Whitish mark in the living hinge of flip top cap
Whitish mark in the living hinge of flip top cap
(OP)
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.
Is this normal or if not, what would be the probable causes and why?
Thank you.






RE: Whitish mark in the living hinge of flip top cap
RE: Whitish mark in the living hinge of flip top cap
Pls. refer to the attached photo.
RE: Whitish mark in the living hinge of 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?
RE: Whitish mark in the living hinge of flip top cap
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Whitish mark in the living hinge of flip top cap
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