Thermal Performance of a Multi-Axis Smoothing Cell

The following material includes a review of thermal and distance metrology equipment, a description of shaping and preparing an aspherical mirror for the ELT ground based telescope involving the use of a robotic smoothing cell. The text covers the calibration of the volumetric workspace of the multi-axis smoothing cell using ISO standard tests with the aim of studying the effects of thermal influences. Plane axis motions errors were measured with a laser interferometer and multi-axis volumetric measurements were carried out with a 6 axis laser tracker. The thermal variation is assessed during operation at high heat load for this type of operation. A Matlab based thermal error model is developed and validated to simulate thermal errors over a range of operating parameters. Using the model and experimental data, direction was given to optimise the robotic cell performance and is due to be implemented for further use