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International Journal of Rapid Manufacturing (7 papers in press)
Mass optimisation of 3D printed specimens using Multivariable Regression Analysis by Cristian-Vasile DOICIN, Mihaela-Elena ULMEANU, Allan E.W. RENNIE, Elena LUPEANU Abstract: Since its introduction in the early 1990s Fused Deposition Modelling (FDM) has become the most popular additive manufacturing technology for a variety of applications. One of the reasons of its popularity amongst users is the affordability of the equipment, materials and the open source software. Given the large variety of combinations optimisation of FDM process parameters can be quite elaborate. The paper provides a method for optimisation of mass calculation using multivariable regression analysis. Layer thickness, printing temperature and printing speed were considered the independent variables for a two-level factorial experimental program. DOE was used to plan 12 sets of programs and analysis was undertaken using Design-Expert Keywords: Optimised Mass Calculation; Material Extrusion; Design of Experiments; Multivariable Regression Analysis.
The effect of geometry on tensile strength of biodegradable polylactic-acid tensile-test specimens by material extrusion by Alper Ekinci, Andrew A. Johnson, Andrew Gleadall, Xiaoxiao Han Abstract: Additive manufactured biomedical devices have been widely used in the biomedical fields due to the development of biomaterials and manufacturing techniques. Biodegradable Polylactic Acid-based polymers are the most common material that can be manufactured using material extrusion, one of the most widely known additive manufacturing methods. However, medical grade polymers are too expensive for degradation studies with common tensile specimens. Therefore, this paper aims to reduce the volume of the material used for manufacturing tensile specimens by introducing a new micro-X tensile specimen developed for steel. The tensile strength of micro-X tensile specimens were compared with the ASTM D1708 standard tensile specimens. Experimental results and statistical analysis showed that there was no significant difference in terms of Tensile Strength. Furthermore, the micro-X tensile specimen reduced the volume and as well as the cost to 1% in comparison to ASTM D638 type V standard tensile specimens. Keywords: Additive Manufacturing; Material Extrusion; Tensile Strength; Biodegradable PLA; Micro Tensile Test; statistical analysis.
Post-printing Characterisation and Design for Additive Manufacturing Considerations for Conductive Tracks 3D Printed by Material Extrusion by Marko Chorbikj, Marco Cavallaro Abstract: The goal of the study is to analyse the post-printing characteristics of conductive tracks 3d printed using Material Extrusion (ME) process with varying slicing strategies. Conductive track samples with constant width and varying heights between 0.4mm and 0.8mm were prepared using two different commercial conductive materials in a single, double and triple layer strategy. Post-printing functional analysis was done by measuring the resistance of samples at different lengths and comparing it to their corresponding counterparts fabricated with different slicing. Post-printing physical characterisation on selected samples was done by measuring the surface area of their cross sections using microscope images and their mass. The conclusions of the study were then transferred in a proposed set of Design for Additive Manufacturing (DfAM) considerations that can be taken into account in the Design and Process Planning phase when manufacturing conductive tracks or objects with such features using ME. Keywords: material extrusion; design for additive manufacturing; conductive tracks; traces; 3d printing; fused filament fabrication.
Investigation on mechanical properties for PolyJet printed parts involving material reduction strategy by Arivazhagan Pugalendhi, Rajesh Ranganathan, Sreekanth M.P., Sivakumar Ganesan Abstract: Additive manufacturing (AM), a tool less manufacturing process has the advantage of saving material; however, this is not a wastage free manufacturing technology. Material wastage is more due to material replacement in the case of PolyJet technology. This work concentrates on finding a solution to minimize the wastage of material and compare the mechanical properties of PolyJet printed specimens in Single Material (SM) mode and Digital Material (DM) mode. In order to minimize the wastage, modified mixed tray strategy is proposed and it is validated by case example. Six different combinations of test specimens are derived from available three printing modes of Objet260 Connex PolyJet is high quality (HQ), high speed (HS) and digital material (DM) along with matte (M) and glossy (G) finish. Those combinations named as: HQ-M, HQ-G, HS-M, HS-G, DM-M and DM-G. It was identified that the proposed technique is capable of saving material. The developed strategy of DM-G saves 45.82% and 41.47% of total material cost in HQ-G and HS-G respectively. Similarly, DM-M saves 32.2% of total material cost in HQ-M and 24.22% in HS-M. Findings indicate that specimens printed by DM mode explicate low mechanical strength than SM mode. Average tensile strength of VeroClear is 6.783% lower in DM-G and 19.57% lower in DM-M, when compared to standard value (57.5 MPa). This work provides the awareness of the material replacement and increase the fidelity of the PolyJet printed parts. Keywords: Additive manufacturing; PolyJet; material reduction; flushing; modified mixed tray.
