Search results

The purpose of this paper is to investigate the mechanical properties and porosity relationships in fused deposition modelling (FDM) fabricated porous structures.

Porous structures of numerous build architectures aimed at tissue engineering (TE) application were fabricated using the FDM. The employment of FDM to fabricate these non‐random constructs offers many advantages over conventional scaffold fabrication techniques as patient specific scaffolds with well‐defined architectures and controllable pore sizes can be fabricated accurately and rapidly. There exist several FDM parameters that one needs to specify during the scaffold fabrication process. These parameters, which can be interdependent and exhibit varying effects on scaffold properties, were identified and examined using the design of experiment (DOE) approach. Essentially, the effects of five FDM process parameters, namely air gap, raster width, build orientation, build layer and build profile, on the porosity and mechanical properties of acrylonitrile‐butadienene‐styrene (ABS) scaffold structures with three‐dimensional interconnectivity were investigated in two designed experiments. Statistical analyses of the data were performed and the respective factors that have significant influence on the porosity and mechanical properties of the scaffolds were identified. The relationship between scaffold's mechanical properties and porosity was thereafter established empirically.

Models of TE scaffolds of numerous build architectures were successfully fabricated using different parameter settings on the FDM. The DOE approach determined air gap and raster width as the most significant parameters in affecting the porosity and mechanical properties of the ABS scaffold structures. The relationship between scaffolds' mechanical properties and porosity was determined to be logarithmic, with the best mechanical properties observed in scaffolds of low porosity.

The paper highlights how the application FDM to tissue scaffold application can overcome most of the limitations encountered in the conventional techniques.

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.

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.

Instructions using multimedia significantly enhances the education process of RP technology. Methods to produce a good multimedia courseware have been introduced.

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.

Rapid prototyping (RP) is fast becoming a “strategic” technology, one that cannot be simply overlooked. This is because the production of a physical prototype from the computer model can be achieved in a very short turnaround time and without the fuss required by NC programming systems. In Singapore, like many countries around the world, there is great interest in this emerging technology. Discusses the evolution of the RP scene in Singapore from 1988 to 1997.

The purpose of this paper is to develop a new bio‐plotter using a rapid freeze prototyping (RFP) technique and to investigate its potential applications in fabricating tissue scaffolds.

The development of cryogenic bio‐plotters including design steps of hardware as well as software is addressed. Effects of structural parameters and process parameters on the properties of tissue scaffolds are demonstrated through simulation and experimental results.

The paper finds that the RFP method is suitable to fabricate macro‐ and micro‐porous scaffolds, especially for temperature‐sensitive polymers. In addition, through simulation and experiment results, it also shows that macro‐ and micro‐porous properties could be manipulated by structural parameters and process parameters, respectively.

This paper shows that the chamber temperature is an important process parameter that can provide the means to control the micro‐porous structure of the scaffold. However, if the temperature is set too high, the fiber is frozen so rapidly that it cannot be fused with other fibers of the previous layer. On the other hand, if the temperature is too low, the fiber is not solidified fast enough. So, the chamber temperature, together with extruding pressure and nozzle velocity, must be optimized, which will be further investigated in future work.

The RFP technique is successfully proposed to construct 3D tissue scaffolds. In addition, a new cryogenic bio‐plotter is designed and developed, in which general algorithms of rapid prototyping method are presented and implemented, facilitating the fabrication of tissue scaffolds with various cross‐hatching patterns in a RFP process.

In recent years, selective laser sintering (SLS) has been used in the biomedical field, including building small‐scaled biomedical devices such as tissue engineering scaffolds and drug delivery devices. A compact adaptation system for the SLS is needed to obtain a more effective and efficient way of sintering small‐scale prototypes so as to reduce powder wastage. Limitations of available smaller‐scale adaptation devices include the need of additional electrical supplies for the device. The purpose of this paper is to report the development of such a system to be mounted at the SLS part bed without any additional energy supply.

