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Entry  Wed Apr 4 12:52:33 2018, awade, Summary, Drawings, Drawings: 2in windows for vacuum can flang and clamp VacuumViewportDesignNotebook.ipynb.zipTwoViewPort_10inchBlankFlange_Modified_v1.PDFTwoInchViewportRetainingRing_v1.PDF2inchWindowAssemb_3degangling_0.5degWedge.PDFSolidWorksFiles_NewVacCanFlanges.zip
    Reply  Wed Apr 11 16:06:31 2018, awade, Summary, Drawings, Drawings: 2in windows for vacuum can flang and clamp 2inchWindowAssemb_explodedView_50frameswtblur_medium.gif
       Reply  Fri Apr 13 11:34:09 2018, awade, Summary, Drawings, Drawings: 2in windows for vacuum can flang and clamp, steve's comments 
Message ID: 2171     Entry time: Fri Apr 13 11:34:09 2018     In reply to: 2168
Author: awade 
Type: Summary 
Category: Drawings 
Subject: Drawings: 2in windows for vacuum can flang and clamp, steve's comments 

I discussed the 2-in window flange design with Steve.  He had a couple of suggested changes.  I'm adding them here for reference as I update the drawings.

He says the angling of the optic into the main flange is fine, 8" 40m flanges have this design.

Changes:

  • The retaining ring should be made of Delrin, this will be more forgiving on the optic when at atmosphere if there happens to be any contact points.  Also easier/cheaper to machine.  The retaining ring is only there to hold the optic in place when not under vacuum;
  • The six #8-32 holding screws should be changed to four #10-24 s.  Orient these equidistant and with lower edge parallel to the table. No helicoil.;
  • Assembly drawing says o-ring part number #2-130 but description is is #2-223 (which is the next size class up). Choose one. The both are good in terms of groove size but maybe choose the smaller one;
  • Include screw part in assembly table;
  • It would be best practice to include a Teflon gasket on the flange side of the assembly between window and metal. Probably a thickness of 0.090".  Even if there is still an air gap left in the design dimensions. If the tolerances are a bit off then having a soft plastic surface is an good idea, it gives the optic something to rest against that won't apply hard localized stress points;
  • Place centering points on assembly drawing of the front face for two windows. Also, add center line on Detail B view; and
  • The two retaining rings are too close together.  Move spacing from 1.5" to 1.662".  This will mean the beams are not centered on the windows but will give some more space between the retaining rings.

Many of the finishing and tolerance parameters don't matter so much.  Over toleranced parts will cost more.  The only place where this might need to be careful is in the spec of the oring grove where vacuum is actually being held back, the 16 Ra in the drawing is fine.

Marco rubber and plastics have a good summary page for best practice design parameters, see: O-Ring Groove Design Directory.

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