×
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

Injection mold - material change from polyprop to ABS
2

Injection mold - material change from polyprop to ABS

Injection mold - material change from polyprop to ABS

(OP)
We have a molded plastic part and the injection tool was manufactured over 10 years ago. The part is a lid/cover for a home electric sliding gate motor.

The tool design was for polypropylene injection molding but we would prefer the material properties of ABS, especially the smooth finish and better rigidity.

Am I correct in saying that the ABS will have about 0.5% shrinkage vs. the 2% of the polyprop?

If we assume that the fit/clearance issue can be solved, is there any foreseeable problem running the tool with ABS?

The tool is modified and run by a third party company so please forgive my lack of knowledge on this topic.

Adriaan.
I am a Mechatronics Engineer from South Africa.
www.martin-electronics.co.za

RE: Injection mold - material change from polyprop to ABS

Without seeing the parts and the mould, I will take a few guesses.

The gates may be to small as PP thrives on small gates.

If there are any undercuts the ABS might stick or on ejection as PP easily jumps over small undercuts.

If there is to much sheer apart from small gate, the ABS might decompose where PP would not.

If the tool has been modified to correct for warping, the lack of warping might actually give the appearance of warping.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Injection mold - material change from polyprop to ABS

Probably best to stick with PP. New grades compete well with ABS on gloss and stiffness. Search for stiffer grades free at www.matweb.com or IDES.

It will save you a lot of headache. Plus I wouldn't make a motor cover out of ABS. Any stray oil and it will fail due to environmental stress cracking.

Chris DeArmitt PhD FRSC CChem

RE: Injection mold - material change from polyprop to ABS

(OP)
Thank you both for the feedback. I think we will stick with PP then.

Adriaan.
I am a Mechatronics Engineer from South Africa.
www.martin-electronics.co.za

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