Hexabundles meet OzPoz
Hexabundle science workshop
University of Sydney
24th November 2008
Andrew McGrath, AAO
Buttons
• Existing OzPoz has single-fibre buttons and mini-IFUs with 20 fibres each
• Mini-IFUs view 2x3 arcsec FoV• FACBs (acquisition bundles) with 19
fibres• Common button package
Bundles
• Single-fibre buttons fed with sleeved fibre
• 19- and 20-fibre bundles also carried in slightly larger diameter sleeve
Retractor
• Take up slack in fibre• Keep mild tension in fibre to button (~1 N)• Diameter of bundle• Bend radius ~24 mm• Flexibility
Magnetic attachment
• Buttons secured magnetically to field plate
• Strong enough – Static friction must hold button stable to ~1 N retractor tension, in arbitrary orientation wrt gravity
• Not too strong – Robot gripper limits to ~4 N
• Clamping force ~2.5 N
Bundle handling experience
• Works well for existing design• No evidence of effects of ‘tangling’ of
fibres against each other within 19- and 20-fibre sleeved bundles
• 2dF retractors carry unsleeved bundles of fibres for guide bundles
FLAMEing Hexabundles?• Can we use the existing arrangement to fit one or
more 61-core hexabundle fibre bundles to OzPoz?• Notionally, assemble a FACB or mini-IFU button with a
hexabundle feed
– Seems OK
FLAMEing Hexabundles?
• Can the existing OzPoz retractor accommodate a bundle of 61 fibres?
• Currently handles 20• Diameter of bundle will increase• Stiffness of sleeved bundle will increase
FLAMEing Hexabundles?
• Need to identify a suitable sleeve• Could increase retractor spring force to
accommodate increased stiffness• Flow-on effects to magnetic force and robot
force capacity could render unfeasible
FLAMEing Hexabundles?
• Could subdivide the bundle to manageable subsets
• Multiple adjacent retractors per button• Minor additional placement limitations• Probable requirement for increased
magnetic force to provide static friction• Robot flow-on effects may render
unfeasible
FLAMEing Hexabundles?
• Unsleeved bundle likely much more flexible• Similar arrangement to 2dF, fibres in a
loose plait• Tangling issues and fibre breakage are
important concerns
FLAMEing Hexabundles?
• Or… consider FLAMEing Hexabundles as a one-off type of test
• Don’t run the fibre bundle through a retractor at all
• Manually place the button on the field plate• Use the robot for metrology only• Tweak the button(s) into place by tapping
with a finger
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