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