool loading have been found to be significantly reduced by using the proposed method. A theoretical study of the process has also been carried out to understand the mechanism of the proposed method. [ABSTRACT FROM AUTHOR]