Electrical-static discharge in single point diamond turning machining of contact lens polymers
- Authors: Kadermani, Mohamed Munir
- Date: 2015
- Subjects: Electric discharges , Electrostatics , Contact lenses , Polymers
- Language: English
- Type: Thesis , Masters , MEngineering (Mechatronics)
- Identifier: http://hdl.handle.net/10948/4055 , vital:20508
- Description: Single Point Diamond Turning (SPDT) is a technology widely applied for the fabrication of contact lenses. One of the limiting factors in polymer machining is wear of the diamond tool due to electrostatic discharge resulting in poor surface quality of the machined products. The research work presented in this dissertation highlights the electrostatic properties of contact lenses during machining operations and the effects these properties have on the surface quality of the work piece materials. Two contact lens samples were experimented on, Definitive 74 (Silicone Hydrogel) and Tyro 97 (Rigid Gas Permeable). The electrostatic surface potentials (ESPs) were measured during turning operations using an electrostatic voltmeter and the surface roughness measurements were taken using a surface profilometer. Response Surface Methodology (RSM) techniques were employed to create predictive models for both surface roughness and ESPs with respect to the cutting speed, feed rate and depth of cut. Predictive surface roughness models were successfully generated for both materials and the cutting speed and feed rate were identified as the parameters with most effect on surface roughness. In addition, an electrostatic model was successfully generated for the Definitive 74 contact lens material which cited the cutting speed and feed rate as the most effective parameters on the material’s electrostatic behaviour. However, no relationship was evident between the machining parameters and electrostatic behaviour of Tyro 97.
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- Date Issued: 2015
Integration of an electrical discharge machining module onto a reconfigurable machine tool
- Authors: Roberts, Bryndan
- Date: 2014
- Subjects: Machine-tools -- Numerical control , Electric discharges , Manufacturing processes
- Language: English
- Type: Thesis , Masters , MEngineering (Mechatronics)
- Identifier: http://hdl.handle.net/10948/6182 , vital:21047
- Description: Electrical Discharge Machining (EDM) is a non-contact manufacturing process in which material is removed from a metal workpiece by high frequency electrical pulses produced between an electrode and the workpiece. EDM machines are usually stand-alone devices, and are quite expensive. The objective of this research was to integrate an EDM machine and an existing reconfigurable CNC machine tool, using a modular approach, to enable conventional milling and EDM to be conducted in a co-ordinated fashion on the same machine tool.
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- Date Issued: 2014