Six-axis vacuum compatible positioning system

12 May 2015

Motion system integrator, LG Motion, has recently delivered a six-axis vacuum-compatible precision motion system to AWE Aldermaston to determine properties of X-ray diffraction crystals prior to installation into X-ray sensitive diagnostics for fielding on laser plasma experiments.

The PC-controlled ‘Two Crystal Characterisation Positioning System’ includes three stepper motor driven rotary tables and a 350mm travel stepper driven linear axis which combine to support optical diffraction mounts and sensors, with two 35mm travel manually adjustable linear stages used to pre-position static optical equipment. 

A pre-programmed user interface enables operator and supervisor level access to set-up and calibrate the optical system, and to load and run coded pre-defined characterisation routines that run across the PC and the motion controller, producing and storing characterisation data.

The complete system supplied by LG Motion includes a control cabinet, housing the motion controller and stepper motor drives, with all positioning mechanics mounted on an aluminium baseplate. AWE has integrated the mechanics into the vacuum chamber with connections through a vacuum bulkhead to the cabinet via 5m cables. The scope of supply included 10-6 vacuum preparation with special lubrication and holes as through-holes or bleeder cross holes to avoid any possibility of cavities forming under vacuum. All motorised axes used vacuum compatible micro-stepping motors from Empire Magnetics, a distribution partner of LG Motion and which are regularly used and specified for use in hostile environments.

The rotary and linear stages were vacuum modified standard tables from LG Motion’s LG series – part of a wide range of standard linear, rotary and elevation stages that are available with stepper or servo motors to form complete multi-axis positioning solutions. The specification for the positioning mechanics called for <0.075 mm for the linear stage and <0.1 degrees for the rotary tables while repeatability was <0.02 mm and <0.05 degrees.

The assembly was fully tested and CE marked at Basingstoke then transferred to the customer where site acceptance testing was carried out with AWE and LG Motion engineers.

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