Articles written in Sadhana

    • Investigations for modelling hardness of biomedical implant during replication of FDM-based patterns by vacuum moulding


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      In the present work, effort has been made for modelling the microhardness of biomedical implant prepared by combining fused deposition modelling, vacuum moulding and stir casting (SC) process. A dynamic condylar screw (DCS) plate was selected as a real ‘3D’ biomedical implant for this case study. The DCS plate,made of acrylonitrile butadiene styrene material, was fabricated as a master pattern by fused deposition modelling. After preparation of the master pattern, the mould cavity was fabricated by the vacuum moulding process.Finally a metal–matrix composite of Al and Al2O3 prepared by SC process has been poured in the vacuum mould for fabrication of DCS plate. This study outlines the replication procedure of DCS plate in detail from the master pattern to final product. The contribution of the paper is towards finding out the effect and optimumvalues of three different process parameters (namely: percentage composition of Al and Al2O3, vacuum pressure and grain size of silica) towards microhardness of the DCS plate manufactured by the combined process.

    • Experimental investigation on shore hardness of barrel-finished FDM patterns


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      Barrel finishing (BF) process is widely used to improve the surface finish and dimensional features of metallic and non-metallic parts using different types of media. As a matter of fact the change in shore hardness (SH) features of fused deposition modelling (FDM)-based master pattern is one of the important considerations from its service point of view. The main objective of present research work is to investigate the effect of BF process on SH of acrylonitrile–butadiene–styrene (ABS)-based master patterns prepared by FDM. Six controllable parameters of FDM and BF, namely, geometry of prototype, layer density, part orientation, types of BF media, weight of media and finish cycle time, were studied using Taguchi’s L18 orthogonal array in order to find their effect on SH of master pattern. Results indicated that process parameters significantly affectthe SH of master patterns. It has been found that FDM part layer density contributed the maximum (about 67.52%) for SH of master patterns

    • Investigations for mechanical properties and biocompatibility of SS-316L implant prepared as rapid investment casting for batch production


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      In this work, a detailed procedure for the development of biomedical implant (SS-316L) by combining fused deposition modeling (FDM), chemical vapor smoothing (CVS), silicon molding (SM) and investment casting (IC) for batch production has been outlined. In spite of being biocompatible and bioactivewithin the body, the implant must possess good surface quality and dimensional accuracy along with sufficient hardness in order to reduce the wear inside the body. So in this research work, investigations have been made on the surface finish, dimensional accuracy and hardness of the implants by varying two controllable factors of the IC process (drying time of primary coating and mould thickness). The tolerance grades for the selected dimension of the casted implants were within the allowable range as defined in UNI EN 20286-I (1995) standardof ISO. The process capability indices (Cp and Cpk) values greater than 1.33 for the surface hardness and radial dimension indicated that the proposed process is statistically controlled. Further, in order to evaluate the biocompatibility, an in vitro study was conducted to ensure the attachment of mouse embryonic fibroblasts cells (NIH-3T3) to the casted samples. The results of invitro study indicated that samples were capable of supporting cell adhesion and cell proliferation and hence can be used for tissue engineering.

    • Partial dentures by centrifugal casting assisted by additive manufacturing


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      This research work focuses on preparation of partial dentures (as functional prototypes) by additive manufacturing (AM)-assisted centrifugal casting (CC). The master pattern for partial dentures was prepared on fused deposition modelling (FDM) set-up (established by AM technique at low cost). The final dentures asfunctional prototypes were prepared with a nickel–chromium (Ni–Cr)-based alloy by varying different proportions of Ni% (N) by weight %. The other input parameters were powder to water P/W ratio (W) and pH value (H) of water used for mixing the investment. The samples prepared were ascertained for dimensional deviation (Δd), surface finish (Ra) and micro-hardness (HV) as output parameters. Finally, multifactor optimization has been applied on output parameters of functional prototypes prepared. This study highlights that partial denture prepared with W-100/15, H-7 and N-61% gives overall better results from mechanical properties and dimensional accuracy viewpoint. The results are also supported by photo-micrographic analysis.

