I was wondering if anyone of you has experienced similar issue with the one we currently face.
Alongside a chair manufacturer we work on a chair design (full plastic, PP + glass-fiber) and in the edge of the seat and back (front side as shown on the picture bellow), after the injection and the chair's cooling-down process, we notice these white marks. 300 chairs were tested and about 50% showed this problem.
Please note, that the chair after is injected looks fine, but after some hours or even a week, we notice gradually appearing these marks. Also, the injection gate (just one) is located exactly behind these marks. Then, we need strong pressure to inject the plastic and to ensure that the material fills all the cavity.
What we have already tried is to :
a) Raise the mold's temperature
b) Adjust the injection pressure, time and temperature (various combinations) but still no result
c) Kept the chairs a bit longer in the mold before ejecting them
d) Modified the mold in the injection gate area (even enlarged for better flow).
If any of you has any idea how to solve this issue, or at least suggest a new direction towards its solution, please drop a line. Thanks!