K.H. Low, K.F. Leong, C.K. Chua, Z.H. Du and C.M. Cheah
There are many applications for rapid prototyping systems and application in the biomedical field is an important domain. Uses selective laser sintering (SLS) in this study to…
Abstract
There are many applications for rapid prototyping systems and application in the biomedical field is an important domain. Uses selective laser sintering (SLS) in this study to build porous cylindrical disc matrices for use as drug delivery devices (DDD). Studies the part‐bed temperature to ascertain its influence over the porosity of the disc matrices. They are found to have an inverse linear relationship. Also investigates the dense walls, the inherent consequences of building porous structures with the SLS, in the disc matrix as they have a direct impact on the performance of the DDD. Discusses the size constraint of the disc matrix due to the limitations of the SLS process. Also investigates the possibility of creating disc matrices of varying porosity. Experimental results demonstrate that SLS is viable in producing DDDs that have variable porosity and micro‐features.
Chee Kai Chua, Kah Fai Leong, Chu Sing Lim and Trong Thien Vu
The purpose of this paper is to detail the development of a multimedia courseware that enhances the learning of rapid prototyping (RP) among professionals, senior year and…
Abstract
Purpose
The purpose of this paper is to detail the development of a multimedia courseware that enhances the learning of rapid prototyping (RP) among professionals, senior year and graduate students.
Design/methodology/approach
The design and development of the multimedia courseware is based on a “visit a science museum” concept where each topic can be accessed depending on the interests or the needs of users. Factors that influence learning curve such as structure of information, application of visual and auditory components and human‐computer interface are addressed and discussed.
Findings
Instructions using multimedia significantly enhances the education process of RP technology. Methods to produce a good multimedia courseware have been introduced.
Originality/value
This paper describes the latest version of the multimedia courseware which is an accompaniment to the third edition of the book entitled Rapid Prototyping: Principles & Applications published in 2009.
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M.W. Naing, C.K. Chua, K.F. Leong and Y. Wang
This paper details the derivation of the mathematical formulae of a novel system for designing and fabricating tissue engineering (TE) scaffolds.
Abstract
Purpose
This paper details the derivation of the mathematical formulae of a novel system for designing and fabricating tissue engineering (TE) scaffolds.
Design/methodology/approach
This work combines the unique capability of rapid prototyping (RP) techniques with computer‐aided design (CAD) and imaging software to design and fabricate customised scaffolds that are not only consistent in microstructure but also readily reproducible. The prototype system, called the computer‐aided system for tissue scaffolds (CASTS), has a parametric library of design units which can be assembled into scaffold structures through an in‐house algorithm. An additional module, the slicing routine, has also been added to improve the functionality of the system. To validate the system, scaffolds designed were fabricated using a powder‐based RP technique called selective laser sintering (SLS).
Findings
It is shown that the CASTS can be used to exploit CAD and medical imaging techniques together with RP systems to produce viable scaffolds that can be customised for various applications to suit the needs of individual patients.
Research limitations/implications
Further research is being done to examine the internal microstructure of the scaffolds and to determine the mechanical properties, as well as to study the inter‐relationship between cell proliferation and the pore shapes of the scaffolds.
Originality/value
The crucial role of scaffolds in TE has long been recognised. Successful TE scaffolds should have controllable characteristics such as pore size, porosity, and surface area to volume ratio as well as interconnectivity within the scaffolds. Much work has been carried out to produce such TE scaffolds with varying degrees of success. One major drawback is that the resultant TE scaffolds are not readily reproducible. The potential of CASTS lies in its ability to design and fabricate scaffolds with varying properties through the use of different unit cells and biomaterials to suit different applications.
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This paper aims to study the effects of inorganic CaCO3 nanoadditives in the polylactic acid (PLA) matrix and fused filament fabrication (FFF) process parameters on the mechanical…
Abstract
Purpose
This paper aims to study the effects of inorganic CaCO3 nanoadditives in the polylactic acid (PLA) matrix and fused filament fabrication (FFF) process parameters on the mechanical characteristics of 3D-printed components.
Design/methodology/approach
The PLA filaments containing different levels of CaCO3 nanoparticles have been produced by mix-blending/extrusion process and were used to fabricate tensile and three-point bending test samples in FFF process under various sets of printing speed (PS), layer thickness (LT), filling ratio (FR) and printing pattern (PP) under a Taguchi L27 orthogonal array design. The quantified values of mechanical characteristics of 3D-printed samples in the uniaxial and the three-point bending experiments were modeled and optimized using a hybrid neural network/particle swarm optimization algorithm. The results of this hybrid scheme were used to specify the FFF process parameters and the concentration of nanoadditive in the matrix that result in the maximum mechanical properties of fabricated samples, individually and also in an accumulative response scheme. Diffraction scanning calorimetry (DSC) tests were conducted on a number of samples and the results were used to interpret the variations observed in the response variables of fabricated components against the FFF parameters and concentration of CaCO3 nanoadditives.
