Detector Positioning System

Detector Positioning SystemDiamond Light Source, the UK’s national synchrotron science facility approached LG Motion to design and manufacture a customised Beamline Detector Positioning System for the I24 Microfocus Macromolecular Crystallography (MX) beamline.

The Science

Minuscule protein crystal samples are illuminated with I24’s intense X-ray beam and the detectors are positioned to a precision of just a few tens of microns to capture scattered light that reveals the complexities of protein structure and their functions.
The I24 beamline is used by chemists and structural biologists for ground-breaking molecular level studies in genomics, immune systems and membrane proteins, and innovative research into drug design that combats major disease and viruses.

The objective for the Scientists was to increase flexibility and research throughput on the I24 beamline. The design specification called for an XZ positioning rig with the ability to load multiple detectors up to 280kg mass with a volume of around 1 m3 over a 1.55 metre horizontal and 0.85 metre vertical travel range.

The Engineered Solution

To solve the problem, UK designer and manufacturer LG Motion applied their core motion technology experience with engineering skills to provide a robust system that met all of the Customers objectives.

The custom-built detector positioning system is based around precision linear rails with integrated linear encoder and precision ground ballscrews that are connected to a servo motor via flexible couplings. The vertical axis includes a safety brake and further in-line planetary gearhead reduction to ensure that it does not back-drive under power off conditions, even if the fail safe brake is disengaged for any reason. Both axes also include datum and over-travel limit switches as a part of the specification.

The 280kg detector load is evenly distributed on the horizontal stage carriage plate using a welded steel framework with four vertical precision linear bearing rails which guide the vertical translation of the detector mounting platform.

Each horizontal rail has three bearing carriages that support the upper moving horizontal stage carriage plate which is approximately 1000mm square and 20mm in thickness. The large base plate of the detector system was bolted to the experiment hutch floor after some precision laser alignment, levelling and grouting on installation.

The vertical axis uses one pair of bearing rails utilising three bearing carriages, with the opposing pair just one carriage, this design is much preferred to a more conventional dual bearing arrangement for overhung loads, but this design allowed the use of smaller linear bearings and simplified the power transmission mechanics to be used.

The Components

The Schneeberger MONORAIL AMS series linear motion guide bearings with linear encoders was selected for its compact, integrated design that offered exceptional loading characteristics, smooth motion and precision feedback. The Schneeberger solution was selected as it is used extensively on large scale precision machine applications with advantages of ‘close to load’ measurement and simplified installation plus cost benefits over separately supplied bearings and encoders.

The beamline detector mounting platform is fabricated from MiniTec modular aluminium profile system which was ideal for design flexibiltiy and fixing mounting brackets to.

The Result

During the design approval, manufacture and commissioning, LG Motion worked closely with scientists and Engineering staff at Diamond Light Source to ensure that the specialist detector positioning system was installed on-budget and on-time.

The successfully completed project met all relevant machinery directives, safety standards and performance specifications originally required for the project.

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