C. Hauser, M. Dunschen, M. Egan and C. Sutcliffe
The purpose of this paper is to report on software development in which mathematical algorithms apply geometric transformations to digitised images in preparation for layer…
Abstract
Purpose
The purpose of this paper is to report on software development in which mathematical algorithms apply geometric transformations to digitised images in preparation for layer manufacturing by printing a binder onto a rotating powder substrate.
Design/methodology/approach
Spiral growth manufacturing (SGM) is a high‐speed rapid manufacturing technique in which objects are built up, layer by layer, by simultaneously depositing, levelling and selectively consolidating thin powder layers onto a rotating build platform. Consolidation occurs by infiltrating the powder layer with a binding agent deposited in droplet form using inkjet technology. During each rotation, the build platform falls away from a stationary doctor blade and print head assembly. This gives a continuous spiralled layer of powder with a constant layer pitch. To faithfully print digitised images onto a rotating substrate, polar and linear transformations have to be applied.
Findings
In support of this work, dimensional accuracy measurements of transformed printed images are reported and the measured results were found to be within ±0.2 mm of their predicted size. The experimental work is briefly extended to the printing of transformed images, using an aqueous binder, onto plaster powder to demonstrate the build speed capabilities of SGM. Primitive multiple layer parts built at speeds of 10 layers/min are reported.
Practical implications
From a practical standpoint, SGM has the potential to increase build speed by an order of magnitude over existing commercial rapid prototyping/manufacturing systems.
Originality/value
There is no commercial system available that allows high‐speed simultaneous deposition and processing of powder material and so this method could have implications in large batch manufacture.
Details
Keywords
Guillermo Zañartu‐Apara and Jorge Ramos‐Grez
The purpose of this paper is to study the effect of different parameters (layer thickness, jetted binder volume per layer and type of binder and temperature) on the mechanical…
Abstract
Purpose
The purpose of this paper is to study the effect of different parameters (layer thickness, jetted binder volume per layer and type of binder and temperature) on the mechanical properties of parts made with an experimental 3D printing (3DP) process. This 3DP device built for this project is based on the spiral growth manufacturing (SGM) device previously introduced by Hauser et al. at The University of Liverpool. It differs from the common 3DP in that it generates the different parts using only one rotating piston instead of two non‐rotating ones.
Design/methodology/approach
Several parts are produced using this device according to an experimental design, repeating each run three times. The experimental machine is able to make every part needed without major issues, demonstrating that it is possible to build a functional device using common and standard components.
Findings
Experimental analysis of the printed parts shows that the layer thickness has the highest effect on apparent density, hardness and fracture strength of the parts made.
Originality/value
Empirical information is provided about mechanical behavior (e.g. apparent density, hardness and fracture strength) of parts made under different processing factors (e.g. binder type, layer thickness, quantity of binder and chamber temperature) using a SGM‐based 3DP experimental device.
Details
Keywords
L. Rickenbacher, A. Spierings and K. Wegener
The integration of additive manufacturing (AM) processes into a production environment requires a cost‐model that allows the precise estimation of the total cost per part…
Abstract
Purpose
The integration of additive manufacturing (AM) processes into a production environment requires a cost‐model that allows the precise estimation of the total cost per part, although the part might be produced in the same build job together with other parts of different sizes, complexities and quantities. Several cost‐models have been proposed in the past, but most of them are not able to calculate the costs for each single part in a mixed build job or are not suitable for Selective Laser Melting (SLM). The purpose of this paper is to develop a cost model, including all pre‐ and post‐processing steps linked to SLM.
Design/methodology/approach
Based on collected data and the generic cost model of Alexander et al., an adapted model was developed for the SLM process including all required pre‐ and post‐processes. Each process was analysed and modelled in detail, allowing an evaluation of the influences of the different geometries on the cost of each part.
Findings
By simultaneously building up multiple parts, the manufacturing as well as the set‐up time and therefore the total cost per part can be significantly reduced. In the presented case study a cost reduction of 41 per cent can be achieved in average.
Originality/value
Using different cost allocation algorithms, the developed cost model enables a precise determination of total cost per part avoiding that any geometry is preferred in simultaneous manufacture. This helps to optimize build jobs and to manufacture SLM parts more economically by pooling parts from different projects, whereas the cost per part can still be precisely determined.
