Under injection refers to the phenomenon that the injection material does not completely fill the mold cavity, resulting in the incompleteness of the part. It usually occurs in the thin-walled area or the area far away from the gate.
Causes of underinjection
1. Insufficient material or padding. Properly adjust until the parts are filled completely.
2. The barrel temperature is too low. For example, in the process of making plastic shoe rack, when the material temperature is low, the melt viscosity is large, and the resistance during mold filling is also large. Appropriately increasing the material temperature can enhance the fluidity of the melt.
3. The injection pressure or speed is too low. During the filling process of molten material in the mold cavity, there is a lack of sufficient driving force to continue to flow remotely. Increase the injection pressure, so that the molten material in the cavity can always obtain sufficient pressure and material supplement before condensation and hardening.
4. Insufficient injection time. It takes a certain amount of time to inject a complete part with a certain weight. For example, making a plastic mobile phone bracket. If the time is insufficient, it means that the injection amount is insufficient. Increase the injection time until the part is fully filled.
5. Improper pressure holding. The main reason is to turn the pressure too early, that is, the adjustment of the pressure maintaining switching point is too large, and the remaining large amount of material is supplemented by the pressure maintaining pressure, which will inevitably lead to insufficient weight and insufficient injection of the parts. The pressure maintaining switching position should be readjusted to the best point to make the parts complete.
6. Mold temperature is too low. When the shape and thickness of the part change greatly, too low mold temperature will consume too much injection pressure. Appropriately increase the mold temperature or reset the mold water channel.
7. Poor matching between nozzle and mold gate. During injection, the nozzle overflows and part of the material is lost. Readjust the mold to make it fit well with the nozzle.
8. The nozzle hole is damaged or partially blocked. The nozzle shall be removed for repair or cleaning, and the forward termination position of the shooting seat shall be properly reset to reduce the impact force to a reasonable value.
9. The rubber ring is worn. The wear clearance between the check ring and the thrust ring on the screw head is large, so it can not be effectively cut off during injection, resulting in countercurrent of the measured melt at the front end, loss of injection component and incomplete parts. Replace the rubber ring with a large degree of wear as soon as possible, otherwise the production will be reluctantly carried out, and the product quality can not be guaranteed.
10. Poor mold exhaust. An appropriate exhaust channel shall be set at the air blocking position of the parting surface. For example, when making an air quick connector, if the air blocking position is not on the parting surface, the original sleeve or thimble can be used to change the internal exhaust, or the gate position can be re selected to discharge the air according to the expected position.
Post time: May-10-2022