CM25 Engineering 1 4 Nov 2009

DIFFUSER

Carousel (~50kg)Driven by air motors – 3 separate ‘actions’1. Carousel rotation2. “30 degree rotation’’

Transfers discs from carousel to carrier3. Carrier

Moves disc in/out of solenoid

CM25 Engineering 2 4 Nov 2009

STATUS – 3 Nov 2009

Mechanics reassembled– Survived basic tests

– more required including: Motor speedsPositioning accuracy Bedding-in of gears….

Electronics & Air Crates working

LabView controls starting (EPICS can wait)

Developing disc transfer operation – critical item

– next slides

CM25 Engineering 3 4 Nov 2009

DISC TRANSFER

Disc Holder Disc Carrier

Carousel rotation

D-H Rotation Carrier motion

Discs transferred between Disc Holders and Carrier

Each disc has 4 pins on each side to fit 4 holesEach disc has 2 SidesThere are 5 DiscsEach has (up to) 4 Orientations

160 pins & holes to align reliably & reproduciblyor something will bend / break / jam

Pin – hole clearance is +/-- 0.5mm

3 sigma positioning < 0.5mm

Position to < 0.15mm for varying loads on Carousel

CM25 Engineering 4 4 Nov 2009

DISC TRANSFER OPERATION

Need to understand this in detail

Forces & reactions

Potential fouls

Friction?

Some latches for pins will help

Being developed

Space is limited

CM25 Engineering 5 4 Nov 2009

• Not easy to achieve required accuracy of 0.15mm or better• Air motors overrun (but deliberately very slow now)

• Now use piston to align Carousel arm• Measured misalignment is ~ 0.5 mm

• Depends on load (lead is heavy)

• Design was not tolerant of any misalignments• Have incorporated float + springs in carrier

• for L – R and U – D misalignment (1mm / 0.3mm)

• Developing overrun & locking mechanisms for discs• Keep pins aligned in disc-holders & absorb overruns

• More springs… .

• Building mock-up of Disc-Holder – Carrier arrangement• Test various ideas for locking the pins • Develop transfer procedure – invisible on real device

• Allowed 9 weeks in schedule for this (& other tests)• May need more inspiration & imagination

• Transfer operation development on critical path

CM25 Engineering 6 4 Nov 2009

DISC XFER MOCK-UP & PIN-LOCKS

CM25 Engineering 7 4 Nov 2009

STILL TO DO

Hardware– Install & commission:

– Shaft encoder read heads– Black / gold rings for disc-holder alignment

Firmware– Develop FPGA firmware & RS232 interface

– Incrementally

Software– Develop LabView controls

– In parallel with firmware

Once LabView controls developed migrate to EPICS– Would be a distraction at present

CM25 Engineering 8 4 Nov 2009

SOME OTHER CONCERNSCompressed air pressure in Oxford is rather low

– Would like > 6 bar; can get 4 – 5 bar depending on other users– Need to understand how speeds depend on P

– Can possibly improve a bit– Motors run a bit slow

Hope overruns are small & do not depend critically on pressure

Installation on Spectrometer Solenoid– Flatness of end plate (align to small fraction of mm…)

– Awkward; may need shimming

Operation in magnetic field– Most – but not all – ferromagnetic components eliminated

– esp. v. small bearings in gear boxes on motors– Have spare motors; run with field off ??

Quenches– Potentially large forces

– Distortion & loss of critical alignment

CM25 Engineering 9 4 Nov 2009

ASPIRATIONAL SCHEDULE