    • Investigations for machinability of primary recycled thermoplastics with secondary recycled rapid tooling


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      This paper highlights the machinability of primary recycled thermoplastics as workpiece (WP) material with secondary recycled (reinforced) thermoplastic composites as rapid tooling (RT). Both WP and RT have been 3D printed on commercial fused deposition modelling. For investigating machinability of primaryrecycled thermoplastics, un-reinforced WP of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) has been selected. The RT materials were secondary reinforced (recycled) LDPE with double particle size Al₂O₃ particles and HDPE with triple particle size Al₂O₃. The machinability has been calculated in terms of weight loss of WP, while machining on a vertical milling set-up. This study also reports the surface hardness, porosity, surface roughness (Ra) and photomicrographic observations of WP and RT under controlled machining conditions. Further thermal analysis suggests that primary recycled thermoplastic can be successfully machined with secondary recycled RT, resulting in improved thermal stability and surface properties.

    • On mechanical and thermal properties of cryo-milled primary recycled ABS


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      The virgin thermoplastics have numerous applications in fused deposition modelling (FDM) process. Commercially, different thermoplastics are recycled through extrusion (without any reinforcement as primary (1°) recycled materials) for enhancing their reusability and sustainability. However, hitherto very littlehas been reported on mechanical and thermal properties of cryogenic (cryo) milled 1° recycled ABS (to be used on FDM-based 3D printer). In the present research article the cryo ball milling of 1° recycled ABS thermoplastichas been reported to explore the influence of cryo environment (-196 °C) on mechanical, thermal and surface properties of the ABS-based feed stock filament (prepared through screw extrusion) for further use on commercial FDM set-up (without any hardware/software change). The process parameters of cryo-milling (like frequency of vibration, milling time and grinding media weight) have been selected for investigations using Taguchi-based design of experiment (DOE). The study results show significant improvement in peak strength (PS) of the cryo-milled ABS in comparison with non-cryo-milled ABS without any degradation of thermal properties (mainly heat capacity). As regards the process parameters of cryo-milling, 30-Hz frequency, 15-min milling time and 32-g media weight are the best settings for maximum PS. The maximum value of PS observed was 61.32 MPa. The optical photomicrographs supported with 3D rendered images were captured to support the surface characteristics and porosity level in the wires (to be used as feed stock filament for FDM) prepared with cryo-milled ABS (powder samples).

    • On flexural and pull out properties of smart polymer based 3D printed functional prototypes


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      In past one decade, the 3D printing of smart polymers/composites by using fused deposition modelling (FDM) for dynamic 4D applications has been widely reported. Some studies have outlined tensile, surface, morphological and piezoelectric properties of barium titanate (BT) and graphene (Gr) reinforcedpolyvinylidene fluoride (PVDF) matrix for 4D applications. But hitherto little has been reported on flexural and pull-out properties of PVDF matrix, which is one of the major requirements in typical structural/non-structuralapplications. In this research work an in-house prepared smart polymer matrix-based feedstock filament(comprising of PVDF-78% by wt. + Gr-2% by wt. + BT-20% by wt.) has been used for 3D printing offunctional prototypes. The 3D printed flexural and pull-out specimens of PVDF-78% by wt. + Gr-2% bywt. + BT-20% were tested for functional ability. The multi optimization has been used to optimize the printingconditions of FDM. It has been ascertained from the multi-optimization that infill speed (IS) 70 mm/s, infillangle (IA) 45°, and infill density (ID) 100% are the best printing conditions. Further, scanning electronmicroscopy (SEM) based photo-micrographic analysis was performed on the fractured surfaces of samples. Theresults of mechanical testing have been supported by 3D rendered images, surface roughness (Ra) profile, andarea mapping for dispersion of elements in the composite matrix of the printed specimens.

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