The plastic melt condenses and solidifies before it can smoothly fill in the cavity part far away from the gate or with thin section, thus the cavity is insufficiently filled and the shape and structure of the molded products are incomplete, which is intrinsically due to the low fluidity and poor filling capacity of the plastic melt. While the extrinsic cause is due to the large resistance against filling and the insufficient filling power.
Specific causes for Insufficiently Filled are as follows:
* The plastic melt is provided with high flow viscosity, resulting in poor flow and filling capacity.
* The thermoplastic melt has poor plasticity, excessively low temperature for plastication and unbalanced melt temperature, which altogether result in the poor plastic melt fluidity.
*Mold temperature is overlow or unbalanced,temperature of some parts is too low and temperature of melt injected into the cavity drops too fast.
*The flow of melt in the mold is too long or too complicated,the resistance against filling is large and and the filling is not smooth, even resulting in stagnation.
*Temperature of the nozzle is too low and the cold-slug well of feed system is improperly set, resuliting in jam and stagnation when the front cold material of melt enters the cavity.
*During the filling, molds are not sufficiently aired and the gas has not been discharged in time,thus resulting in the exansion of filling resistance.
Injection Molding Machine
*The actual quantity of injection for the injection machine is too small and the melt required for filling is insufficient, thus directly resulting in material shortage in the cavity.
*The injection stroke of screw is ended and the plastic stocked in the plastication room is scarce, resulting in poor transmission of injection pressure and insufficient poststage power of filling.
*Injection rate of screw is excessively low, the injection pressure is overlow and the filling power is insufficient.
Plastic Products Design
*Wall thickness of products is uneven and the filling resistance is large.
*Wall of products is too thin and the filling resistance is large;above all, temperature of melt drops too fast when it flows through.