B. Wiedemann, K.‐H. Dusel and J. Eschl
To facilitate the selection of stereolithography resins, methods have been developed which evaluate photopolymers with respect to dynamics of polymerization and shrinkage, and…
Abstract
To facilitate the selection of stereolithography resins, methods have been developed which evaluate photopolymers with respect to dynamics of polymerization and shrinkage, and also the sensitivity of polymerization with respect to process conditions and ambient influences. To use the whole potential of a resin it is necessary to identify the material behaviour related to the build process. The process parameters have to be adapted to the individual material. Describes how numerical simulation of part distortion can help in understanding the interaction between material properties and process parameters. Concludes by stating that the build process must be optimized to reduce internal stresses and to cater for post‐curing effects.
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Susanne Femers, Joachim Klewes and Klaus Lintemeier
The paper structures the life cycle of issues, thus allowing a systematic discussion of their practical aspects. It is designed to help public relations professionals handle…
Abstract
The paper structures the life cycle of issues, thus allowing a systematic discussion of their practical aspects. It is designed to help public relations professionals handle issues by providing them with parameters that can be influenced systematically. The authors differentiate between four different phases in the life cycle of an issue: emergence, dissemination, establishment and erosion. These phases reflect the different degrees to which an issue penetrates society. An issue emerges when a ‘crystallisation’ and certain interpretation of a specific social reality comes out. Dissemination comes up when protagonists pick up the issue and disseminate it. The issue is established when it becomes known to a large part of society. And it undergoes erosion when public interest in the issue stagnates. In each of the four phases intermediary groups and media are involved in different ways and to different degrees. The issue's factual structure, ie the degree of complexity, is also different in each phase. Public relations professionals can systematically influence the different parameters in each phase of the issue: by doing this they gain improved control of the issues.
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Cho‐Pei Jiang, You‐Min Huang and Chun‐Ho Liu
This paper aims to introduce the principle of the mask exposure and scanning stereolithography (MESS) and to develop a simulation code to analyze the MESS process.
Abstract
Purpose
This paper aims to introduce the principle of the mask exposure and scanning stereolithography (MESS) and to develop a simulation code to analyze the MESS process.
Design/methodology/approach
Photopolymerization is a key reaction in stereolithography. It brings about molecular linkage and releases exothermic temperature. The shrinkage effect is the major cause of prototype deformation, and the shrinkage resulting from scanning and mask exposing is different. It is important to analyze the inaccuracy of each curing layer after the mask exposing in order to optimize the scanning parameters. A simulation code, based on dynamic finite element method, to analyze the shrinkage effect in accordance with scanning path and mask exposure pattern. A benchmark model has been proposed to validate the implementation of the developed code.
Findings
The simulation results show that the developed code can analyze the deformation in laser scanning, masking exposing and the MESS process. In benchmark model study, the sharp corner shrinks faster than rounded edge in mask pattern curing. Although the profile scanning can maintain the high accuracy in the MESS process, the residual stress is easily discovered inside of the sharp corner.
Originality/value
The developed simulation code can be applied for optimizing scan path and exposing time due to the analysis process in accordance with the drawing path and fabrication parameters.
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A. Garg, K. Tai and M.M. Savalani
The empirical modelling of major rapid prototyping (RP) processes such as fused deposition modelling (FDM), selective laser sintering (SLS) and stereolithography (SL) has…
Abstract
Purpose
The empirical modelling of major rapid prototyping (RP) processes such as fused deposition modelling (FDM), selective laser sintering (SLS) and stereolithography (SL) has attracted the attention of researchers in view of their contribution to the overall cost of the product. Empirical modelling techniques such as artificial neural network (ANN) and regression analysis have been paid considerable attention. In this paper, a powerful modelling technique using genetic programming (GP) for modelling the FDM process is introduced and the issues related to the empirical modelling of RP processes are discussed. The present work aims to investigate the performance of various potential empirical modelling techniques so that the choice of an appropriate modelling technique for a given RP process can be made. The paper aims to discuss these issues.
Design/methodology/approach
Apart from the study of applications of empirical modelling techniques on RP processes, a multigene GP is applied to predict the compressive strength of a FDM part based on five given input process parameters. The parameter setting for GP is determined using trial and experimental runs. The performance of the GP model is compared to those of neural networks and regression analysis.
Findings
The GP approach provides a model in the form of a mathematical equation reflecting the relationship between the compressive strength and five given input parameters. The performance of ANN is found to be better than those of GP and regression, showing the effectiveness of ANN in predicting the performance characteristics of the FDM part. The GP is able to identify the significant input parameters that comply with those of an earlier study. The distinct advantages of GP as compared to ANN and regression are highlighted. Several vital issues related to the empirical modelling of RP processes are also highlighted in the end.