The compact adaptation device works on the concept of transferring the motion of the SLS part bed onto the part bed of the compact adaptation device. The device is an integrated attachment that is fixed onto the building platform of the SLS. The gear system of the device lifts the powder supply bed at both sides of the device simultaneously when the part bed at the center of the device is lowered. To further increase powder saving, an improved powder delivery system named alternative supply mechanism (ASM) is mounted on top of the roller to be coupled together with the compact adaptation device.

Powder saving up to 6.5 times compared to using full build version of the Sinterstation 2500 has been achieved by using the compact adaptation device. Furthermore, powder wastage has been reduced by 84 percent when using the ASM compared to the compact adaptation device alone.

The paper demonstrates the development and viability of adaptation devices for SLS to significantly reduce powder consumption by using solely mechanical means to build small parts without using external power supply.

This paper presents a new indirect scaffold fabrication method for soft tissue based on rapid prototyping (RP) technique and preliminary characterization for collagen scaffolds.

This paper introduces the processing steps for indirect scaffold fabrication based on the inkjet printing technology. The scaffold morphology was characterized by scanning electron microscopy. The designs of the scaffolds are presented and discussed.

Theoretical studies on the inkjet printing process are presented. Previous research showed that the availability of biomaterial that can be processed on a commercial RP system is very limited. This is due mainly to the unfavorable machine processing parameters such as high working temperature and restrictions on the form of raw material input. The process described in this paper overcomes these problems while retaining the strength of RP techniques. Technical challenges of the process are presented as well.

Harnessing the ability of RP techniques to control the internal morphology of the scaffold, it is possible to couple the design of the scaffold with controlled cell‐culture condition to modulate the behavior of the cells. However, this is just initial work, further development will be needed.

This method enables the designer to manipulate the scaffold at three different length scales, namely the macroscopic scale, intermediate scale and the cellular scale.

The work presented in this paper focuses on important processing steps for indirect scaffold fabrication using thermal‐sensitive natural biomaterial. A mathematical model is proposed to estimate the height of a printed line.

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.

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.

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.

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.

The paper can be the foundation for extension to other types of biomaterials including biopolymers, bioceramics and biocomposites.

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.

Rapid Prototyping (RP) technology is being widely used in diverse areas including mold manufacturing. However, the quality of RP parts is significantly affected by the property of adopted material and process parameters of the rapid prototyper. The aim of this paper is to investigate the powder material and to optimize the process parameters for Zcorp 402 3DP rapid fabricator. Taguchi's method was employed to investigate the possible process parameters including binder setting saturation value (shell & core), layer thickness, and location of made‐up parts. The experimental result shows that these optimal parameters can shorten parts building time and reduce the use of powder and glue about 20 per cent for ZP100 and 10 per cent for ZP11. Additionally, the quality of RP parts is also improved dramatically. The observation of experiments also shows that the parts made by ZP11 powder is difficult to clean up because of its starch‐based property.

The paper seeks to bridge the already familiar benefits of 3D printing (3DP) to the rehabilitation of cultural heritage, still based on the use of complex and expensive handcrafted techniques and scarce materials.

A compilation of different information on frequent anomalies in cultural heritage buildings and commonly used materials is conducted; subsequently, some innovative techniques used in the construction sector (3DP and 3D scanning) are addressed, as well as some case studies related to the rehabilitation of cultural heritage building elements, leading to a reflection on the opportunities and challenges of this application within these types of buildings.

The compilation of information summarised in the paper provided a clear reflection on the great potential of 3DP for cultural heritage rehabilitation, requiring the development of new mixtures (lime mortars, for example) compatible with the existing surface and, eventually, incorporating some residues that may improve interesting properties; the design of different extruders, compatible with the new mixtures developed and the articulation of 3D printers with the available mapping tools (photogrammetry and laser scanning) to reproduce the component as accurately as possible.

This paper sets the path for a new application of 3DP in construction, namely in the field of cultural heritage rehabilitation, by identifying some key opportunities, challenges and for designing the process flow associated with the different technologies involved.