Lack of materials refers to the phenomenon that the injection material is not completely filled with the mold cavity of the plastic shell, resulting in the incomplete plastic shell, which usually occurs in the thin-walled area and the area away from the gate. For some internal is not important and does not affect the appearance of the undernote can not be adjusted, if you want to adjust it may lead to the appearance of the cap. There are many reasons for the lack of glue and underinjection, mainly the following situations: 
1. Insufficient injection plastic material. Moderate adjustment until plastic shell filling complete. 2. The temperature of injection molding machine barrel is too low. When the temperature of the barrel is low, the viscosity of the hot melt adhesive is larger, and the resistance of the mold filling is also large. 3. Injection pressure or speed is too low. The filling process of hot melt adhesive in the cavity lacks sufficient impetus to continue to flow to the long distance. Increase the injection pressure, so that the hot melt adhesive in the mold cavity always get sufficient pressure and hot melt adhesive supplement before condensation hardening. 4. Insufficient injection time. It takes a certain amount of time to complete the injection of a certain weight of the plastic shell, if the time is insufficient, it means that the injection amount is insufficient, and the injection time is increased until the plastic shell is complete. 5. Improper pressure preservation. It is mainly premature pressure transfer, that is, the pressure holding switch point is adjusted too much, and the remaining amount of hot melt adhesive is supplemented by the pressure holding pressure, which will inevitably make the plastic shell insufficient weight and underinjection, and the pressure holding conversion position should be re-adjusted to the best point to make the plastic shell complete. 
6. The mold temperature of the plastic shell is too low. When the shape and thickness of the plastic shell change greatly, too low the mold temperature of the plastic shell will consume too much injection pressure, appropriately raise the mold temperature or reset the mold channel. 7. The nozzle is not compatible with the mold gate of the plastic shell. During injection, the injection nozzle overflows and loses part of the hot melt adhesive. Adjust the plastic shell mold to make it fit well with the injection nozzle. 8. The nozzle hole is damaged or partially blocked. When selecting the back production, the injection nozzle and the plastic shell mold are easy to make the injection hole smaller due to the continuous impact for a long time, that is, the material flow channel becomes smaller, the area specific volume of the material strip increases, which will cause the cold material to block the injection nozzle hole or consume too much injection pressure. The nozzle should be removed for repair or cleaning, and the forward termination position of the seat should be appropriately reset to reduce the impact force to a reasonable value. 9. Rubber ring wear. The wear gap between the check ring and the thrust ring on the screw head is large, which can not be effectively cut off during injection, causing the hot melt adhesive material measured at the front end to produce countercurrent, loss of injection weight, resulting in incomplete parts. Verify the ring wear method: After the last cycle of injection is completed, the manual operation mode is changed, and the injection pressure and speed are adjusted to a lower value, and then the material storage is completed. At this time, when observing the manual execution of glue shooting, the screw position indicates the degree of obstruction of the progress of the ruler, that is, the degree of leakage of the rubber ring is checked. The less blocked, the greater the degree of leakage. For the large degree of wear of the rubber ring, should be replaced as soon as possible, otherwise forced production, product quality can not be guaranteed. 10. The plastic shell mold has poor exhaust. During the injection process, the air in the mold cavity of the plastic shell mold is too late to discharge from the parting surface or the thimble gap, resulting in the final hot melt adhesive being blocked by the high pressure of continuous compression in the mold cavity, leaving a defect that is blocked and cannot be fused at the end of the hot melt adhesive flow. Set up a moderate exhaust channel at the position where the parting face should be blocked. If the choke level is not in the parting surface, use the original sleeve or thimble to change the internal exhaust can also be used, or re-select the gate position, so that the air is discharged according to the expected position. 11. Plastic shell rib is too thin or too deep. These are easy to store air dead Angle, is also difficult to fill the mold, should be thickened the rib glue or increase the root arc Angle, the most thorough method is to increase the exhaust groove. 12. Uneven diverter or gate access. Due to the continuous improvement of the manufacturing technology and design level of the plastic shell mold, the flow path design of the single head mold is mostly reasonable and meets the molding requirements. Here refers to the multi-cavity flow channel distribution, often there is a small difference in the gate, will lead to the injection of hot melt glue into the cavity of the uneven weight, so that some cavity filled, some cavity is still underinjection.
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