Products Appear Insufficient Melt Glue In The Injection Molding?
When such problems occur, it is necessary to observe the movement stroke of the screw of the injection molding machine while injection molding. Pay special attention to the position of the screw when the pressure is completed and when the glue is completed.
In the first case, the screw position of the injection molding machine reaches the set value, and the position of the injection molding pressure is 0 (the residual glue amount is 0). Possible causes:
1. Leakage. In this case, first check the injection molding machine barrel for leaking glue; whether the matching position between the injection molding machine nozzle and the main bushing of the mold leaks. If there is leakage of glue, the product is not full of glue is a natural phenomenon, should be excluded first. The following checks are performed only if it is confirmed that there is no melt leakage.
When the product is not full of glue, and there is no colloid leakage, it may be insufficient. At this time, it is necessary to increase the melt stroke and increase the amount of glue. After increasing the melter stroke, continue to observe the residual glue amount of the screw, the course of the melt glue and the feeding condition of the product while injection molding.
2. The amount of glue is not enough. After increasing the melt glue stroke, the product is increased in glue, indicating that the amount of glue is not enough, and it is necessary to continue to increase the melt stroke. When the melt stroke reaches the maximum and the product is still not full, you need to replace the large injection molding machine.
3. The rubber meson leaks. For example, as the melt rubber stroke increases, the amount of glue injected into the product during injection molding does not increase correspondingly, which may be the glue leakage of the injection molding machine.
Check the glue meson leaking method: keep the product of a certain injection cycle in the cavity, and use manual injection. The injection pressure is changed from small to large. Observing the advancement of the screw can judge the leakage of the rubber meson. When the rubber is manually injected, the screw does not advance, indicating that the rubber meson is well sealed and does not leak. Under a large injection pressure, the screw has a small amount of advancement, which is allowed. At this time, it is not a melt leakage, but a shrinkage of the melt.
In the case of product dissatisfaction, first of all, it is necessary to check whether there is leakage of glue between the barrel of the injection molding machine and the nozzle of the injection molding machine; secondly, check whether the rubber meson at the front end of the screw of the injection molding machine has leaked glue. Only after the exclusion of these two situations can other aspects be judged. The following determination methods are based on the case where the two cases are excluded and will not be repeated.
The second case: the screw of the injection molding machine can reach the set melt stroke, but it can not reach the set injection stroke (the amount of residual glue). This means that there is melt glue in the barrel, but the injection does not enter the mold. Possible causes of the cavity:
1. The fluidity of the melt adhesive is not enough. The fluidity of the melt adhesive is insufficient, and the flow resistance is large. It is difficult for the colloid to be filled into the mold. This may be caused by the following reasons. :
(1) The raw material itself has poor fluidity;
(2) The processing temperature of the barrel is set too low or the temperature does not reach the set value, such as the temperature display is not true.
(3) The mold temperature is low. Although the colloidal fluidity in the barrel is good, after flowing into the mold flow path, the temperature is too fast, and the fluidity in the mold cavity in the mold flow path is poor, resulting in dissatisfaction of filling.
2. The injection molding process parameters are not set properly.
The injection pressure is low, the colloid can not overcome the filling resistance; the injection speed is low, the melting time of the glue is long when filling, the fluidity is reduced, resulting in a large filling resistance; the injection holding time is short, the filling is stopped before the product is filled, etc. Causes the product to be less than glue.
3. The filling channel is blocked.
Because the cold glue, impurities or other substances block the filling channel and cause the glue to not be filled, the product may also be dissatisfied with the glue. At this time, it is necessary to check the injection nozzle of the injection molding machine, whether the main flow channel, the runner, the gate, etc. are unblocked, and if it is blocked, it needs to be cleaned.
4. Mold casting system defective The defects of the mold casting system are divided into the following aspects:
(1) The flow path is too small, too thin or too long, increasing fluid resistance;
(2) The runner, the gate is rough and has flaws, or has an acute angle, and the surface roughness is poor, which affects the flow;
(3) The cold well is improperly set or not set, and the cold glue collection is incomplete, resulting in blockage of the runner or gate;
(4) The position or quantity of the gate is improperly set, the filling resistance is greater than the injection pressure, and the glue is not charged into the mold;
(5) The mold is poorly exhausted or the exhaust position is improperly set, and the mold is partially trapped and the product is not filled.
5. Poor product design.
The product structure is poorly designed, the glue position design is not uniform, and the local glue position is too thin, resulting in product filling dissatisfaction.