Many people do not quite understand what is underfill? Simply put, underfill refers to the phenomenon of incomplete material flow end or a part of a mold cavity is not filled.

　　1, the material flow is not good, the material flow can not fill the whole cavity. Countermeasure: we should use the plastic with better flowability.

　　2, mold exhaust poor so that the air or plastic degradation gas can not be discharged, resulting in the end of the cavity pressure is too high, the material flow can not fill the cavity. Countermeasure: In such a case, we can open an exhaust slot at the last mold filling of the melt.

　　3, mold pouring system design is not reasonable, such as: gate location is not reasonable, gate size, runner size is too small, so that the melt flow is not smooth, will cause the material flow can not fill the cavity. Countermeasures: improve the mold runner and gate design, expand the size of the gate and runner.

　　4, material flow front cooling material blocking gate, runner and injection port, resulting in products filled with insufficient, countermeasures: this time should be expanded cold material well size.

　　5、Nozzle and mold mouth R value is not consistent, so that the effective amount of melt and effective pressure decreases, resulting in underfilling, countermeasures: should ensure that the nozzle and mold mouth R value consistent.

　　6, the amount of material is too large so that the effective pressure of the melt decreases, the material flow can not fill the cavity, countermeasures: reduce the supply, can be used to control the supply throttle method of slippery granular material super supply.

　　7, the nozzle temperature is too low, so that the temperature of the melt shot into the mold cavity is reduced, thus causing the mold filling length to be shortened, countermeasure: when opening the mold should make the nozzle and mold separation, reduce the influence of mold temperature on the nozzle, so that the nozzle temperature is kept within the process regulations.

　　8, multi-cavity mold, the casting system is not balanced, resulting in away from the main sprue cavity can not be filled, countermeasures: can be adjusted by adjusting the size of the gate width or make the length of each manifold consistent, casting system balance, so that the material flow at the same time full of cavity.

　　9, multi-cavity mold, the injection speed at all levels is not set properly, resulting in inadequate filling of products, countermeasures: should improve the injection speed of the first level, that is, set high-speed injection, when the material through the gate, reduce the injection speed, lengthen the time.

　　10、Injection stroke is too short to meet the product requirements for injection volume, resulting in insufficient material supply. Countermeasure: At this time, you should adjust the injection stroke and check the material supply port of the particle bridge or adjust the nozzle backflow valve.