Investigating diamond turning process to achieve optical flatness in an aluminium alloy

• Main Author: Rajarathinam Manikanta Saravanan
• Other Authors: Sathyan Subbiah
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/54705
• Institution: Nanyang Technological University

Optically flat components are very versatile and used in many applications such as: inspection of gauge block accuracy and its wear, testing several modules containing lenses, mirrors, prisms, filters etc. They also meet recruits for high demanding interferometry where exceptionally flat optical windows are needed. Such optically flat components require a high degree of surface preparation; characteristics such as surface finish and flatness often have to be within fractions of light wavelengths. Such demanding surfaces can be fabricated by machining processes such as the Single Point Diamond Turning (SPTD) process. The aim of this project is to improve flatness in ultra-precision machining (diamond turning) of an Aluminium alloy optical component. Experiments were carried on an ultra-precision lathe, with single crystal ultra-sharp diamond tools. Surface characterization is carried using interferometry to identify the degree of flatness. Process parameters, fixturing techniques and material effects (where possible) are varied to understand their effects on the surface generated. This is expected to be of interest to companies such as Qioptiq (Singapore). Form accuracies of less than or equal to 0.15Jlrn (6") and finish tolerance reaches less than or equal to 5nm Ra are shown using proposed improvements. It is shown that by providing a very strong, dynamically stiff fixturing using Light Activated Adhesive Grippers (LAAG) technology, a relatively new work holding technology, the workpiece can be gripped with minimum pre-loaded distortion, with maximum approachability and dynamic rigidity during the machining process. Additionally, such joints can be cured or destroyed using light on demand within seconds.