jason tarrant / november 2008 mice target mechanical design l jason tarrant – stfc l introduction...
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Jason Tarrant / November 2008
MICE Target Mechanical Design
Jason Tarrant – STFC
Introduction» Investigations into target
shaft failure» Current suspicions and
solutions» Shaft re-design» QA» Milestone plan
Jason Tarrant / November 2008
MICE Target Mechanical Design
Investigate Reason for Seizure of Shaft» High speed camera (see http://www.hep.shef.ac.uk/research/mice/target_videos/ )
» Vibration analysis (accelerometers)
» Magnetic field measurement & analysis» DLC-DLC coating suitability
– Friction / heat generated at bearing interface– Quality of DLC coating
» +Differences between R78 & Sheff. Targets– Mounting– Dimensions– Surface finish
MICE Target Mechanical Design Present thinking with indication of vibration =
possible hammering between shaft and bearings No solutions viable before January, but by April…
» Improved DLC-DLC or alternative e.g. – Nitride type coating by HIPIMS process…– WS2…
» Alternative shaft & bearing design to eliminate vibration
All of course dependant on investigation findings
Jason Tarrant / November 2008
MICE Target Mechanical Design Alternative Shaft & bearing
» Current cruciform shape– Bearing more a guide due to
clearances potential to rattle or hammer
– ‘+’ or ‘x’ same stiffness but for 11mm2 CSA I = ~18mm4, for a round shaft same CSA @ 6mm OD I = 39mm4 > 2 x as stiff.
Jason Tarrant / November 2008
MICE Target Mechanical Design Alternative Shaft & bearing…
» Round shaft– Needs anti-rotation device
Sprung follower on flat Key in slot (slot on shaft)
– Target attachment Round tubular end as target Formed flat target from tubular end Threaded, pinned & welded
Jason Tarrant / November 2008
MICE Target Mechanical Design Alternative Shaft & bearing…
» Bearing alignment– Clearance to be reduced as far as practical but
dependant on: Manufacturing tolerances on shaft and bearing (min and
max clearance) Bearing alignment (position and orientation) Straightness of shaft
Jason Tarrant / November 2008
MICE Target Mechanical Design QA
» Define all characteristics that could influence the running of the shaft in the bearings, e.g.
– Coating thickness / hardness
– Actual dimensions and shape of components
» Control, Measure and record these important for… Install in ISIS
» Use R78 assembly? (determine wear / predict life) or refurbish» Use different assembly with close to identical characteristics
Jason Tarrant / November 2008
MICE Target Mechanical Design
Schedule» Milestones
– Coating investigations – Jan 09– Shaft / bearing redesign review and approval – Dec 08– First test pieces of new design – Feb 09– Testing Sheffield / R78 complete – March 09– Refurb / build & install in ISIS complete – April 09– 2nd Target start cycling – April/May 09
Jason Tarrant / November 2008