Details
Keywords
Shane R. Jimerson, Aaron Haddock and Jacqueline A. Brown
During the past decade, amid the current context emphasizing educational standards and accountability, the practice of grade retention has increased. The call for an end to social…
Abstract
During the past decade, amid the current context emphasizing educational standards and accountability, the practice of grade retention has increased. The call for an end to social promotion has generated a variety of recommendations and legislation regarding promotion policies. This context has served as a catalyst for numerous debates regarding the use of grade retention and social promotion. In an era emphasizing evidence-based interventions, research indicates that neither grade retention nor social promotion is a successful strategy for improving educational success. Meta-analyses of studies during the past 100 years reveal deleterious outcomes associated with grade retention. Moreover, research also reveals prevention and intervention strategies that are likely to promote the social or academic competence of students at-risk of poor school performance. It is essential that educational professionals are familiar with the research when implementing interventions to promote student success. This chapter provides a brief synthesis of contemporary concerns and empirical studies examining student outcomes associated with grade retention, and also describes alternatives to grade retention. Particular consideration is given to implications for students with learning and behavioral disabilities, and the importance of focusing empirically supported strategies to promote student social and cognitive competence. Overall, educational professionals are encouraged to incorporate evidence-based programs and policies to facilitate the success of all students.
Alva E. Tontowi and T.H.C. Childs
The effect of powder bed temperature setting on the prediction of density of sintered parts produced by the selective laser sintering (SLS) process is reported. A crystalline…
Abstract
The effect of powder bed temperature setting on the prediction of density of sintered parts produced by the selective laser sintering (SLS) process is reported. A crystalline polymer, nylon‐12 – commercially named Duraform polyamide – has been used in this work. To study the effect of the powder bed temperature, a two‐dimensional model of the sintering process for crystalline polymers has been developed. Latent heat has been considered in the model. Three powder bed temperature settings, 174, 178 and 182○C, have been applied to study their effect on the sintered parts’ density and size accuracy. This paper only reports on density. Results show that at a powder bed temperature of 182○C, a fully solid density, 970kg/m3, can be obtained at a default energy density of 0.0284J/mm2. By reducing powder bed temperature to 178○C, at the same energy density, density of a sintered part decreases by about 4 per cent.
Details
Keywords
Discuss in detail the uses which might legitimately be made of the following passage by the writer of a profound study of economic life and thought in France at the end of the…
Abstract
Discuss in detail the uses which might legitimately be made of the following passage by the writer of a profound study of economic life and thought in France at the end of the reign of Louis XIV. In answering the question make full use of your knowledge of (a) historical criticism; (b) French economic and general history.
Shekhar Srivastava, Rajiv Kumar Garg, Vishal S. Sharma, Noe Gaudencio Alba-Baena, Anish Sachdeva, Ramesh Chand and Sehijpal Singh
This paper aims to present a systematic approach in the literature survey related to metal additive manufacturing (AM) processes and its multi-physics continuum modelling approach…
Abstract
Purpose
This paper aims to present a systematic approach in the literature survey related to metal additive manufacturing (AM) processes and its multi-physics continuum modelling approach for its better understanding.
Design/methodology/approach
A systematic review of the literature available in the area of continuum modelling practices adopted for the powder bed fusion (PBF) AM processes for the deposition of powder layer over the substrate along with quantification of residual stress and distortion. Discrete element method (DEM) and finite element method (FEM) approaches have been reviewed for the deposition of powder layer and thermo-mechanical modelling, respectively. Further, thermo-mechanical modelling adopted for the PBF AM process have been discussed in detail with its constituents. Finally, on the basis of prediction through thermo-mechanical models and experimental validation, distortion mitigation/minimisation techniques applied in PBF AM processes have been reviewed to provide a future direction in the field.
Findings
The findings of this paper are the future directions for the implementation and modification of the continuum modelling approaches applied to PBF AM processes. On the basis of the extensive review in the domain, gaps are recommended for future work for the betterment of modelling approach.
