Y. S. Wong

Selective Laser Sintering

For a given material system, the laser energy density, E s is a key factor which affects quality of the laser sintered structure. A laser energy density is defined by the laser power, laser scan speed and laser beam spot size: n n

Fabrication of 3D Scaffolds via E-Jet Printing for Tendon Tissue Repair

{E_s} = frac{P}{{vdelta }}left( {J/c{m^2}} right)

Study of the Diffusion of Carbon, Its Sources, and Effect on Finishing Micro-EDM Performance of Cemented Carbide

n n(5.1) n nwhere P is the incident laser power (Watts), v, the laser scan speed (cm/s) and δ, the laser beam spot diameter (cm).

11.01 – Introduction to Advanced Machining Technologies

When neural networks are used to identify tool states in machining processes, the main interest is often the recognition ability. It is usually believed that a higher classification rate from pattern recognition can improve the accuracy and reliability of tool condition monitoring, thereby reducing the manufacturing loss. Nevertheless, the two objectives are not identical in most practical manufacturing systems. The aim is to address this issue and propose a new performance evaluation function so that the recognition ability of tool condition monitoring can be evaluated more reasonably. On this basis, two kinds of manufacturing loss due to misclassification are analysed: the over-prediction caused by misclassifying the worn tool condition; and the under-prediction caused by misclassifying the fresh tool condition. By using both to calculate corresponding weights in the performance evaluation function, the potential manufacturing loss is introduced to evaluate the recognition performance of tool condition monitoring. Based on this performance evaluation function, a modified support vector machine approach with two regularization parameters is employed to learn the information of every tool state. In this support vector machine design, the effective feature set extracted from acoustic emission signals is used as inputs, and a five-fold cross-validation is used to tune the parameters. The experimental results show that the proposed method can reliably identify tool flank wear and reduce the overdue prediction of worn tool conditions and its relative loss. Experimental results show that this approach may effectively identify tool state over a range of cutting conditions and reduce the manufacturing loss in the practical industry process.

Model Compression for Design Synchronization within Distributed Environments

Current clinical grafts used in tendon treatment are subject to several restrictions and there is a significant demand for alternative engineered tissue. The previously reported tendon scaffolds mainly based on electrospinning and textile technologies showed promising results for tendon regeneration. However, limitations, such as small pore size, nutrition transmission, cell attachment, exist universally in such scaffolds. In this work, a novel tissue engineered polycaprolactone (PCL) tendon scaffold based on electrohydrodynamic jet printing (E-Jetting) was developed for investigation. In preliminary in-vitro study, human tenocytes were seeded in scaffolds with pore size of ∼106 μm to investigate the cell attachment, morphology and alignment. This study suggested that E-jetted tendon scaffold highly mimicked hierarchical construction from fiber to fascicle level of the native tendon, and has potential to be an alternative tendon regeneration tool.Copyright

FABRICATION OF FUNCTIONALLY GRADED HYDROXYAPATITE/TITANIUM OXIDE COATING VIA DROP-ON-DEMAND TECHNIQUE

Dimensional metrology for micro/nano structure is crucial for addressing quality issues and understanding the performance of micro-fabricated products and micro-fabrication processes. Most of the established methods are based on optical microscopy for planar dimensions and stylus profilometry for out-of-plane dimensions. Contact profilers suffer from slow speed of measurement for three-dimensional profiles and are not suitable for delicate surfaces and parts. Advanced systems using white light interferometer are equipped with CCD cameras and interfaced with a microscope to conduct an array of measurements ranging from two-dimensional to three-dimensional profiles and surface roughness analysis. This paper presents a methodology based on white light interferometer for the dimensional measurement of 3D micro-structures, demonstrated on micro-gears and moulds produced by UV lithography and vacuum casting, respectively. Physical artifacts, such as gauge blocks, are also utilized to verify and validate the measurements on the microcomponents.

Improvements of Mechanical Properties by Reinforcements

Apart from the necessity of surface modification based on different applications, in most of the cases, diffusion of carbon or foreign particles on the workpiece surface during micro-electrodischarge machining (micro-EDM) is avoidable, especially in finishing micro-EDM. This study aims to investigate different sources of materials that migrate to the machined surface during fine-finishing of micro-EDM of cemented tungsten carbide (WC-Co). The machined surfaces have been examined under scanning electron microscope and energy dispersive x-ray to investigate the changes in chemical composition. It has been observed that during finishing of micro-EDM, the major source of materials transfer to both the workpiece and electrode is the diffusion of carbon that comes from the decomposition of the hydrocarbon dielectric. In addition, materials from both workpiece and electrode transfer to each other based on machining conditions and discharge energy. The migration occurs more frequently at lower gap voltages during die-sinking with micro-EDM because of low spark gap and stationary tool electrode. Milling micro-EDM results in lower amount of carbon migration and fewer surface defects that improve the overall surface finish significantly.

Fabrication of Electronics Devices with Multi-material Drop-on-Demand Dispensing System

Widespread demand of miniaturization and variety of material choices from all facets of engineering applications leveraged the development of various tool-based micromachining technologies at par with semiconductor-based processing technologies. Present state of the art tool-based micromachining techniques include micromilling, microturning, microdrilling, microgrinding, and micro-EDM. To further enhance these processes beyond their physical limit of miniaturization, compound micromachining techniques have been proposed where combination of multiple processes are utilized in situ to combine the strengths of multiple processes and overcome the weaknesses.