Originality/value
For the first time, a review of the application of empirical modelling techniques on RP processes is undertaken and a new GP method for modelling the FDM process is introduced. The performance of potential empirical modelling techniques for modelling RP processes is evaluated. This is an important step in modernising the era of empirical modelling of RP processes.
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Daria Arkhipova, Marco Montemari, Chiara Mio and Stefano Marasca
This paper aims to critically examine the accounting and information systems literature to understand the changes that are occurring in the management accounting profession. The…
Abstract
Purpose
This paper aims to critically examine the accounting and information systems literature to understand the changes that are occurring in the management accounting profession. The changes the authors are interested in are linked to technology-driven innovations in managerial decision-making and in organizational structures. In addition, the paper highlights research gaps and opportunities for future research.
Design/methodology/approach
The authors adopted a grounded theory literature review method (Wolfswinkel et al., 2013) to achieve the study’s aims.
Findings
The authors identified four research themes that describe the changes in the management accounting profession due to technology-driven innovations: structured vs unstructured data, human vs algorithm-driven decision-making, delineated vs blurred functional boundaries and hierarchical vs platform-based organizations. The authors also identified tensions mentioned in the literature for each research theme.
Originality/value
Previous studies display a rather narrow focus on the role of digital technologies in accounting work and new competences that management accountants require in the digital era. By contrast, the authors focus on the broader technology-driven shifts in organizational processes and structures, which vastly change how accounting information is collected, processed and analyzed internally to support managerial decision-making. Hence, the paper focuses on how management accountants can adapt and evolve as their organizations transition toward a digital environment.
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Kamran Kardel, Ali Khoshkhoo and Andres L. Carrano
The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding of its…
Abstract
Purpose
The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding of its behavior in material jetting technology.
Design/methodology/approach
Specimens with two layer thicknesses (14 and 28 µm) were printed in two aspect ratios (2:1) and (10:1), four thickness values (1, 2, 3 and 4 mm) and three build orientations (45d, XY and YX) and scanned with a wide-area 3D surface scanner to quantify distortion. The material used to build the test specimens was a commercially available resin, VeroWhitePlus RGD835.
Findings
The results of this study showed that all printed specimens by material jetting 3D printers had some level of distortion. The 1-mm thickness specimens, for both layer thicknesses of 14 µm and 28 µm, showed a wide range of anomalies including reverse coil set (RCS), reverse cross bow (RCB), cross bow (CB), wavy edge (WE) and some moderate twisting (T). Similar occurrences were observed for the 2-mm thickness specimens as there were RCS, WE, RCB and T anomalies that show the difference between the thinner specimens (1- and 2-mm) with the thicker ones (3- and 4-mm). In both 3- and 4-mm thickness specimens, there was more consistency in terms of distortion with mainly RCS and RCB anomalies. In total, six different types of flatness anomalies were found to occur with the following incidences: reverse coil set (91 specimens, 63.19%), reverse cross bow (50 specimens, 34.72%), wavy edge (23 specimens, 15.97%), twist (19 specimens, 12.50%), coil set (11 specimens, 7.64%) and cross bow (7 specimens, 4.86%).
Originality/value
This study expands the research on how the preprocess parameters such as layer thickness and build orientation and the geometrical parameters such as part thickness and aspect ratio cause dimensional distortion. Distortion is a pervasive consequence of the curing process in photopolymerization and explores one of the most common defects that come across in polymeric-based additive manufacturing. In addition to the characterization of the type and magnitude of distortion, the contributions of this work also include establishing the foundation for design guidelines aiming at minimizing distortion in material jetting.
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C.M. Cheah, J.Y.H. Fuh, A.Y.C. Nee and L. Lu
The effects of the addition of short glass fibers into an acrylic‐based photo‐polymer (De Solite SCR310) used in the laser solidification process have been studied. Comparisons of…
Abstract
The effects of the addition of short glass fibers into an acrylic‐based photo‐polymer (De Solite SCR310) used in the laser solidification process have been studied. Comparisons of the mechanical properties between pure‐polymer specimens and their fiber‐filled counterparts were made by subjecting the parts to tensile tests. It was observed that the fiber‐reinforced specimens yielded higher measured values of elastic modulus and ultimate tensile strength. The amount of shrinkage encountered by the reinforced prototypes during post‐curing was also found to be less than their non‐reinforced counterparts. It was also found that the mechanical properties of the post‐cured fiber‐reinforced specimens were functions of the layer pitch and laser exposure density used during fabrication. By increasing the laser exposure density and decreasing the layer pitch, the mechanical properties of the post‐cured fiber‐reinforced prototype can be improved, leading to the realization of end products with higher mechanical strengths and better dimensional accuracy.