Building Additive Manufacturing A Materials Evaluation by Phil Hackney, Laurence Foster, A. Viney, K. Kelly Abstract: The United Kingdom is currently in the grip of a housing crisis, a recent report from the House of Lords stated that the shortage of affordable housing in Britain could jeopardize our standards of living for future generations. This paper aims to attempts to influence the problem of housing shortage by evaluating the potential of implementing fast Building Additive Manufacturing (BAM) as a construction process. To validate the feasibility of BAM as a building process a variety of compressive and slump tests were conducted to assess the capabilities of concrete paste as a layer-by-layer build material. A structure was fabricated to represent a Fused Filament Fabrication (FFF) based BAM Process; the tests determined that nozzle design limitation, the flowability of concrete and resistance to slump are key material characteristics in constructing a house structural elements. Furthermore, the use of recyclable natural and steel wool fibres did not contribute to mixtures compressive strength but did significantly increase its flexural strength. Keywords: Building Additive Manufacturing; Digital Construction; Lightweight Construction.
Impact of processing parameters on fatigue life of fused filament fabricated parts: application of central composite design and genetic algorithm tools by Boppana Chowdary, Aaron Bob Abstract: Several studies have been conducted on plastics where engineered plastics can replace their metal counter parts. Generally, components tend to fail due to cyclic loading therefore study of fatigue life of products is a critical issue. The purpose of this study is to develop a predictive model relating the process parameters with fatigue life of Fused Filament Fabrication (FFF) technology based 3D printed parts.
A comprehensive review of literature was performed first to find common process parameters used in the past. Test specimens are printed using a desktop FFF 3D printer to suit a laboratory based fatigue testing machine. Response Surface methodology (RSM) based Central Composite Design (CCD) method was used for the Design of Experiments (DOE) to obtain a regression model for prediction of response. Lastly, Genetic Algorithm (GA) solver was used to optimise the predictive model results.
Number of contours, layer thickness and raster width were found to have a significant effect while raster angle had very little effect on the fatigue life of FFF based 3D printed parts. In addition, it was observed a high significant interaction between layer thickness and raster width of the FFF specimens. The study findings give optimal process parameters settings for predicting fatigue life of Polylactic Acid (PLA) which has not been fully explored in previous studies.
Keywords: additive manufacturing; fused filament fabrication; PLA; fatigue life; genetic algorithm; optimisation; central composite design.
Investigation on the Greyscale Pixel Methodology for Additive Manufactured Part: An In-Situ Quality Assessment Approach by Brahmansh Kaushik, Anand Kumar Subramaniyan Abstract: This present work investigates the computer vision and machine vision algorithms in the selective laser melting (SLM) process to additively manufactured the product. The proposed method provides a real-time layer by layer sequence monitoring feature during the layer deposition process. This real-time monitoring helps reduce waste by deciding on the termination or continuation of the production process. The method proposed and elucidated is monitoring by capturing the layer image after the laser melting process completes. Total eight layers are simulated and analyzed in the proposed work. The images are analyzed using the greyscale pixel value algorithm. The present work results demonstrate the capability of greyscale pixel analysis to identify and quantify defects in the SLM processed layer. The analysis results show the feasibility and potential of exploiting bulk manufacturing quality control and inspection in an industrial environment. Keywords: Additive Manufacturing; Selective Laser Melting; Grey Scale Pixel Value; Quality Assessment; In-situ monitoring.