×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

nonmagnetic/electrically nonconductive/low outgassing

nonmagnetic/electrically nonconductive/low outgassing

nonmagnetic/electrically nonconductive/low outgassing

(OP)
Hi,

I was looking for the right materials for a rack/pinion design to open a door.  Here are some constraints.
Temp=160F
Pressure=10^-6Torr
all parts must be low outgassing, nonmagnetic and electrically nonconductive.

I thought of using aluminum for the door/rack/pinion since it is nonmagnetic. I then planned on using a class II anodize on the aluminum to make it nonconductive.  However the anodizing will cause high outgassing which is not allowed.  I am unsure exactly what other nonmetals would work under these conditions.  I do know of nylon gears, however I understand nylon becomes brittle at high temperatures.  

Any suggestions would be GREATLY appreciated.

Frank

RE: nonmagnetic/electrically nonconductive/low outgassing

Maybe teflon (not sure bout the out gassing/volatiles thou) other plastics, maybe even bakelite or other filled phenolic, or even an aramid strengthened epoxy. These should all give you your temperature performance. I'm not too sure bout outgassing since Ive only worried with SEM samples and we usually coated the non-metallics under vaccumn helping to remove the volatiles etc before being put into the airlock of the scope.

Can you "bake out" your parts after production, hold at 200F and subject to the low pressure for a few days?

nick

RE: nonmagnetic/electrically nonconductive/low outgassing

Why not use a ceramic coating on a 300 series stainless steel? It would be non-magnetic, non-conductive, and would not outgas. And, if designed properly, it would have the mechanical strength for your application.


                                             Maui

RE: nonmagnetic/electrically nonconductive/low outgassing

The concern with nylon at high temperature is more related to the limiting pressure on the gear surface, since the strength/stiffness decreases with temperature.  I am not a plastic gear expert, but there are a number of heat-stabilized nylons available that should be able to perform adequately at ~ 70 C (160 F).  I would discuss this further with someone from DuPont, Bayer, DSM, etc.

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Maui,
Do you know what that would cost and what companies can do that?   I was thinking of using Delrin, though I am unsure if it can handle the low pressure. I am almost positive it is low outgassing.

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
I have found some gears made from DURACON (M25-44).  Does anyone know if they will survive the temp and press and if they are low outgassing?

RE: nonmagnetic/electrically nonconductive/low outgassing

Duracon is another type of acetal/POM similar to Delrin or Celcon.  Nylon has better heat resistance than acetal.

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Is there a way to make a C1018 steel gear rack nonmagnetic?  I have tested aluminum in the chamber and the fact that it is conductive has not affected the process.  Therefore, the material I am looking for no longer has to be electrically nonconductive, only nonmagnetic.  

RE: nonmagnetic/electrically nonconductive/low outgassing

Macor the machinable ceramic ,,, although it is brittle
Or Pyrofolite , easy to machine, then baked hard

123cat

RE: nonmagnetic/electrically nonconductive/low outgassing

Then its 304SS Trix
123Cat

RE: nonmagnetic/electrically nonconductive/low outgassing

  If the material does not have to be non-conductive anymore, just non-magnetic, why not use a non-magnetic stainless steel (maybe 304) ?  

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Thanks guys.  Now I am looking for 304 stainless or aluminum gears with a max height of 3/8" for the rack but none of the gear companies have responded.  I received a quote from rush gears for close to $2000 for a 6ft length using aluminum!!

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Anyone know if a 3/8x3/8x40" brass rack will outgass at T=160F and P=10^-6Torr

RE: nonmagnetic/electrically nonconductive/low outgassing

Once upon a time when I worked in the vacuum field, we used to have things electroless nickel plated to prevent outgassing. That way you can just use standard components and have them plated. But I don't know how well it stands up from a wear perspective.

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Unfortunately, the budget of this project won't allow the high prices of electroless nickel plating.  But I did think of that option.  That size brass rack was quoted at $250 for plating.

RE: nonmagnetic/electrically nonconductive/low outgassing

Well, it still might be cost effective if by so doing you can use off the shelf stuff. Just a thought.

RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Thanks.  You have a point.

RE: nonmagnetic/electrically nonconductive/low outgassing

Trix4kids,
Agree with choice of either 304 SS or an Al alloy. EN plating would provide wear & galling resistance.

Advise getting more competitive bids on the EN plating. If no masking and an easy-to-plate substrate (i.e., not free-machining leaded crap), 0.001" of mid-phos EN runs $0.10/sq. inch in my area.  [However, your job would be a minimum lot charge of $75]. Surcharges for lengths more than 5 ft and for baking (advisable for gearing).

Lots of machine shops are looking for work. $2000 is outrageous unless there is some geometry I don't understand. What do you mean by a 3/8" high x 6 ft long gear (or is this the rack?).


RE: nonmagnetic/electrically nonconductive/low outgassing

(OP)
Yes that is the rack with a thickness of 3/8" and length of 6'.  I have searched hard for aluminum and nonmagnetic stainless racks but they are all custom jobs with high pricing.  Mcmaster does sell the size but only in brass and magnetic stainless.  The brass rack is about $50.

RE: nonmagnetic/electrically nonconductive/low outgassing

anodized Al is fine for 10(-6) torr, but it has to be done right.

the cheap/quick anodizing processes produce a thick and porous film, but the modern solutions leave a uniform hard film that is abs. okay.

304 ss is non-magnetic until you machine it otherwise cold work.

you can reduce the need for non conductive materials if you incorporate insulating bushings or washers in your design

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!


Resources