×
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

UHMW vs. Delrin

UHMW vs. Delrin

UHMW vs. Delrin

(OP)
I am currently designing a mill fixture. The application of the component that I'm making this particular material selection for will be to hold the flange of a part during a drill operation. It slides up to the flange after the part is loaded onto the fixture, and is then held into place by three 3/4" bolts. Dimensions are 1" X 5" x 59".

Must be:
1) Lightweight so that 1 person can lift and bolt into place
2) Resistant to vibration fatigue
3) Easily machinable
4) Cheap
5) Since it will be on shop floor, it must not break if something bangs up against it.

I've narrowed down my options to UHMW Polyethylene and Delrin and wanted to get some input from people that have worked with both. Is the high cost of delrin worth it? What are some advantages/disadvantages of each?

Thanks in advance.

-Rich

RE: UHMW vs. Delrin

You've given essentially no quantifiable information for anyone to base any recommendation on.

How did you manage to narrow down the options to UHMW or Delrin?

Neither of those materials are particularly well suited for machining fixtures.  They are hydroscopic, and will thus change dimensionally with changes in moisture.

They both have relatively high coefficients of thermal expansion.

Neither are particularly rigid.  

RE: UHMW vs. Delrin

Prefer to work with Delrin and for both you will need very sharp drills, milling cutters etc have you considered Tufnol a superb material to machine  Tufnol.com  

RE: UHMW vs. Delrin

(OP)
Mint.. Thank you for your insight into the properties of these materials. I have narrowed down the choices to UHMW and Delrin because they have low friction coefficients (so that it can slide up and down a guide), and was also told that they have good moisture resistance.. which seems to be the opposite of what you're telling me..? Thermal effects are negligible in this particular application. The mill simply drills pilot holes through a 1/4" aluminum flange, and this part is there to reduce vibration and deflection. There are no quantifiable requirements for this design, simply a need to use a material that will do a good job of supporting the flange through multiple uses.

How do the impact resistances of these materials compare?

RE: UHMW vs. Delrin

Plywood.

RE: UHMW vs. Delrin

(OP)
The fixture itself is made of steel. This part of the fixture only supports the flange. Metal is not an option because the flange support has to be lifted up into its locked position by one person. Given the dimensions, this would be way too heavy.

RE: UHMW vs. Delrin

I have used them both. They are not particularly hydroscopic compared to e.g. Nylon. Delrin is dimensionally more stable and easier to machine, but if you just have to supply a sliding surface UHMW is plenty good and a lot cheaper.

RE: UHMW vs. Delrin

Not sure on all the details, but in the past we have worked with nylon which is easil machinable, unbreakabe, and I think affordable

RE: UHMW vs. Delrin

mxrethoret,

   When I want plastic, I usually specify Delrin because our machinists like it.  I figure I get a cheaper part.  I only specify other plastics when the requirement is tricky, and I need high performance of some sort.  

               JHG

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