Plastic injection molding parts Dull Areas Near Sprue Improvements
2022/7/26 109

What is plastic injection molding parts Dull Areas Near Sprue?

Apparently, there is a discernible ring around the sprue - if a central gate is used, it is a central circle, and if a side gate is used, it is a concentric circle. This is because the ring size is small and looks like a halo. 


Plastic injection molding parts Dull Areas Near Sprue  Form physical reasons:

If the injection speed is too high, the melt flow speed is too fast and the viscosity is high, and the surface part of the material near the material head is easily dislocated and infiltrated. These dislocations appear as halos in the outer layers.

This occurs mainly when processing highly viscous (low flow) when the plastic injection molding parts use materials such as PC, PMMA and ABS.


Near the material head, the flow velocity is particularly high, and then gradually decreases. As the injection velocity becomes constant, the front end of the flow body expands into a gradually widening circle. At the same time, in order to obtain a low front flow velocity of the fluid near the material head, multi-stage injection must be used, for example: slow-fast-fast. The goal is to obtain a uniform pre-melt flow rate throughout the filling cycle.

improvement measures for plastic injection molding parts Dull Areas Near Sprue.jpg

It is usually thought that plastic injection molding parts Dull Areas Near Sprue  is caused by dislocation of the melt during the holding pressure stage. In fact, the effect of the forward flow effect is to move the melt into the interior of the product during the pressure holding stage.

Reasons and improvement measures related to processing parameters:

1. The flow rate is too high to use multi-stage injection

2. If the melt temperature is too low, increase the barrel temperature and increase the screw back pressure

3. The mold wall temperature is too low to increase the mold wall temperature


Design-related reasons and improvement measures for plastic injection molding parts Dull Areas Near Sprue:

1. The gate and the product form an acute angle, forming an arc between the gate and the product

2. The gate diameter is too small to increase the gate diameter

3. Wrong gate position, gate repositioning