IMACS Engineering Run, Oct 05
- IMACS Engineering Run, Oct 05
- Overview
- Tasks
- Report
Overview
Goals:
- Recover IFU capability
- Fix slit mask insertion mechanism
- Install Delrin plates with slots to replace existing rails
- Build and install channels to constrain slitmasks along their edges (see Frank)
- Understand encoder stability (is it OK? what automatic tests are available?)
- Analyze "No mask in slot" error; fix it?
- Analyze "does not init when told to" error on mask server; fix it?
- Adjust wings on IFU (too narrow now; see Dave)
- Pin wings on IFU (prevents later misadjustment)
- Nighttime checkout of IFU optics, alignment, etc. (Plan from Dave)
- Make progress to correct rotational imbalance (see this
![[WWW]](/wiki/img/moin-www.gif "[WWW]")
email from Charlie Hull) - Redistrubute weight on disperser wheel. Write a plan. Move MOE next to hole?
- Weigh and find CG of every disperser.
- Overall balance analysis (start with Charlie's document)
- Develop counterweight scheme for disperser wheel
- Consider solution for centerfield guider balancing
- Get MMTF weight and CG in Pasadena
- Discuss assist motor for IMACS pros and cons. Pro: only one project, little continuing adjustment (minor weight movements not needed), easy fix for centerfield guider. Con: requires controls, likely to burn out rotator motor if it malfunctions or fails.
- Write recommendation for how to fix the rotational imbalance
- Review detector stage flexure performance, perhaps reviewing the lookup table for piezo stage (Dave)
- Begin campaign to tighten/replace/Loctite screws throughout the instrument so they don't come loose (Tyson)
Other things to work on:
- New sensor status window available in the user (observing) GUI (Christoph in Pasadena)
Tasks
SMS
- change rails in SMS
- investigate proximity sensor function and alignment
- check that three spring loaded rollers are installed (along upper track)
- check state of fixed rollers
- inspect frames for missing proximity sensor metal trips
- inspect frames for loose screws and hardstops
- investigate slit mask motion when inserted
- measure mask flexure wrt SMS base and guider motion stage
DSS
- assemble change tool and demonstrate use
- investigate DSS errors as reported last week
Miscellaneous
- look into dewar coolant plumbing issues
- change coolant plumbing
- investigate disperser server balance
- investigate instrument balance
- look into changing MOE prism angle
- look for MMTF cable and connectors
- inspect guider drive chains
- platform bench progress
Report
SMS
- Initial inspection of the SMS showed it to be performing as expected. To start, the SMS was cycled through several mask insersions and functioned properly. The slots on the cassette and the v-groove rollers appeared to line up at each postion. Next, mask were commanded to the insert position and with the air pressure turned down, inserted manually to get a feel for the force required to insert the masks (force required to overcome the spring force applied by the spring loaded rollers).
- Mask assemblies were inspected next. All hard point fittings and sensor trips were inspected. Two mask assemblies were found to have a loose hard point screw on the top wing. All others were found to be finger tight, but could be further wrench tightened a 1/4 turn. All sensor trip hardware (two on each assembly) were found epoxied in place.
- All long slit mask assemblies were inspected and found slightly misaligned. The masks were realigned with the mask alignment jig. This procedure was demonstrated to D. Osip and M. LeRoy.
- The sensors on the mask stage were inspected and found to be firmly affixed in their mounts, as was the 'mask in' sensor on the instrument.
- The locating screws on the slit mask base were found to be tight. With a mask inserted, the fixed roller at the end of the bottom line was finger turnable with a minor amount of friction between the roller and wing. Further, a gap between the mask hard point and locating screw was discovered. If the cammed v-groove rollers were loose on their axel screws (as suspected when the IFU fell) then it is highly likely that an inserted mask is not longer held in proper alignment. These issues are most likely the cause of the mask motion during the night.
- New delrin slide blocks were installed in the cassette. A 0.6 mm shim was placed under the bottom block to reduce the slot gap and provide for insertion key clearance.
- The (0.020") spacers between the SMS and FOS disk (for horizontal alignment) where replaced with 0.010" spacers. This was required to align the upper slots with the vee groove rollers.
- The position of the proximity sensors were adjusted for the new rails, but the vertical motion of the mask (due to the slot gap) is at about the limit of the sensor distance range. This problem should be resolved when the new sensors are installed.
- Slit mask motion was measure (with the Heidenhein digital linear gauges) to be +/- 2 um (when inserted).
- IFU motion was measure to be +/- 3 um (when inserted).
- Slide blocks should be remade with blind mounting holes (as originally designed), add tapped holes to use all mounting screw possibilities (as allowed by the cassette frame), change groove profile to be more trapazoidal (reducing mask motion perpendicular to insertion motion).
- (Bottom) block could be 0.6 mm thicker (due to slot width and insertion key interference issues).
- Making the grooves on the slide blocks more trapazoidal would reduce motion perpendicular to the sliding motion. Also, these blocks could have a slight lead-in to allow for minor misalignment on return to the cassette.
- The trailing edge on mask wings do not have a chamfered lead-in of any kind (they are almost knife-like sharp) and scrape the Delrin slides when returning to the cassette.
- Lack of a lead-in on the leading edge of the wing and mask motion perpendicular to the groove in the slide block appear to be the cause of mask 'jamming' against the first v-roller.
- Consider labeling frames and wings (this would help with troubleshooting problem mask assemblies).
- Consider drilling wing screw access holes in mask frames.
- Add M4 washers to wing screws (to better distribute clamping force).
- Consider adding pins at wing/frame interface.
- A rail guard should be added to the SMS mounting base that would stop unintended insertions of misaligned masks.
- The latch pin groove on the wings could be opened up to allow for more forgiving pinning action.
- A spare insertion key should be made (reduce the neck diameter to 5 mm and add tapper to key).
DSS
- Moved MOE from position 3 to postion 5 to improve wheel balance.
- New revision of change tool proved difficult to use and further development is needed.
Miscellaneous
- Delivered parts for Clay GCAM to P. Jones
- Temperature reading on Chip 3 is malfunctioning (current reading is -247 C)
- send mask file to cut new 0.7 arcsec long slit mask
- Located MMTF Bulkhead Feedthrough Couplers
- 1 x LEMO RGJ.2B
- 1 x LEMO RAD.1S
- 3 x LEMO RAD.00
- Changed plumbing on dewar. Installed new Swagelok Miniature DESO Quick Connect fittings and Swagelok vinyl tubing.
- Panel 10 has surface damage (torn by earthquake clip) and should be replaced.
- Panels need new (more permanent) labels.
General Notes
- Normal operating functions shouldn't flag as errors
- when inserting IFU or CFG
- guide camera 'collision errors'
- Required Parts
- order M6 washers
- M6 x 10 FHCS for the slit mask assemblies
- Future Work
- revise change tool design
- replace worn 1/2 turn compression panel latches
- repair panel 10
- place new lables on panels
- replace plumbing hardware on CFG - 2X 1/4" Swage to 1/8" FNPT 90 deg elbow
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2008-11-21