Research limitations/implications
This paper is limited to review only the modelling approach adopted by the PBF AM processes, i.e. modelling techniques (DEM approach) used for the deposition of powder layer and macro-models at process scale for the prediction of residual stress and distortion in the component. Modelling of microstructure and grain growth has not been included in this paper.
Originality/value
This paper presents an extensive review of the FEM approach adopted for the prediction of residual stress and distortion in the PBF AM processes which sets the platform for the development of distortion mitigation techniques. An extensive review of distortion mitigation techniques has been presented in the last section of the paper, which has not been reviewed yet.
Details
Keywords
Bengi Ertuna, Maria D. Alvarez and Burcin Kalabay Hatipoglu
This chapter examines the role of higher education institutions (HEIs) as partners in multi-stakeholder initiatives to implement sustainable development goals (SDGs) in tourism…
Abstract
This chapter examines the role of higher education institutions (HEIs) as partners in multi-stakeholder initiatives to implement sustainable development goals (SDGs) in tourism. Accordingly, the study describes the actions and leadership of the HEIs, explaining how they engage with diverse stakeholders to enable transformative change at various levels. A conceptual model is proposed and used to evaluate the 12 case studies identified by a systematic literature search. The results generate insights into the actions of the HEIs in terms of modes of partnership and their commitment. The cases document the diversity of roles assumed by HEIs for creating impact at different levels when integrating SDGs in tourism and paving the way for transformative change and sustainable development through tourism. The findings suggest a critical leadership role for HEIs through sense-making, interpretation of societal challenges, and alignment of stakeholders’ values and goals by facilitating multi-stakeholder consultations.
Details
Keywords
Miguel Ângelo Vieira, Sérgio M.O. Tavares and Silvina L. Félix
The effects of climate change have been contributing to coral reef degradation. Artificial reefs are one method being used to counteract this destruction. However, the most common…
Abstract
Purpose
The effects of climate change have been contributing to coral reef degradation. Artificial reefs are one method being used to counteract this destruction. However, the most common artificial approaches, such as sunken vehicles and prefabricated cement reefs, do not allow adequate coral development. This paper aims to demonstrate how designers, using additive manufacturing and computational design techniques, can create artificial reefs that better mimic natural reef structures.
Design/methodology/approach
This research focuses on developing three-dimensional matrices through computational design using additive manufacturing to achieve better coral settlement. A “Nature Centered Design” approach was followed, with the corals at the center of the design project. Samples with different geometries and roughness, produced using paste-based extrusion with porcelain and porcelain with oyster shell, were tested in a controlled environment to investigate the settlement preference of soft corals.
Findings
The rapid prototyping of samples confirmed the preference of corals to settle to complex surfaces compared to smooth surfaces. Porcelain showed comparable results to Portland cement, suggesting further testing potential. A closer resemblance to the natural and intricate forms found in coral reefs was achieved through computational design.
Originality/value
This paper proposes a new approach combining rapid prototyping with coral’s biological responses to enhance the understanding of their surface settlement preference. The Nature Centered Design approach, with additive manufacturing and computational design, made it possible to create an innovative working model that could be customized depending on the implementation area or intended coral species, validating the design approach as a method to support environmental conservation.
Details
Keywords
Xubin Su, Yongqiang Yang, Di Wang and Yonghua Chen
The purpose of this paper is to obtain more design freedom and realize fast fabrication of mechanism which is the core subsystem of many machines and always consists of several…
Abstract
Purpose
The purpose of this paper is to obtain more design freedom and realize fast fabrication of mechanism which is the core subsystem of many machines and always consists of several parts with assigned relative motion.
Design/methodology/approach
The mechanism is digitally assembled and later directly fabricated by selective laser melting (SLM) without post‐assembly. The joint is re‐designed to facilitate powdered material removal; the displays and the corresponding support additions are discussed to avoid too many supports within the clearances. Then, a series of universal joint are directly fabricated using SLM machine and a minimum clearance of 0.1 mm is obtained; a crank rocker mechanism is also fabricated and it can achieve the required performances.
Findings
The digitally assembled mechanism can be successfully fabricated by SLM technique using metal powdered material.
Originality/value
It is well known that the components fabricated by SLM have good mechanical properties. Therefore, it can be expected that more mechanisms with more design freedom will be developed and be used in some practical fields with improvement of fabrication quality.