Injection mold - material change from polyprop to ABS 2

[bithkits]

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.

http://www.martin-electronics.co.za

 

[patprimmer]

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 for tips on use of eng-tips by professional engineers &

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[Demon3]

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

http://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

 

[bithkits]

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

Adriaan.
I am a Mechatronics Engineer from South Africa.

http://www.martin-electronics.co.za