Papers by Author: Kui Liu

Abstract: In this study, a computer numerical control (CNC) programming software platform for ultra precision machining of optical surfaces was developed based on an MS Windows application framework and openGL. Using cylindrical coordinates, the tool path can be generated based on the polar angle, radius and a linear coordinate of the Z-axis, as well as cutting tool nose radius compensation. A 3D simulation based on tool path generation was developed for machining verification, which largely reduces the oscillation of the machine during the ultra precision machining process. Ultra precision machining of an optical lens array was carried out on a 5-axis ultra precision machining centre using a single crystalline diamond cutter. The experimental results indicated that the oscillation effect can be largely reduced using the cutting tool path using a super steady machining strategy. This software platform is designed as a framework, where the capability and functions can be expanded by adding in more freeform surface packages.

Abstract: This paper presents micro-ball end milling of tungsten carbide using a CBN cutter to investigate its capability for machining slots for micro-moulds. Crack-free slots were machined at different axial depths of cut by inclining the work piece surface at different angles to the spindle axes to study the influence of these machining parameters on the cutting mechanism and surface finish. The experimental results show that up to 150 µm deep slots can be finished efficiently on tungsten carbide work pieces without leaving any fracture marks. It was identified that the chip disposal ability of micro-ball end milling reduced with increase in axial depth of cut. The cutting action was more efficient in up milling cuts compared to that in down milling when machining a slot. The inclination of the work piece proved propitious for machining slots with high-quality finish on tungsten carbide work pieces and a larger inclination angle also facilitated chip disposal.

Abstract: There are increasing demands for polymer based microfluidic devices as polymer devices can be mass produced using the injection molding process for disposable analytical applications. However, fabrication of precision injection molds with micro features down to tens of micro meters is a challenging task. The most efficient manufacturing method for this type of high precision micro mold is the tool-based micro machining. In this paper, studies have been conducted to develop metal injection mould manufacturing technologies for polymer microfluidic device fabrication. An injection mould with a micro feature of 29m wall thickness, 20m height and 9.8mm length has been successfully achieved on brass with very precise dimensional accuracy and surface quality for molding process of polymer microfluidic devices. Polymer microfluidic chips with micro channels of 30m width have been successfully produced using the machined metal injection mould.

Abstract: Super polishing experiments were carried out to investigate the effects of polishing parameters on surface quality of stainless steel lens moulding inserts, and to optimize polishing conditions. Experimental results indicated that optical quality surface of stainless steel lens moulding inserts can be achieved through a two-step polishing process: fast polishing with a soft wood head and coarse diamond paste, and fine polishing with a nylon-covered steel ball head and fine diamond paste. A diameter of 20 mm stainless steel lens moulding insert with a surface roughness Ra of 7.6 nm has been successfully achieved using the two-step super polishing process.