Dislocation trace of injection molding products
Dislocation trace of injection molding products
The halo near the gate occurs at the beginning of the injection, rather than at the holding stage as is usually assumed.
Surface phenomenonThere is a discernible ring around the gate - the center circle if the center gate is used, and the concentric circle if the side gate is used, because the ring size is small and looks like a faint. This phenomenon mainly occurs when processing high viscosity (low fluidity) materials, such as PC, PMMA, ABS.
Physical reasons
If the injection speed is too high, the melt flow speed is too fast and the viscosity is high, part of the surface material near the material mouth is easy to be dislocated and infiltrated. These dislocations will darken the outer layer.
In the vicinity of the material mouth, the flow velocity is very high, and then decreases gradually. As the injection velocity becomes constant, the front flow of the fluid expands into a gradually widened circle. At the same time, in order to obtain low flow velocity near the material mouth, multi-stage injection must be used, for example, slow fast fast. The aim is to obtain uniform melt velocity in the whole filling cycle.
Causes related to process parameters countermeasure
Flow too high Multi polar injection: slow fast fast
Melt temperature too low Increase barrel temperature and screw back pressureMold wall temperature too low Increase mold wall temperature
Design related causes countermeasure
No smooth transition between gate and product Provide camber between gate and product
Gate diameter too small Increase gate diameter
Gate position error Gate repositioning
Product acute angle transition Change the smooth transition