Findings
The results of optimization in an accumulative scheme showed that the samples of linear PP, fabricated at high PS, low LT and at 100% FR, while containing 0.64% of CaCO3 nanoadditives in the matrix, would possess the highest mechanical characteristics of 3D-printed PLA components.
Originality/value
FFF is a widely accepted additive manufacturing technique in production of different samples, from prototypes to the final products, in various sectors of industry. The incorporation of chopped fibers and nanoparticles has been introduced recently in a few articles to improve the mechanical characteristics of produced components in FFF technique. However, the effectiveness of such practice is strongly dependent on the extrusion parameters and composition of polymer matrix.
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Swee Leong Sing, Wai Yee Yeong, Florencia Edith Wiria, Bee Yen Tay, Ziqiang Zhao, Lin Zhao, Zhiling Tian and Shoufeng Yang
This paper aims to provide a review on the process of additive manufacturing of ceramic materials, focusing on partial and full melting of ceramic powder by a high-energy laser…
Abstract
Purpose
This paper aims to provide a review on the process of additive manufacturing of ceramic materials, focusing on partial and full melting of ceramic powder by a high-energy laser beam without the use of binders.
Design/methodology/approach
Selective laser sintering or melting (SLS/SLM) techniques are first introduced, followed by analysis of results from silica (SiO2), zirconia (ZrO2) and ceramic-reinforced metal matrix composites processed by direct laser sintering and melting.
Findings
At the current state of technology, it is still a challenge to fabricate dense ceramic components directly using SLS/SLM. Critical challenges encountered during direct laser melting of ceramic will be discussed, including deposition of ceramic powder layer, interaction between laser and powder particles, dynamic melting and consolidation mechanism of the process and the presence of residual stresses in ceramics processed via SLS/SLM.
Originality/value
Despite the challenges, SLS/SLM still has the potential in fabrication of ceramics. Additional research is needed to understand and establish the optimal interaction between the laser beam and ceramic powder bed for full density part fabrication. Looking into the future, other melting-based techniques for ceramic and composites are presented, along with their potential applications.
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Amara Mouna, Fatima Zahra Khedim, Hadjer Didouh, Hayet Tati, Lamsadfa Sidamar, Mohammed Hadj Meliani and Rami K. Suleiman
It is now well-known in the fracture-mechanics community that a single fracture parameter alone may not be adequate to describe crack-tip condition. To address this problem, there…
Abstract
Purpose
It is now well-known in the fracture-mechanics community that a single fracture parameter alone may not be adequate to describe crack-tip condition. To address this problem, there has been a recent surge of interest in crack-growth behaviour under conditions of low crack-tip stress triaxiality. This paper exploited the K-A3 crack approach, which was derived from a rigorous asymptotic solution and has been developed for a two-parameter fracture.
Design/methodology/approach
The material failure curve or master curve, has been established as a result of the notched specimen tests. It was shown that the notch fracture toughness is a linear decreasing function of the stress. The use of the material failure curve to predict fracture conditions was demonstrated on gas pipes with the longitudinal surface notch.
Findings
No finding.
Originality/value
This approach requires that the constraint in the test specimen approximate that of the structure to provide an “effective” toughness for use in a structural integrity assessment. The appropriate constraint is achieved by matching thickness and crack depth between the specimen and structure.
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A. Touati, S. Corbel and J.P. Corriou
Photolithography allows the fabrication of a solid polymer object through polymerization of a monomer resin by means of a laser source guided according to the data of computer…
Abstract
Photolithography allows the fabrication of a solid polymer object through polymerization of a monomer resin by means of a laser source guided according to the data of computer aided design. However, one drawback of this method is the inaccuracy of the dimensions of the objects related to the shrinkage phenomenon which depends on the polymerization, on the laser flux and on the used sweeping procedure. In this paper, the deformation of an isolated voxel (elementary volume) or a voxel interacting with its neighbor is described. This simulation is based on a kinetic model that takes into account the gel effect and a model of volumetric variation due to the difference of the length of the bonds between the monomer and polymer molecules.
