×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Sapphire Optics

Sapphire Optics

Sapphire Optics

(OP)
   I am working on an optical system that must be sealed to IP65 and will be used in a mine.  There is very little room in the housing because we are going for the largest aperture possible and the smallest housing.  If I glue the window in with RTV, I will save space and it will be sealed and somewhat shock protected.  I expect this thing to be abused.

   Has anyone here worked with sapphire windows?  I understand they are scratch resistant.  How shatter resistant are they?

   My alternate design is a glass window with a clamp.  This will be cheap enough that we can ship spares, and fairly easy to replace, but I would rather not provide the space for it, especially if I want my seal to work.

   Thanks.

                       JHG

RE: Sapphire Optics

How thick is the window going to be?  If you expect it to survive impacts, then you'd need tempered glass.

Sapphire is used for windows for a variety of applications (http://www.crystalsystems.com/abssa.html), but it's probably much more expensive than tempered glass.  

TTFN



RE: Sapphire Optics

(OP)
IRstuff,

   I do not know yet how thick it will be.  The vendor's manuals claim that it can be thinner than a glass window, but I do not know what the parameters are.  

   It will be more expensive than the first glass window.  After that, it depends on what we break.  :)

                          JHG

RE: Sapphire Optics

If you expect lots of impacts, then you'll need some sort of grid or other sacrificial agent.

TTFN



RE: Sapphire Optics

Sapphire in simple geometries and modest sizes is surprisingly, well, not all that expensive.  And it is hard and strong.

It's also birefringent.  Beware.

Mike Halloran
Pembroke Pines, FL, USA

RE: Sapphire Optics

For shock resistance you want to go as thin as you can. The integrity of the mount is most imprtanat. Depending on how you mount, any flexure will crack the window.

There are several way to mount the window. If space is critical, i would sugest a cirular window. Machine the mount so that the window rests on a "knife edge".

To adhear, you best choicese are:
Glass frit (Dimet)
Structural epoxy, optically match, (TRA-CON 2151 I think)
RTV, theopticl standard being RTV 566

If you are making many of these, I suggest the Glass frit activiated with and inductor, for experiment, you can just stick you assembly in the oven.

Material choice is probably the most important.

CTE MUST BE MATCHED!!

Quartz, Saphire - Invar or zerodur
Pyrezt, BK7 - Kovar
Amorphus Quartz - Titanium
And so on


Hopw this helps

RE: Sapphire Optics

(OP)
canyoncruz,

   My plan with the RTV was to fixture the window about 1mm away from the structure, then fill the void with RTV.  This provides some springyness and it works around thermal expansion somewhat.  I am trying to save weight.  I strongly prefer aluminium to invar.  

   Definitely, I will look into your RTV specification.  Thank you very much.

                      JHG

RE: Sapphire Optics

Fastening saphire windows with GE rtv 566 with a 1 mm bond gap will probably be the best you can do BUT you must use the recommended primer and allow it to fully cure. (equivalent material is nusil cv2566)

_A fem analysis would set some guidelines for performance but will not likely deal with scratches, titanium mount hardware is probably best thermal match next to Kovar or Invar.
-Book by P Yoder on mounting optical element recommended reading.
-Alternate may be 3M 2216 translucent bonding which remains somewhat flexible and is good at high temperatures as is the 566.  Also consider DC 1104

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close