How to solve the problem of wire drawing in preforms gate for preform injection molding?
Wiredrawing refers to the phenomenon that during the injection molding process, a long filament will be drawn out from the end of the gate when the mold is opened. This filament is connected to the molten material at the nozzle, or it is disconnected after the mold is opened. Wiredrawing at the gate will not only affect the appearance quality of the product, but also damage the mold due to residual waste matreial, and even affect production efficiency. The main reasons for the wiredrawing phenomenon at the gate of PET preforms include low viscosity of PET material, high injection temperature, unreasonable mold structure design, etc.
Solution
Replace PET raw materials
Ensure that the PET raw materials used in injection molding production have appropriate viscosity within the normal operating temperature range. If the viscosity of the material itself is too low, it is easy to cause wire drawing. This can be solved by improving the mold structure design, optimizing the production process, or replacing the machine injection nozzle etc.
Reduce the injection temperature
Too high an injection temperature may cause the material viscosity to be too low, thus causing the wire drawing phenomenon. It can be reduced the injection temperature or choosed to adjust other suitable preform injection molding process parameters.
Optimize mold structure design
Ensure that the mold design is reasonable to avoid wire drawing at the contact point between molten plastic and quasi-solid plastic. Wire drawing can be reduced by optimizing the mold structure, adjusting the injection gate position and gate size, etc.
Strengthen cooling and pressure holding
Strengthen cooling at the nozzle and hot runner, use high-pressure chillers, or optimize the mold chilled water system to increase the cooling effect, reduce the interface between the molten material and the quasi-solid material, and thus avoid the wire drawing phenomenon. Properly increasing the pressure holding can also reduce the wire drawing phenomenon. Too low a pressure holding may cause the molten plastic to be pulled out to form filaments when the mold is opened.
Through the above measures, the wire drawing phenomenon of injection bottle preform can be effectively reduced or avoided, and product quality and production efficiency can be improved.