In injection molding, the hesitation is one of the situations where molten plastic flows inside cavity with different velocities at the front as a result of different resistance to flow. At a region with higher resistance, the melt front tends to stagnate and slows down. The causes can be high variations in wall thickness and locally low mold wall temperature. The hesitation could lead to molding defects such as short shot, burn mark, air trap and poor part surface.
In perspectives of part and mold designs, the hesitation can be avoided by uniform wall thickness and cooling layout. On the other hand, higher melt temperature, higher mold temperature, and higher injection speed could ease the hesitation during the production.

Hesitation in Plastic Industry

Injection Molding Defect: Mold halves are not centered to each other leading to non-uniform wall thickness and hesitation effect subsequently.

Hesitation in Plastic Industry

Injection Molding Defect: At narrow lines of the filling contour hesitations occur.

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This glossary of plastic industry is provided by PLEXPERT Canada Inc.