MICE Target Mechanical Design

Issues with current design #1
-
Stiffness of main cruciform shaft can be improved
-
-
Sheffield’s high speed camera investigation shows off
axis movement attributed to more than just clearances
of bearings, indicates mode shape is forced into shaft
when firing
Changes
-
-
Make cross section of longer lower section of shaft
stiffer = tubular
Shorten and lighten shaft as much as possible
- Compress assembly above to allow main section to
be cut down
- Rivet on vane rather than use heavier fasteners
Jason Tarrant / Jan 2009
MICE Target Mechanical Design

Issues with current design #2
-
Clearances between cruciform shaft and lower
bearing (up to 0.1mm each side) = lateral play
-
-
May cause hammering during motion (shaft on bearing)
May contribute to lateral movement of target tip seen
with high speed camera
Changes
-
-
Change to round shaft and round bearing hole = easier
to machine to tight tolerances and surface finish
Improve bearing alignment: Reconfigure assembly so
bearing seats and bearing holes machined in one
setting on machine (current assembly cannot be
machined easily due to the protruding wires and cooling
tubes)
Jason Tarrant / Jan 2009
MICE Target Mechanical Design

Issues with current design #3
-
DLC coating adhesion and recommendations
-
-
Poor adhesion of DLC coating to substrates suspected for failure
seen in first failed shaft and bearings
Changes
-
-
Ensure no polish left on from polishing (at Tecvac)
No contact with silicon based chemicals or cutting oils
Do not wire erode / spark erode parts = excessive oxidisation
Improve surface finish (current 1.6 Ra, 0.1-0.02 Ra
preferable)
Differences in electro-potential can cause a build up (like
electroplate) so relieve critical edges and corners
Jason Tarrant / Jan 2009
MICE Target Mechanical Design

Issues with current design #4
- Clamping of stator housing
-
-
No rigid spacing of flanges into which vacuum tube is held (risk of
misalignment during assembly and damage to weld or vacuum tube
if knocked / screw tension lost / force applied when assembling
optics, uneven thermal strains etc.
Changes
-
Stator housing to be the strong ‘core’ onto which other components fix.
Clamping arrangement to support main core of components not clamp it.
Possibility of placing uneven (skewed)
load on vacuum tube and weld with
bolt array
Fixed height
stator housing
Welded vacuum tube
fixes flange separation
MICE Target Mechanical Design

Alternative core design
-
Machining bearing seats and bearings
in a single set-up on a machine
-
-
Fit blank flanges, align & dowel
Machine bearing bores
Fit blank bearings, align & dowel
Machine shaft holes in bearings
Stator assembled after central
support core accurately machined
-
Remove bearings and upper flange and
fit stator
Jason Tarrant / Jan 2009
MICE Target Mechanical Design

Alternative bearing design
Wire cut from
single piece for
accurate wedge fit
(but not wire cut
bearing faces)
Single piece
main body
Clearance for vane
(bearing added after
shaft assembled to
prevent damage to
delicate shaft)
Wedge & dowel for full
x,y,z location of clamp
Anti rotation
Feature (rounded
or flat bearing face
options)
Full bearing
section merges
into section for
anti-rotation
MICE Target Mechanical Design

Schedule

Long lead items – identify now, into production
immediately after a review (order materials now?)



Core tube = order materials, rough m/c, weld, stress relieve,
final machine
Ti tube for target shaft = 0.7 has 4-6 wk delivery, 0.5 is 12 wk,
then manufacture, weld, stress relieve, m/c / straightening,
polishing, coating, assembly of magnet & vane
Timescale

Every attempt to achieve March assembly ready for offline
testing
Jason Tarrant / Jan 2009