Mechanical design of optics bench for UV-LED based liquid chromatography detector

Abstract

The proposal for a new detector for liquid chromatography instruments that uses Ultraviolet Light Emitting Diodes (UV-LEDs) as the light source as opposed to currently used deuterium lamps required new design of the mechanical and structural components associated with it. The optics bench assembly is the heart of the detector system on which the detector optical components are mounted. The focus of this thesis is the mechanical design of the optics bench assembly of the UV-LED detector. The thesis first briefly describes the technology and operational theory of the new detector and then discusses the considerations when designing the optics bench. The thesis then presents a step by step methodology of mechanical design of the optics bench assembly. Based on functional requirements of the bench, the best suited material which minimizes vibration sensitivity, thermal gradient, distortion due to impact loading, and cost was selected. The optimal wall thickness of the optics bench was determined by analyzing the results of drop test and vibration analysis. Features to isolate the optics bench assembly from vibration, shock, dust and humidity are also discussed. Thermal analysis was carried out to find out the amount of thermal gradient produced in the optics bench assembly due to thermal heat sources. Based on the results of the thermal analysis, the design of a robust thermal management system is proposed. Guidelines for design for manufacturing, assembly and serviceability were considered at each step of the design process. On the basis of the design requirements and cost considerations, the best suited manufacturing process and surface coating was determined. In conclusion, this thesis offers a foundation and a starting point for the detailed mechanical design of optics bench assembly for UV-LED detector.