Vapour polishing of fused deposition modelling (FDM) parts: a critical review of different techniques, and subsequent surface finish and mechanical properties of the post-processed 3D-printed parts

Fused deposition modelling (FDM), one of the most commonly used additive manufacturing techniques in the industry, involves layer-by-layer deposition of melted material to create a 3D structure. The staircase and beading effect caused by the printing process and temperature variation cause delamination and poor surface finish in FDM-printed parts. This hinders the use of these specimens in various applications, which are then usually resolved using pre-processing and post-processing techniques. Higher surface finish in pre-processing is achieved by increasing the resolution, changing layer thickness and optimizing build orientation. However, this increases the processing time considerably. On the other hand, post-processing techniques involve different processes such as mechanical, chemical, thermal and hybrid methods but can affect the mechanical and structural properties of the printed components. This review paper analyses three different aspects in the area of improving the surface finish of FDM-printed parts. First, this article reviews the state-of-the-art attempts made to improve the surface finish of FDM-printed parts concentrated mainly on different vapour polishing techniques and their respective merits and demerits. Second, it focuses on the changes in mechanical properties before and after polishing. Finally, the paper explores the development in the 3D printing of thermosets and composite materials and their post-processing processes and process parameters

Effect of Cryogenic Treatment on the Wear Behavior of Additive Manufactured 316L Stainless Steel

In this research work, an investigation is done to study the effect of cryogenic treatment on 316L SS fabricated using Direct Metal Laser Sintering process. Cryogenic treatment is done at -196°C for 24 hours in a chamber filled with liquid nitrogen. The post effects of this cryogenic treatment over the properties of the material such as hardness, wear behaviour and microstructure have been studied. The result showed that the porosity present in additive manufactured 316L SS is greatly reduced after cryogenic treatment. Tribological properties were analyzed, using zirconia pin-on- additive manufactured 316L SS disc, the result showed that the treatment has considerable effect on decreasing coefficient of friction. Wear track surface morphologies shows the evidence for the indentation of the abrasives in pores in the untreated AM sample. Hardness increases significantly due to strain-induced phase change in the sample after cryogenic treatment

Structural, Mechanical And Invitro Study On Pulsed Laser Deposition Of Hydroxyapatite On Additive Manufactured Substrate

The convergence of engineering and life science has evolved into a new paradigm called Bio Additive Manufacturing (BAM). This BAM encompasses the biofabrication using cells, biological or biomaterials as building blocks to fabricate biological and bio-application oriented substance, device and therapeutic products through a broad range of engineering and biological processes. Furthermore bioactive coating on BAM surface facilitates biological fixation between the prosthesis and the hard tissue which increases the long term stability and integrity of the implant. In this paper, Hydroxyapatite (HA) Powder was coated over Additive Manufactured polyamide substrate using Pulsed Laser Deposition. Coating Morphology was characterized using SEM analysis and observed that the coating was dominated by the presence of particle droplet with different size. Compounds like tricalcium phosphate and few amorphous calcium phosphate were found along with HA which was confirmed by XRD analysis. Nano-indentation and pull-out test reveals that the layer was strong enough and withstands higher load before it peels-off. Cell line study has been carried out with MG-63 Osteosarcoma cells and results showed that the cells on coated surface multiplied better than on uncoated surface. It was evident from the results, that this kind of coating favors the long-term stability of implant fabricated using Additive Manufacturing.Published versio

Influence of Reinforcement Volumetric Percentage and Aspect Ratio on Additive Manufactured Multi Material Structure in Uniaxial Loading

Additive Manufactured multi material structures have an attractive combination of mechanical and thermal properties and are being increasingly used in engineering applications. To meet this need, additive manufacturing has shown the possibilities of processing multiple material with complex geometry in part fabrication. As a result, AM opens a new opportunity for designers to create multi material structure that were unfeasible to be manufactured in traditional techniques. And also it has been noticed that some products may require positioning and orientation of secondary material in a specific way to achieve desired functional properties. In this study the randomly oriented multi material were modelled based on parameters such as aspect ratio and volumetric percentage of secondary material/reinforcement and the same was fabricated using polyjet 3D printing technique. Influence of the parameters on behaviour of randomly oriented multi material structure under tensile loading was investigated. Experimentation results confirmed that the reinforcement parameter influences macroscopic behaviour of the multi material structure, which depends on the reinforcement intersecting point and the size of multi material structure. Multi material structure with higher aspect ratio has increased tensile modulus, where as with increase in volumetric percentage of reinforcement the tensile modulus get decreases.Published versio

