×
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

Plastic counterpart for Stainless Steel

Plastic counterpart for Stainless Steel

Plastic counterpart for Stainless Steel

(OP)
I'm working on replacing a steel door frame with a plastic one and looking for high stiffness plastic material which can sustain 50 lbs load without deflecting more than 5". I tried doing analysis on sides tubes of frame (80" long) using uPVC (extruded quality) and results were not so good. Nylon 6 30% glass filled did show better results but I'm looking for even better material, any suggestions?

RE: Plastic counterpart for Stainless Steel

Succesful plastic products typically have _much_ thicker and larger sections than equivalent metal products,
in order to compensate for the difference in flexural modulus, which is shrinking but still quite large.



Mike Halloran
Pembroke Pines, FL, USA

RE: Plastic counterpart for Stainless Steel

(OP)
I did increase the thickness as much as I could but being door frame, not able to increase outside diameter, hence looking for better plastic materials to compensate for flexural modulus for slightly thicker and better cross section than SS.

RE: Plastic counterpart for Stainless Steel

The stiffest plastics typically comprise carbon fiber, which is expensive but slowly becoming less so, and any of several resins whose names I do not recall now, all of which are hideously expensive, only available in a few forms or very limited quantities, difficult to process, destructive to molding machines, or all of the above.

You have painted yourself into a corner, before you really got started.

I suggest you find another project.

Mike Halloran
Stratford, CT, USA

RE: Plastic counterpart for Stainless Steel

Google "pultruded sections" - you might find what you're after.

www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

RE: Plastic counterpart for Stainless Steel

(OP)
How do you think acetal copolymer would do?

RE: Plastic counterpart for Stainless Steel

(OP)
@Pud Thanks, pultruded fiber glass would serve my purpose stiffness wise but I'm not sure about the pricing.

RE: Plastic counterpart for Stainless Steel

Pricing of any plastic replacement will likely exceed that of a simple light-gauge formed steel frame. Steel is cheap! What is your objective in seeking an alternate material?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Plastic counterpart for Stainless Steel

(OP)
@ornerynorsk my purpose was to reduce cost by replacing steel frame with plastic one, looks like I'm running out of luck.

RE: Plastic counterpart for Stainless Steel

Plastic is not a cheap material. Plastic components tend to be less cost than a metal counterpart usually because the processing of plastic is usually a one-step operation so the in-position cost is less.

The cheapest plastic is generally polypropylene. Here in the UK it's currently around the GBP 1200/metric tonne.

www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

RE: Plastic counterpart for Stainless Steel

(OP)
@Pud With plastics i.e. with Nylon 6 same part is costing me $40 and with uPVC it is costing around $20 against $70 for SS . Nylon 6 30% GF brought me closer to the required strength but not up to the mark, other plastics with higher strength are costing nearly the same as SS or even more. So substantially increasing cross section with uPVC and getting the costing done is the option I'm left with unless I find any high strength cheaper material.

RE: Plastic counterpart for Stainless Steel

The mechanical properties of plastics are an order of magnitude lower than metals in terms of strength and stiffness. Composites combine the benefits of both at added cost for manufacturing. Adding a wire or strip of sheet metal can get the strength needed in a plastic part with little material cost added. In large volume, automated manufacturing this can be done at lower cost. But this is new technology and not readily available.

RE: Plastic counterpart for Stainless Steel

(OP)
@compositepro thanks! looks like I'll meet my requirement but cost will significantly go high for this plastic overmolding process?

RE: Plastic counterpart for Stainless Steel

Perhaps wood? Laminated or coated with very thin.. something, could be a lot cheaper.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Plastic counterpart for Stainless Steel

Did you try PPS+40%GF and Nylon+50%GF ?
They were used to replace some metal monitor panel.

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


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