Harish Kumar

Titanium alloy Ti–6Al–4V finds its suitability for aerospace applications along with compatibility with biological components. Creation of holes is a common requirement in the application of the alloy; these holes are created using abrasive water jet machining (AWJM) with variation of parameters against an L25 orthogonal array of Taguchi design. The work is aimed at obtaining a high-quality surface finish, a kerf taper angle as low as possible and a maximized machining rate (mm/s), relying on AWJM. The process parameters [water pressure, stand-off distance, abrasive flow rate and transverse speed (in terms of quality)] were also systematically evaluated to explore the combined effect on machining rate and surface integrity by plotting a contour plot of responses. Complex proportion assessment (COPRAS) multi-criteria decision-making technique that delivers balancing machining setup for number of process parameters which can provide maximum geometrical accuracy while maintaining satisfactory surface finish and production rate at 45 kPsi, abrasive flow rate at 300 g/min, and transverse speed in 75 mm/min at Quality 5 keeping stand-off distance as 2 mm. unique finding obtained by kerf taper measurement technique which indicate that the response is proportionally connected with depth of penetration, also not uniform throughout the depth. Experimental results exhibit the least deviation of machining rate and moderate deviation of surface roughness, while maximum variation is observed in the kerf taper angle and appears highly sensitive. Scanning electron microscopy (SEM) and digital microscopic morphology confirm the mechanism of surface integrity deviation and taper formation and validate the statistical findings.

Inconel-718 (IN-718) is a nickel-based superalloy widely employed in aerospace, nuclear, and gas turbine applications owing to its excellent high-temperature strength, oxidation resistance, and mechanical stability. However, its low thermal conductivity, high toughness, and pronounced work-hardening tendency make it difficult to machine using conventional methods. This study investigates the machining performance of an in-house developed multi-axis near-dry electrical discharge machining (MX-ND-EDM) system for machining IN-718 using copper and brass tubular electrodes. A compressed air-assisted liquid mist was utilized as the near-dry dielectric medium to improve flushing efficiency and reduce dielectric consumption. The effects of discharge current, gap voltage, and pulse-on time on material removal rate (MRR) and electrode wear rate (EWR) were evaluated using a Taguchi L ₉ orthogonal array and signal-to-noise ratio analysis. Experimental results revealed a significant influence of electrode material on machining performance. The brass electrode produced the highest MRR of 10.21571 mm³/min, nearly twice that achieved with the copper electrode (5.37241 mm³/min), indicating superior erosion efficiency and spark energy transfer. Conversely, the copper electrode exhibited lower wear characteristics, with EWR values ranging from 4.582 to 5.742 mm³/min, while the brass electrode showed higher EWR values between 12.119 and 14.075 mm³/min. These variations were attributed to differences in the thermophysical properties of the electrode materials. Surface characterization further revealed crater formation, localized melting, material transfer, and re-solidified debris on the electrode surfaces. The findings demonstrate the feasibility of MX-ND-EDM as a sustainable machining approach for IN-718 and provide insights into electrode selection for balancing productivity and tool life under near-dry machining conditions.

Fused filament fabrication (FFF)-based additive manufacturing is constrained by functional reliability in terms of wear resistance and surface finish, which impinge upon the performance of printed parts. This study evaluates whether a low-cost, in-house extruded polylactic acid (PLA) filament can achieve comparable or superior performance to commercially available PLA filaments in functional fused filament fabrication applications. PLA pellets were dried, and 1.75 mm diameter filament was extruded, and comparative test pieces were printed with a Flashforge Adventurer 4 printer. A Box–Behnken design was used to evaluate the impact of layer thickness, printing speed, and the number of top layers on wear and surface roughness. Wear (pin-on-disc) and surface roughness (Mitutoyo SJ-410) were evaluated, and the findings indicate that the in-house PLA filament provides lower wear rates and moderate surface finish, especially at optimized settings, compared to commercial filament. These results show that PLA filament produced in-house is not only economically viable but also an environmentally friendly material that extends the field of FFF applications, demanding improved tribological behavior and surface finish.

Fused filament fabrication (FFF) additive manufacturing process produces intricate designs with minimal material waste by feeding the filament into a heated nozzle, which melts and deposits the material according to the digital model. The current work focuses on the filament extrusion of an in-house manufactured Acrylonitrile Butadiene Styrene (ABS) material using a 3-Devo extruder to give customized ABS filament and its comparison with commercially available ABS filament. The most important factors to consider are the filament’s diameter and accuracy over its whole length. This experimental study examines how printing characteristics, such as layer thickness, printing speed, and the number of top solid layers, affect the wear rate and surface quality of printed products. An L9 orthogonal array drawn from the Taguchi design was utilized in order to systematically examine process parameters. The findings show that for filaments sourced commercially, layer thickness has a strong influence on wear and surface quality, while printing speed is more influential for in-house filaments. Analysis of variance (ANOVA) and signal-to-noise ratio (S/N) analysis show that optimized parameters can significantly improve functional behavior of printed parts. While all factors were not statistically significant at a 95% confidence level, trends in the main effects plots and regression models establish the significance of parameter selection in reducing wear and enhancing surface finish. The results help in the optimization of FFF printing for polymer-based functional parts, providing insights for other industrial applications.

Four‐dimensional bioprinting incorporates the notion of time with three‐dimensional bioprinting as the additional dimension and offers the prospect of constructing detailed and essential biological frameworks. It has been considered the future of biomedical applications, namely tissue engineering, wound repair, drug delivery systems, etc. Through the adoption of stimulus‐responsive materials, Four‐Dimensional bioprinting is an excellent way to construct dynamic, three‐dimensional‐structured biological constructs that morph their shape in reaction to varied stimuli. A new frontier in tissue engineering, i.e. four dimensional bioprinting, refers to the operational development and maturation of cell‐loaded printed structures over time. This review article is concerned with the idea of four‐dimensional bioprinting and the latest advances in smart/intelligent materials, which can be activated by various stimuli to create biomimetic constructs and materials, along with brief insights into biomedical applications. These advancements have significant possibilities for biomedical research while also offering promising future prospects.

Abrasive water jet (AWJ) machining does not impact material quality and modern machining processes. The trials follow the Taguchi L25 orthogonal array and the workpiece material is Ti grade 5 alloy. The optimal process parameters are determined using response surface methodology and these parameters include transverse speed (TS), pressure (P), abrasive flow rate (AFR) and stand-off distance (SoD). The aim of this research is to identify, evaluate, and improve the impression of AWJ machining parameters on response variables (machining time [MT], surface roughness [SR], and hardness). Achieving this objective involves utilizing grey relational analysis in conjunction with principal component analysis. TS has the least influence on performance while AFR has the greatest. The best configuration for the lowest MT, SR, and Highest Hardness Rockwell C scale (HRC) is (AFR [ ] 600 g/min, SoD [ ] 4 mm, P [ ] 20 kpsi, and quality [ ] 5 approximately, speed 75 mm/min). Here, quality [ ] 5 corresponds to a TS of approximately 75 mm/min and the factor AFR has the greatest impact on material machining performance, according to the analysis of variance, followed by factors P, standoff distance, and TS. The chronological sequence of influence is as follows: AFR > P > SoD > TS with contributions of 85.45%, 8.06%, 2.90%, and 2.09%, respectively. Experiments showed that the proposed methodology enhanced AWJ machining performance by 0.3665 which is represented as multi-response performance index.