Insufficient injection refers to the phenomenon that the injection material does not completely fill the cavity of the mold, resulting in incomplete parts, usually occurring in thin-walled areas or areas away from the gate. Some of the insignificant internal defects that do not affect aesthetics can be adjusted without adjustment. If you want to adjust it, it may lead to the appearance of a fur flag.
The reasons for the lack of attention are many, mainly in the following situations:
1. Insufficient amount of material or litter. Appropriately adjusted to the complete filling of the parts.
2. The temperature of the cylinder is too low. When the temperature of the material is low, the viscosity of the molten material is large, and the resistance during filling is also large. If the material temperature is properly increased, the fluidity of the molten material can be enhanced.
3. The injection pressure or velocity is too low. During the filling process of the molten material in the cavity, there is insufficient driving force to continue the remote flow. Increase the injection pressure so that the molten material in the cavity is fully pressurized before condensing and hardening. The amount of material added.
4. Insufficient injection time. It takes a certain amount of time to inject a certain weight of the part. If the time is not enough, it means that the injection volume is insufficient. Increase the injection time to complete the filling of the part.
5. Inadequate holding pressure. The main reason is that the pressure is changed too early, that is, the pressure switching point is adjusted too much. The remaining amount of material is supplemented by the holding pressure. It is inevitable that the weight of the workpiece is insufficient and the pressure is insufficient. The pressure should be readjusted. Change the position to the best point to make the parts complete.
6. The mold temperature is too low. When the shape and thickness of the part change greatly, an excessively low mold temperature will consume too much injection pressure, and appropriately increase the mold temperature or reset the mold water channel.
7. The nozzle and the mold gate have a bad match. When the injection nozzle overflows, some of the material is lost, and the mold is re-adjusted so that it can work well with the nozzle.
8. The nozzle hole is damaged or partially blocked. When you choose to turn back the production, the nozzle and the mold will be constantly impacted by a long time, so that the injection hole will become smaller by the Zhejiang, that is, the material flow channel becomes smaller, and the area ratio of the material bar is relatively small. If it is enlarged, it will block the nozzle hole or consume too much injection pressure. The nozzle should be removed for repair or cleaning, and the injection end position should be properly reset to reduce the impact force to a reasonable value.
9. Collar wear. The wear gap between the check ring and the thrust ring on the screw head is large, and it cannot be cut off effectively during injection. This will cause the forward end of the molten material to be measured to have a backflow and lose the injection component, resulting in incomplete parts.
The rubber ring wear method has been verified: After the previous cycle injection is completed, it is converted to the manual operation mode, and the injection pressure and speed are adjusted to a lower value, and then the stocking is completed. At this time, when the manual injection is performed, the screw position is observed. The degree of hindrance of the direction of the ruler, that is, the degree of leakage of the rubber ring has been checked. The less the obstruction, the greater the degree of leakage.
For plastic rings with a large degree of wear, they should be replaced as soon as possible. Otherwise, production will be limited and product quality cannot be guaranteed.
10. Poor exhaust of the mold. During the injection process, the air in the mold cavity is too late to be discharged from the split surface or thimble crevice so that the last-entered melt material is blocked in the mold cavity by the constantly compressed high pressure, in the material flow. A defect that is blocked but not fused at the end.
In the parting plane, a suitable exhaust passage is set for the position of the gas barrier. If the gas barrier position is not on the parting plane, use the original sleeve or thimble to change the internal exhaust, or re-select the gate position. The air is discharged according to the expected position.
11. The parts are too thin or too deep. These are dead corners where air is easy to store. It is also a place where filling is difficult. The ribs should be thickened or the arc angle of the root should be increased. The most thorough method is to add rows. Gas measures.
12. Inhomogeneities in runners or gates. Due to continuous improvement of mold manufacturing technology and design level, most of the flow path design for single-head molds is reasonable and meets molding requirements. This refers to multi-cavity The distribution of runners, often with small differences in the gates, will result in uneven injection of material into each cavity, causing some pockets to fill up, and some pockets are still undershot.