MICE Target Shaft Joint Change MICE Target Ti shaft

» Baseline stock material = drawn tube lower joined to solid upper (rather than manufacture from solid)

» Baseline joint– 4° Taper fit, joins at roomT with no galling / seizure between

parts

– Electron Beam full 360° orbital weld (fine weld, relatively low heat, accurate)

» 2 parallel methods for manufacture of shaft were undertaken

– Weld together stock materials and grind down to size

– Pre-grind shaft pieces and join these accurate parts

MICE Target Shaft Joint Change MICE Target Ti shaft

1 piece shaft drawing

MICE Target Shaft Joint Change Weld then grind stock materials

» Predicted issue– Poor concentricity between OD & ID of tube and/or OD of

lower and upper shafts (6mm & 4mm)– Concentricity required = 20m over bearing region and 50 m

overall between upper & lower shafts– Actual concentricity achieved >> 100m between upper and

lower shafts, so out of specification (centreless grinding technique)

» Unexpected issue– Grinders ground part way through weld, one shaft fell apart

» No resolution for these problems

MICE Target Shaft Joint Change Pre-grind and join accurate parts

» Predicted issue– Welding might distort shaft in the middle

– Stock material orbital weld did distort significantly at weld Cannot achieve even width of weld over 360°

– Find alternative weld type or method to join

» Alternatives– Through-hole type

– Large spot weld 0.9mm deep

– Use interference fit rather than taper fit

MICE Target Shaft Joint Change Change to joint from taper fit

» 10m parallel Interference fit– Joints made with 10m of parallel

interference– If pressed together at roomT likely to

gall, push off centre and/or seize– Borrowed precision jig for alignment– Used heat hot air gun with

thermocouple to 250°C on socket, and nitrogen for -197°C on plug before assembling (quickly). Interference created as they reach roomT

Features of Upgraded Design Results of weld trial

» Ease of manufacture / weld– Difficulty moved from machining accurate matched tapers

to maintaining tight interference tolerances on parallel socket and plug = ~ no difference

– No negative feedback from EB welding, though plastic bushes in weld jig exhibited melting with through-hole weld indicating more heating of the parts being joined

» Deformation– Measured run-out of shafts before and after weld

– Through-hole distorted significantly (>200 m)

– Spot weld no difference

MICE Target Shaft Joint Change Results of weld

trial...continued» Stiffness

– FEA predicted ~265m of deflection for the 31mm wide 149.5g ‘saddle’ mass used to determine deflection

– Shafts clamped in lathe collet with 160mm protruding

– Plain diameter material and both types of joint exhibited same deflection of ~260m

MICE Target Shaft Joint Change Stiffness most important as increased stiffness =

higher 1st mode» 1st mode previously 28-33 Hz with ‘+’ shaped

shaft» Now 50Hz (lower section) with new shaft

shape and bearing support locations

MICE Target Shaft Joint Change Strength

» Can do tensile test on 2 types of joint but knowledge of tensile strength unlikely to enable failure prediction, most likely to fail by fatigue

» Fatigue difficult to determine outside of the assembly & actual operating conditions due to subtleties in loading conditions, only tests in actual situation give valid results, i.e. offline running.

MICE Target Shaft Joint Change Conclusion

» Orbital EB weld joint creates too much distortion for accurate joining of pre-ground parts

» Of 2 types of alternative joint a parallel interference plug and socket with spot weld to secure = most appropriate

– No problems with manufacture or welding

– No perceptible distortion

– As stiff as machining from solid

– Fatigue life to be tested in offline running

» QC discussed with EB welder, pre-production samples (PPS) will be cross-sectioned & micrographed, as was original QC with orbital weld