Some aspects of high precision machines for astronomical applications

Cranfield Precision are not specialists in astronomy but their expertise in designing and building very precise special-purpose machines has contributed to several important astronomical projects. In this talk I will show several machines with astronomical applications and select some features of particular interest for discussion.

1. LDTM: a vertical axis diamond turning lathe designed and used to cut the mirror surface for some of the first X-Ray telescopes. How cleverly designed metrology enabled a more economical mechanical design to succeed. One of the first applications of computer error compensation to a machine tool.
2. OAGM 2500: A very large capacity (2.5m × 2.5m) grinding machine for telescope mirror segments. A “metrology frame” isolates measurement functions from the load-bearing mechanics. Mechanical error motion is compensated in real time within the axis servos.
3. CIDI: An instrument for mechanical contact measurement of the AXAF (Chandra) X-Ray telescope mirrors. An urgent order after the Hubble metrology disaster!
4. Nanocentre: A smaller, horizontal axis, diamond turning lathe. We will see the method for machining the image slicing optics for the JWST Mid Infra-Red Instrument (MIRI).
5. “BoX” A machine designed to grind ELT primary mirror segments; OGM Optics Grinding Machine: Technological advances and new design priorities result in improvements and new challenges for machine control.

Local contact: Enrique Perez Montero