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Acquisition Camera: Task-List to check Flexure

Date first created: 02/05/04

Date last modified:02/06/04

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Task1 (Repeat George’s Measurements)a) To Do:b) Remove Cover on

Acquisition Camera=AC and check to make sure all of the guts are bolted down adequately. Also check bolts holding structure together

c) Replace covers, making sure all bolts are torqued down adequately

d) Also, check George Mount bolts

e) Check bolts that secure the XY stage from inside AC

Question: Is this possible without removing the AC from the Telescope? George?

George’s Measurements: 10-29-03 (Phone)a)Attached indicator to George Mount; measured flexure on XY stage; saw from .004” to .006” movement.b)Measured flexure at location of POM; saw .013” movementGeorge: for b) where did you attach the magnetic base to? AO-Spool?

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Task2 (XY Stage)

To Do:

• Check XY stage for proper functioning.

• Check anti-backlash feature.

• Does stage repeat!

• Is the holding torque of brakes adequate to prevent movement of AC assembly?

NOTE:Weights:AC 79 lbsStage 50 lbsGeorge Mount 30 lbsPOM 3 lbs

To check for backlash: Can unit supported by XY stage be moved when brakes are To check for backlash: Can unit supported by XY stage be moved when brakes are on?on?

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Specs for:XYR Stage: XYR-1212-P-5TPI-150SM

Features:

• X-rolled ways

• Hall Limit Switch

• Anti-backlash nut

• Precisions grade

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Task3-1(Deflection Tests)To Do:

Check the stiffness of the interface shown at right

Use Push-Pull scale and indicator (Strain Gauge)

Do this with Telescope at Zenith. Push with 5 lbs and measure deflection at same location. See next slide.

Weak side

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Task3-2

F

Dial GageAttached to AO-Spool withMagnetic Base

Top covers must beon for thismeasurement

Dial Gauge

See also FEA analysis of the support structure at the end of .pptSee also FEA analysis of the support structure at the end of .ppt

Use F=5 lbs, same as in FEA AnalysisUse F=5 lbs, same as in FEA Analysis

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Task4 (POM Assembly Integrity)To Do:

a) Is POM Assembly accessible while on Telescope? George? If so….

b) Check if POM itself is moving in its housing

c) Are Springs working properly?

d) Are Springs made from Spring Material?

e) Are Bendix Pivots clamped tight?

f) Is anything touching the top of the AO Structural Assembly

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FEA on George Mount: Results

This FEA was done :10-29-03

From e-mail to George….Hi, To get an idea for the structural stiffness of the George Mount a simulation was done.  A jpg showing the results of the FEA is attached. (georgefea01.jpg) FEA Model Setup: 1) The Load was taken to be 160 lbs and is acting in the z-direction.(see triad in jpg.) The load is due to the Acquisition Camera and its contents, in addition to the large X-Y Stage. This is a worst case scenario,the case where the telescope would be horizontal. 2) The mounting surface that in practice bolts the George Mount to the AO Spool, is held fixed in the Simulation Model.  FEA Results: The maximum displacement seen in the FEA Model is .0021 inch with a top stress of 1540 lbs/in^2 I recall a number .013 inch that George measured. It appears that the George Mount is not wholly responsible for the flexure. Where does the rest of the flexure come from? The  stiffness of the Structure that holds the POM was analyzed when the Acquisition Camera was built. Deformations were found to less than .001 inch.In this case, a 10 lbs load was assumed for the POM. Further Comments: The structures were analyzed not using any bolted joints. If the bolts in the real structures are not fully tightened, flexures are the result.  A further area to check is the POM and its mounting. Did anything change? Has this flexure been seen when the Acquisition Camera was in place? Has it been measured the same way? Vern    

For an analysis of the Acquisition Camera see end of .ppt

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Acquisition Camera FEA-1POM simulated with a 5 lbs load;Gravity included in Analysis, both acting in –y direction. Max deflection is 0.00094 inch

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Acquisition Camera FEA-2Summary: No deflection greater than .001 inch observed in analysis with a simulated POM load of 5 lbs and Gravity included

Length of Finger is 19.75 inch

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Summary• The .004 to .006 inch movements that George measured between the

George Mount and the XY stage tells us that we need to take a closer at this stage. If memory serves me correctly, the stage was once driven to its ends and had to be forced out of this position.

• Adding the maximum deflections that were obtained in the FEA analysis of the George Mount and the Acquisition Camera we should observe a relative movement from the George Mount to the location of the POM of about .003 to .005 inch.This is nowhere near the .013 inch that George reported seeing.

• Since the Acquisition Camera, when either mounted on the George Mount or on the AO Structural Assembly, is directly coupled to the AO Spool, there should be no differential movement between them.

• George and Doug: Can you please review this document. Give me whatever feedback you can think of. George, there are also some questions for you on some of the slides.