Chor Yen Yap

Bio: Chor Yen Yap is an academic researcher from Nanyang Technological University. The author has contributed to research in topics: Selective laser melting & Ceramic. The author has an hindex of 6, co-authored 8 publications receiving 1138 citations.

Review of selective laser melting : materials and applications

Abstract: Selective Laser Melting (SLM) is a particular rapid prototyping, 3D printing, or Additive Manufacturing (AM) technique designed to use high power-density laser to melt and fuse metallic powders. A component is built by selectively melting and fusing powders within and between layers. The SLM technique is also commonly known as direct selective laser sintering, LaserCusing, and direct metal laser sintering, and this technique has been proven to produce near net-shape parts up to 99.9% relative density. This enables the process to build near full density functional parts and has viable economic benefits. Recent developments of fibre optics and high-power laser have also enabled SLM to process different metallic materials, such as copper, aluminium, and tungsten. Similarly, this has also opened up research opportunities in SLM of ceramic and composite materials. The review presents the SLM process and some of the common physical phenomena associated with this AM technology. It then focuses on the following a...

An effective analytical model of selective laser melting

Abstract: Selective Laser Melting (SLM) is a laser-based powder bed Additive Manufacturing process that can produce near net shape products with metallic powders according to Computer-Aided Design models. In this paper, a useful analytical model of SLM is proposed by investigating the energy requirement of the process. Results from the experiments on SLM of pure nickel and pure tin are reported. By compiling process parameter data from various literatures and experiments, this model has shown to enable predictions of the energy input required to process different metallic materials to an order of magnitude despite the many assumptions made. Possible explanations for the deviation in predictions and actual energy inputs are also discussed.

Selective laser melting of nickel powder

Abstract: Purpose Selective laser melting (SLM) is an additive manufacturing technology that is gaining industrial and research interest as it can directly fabricate near full density metallic components. The paper aims to identify suitable process parameters for SLM of processing of pure nickel powder and to study the microstructure of such products. The study also aims to characterize the microhardness and tensile properties of pure nickel produced by SLM. Design/methodology/approach A 24 factorial design experiment was carried out to identify the most significant factors on the resultant porosity of nickel parts. A subsequent experiment was carried out with a laser power of 350 W. The scanning speeds and hatch spacings were varied. Findings Scanning speed and hatch spacing have significant effects on the porosity of SLM components. A high relative density of 98.9 per cent was achieved, and microhardness of 140 to 160 Hv was obtained from these samples. A tensile strength 452 MPa was obtained. Research limitations/implications As the energy input levels were made in steps of 20 J/mm3 for the optimization study, the true optimal combination of parameters may have been missed. Therefore, researchers are encouraged to test the parameters with smaller variations in energy levels. Practical implications The paper provides a set of optimized parameters for the SLM of pure nickel. This study enables the three-dimensional (3D) printing of objects with nickel, which has applications in chemical catalyses and in microelectromechanical systems with its magnetostrictive properties. Originality value This research is the first in direct processing of pure nickel using SLM, with the identification of suitable process parameters. The study also provides an understanding of the porosity, microhardness, strength and microstructure of SLM produced nickel parts. This work paves the way for standardization of 3D printed nickel components and enables the applications of pure nickel via SLM.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Abstract: Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Review of selective laser melting : materials and applications

Abstract: Selective Laser Melting (SLM) is a particular rapid prototyping, 3D printing, or Additive Manufacturing (AM) technique designed to use high power-density laser to melt and fuse metallic powders. A component is built by selectively melting and fusing powders within and between layers. The SLM technique is also commonly known as direct selective laser sintering, LaserCusing, and direct metal laser sintering, and this technique has been proven to produce near net-shape parts up to 99.9% relative density. This enables the process to build near full density functional parts and has viable economic benefits. Recent developments of fibre optics and high-power laser have also enabled SLM to process different metallic materials, such as copper, aluminium, and tungsten. Similarly, this has also opened up research opportunities in SLM of ceramic and composite materials. The review presents the SLM process and some of the common physical phenomena associated with this AM technology. It then focuses on the following a...