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!

*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.

Jobs

Plastic machining accuracy & surface finish.

Plastic machining accuracy & surface finish.

(OP)
Hi,

I am reviewing a circular part, made by "polypropelene, homopolymer, natural".Which is having o-ring groove for vacuum sealing and oring groove finishing requirement is 16Ra Circular Lay. Most of the dimensions are in 3 decimal(inch)accuracy and +/-.005(for general feature location), +/-.003 for oring groove width.

1) i would like to know whether i can achieve 16Ra in plastic material ?. (i cant go with polishing process on the component because it result cross contamination on the part.)

2) what is the maximum finishing value can achieve by machining on plastic ?

3) what is the dimensional tolerance, we have to go for position the feature from edges, center to center of holes ?

4) what are all the secondary operations i can do on plastics to achieve the finishing value?

Thanks
Vimal VV


RE: Plastic machining accuracy & surface finish.

Can you flame polish the groove? We used to do this with acrylic parts used in vacuum systems.

Timelord

RE: Plastic machining accuracy & surface finish.

Solvent polishing is another technique

RE: Plastic machining accuracy & surface finish.

I don't think solvent polishing will affect PP.

You can get a decent finish by injection molding the stuff to finished size and shape.

If you're attached to starting with sheet or billet, you can probably add features by embossing with a hot iron, but you have to control the process tightly, and it will always be slow.

Mike Halloran
Pembroke Pines, FL, USA

RE: Plastic machining accuracy & surface finish.

Dear Vimalmechs,

By now this info isn't probably new. Vapor polishing normally allows to achieve very low surface roughness, other methods such as cryogenic polishing are used to get well finished optical fibers. I am not sure what do you mean with cross contamination but for example vapor polishing is sometimes used to produce medical devices and there must be a way to go around the contamination issue.

Few months ago I was looking for companies working with vapor polishing and I found an USA company: ConnecticutPlastics they have some nice examples on their website.

Cheers,
Roserio

RE: Plastic machining accuracy & surface finish.

Have a look at din iso 2768 medium. That's what we use on our drawings for plastics.

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


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