MICE Target Shaft Joint Change l 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 l MICE Target Ti shaft 1 piece shaft drawing

MICE Target Shaft Joint Change l 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 = 20  m over bearing region and 50  m overall between upper & lower shafts –Actual concentricity achieved >> 100  m 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 l Pre-grind and join accurate parts »Predicted issue –Welding might distort shaft in the middle –Stock material orbital weld did distort significantly at weld l Cannot achieve even width of weld over 360° –Find alternative weld type or method to join »Alternatives –Through-hole type –Large spot weld l 0.9mm deep –Use interference fit rather than taper fit

MICE Target Shaft Joint Change l Change to joint from taper fit »10  m parallel Interference fit –Joints made with 10  m 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 l 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 l Results of weld trial...continued »Stiffness –FEA predicted ~265  m 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 ~260  m

MICE Target Shaft Joint Change l Stiffness most important as increased stiffness = higher 1 st mode »1 st mode previously Hz with ‘+’ shaped shaft »Now 50Hz (lower section) with new shaft shape and bearing support locations

MICE Target Shaft Joint Change l 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 l 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