Frozen layer percentage at ejection result

The Frozen layer percentage at ejection result represents the percentage of thickness frozen at the end-of-process (ejection).

The values of this result range from 0% to 100%. A higher value represents a thicker frozen layer and a thinner layer of molten polymer. A polymer is considered to be frozen when the temperature falls below the transition temperature (Ttrans).

During the filling phase, the frozen layer usually maintains 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 during the packing phase, the heat loss through the thickness dominates, resulting in a rapid increase in the thickness of the frozen layer. The Frozen layer percentage at ejection result is generated at the end-of-process when the analysis time has reached the summation of filling time, packing time, and cooling time.

Going through solidification, a polymer will gain strength mechanically. Obviously, the mechanical strength of a part is positively correlated to the thickness of the frozen layer. The ideal time to demold a part is when the frozen layer has become thick enough to provide the part minimum mechnical strength required for ejection.

Using this result

This result can be used to detect premature ejection. If the frozen layer percentage at the end-of-process is too low (<50%, for example), the cooling time may need to be extended so that the part can gain more mechanical strength needed for ejection. On the other hand, if the frozen layer percentage at the end-of-process has reached 100% everywhere in the part, the cooling time can be reduced to shorten the cycle time and thus increase productivity.