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M. Tarik Arafat, Ian Gibson and Xu Li
This paper aims to review the advances in additive manufactured (AM) scaffolds for bone tissue engineering (TE). A discussion on the state of the art and future trends of bone TE…
Abstract
Purpose
This paper aims to review the advances in additive manufactured (AM) scaffolds for bone tissue engineering (TE). A discussion on the state of the art and future trends of bone TE scaffolds have been done in terms of design, material and different AM technologies.
Design/methodology/approach
Different structural features and materials used for bone TE scaffolds are evaluated along with the discussion on the potential and limitations of different AM scaffolds. The latest research to improve the biocompatibility of the AM scaffolds is also discussed.
Findings
The discussion gives a clear understanding on the recent research trend in bone TE AM scaffolds.
Originality/value
The information available here would be useful for the researchers working on AM scaffolds to get a quick overview on the recent research trends and/or future direction to work on AM bone TE scaffolds.
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The purpose of this paper is to use rapid prototyping (RP) technology to build physical models based on axisymmetric finite element (FE) simulation deformation results. To this…
Abstract
Purpose
The purpose of this paper is to use rapid prototyping (RP) technology to build physical models based on axisymmetric finite element (FE) simulation deformation results. To this end, an algorithm which extracts stereolithography (STL) model from axisymmetric ring element mesh is developed and realized by MATLAB programming.
Design/methodology/approach
The algorithm first identifies boundary element edges, which compose the contour(s) of an axisymmetric ring FE mesh. Then, the identified contour edges are around the symmetry axis revolved a specific angle, at certain intervals according to certain approximate criterion, to generate new nodes to form a group of oriented triangles whose normal vectors conform to the right-handed rule. Finally, a completely closed STL model is obtained by necessary triangulation processing and rotation mapping based on original mesh.
Findings
It is validated that the extracted STL model is sound and the proposed algorithm is feasible, right and characterized by linear time complexity for extracting STL model from either triangular, quadrilateral, or mixed triangular/quadrilateral axisymmetric mesh.
Research limitations/implications
Color is important for expressing FE simulation results, which is not involved in STL model. Among the alternative data file formats, VRML representation is an applicable one that is complimentary to existing RP processes and suitable for color 3D printing. Based on the current work, coloring VRML model could be extracted from axisymmetric FE simulation results conveniently.
Originality/value
The study of this paper provides a RP-based materialized mode to characterize axisymmetric FE simulation deformation results, which is more intuitive and visible than the computer graphics-based visualization.
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Florencia Edith Wiria, Kah Fai Leong and Chee Kai Chua
Tissue engineering (TE) involves biological, medical and engineering expertise and a current engineering challenge is to provide good TE scaffolds. These highly porous 3D…
Abstract
Purpose
Tissue engineering (TE) involves biological, medical and engineering expertise and a current engineering challenge is to provide good TE scaffolds. These highly porous 3D scaffolds primarily serve as temporal holding devices for cells that facilitate structural and functional tissue unit formation of the newly transplanted cells. One method used successfully to produce scaffolds is that of rapid prototyping. Selective laser sintering (SLS) is one such versatile method that is able to process many types of polymeric materials and good stability of its products. The purpose of this paper is to present modeling of the heat transfer process, to understand the sintering phenomena that are experienced by powder particles in the SLS powder bed during the sintering process. With the understanding of sintering process obtained through the theoretical modeling, experimental process of biomaterials in SLS could be directed towards the appropriate sintering window, so as not to cause unintentional degradation to the biomaterials.
Design/methodology/approach
SLS uses a laser as a heat source to sinter parts. A theoretical study based on heat transfer phenomena during SLS process was carried out. The study identified the significant biomaterial and laser beam properties that were critical to the sintering result. The material properties were thermal conductivity, thermal diffusivity, surface reflectivity and absorption coefficient.
Findings
The influential laser beam properties were laser power and scan speed, which were machine parameters that can be controlled by users. The identification of the important parameters has ensured that favorable sintering conditions can be achieved.
Research limitations/implications
The selection of biopolymer influences the manner in which energy is absorbed by the powder bed during the SLS process. In this paper, the modeling and investigative work was validated by poly(vinyl alcohol) which is a biomaterial that has been used for many biomedical and pharmaceutical purposes.
Practical implications
The paper can be the foundation for extension to other types of biomaterials including biopolymers, bioceramics and biocomposites.
Originality/value
The formulation of the theory for heat transfer phenomena during the SLS process is of significant value to any studies in using SLS for biomedical applications.