Frozen layer fraction result

The Frozen layer fraction result shows the thickness of the frozen layer as a fraction of the part thickness.

The values of this result range from zero to one. A higher value represents a thicker frozen layer, a higher flow resistance, and a thinner polymer melt or flow layer. A polymer is considered to be frozen when the temperature falls below the transition temperature (Ttrans).

During filling, the frozen layer should maintain a constant thickness in areas with continuous flow because the heat loss to the mold wall is balanced by the hot melt coming from upstream. When the flow stops, the heat loss through the thickness dominates, resulting in a rapid increase in the thickness of the frozen layer.

Frozen-layer thickness has very significant effects on the flow resistance. The viscosity exponentially increases with decreasing temperature. The thickness of the flow layer is also reduced as the thickness of the frozen layer increases.

The effect of the thickness reduction can be roughly estimated with the definition of fluidity, as with representative shear rate. The fluidity is proportional to the cubic power of the part thickness. A 50 percent reduction in part thickness reduces the fluidity by a factor of eight, or increases the flow resistance by a factor of eight. A 50 percent reduction in thickness in runners reduces the fluidity by a factor of 16.