Mold Fill time is another name for melt front advancement. Our fill time animations provide the visualization of the part cavity filling before your very eyes! As you can see from the animation, phenomena such as race tracking, weld lines formation and air trap formation are easy to visualize. Race tracking is when the plastic flow fills the thicker section of the parts prior to filling the thinner sections. Race tracking moves the plastic in non intuitive ways which will trap air in the tool in places that are hard to vent. The use of the melt front advancement tool solves these problems before the tool is built avoiding the quality problems in the part.