Experimental investigation on fracture resistance behavior of additivemanufacturedmultimaterial structure with corrugated interface

It has been a curiosity and the need which has prompted many researchers to work in the area of design and manufacturing for the possibility of building polymer parts with complex shape using additive manufacturing [AM]. As interactions at interfaces have long been of interest in the area of composite materials and adhesive bonding, similar issues need to be addressed for additive manufactured multi material structures. In this study, a PolyJet system is used to fabricate multi material structure which consists of matrix layers (Tango black plus) sandwiched by two reinforcement layers (Vero white).In this work, interface between reinforcement and matrix layer in flat and corrugated shape (sine-wave ridged pattern) is employed. Corrugated shape is commonly found in nature and engineering structure in order to produce a compliant bending was employed in AM multi material structure to enhance its flexural properties. A common experimental approach to characterize shear performance, were evaluated to characterize the fracture resistance of the interface layers with flat and corrugated structures. Experimental results show that corrugated shape interface has the ability to induce passive shear behavior on AM multi material structures than flat shape interface. From this investigation it can be concluded that interface layer with mechanical linkage such as corrugated shape interfaces shows promising results on performance and durability of AM multi material structure.Published versio

Supervised retinal biometrics in different lighting conditions

Retinal image has been considered for number of health and biometrics applications. However, the reliability of these has not been investigated thoroughly. The variation observed in retina scans taken at different times is attributable to differences in illumination and positioning of the camera. It causes some missing bifurcations and crossovers from the retinal vessels. Exhaustive selection of optimal parameters is needed to construct the best similarity metrics equation to overcome the incomplete landmarks. In this paper, we extracted multiple features from the retina scans and employs supervised classification to overcome the shortcomings of the current techniques. The experimental results of 60 retina scans with different lightning conditions demonstrate the efficacy of this technique. The results were compared with the existing methods

Additive manufacturing of fractal antenna for electronics applications

Modern electronics device requires miniaturization and advanced functionality. Fractal antenna is one of the current research for such requirement. A fractal antenna is an antenna with fragmented geometry that has the characteristics of self similarity, which means, each part of the geometry is a smaller version of the original geometry. This self-similarity will increase the perimeter of antenna geometry that can receive or transmit electromagnetic radiation. Compare to conventional antenna, fractal antenna take less area due to the many contours of the shape while keeping high radiation efficiency and multi bandwidth. However, fabrication of fractal geometry is a difficult task due to the complexity associated with it. In this work, the Additive manufacturing process is proposed for the fabrication of these complex shape fractal antennas. Fabricated fractal geometry is tested on the VNA network to measure the reflection and transmission. From the experimentation, it is observed that the reflective coefficient of additive manufactured fractal antenna is -16.87 which is in the acceptable range for the commercial electronic device. In addition, experimental result is also validated by simulation using electromagnetic simulation software CST studio.Published versio

Additive manufactured and topology optimized flexpin for planetary gears

This paper shows how the interdisciplinary use of additive manufacturing (AM) and topology optimization (TO) lead to a better load distribution and a related increase in performance within a planetary gearbox. For this, it has been investigated how to use TO for designing the flexible support of the planets pin and to reduce thereby the load sharing factor (Kγ). 18 digital experiments were performed to evaluate the best setting for this TO. A completely new shape for a “flexpin” design was found which offers significant advantages in terms of compliance and misalignment for the flexible support structure of planet gears. Because of AM, the focus can stay on the main function of the flexpin including the component reduction. Critical interfaces are no longer necessary. This allows a much better definition of the compliance, an improved assembling, and a safer operation. The best TO-design concept was selected and edited for additive manufacturing. The final validation by FEM showed an increase in load capacity by 13% and an additional reduction of the misalignment of 77%