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D. Karalekas and D. Rapti
This paper presents an experimental study undertaken to determine the polymerisation‐induced residual stresses generated in stereolithography (SL) built test specimens, by using…
Abstract
This paper presents an experimental study undertaken to determine the polymerisation‐induced residual stresses generated in stereolithography (SL) built test specimens, by using the hole‐drilling strain gage method of stress relaxation. Experimentally measured strains, using special three‐element strain gage rosettes, were input into the blind‐hole analysis to calculate the induced residual stresses. The mechanical properties of resin specimens fabricated by the solidification process using an epoxy based photopolymer and post‐cured under ultraviolet (UV) and thermal exposure were determined and incorporated into the subsequent drill‐hole analysis. The effect of the pre‐selected fabrication parameters (hatching space and curing depth) and subsequent by the post‐curing procedure (UV, thermal curing) on the magnitude of the recorded strains is also presented.
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The objective of this study is to investigate the use of a fibre Bragg grating (FBG) sensor for measuring of curing strains that develop during the solidification of a…
Abstract
Purpose
The objective of this study is to investigate the use of a fibre Bragg grating (FBG) sensor for measuring of curing strains that develop during the solidification of a photocurable resin used in 3D microfabrication.
Design/methodology/approach
The followed approach consists of embedding a 1,300 nm FBG into a cylindrical specimen, fabricated into a transparent mould, being exposed to ultraviolet laser light. The further development of the cure induced strains under thermal treatment was also studied by post‐conditioning the cylindrical specimen in an oven at 70°C.
Findings
The experimental results demonstrate the capability of the FBG sensor to provide useful information on the strain build‐up during laser solidification and their post‐cure evolution under the presence of a thermal environment.
Research limitations/implications
Future work should involve the use of smaller diameter FBG sensors in microstereolithography built parts.
Practical implications
It is shown that considerable cure strains are developed at the end of the photo‐polymerisation process that eventually can affect the structural resolution of final parts fabricated by microstereolithography.
Originality/value
The presented method can be used to investigate other photopolymers used in micro‐stereolithography.
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Philip Mark Hackney and Richard Wooldridge
Metal casting industry is in recovery phase after the crisis in 2008; customer demand continues to increase, with 98.6 million metric tons cast in 2011. Traditional ferrous and…
Abstract
Purpose
Metal casting industry is in recovery phase after the crisis in 2008; customer demand continues to increase, with 98.6 million metric tons cast in 2011. Traditional ferrous and non-ferrous casting techniques require one shot or permanent moulds which require tooling to produce. Tooling particularly for developmental projects can be costly and take valuable time to produce. Additive manufacturing (AM) has been used to manufacture sand patterns for metal sand casting using laser sintering and sand bonding. This research aims to focus on characterising the sand-bonded process developed by ExOne GmbhH Germany.
Design/methodology/approach
The approach taken in this research is to evaluate characteristics of parts built in the build volume for dimensional accuracy, tensile and compressive crush strength, density, impact strength and high temperature resistance. These properties are required to compare the 3D sand printing (3DSP) process to direct laser sand sintering (DLSS) and traditional Furan-based casting sand mixtures. The samples were taken from a production machine over a period of 30 days to ensure consistency.
Findings
The 3DSP process has the capability to manufacture sand patterns to an accuracy of ±0.5 mm or error less than 0.3 per cent; it has also demonstrated the best build position to achieve accurate parts. The research has demonstrated the 3DSP patterns are comparable to traditional methods for important casting material characteristics such as tensile, compression and impact strength. It has been shown that the 3DSP process is capable manufacturing significantly larger parts, with build production rates up to 30 times higher compared to similar parts manufactured via the DLSS process.
Research limitations/implications
As they has been very few 3DSP machines sold in Europe and particular UK, they has been little research into this new technique, and, therefore, they is a reliance on machine manufactures data for assessment. This research into 3DSP has increased the knowledge of this process significantly.
Practical implications
This research would be of interest to designers and manufacturing engineers wishing to take advantage of the implications of having new design freedom, tool less manufacturing with short lead times in a wide range of materials using fundamentally tried and tested century’s old casting techniques.
Originality/value
The research for this paper revealed very little published academic research in this area; therefore, this work will increase the body of knowledge for this niche AM process.