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




This Electrical Engineer is working on some electronics that will be in a small enclosure with free space optics in an industrial application. Are there any standards for outgassing limits for optical components (I don't want to fog the optics). Space electronics use TML (total material loss) and CVCM (collected volatile condensable material) specifications (1% TML and 0.1 CVCM). Are there similar specs for optical components?


RE: outgassing

Interesting. This may be apples and oranges, as I see some RTV compounds qualify for space applications, but the optical engineers that I know avoid RTV like the plague.


RE: outgassing


(1) ar eyou in a pure vacuum environment, where the outgassing will be the only gas being generated?

Are you in a "controlled ventilated" (atmospheric) but very "pure" atmosphere like a IC chip maker cabinet, where atoms/cubic meter matter?

RE: outgassing

I'm in a hermetic enclosure, so my gases are controlled. My light source is a 9 micron fiber optic, so while I don't think I'll be counting atoms, any obfuscation above 0.9 micron in diameter could have a significant effect.


RE: outgassing

Tough call.

It is always easier for a company (an engineer) to call out some "official" specification so the contract appears more "official" than it really is. And, by appearing :official" the contract often gets by review back in back offices easier than if the specifications are made up to fit the real world as it really is. 8<)

Ain't gonna be the case here.

If the outgassing is going to cause a major impact, and if in your judgement as an engineer responsible for the assembly the owner and bid-receiver of the contracted part and assembly are going to be affected by the outgassing of material from the part being bought - then, well, you HAVE to specify in the contract that "Materials supplied will NOT out gas no more than 0.0001 of (material) at (1.234 of wyyz concentration of vacuum at 3.455 of pressure after 1.234 of hours of exposure at 5.678 degrees (C?/F?) for 6.789 hours measured by jklmnop calibrated instrument at s.tuvwy temperature conditions."

YOU are the person writing the contract. For $$$,$$$.$$ YOU get to write the specifications that are needed.

RE: outgassing

Contract, what contract? I just get to design it to the poorly written spec and then take responsibility if it fails. My optical engineers want it 'clean'. Space electronics want 1% TML and 0.1 CVCM. I expect I'll end up somewhere in between.


RE: outgassing

Well, the "contract" is your specific written requirement to another person to the work.

Now, if you are "buying" goods or services from another company, then - well, yes, it is a formal contract we are used to seeing complete with bid specifications and warranties, and "lawyer-talk" about money, etc. But a 'contract": is also a simple drawing or requirement for a welder and supplier in the back office to buy and install a resistor or a motor, weld up a fabricated support for the motor, and hookup a battery strong enough so the rocket motor vibrations won't break both the motor and battery.

What does help while writing the contract/drawing/specification/purchase order is a formal ANSI or NASA or MIL-SPEC because those have been tested and people are used to seeing them. They might be more rigorous than what you need, thus more expensive. But they are also "expected" and so can be delivered at the higher price. A local specification from a local single company might be more expensive, and you are making assumptions - as you wrote above - about the trade-offs.

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


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