（31） Incomplete parts (insufficient filling) Injection Molding Process Defect Handling Manual

The main reasons are lack of material and improper injection pressure and speed (including excessive pressure consumption caused by resistance). Insufficient filling refers to the inability to completely fill the molded product.
Normal products will obtain products consistent with the mold, while products with insufficient filling will not achieve the desired shape.
Insufficient filling occurs when the resin fluidity is insufficient or the resin metering value is too low.
1. Machine:
The plasticizing amount or heating rate of the machine is variable, and a machine with large plasticizing amount and heating power should be selected;
The abrasion between the screw and the material barrel or the rubber head causes the material to return and the actual filling modulus is not correct; The actual temperature of the barrel is too low due to heating system failures such as thermocouples or heating coils; The wear of the sealing components of the injection cylinder causes oil leakage or backflow, which cannot reach the required injection pressure; Excessive resistance caused by too small nozzle inner hole or improper nozzle center adjustment leads to pressure consumption.
2. Mold aspect
(1) If the temperature of the part or the whole of the mold is too low, causing difficulty in feeding, the mold should be appropriately raised
(2) The distribution of the mold cavities is uneven. The thin wall thickness of the workpiece causes excessive pressure consumption and insufficient mold filling. The wall thickness of the entire or partial part of the workpiece should be increased or an auxiliary flow or gate can be set near the insufficient filling area to solve the problem. 3) The mold's flow path is too small, resulting in pressure loss; When it is too large, there will be weak glue injection; Too rough can cause dissatisfaction with the product. The size of the flow path should be appropriately set, and the transition between the main flow path and the diversion path, or the transition between the gates or their own turns should be appropriately rounded. 4) The exhaust of the mold is poor. The material entering the mold cavity is blocked by the pressure of the gas that cannot be discharged, resulting in insufficient filling. The gap of the screw can be fully utilized for exhaust or the clamping force can be reduced to use the parting surface for exhaust. If necessary, exhaust channels or pores should be opened. Product shape and mold construction are also causes of insufficient filling. When the gate size is too small and the flow path is too narrow, the fluidity will decrease, which can easily lead to insufficient filling. In addition, if the wall thickness of the product is too thin, it is also easy to have insufficient filling.
Processing and adjustment: The injection pressure is too low, the speed is too slow, the time is too short, the temperature is too low, and the melting position is too small.
If insufficient filling is only caused by insufficient liquidity, it is estimated that there are several conditions:
(1) Low resin temperature
(2) Low mold temperature
(3) Insufficient material fluidity
(4) Low injection speed
(5) Low injection pressure
If the measured value is less than the amount required for the product, it will inevitably lead to insufficient filling. Sometimes it is not only due to insufficient measurement values, but also due to errors caused by poor measurement that lead to insufficient filling. Check whether pre drying has been adequately performed. The recommended drying conditions for each resin are indicated on the product bag. Please compare the actual results with this value.
At the same time, check whether the exhaust port at the flow end is intact. If there are signs of burning, it is likely that the exhaust gas is poor. Try to expand or add exhaust ports.
If a large amount of gas is generated due to the same reasons as above, insufficient filling can sometimes occur at the end of the flow. Appropriate drying must be carried out in advance to remove moisture, etc. Refers to the switching position from injection to pressure maintaining. If this switching position is too early (that is, it shifts to the pressure maintaining stage too early), the overall fluidity will decrease, leading to insufficient filling. Check whether pre drying has been adequately performed. The recommended drying conditions for each resin are indicated on the product bag. Please compare the actual results with this value.
At the same time, check whether the exhaust port at the flow end is intact. If there are signs of burning, it is likely that the exhaust gas is poor. Try to expand or add exhaust ports.