Surface roughness analysis when diamond turning optical grade rapidly solidified aluminium RSA 905

摘要

Ultra-high precision machining is used intensively in the photonics industry for the production of various optical components. Aluminium alloys have proven to be advantageous and are most commonly used over other materials to make various optical components. Recently, the increasing demand from optical systems for optical aluminium with consistent material properties has led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. These new aluminium grades are characterised by their finer microstructures and refined mechanical and physical properties. However, the machining database of these new optical aluminium grades is limited and more research is still required to investigate their machinability performance when they are diamond turned in ultrahigh precision manufacturing environment. This work investigates the machinability of rapidly solidified aluminium RSA 905 by varying diamond-turning parameters and measuring the surface roughness over a cutting distance of 4 km. In addition, a predictive surface roughness model was developed. The machining parameters varied in this study were the cutting speed, feed rate and depth of cut. The results showed a common trend of decrease in surface roughness with increasing cutting distance. The lowest surface roughness R_a result obtained after 4 km in this study was 3.2 nm. This was achieved using a cutting speed of 1750 rpm, feed rate of 5 mm/min and depth of cut equal to 25 µm. The work carried out provides a reference for machinists and researchers using the material allowing expected results to be predicted and appropriate machining parameters to be selected based on the surface roughness requirements.