How to avoid transition marks due to change in flow rate while using Sequential gating?

[Nagarjun]

Hello, I have a query regarding transition marks while molding using sequential gating. These transition marks are mostly evident in dark coloured parts. There is also an issue with colour change especially while using Black coloured PP. Different zones of the part appears in different shades of Black you can call it as patch marks. Part weight is around 1200 gms; Part Name Door panel, No of sequential gates 7; RM is PP+20% Talc filling.
Request you to suggest possible remedies for this concern.

Regards,
Nagarjun.

[Pilot]

hi, if is mouldflow study availble, please check the proper timing fot cascades.
sometime is not possible to follow right cascade opening and you have to adjust filling speed in relatioship to gate opening.
Is also better to open only one gate in one time, the pressure drop will be smaller. Is hard to say, what is better. It depends on part.
you can aslo try to use slower injection speed and switchower point set on 99.9% of filling with small holding pressure for short time.

Next possibility is to use electrical FLEXflow for ex. https://www.hrsflow.com/ww/en/products/flexflow-family/flexflow-evo-servo-driven-valve-gate-system

[rickbatey]

The color changes are more than likely due to the flow direction changes and enhanced by the pigment particle shape from the colorant. We’ve seen this many times and our process fill pattern could be TOTALLY different from the MoldFlow.
I’ve used all of the gates open to start showing me what fill patterns were totally unacceptable. You may even end up not using 2-3 of the gates in the mold!
Rick