This is what burn marks are in molding & how to fix them. Go over what a vent is & how they work in molding. Here are a couple thing to try to fix burn marks,
#1 Clean the Mold
#2 Decrease Injection speed
#3 Decrease Clamp Tonnage
#4 Decrease Melt Temperature
#5 Decrease Back pressure
#6 Reduce screw speed
#7 Add more vents if needed
I hope this helps in some way going forward in molding.
