×
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

Help with material

Help with material

Help with material

(OP)
I am in charge of designing a part but I am not familiar with plastics or rubber.  I was hoping some of you pros could help.  Here is what I need:

This part will be used as an insert compressed between two stationary metal pieces.  The part is to prevent scratching or damage to metal pieces, but needs to provide some "grip" as to minimize twisting and slippage.   

1.  Part needs to be molded (odd in shape)
2.  Coefficient of friction needs to be as high as possible
3.  UV stable
4.  Thickness of part will range from .125"-.375"

I have considered rubber but I'm concerned about the "squish factor."  Maybe a very hard rubber??

RE: Help with material

Skinnyj.

The "squish factor" as you call it really isn't that much of a problem - it's the weight of the top plate that counts.  If you are allowed to, send me a .pdf of the application and as much detail as you have available and I'll ask around for you at TARRC.

Regards,
Graham Bennett

RE: Help with material

(OP)
Thanks for the reply Graham.  My application doesn't really make too much sense now that I look back at my original post.  Let me shed some light on this.

A steel collar fits over a steel shaft.  This collar is larger than the shaft, but needs to clamp down on the shaft to provide a slip-free fit.  However, the steel shaft varies in size from shaft to shaft.  We need a molded rubber part that will fit between the collar and shaft.  The rubber parts will range in sizes to accomadate the different size shafts.  I hope this makes sense.

The collar is attached to other hardware and is subjected to some torque.  This is why we need a product to minimize slippage and movement between the collar and shaft.  I was thinking a very hard rubber, but there may be something better for this?

RE: Help with material

(OP)
Oops...I forgot to add that the shafts are about 1.5" in diameter.  

BTW, what is TARRC?

RE: Help with material

Skinnyj - thanks for the clarification.  What you are talking about is essentially a rubber bush.  As torque is applied it would be best to coat both metal surfaces with something like Chemlock adhesive, apply an uncured rubber to the shaft, then fit the collar.  Finally, you need to cure it at elevated temperatures (around 150 or 160°C) in a heated press.  Depending on the torque, a compound with Shore A hardness between 40 and 60 should be OK.

RE: Help with material

What about casting urethane between the two metal pieces?  Does this thing need to be dissasembled?  If not, you could bond them together when casting. A primer is likely required to achieve an acceptable bond to metal.

Regardless of the disassembly issue, many urethanes are easy to work with (pourable and therefore castable)and provide very good mechanical properties.

http://www.conap.com/index.cfm?page=ToolingList

Look at the bottom half of the page under "Flexible Urethane Tooling and Mechanical Elastomers"

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