In this paper, experiments in Electrochemical Micromachining (ECMM) were conducted to produce micro-holes of high aspect ratio using a cathode ‘Polymer Graphite Electrode’ (PGE). The effect of electrochemical dissolution of ASTM A240 type 304 stainless steel is comparatively studied using cryogenically treated PGE (CTPGE) tool and non-treated PGE tool (NTPGE) that owes to enhance the overall quality of micro-hole produced, which is assessed on the basis of the most imperative output responses namely the material removal rate (MRR), and the Overcut (O_c) in relation to the predominant input process parameters namely, Voltage (S₁), Electrolytic concentration (S₂) and the Duty cycle (S₃). Response surface modeling based on Box-Behnken (BB) DoE was used to obtain the corresponding responses for the process factors. Numerical models were developed to study and effects of process factors individually and their interactional effect. ANOVA was used to study the statistical significant process factors. The outcome of the multi-objective optimization based on cuckoo search algorithm (MOCS) was found to be enhanced, owing to better surface characteristics of the workpiece machined using the CTPGE tool. The effect of the micro spark and stray current have dwindled when using CTPGE electrode that can be visually seen via SEM.

Electrochemical micromachining (EMM) process is a contactless versatile electroforming process, used to fabricate highly precise micro-features and complex contours with the desired surface finish. In this research work, a fabricated-tapered hollow tool (THT) close to Ø0.3 mm is fabricated adopting reverse potential drop off approach and compared against the standard cylindrical hollow tool (CHT) of Ø0.3 mm for EMM which is aimed to enhance MRR, geometrical accuracy by reducing the overcut and the surface finish. The tools are then used in EMM setup to machine Co-Ni-Cr-W-based superalloy for the first time, considering the most predominant process factors including Voltage (V), Duty ratio (%), Feed rate (mm/min) and electrolyte concentration (gl⁻¹). Taguchi’s design of experiment having 2 × L9 OA’s is used in this study. ANOVA was used to statistically analyze the most significant parameter and to study its influence over the output responses. The desirability function-based optimization suggests that the experimental run #9 has the desired optimal parametric combination resulting in increased MRR by 2.04%, 24.57% reduction in overcut, and with reduced surface roughness while using THT when compared to the CHT. EBSD, EDS, SEM, VMS, and non-contact surface tester were inured with to examine surface morphology of electrodes.

India is the world’s 3rd largest shrimp producer at the same stint the shrimp industry generates 40%–70% waste of the catch volume. In this research, chitosan from shrimp (Penaeus indicus) waste was extracted at 75% degree of deacetylation and was brought down to powder form. Parallelly, a wet chemical precipitation method was adopted to produce hydroxyapatite suspension. The Chitosan powders were blended with the HAp suspension and finally ball milled to achieve composite powders of particle size 0.020 mm having mesoporous nature (3.17 nm) when quantified with BJH model. The scaffold was designed considering four design models namely the hollow cube, dumbbell, dual cone and honeycomb models with 62–67% of porosity. Post FE simulation analysis and design optimization using Pugh’s matrix revealed that the honeycomb model was superior considering the mass (g), porosity (%), compressive stress (MPa) and the level of complexity in mesh array. The composite powders were preheated up to 200°C and then the laser with spot of 0.5 mm width sinters the composite powder forming a scaffold as per design using the Selective Laser Sintering (SLS) process. The final part was subjected to cell viability assay using MG63 osteoblast cell line resulted in an increased cell level on the sixth day. Graphical Abstract