May 6, 2021
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.
Injection Molding Defect:
Mold halves are not centered to each other leading to non-uniform wall thickness and hesitation effect subsequently.
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.
Jan 8, 2019
In injection molding, the resin to be processed is fed via a hopper into the injection molding machine.
The shape of the hopper can be rounded or squared. The hopper leads into a cylindrical drain inlet connected to the screw cylinder.
The hopper can be moved in axial direction before a material change.
This way its content can be released before it is filled with another material.
The filling of the machine hopper is either be done manually or automatically via a central material supply.
Depending on the application, the hopper is often also equipped with dryers or mixers.
Nov 15, 2018
In an injection molding tool, the melt channel between cylinder and cold runner / cavity is called hot runner.
The difference from a cold runner is that the hot runner has at least one heater band to keep the hot runner at temperature.
The melt inside the hot runner stays fluid during the complete cycle and will be used directly for the next shot.
No waste is produced.
Hot runners are used to save material or to avoid weld lines (sequential injection).
Nov 27, 2018
In a hot runner system, the hot runner nozzle is located between the manifold and cold runner or cavity.
As it is the last heated area for the melt, a good temperature control is important.
There are both, open and closed nozzles (valve gates).
Oct 16, 2025
This device is used for precise temperature control in hot runner systems of injection molds. By accurately regulating the heaters in the manifold and nozzles, it ensures a consistent melt temperature, which is essential for uniform cavity filling and avoiding quality deviations. Modern devices feature zone control, diagnostics, and overheating protection. Optimal temperature management reduces energy consumption and extends the service life of tool components.
Regler mit vier Regelzonen
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
