Whitish mark in the living hinge of flip top cap

Noel.Abaricia · Jul 17, 2017

Hi, I'm Noel, handling injection molding stuffs. I would to ask regarding living hinge problem in PP flip top caps. We observed a whitish mark in the living hinge of the flip top cap. This happened right after ejection in the mold
Is this normal or if not, what would be the probable causes and why?

Thank you.

hendersdc · Jul 17, 2017

Can you provide any pictures?

Noel.Abaricia · Jul 17, 2017

Hi Sir,

Pls. refer to the attached photo.

Noel.Abaricia · Jul 17, 2017

The issue is whitish mark in the hinge part of the flip top cap.
My hunch is that a stress whitening occurred right after ejection of the caps in the mold. I suspect that they have in mold closing mechanism in their injection machine which will flex the hinge (before ejection) to provide orientation . Thus, may result to whitish marks. Is this normal?

MacGyverS2000 · Jul 18, 2017

A 100x100 pixel image is the best you can do?

Dan - Owner

http://www.Hi-TecDesigns.com

Paulkuklych · Aug 14, 2017

Never seen that before.
Could be several things causing it: bad part design, bad mold design or wrong material selection.
Could also be wrong processing conditions.
Needs further investigation.

Paul Kuklych

http://www.improve-your-injection-molding.com

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Whitish mark in the living hinge of flip top cap

Noel.Abaricia

Materials

hendersdc

Mechanical

Noel.Abaricia

Materials

Noel.Abaricia

Materials

MacGyverS2000

Electrical

Paulkuklych

Mechanical

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