Solutions To The Problem Of Insufficient Filling During Injection Molding

In the field of injection molding processing, it is common to encounter various problems. These problems include breakage, buckling of the front edge, ink flushing at the gate, obvious ejector pin marks, trapped air burning, etc. Among them, insufficient filling (lack of glue) is a common and thorny problem. In injection molding jargon, this is often referred to as "undershot," "short shot," "underfill," or "unsatisfied part." It refers to the failure of the plastic flow to fill certain parts of the mold cavity during the injection molding process, especially in thin-walled areas or end areas of the flow path. This problem occurs when the melt begins to condense without completely filling the mold cavity, or when the molten material enters the mold cavity and fails to completely fill it, resulting in defects in the final product.

Next, let’s dive into this common injection molding problem and possible solutions.

Causes of insufficient filling:

1. Insufficient pressure in the mold, such as the gate is too small, the flow channel is too long, and there are too many turns;

2. Insufficient fluidity of the material and the glue level of the product is too thin;

3. There is poor exhaust in the mold cavity, no exhaust groove or the position of the exhaust groove is unreasonable;

4. Unbalanced filling, which is more prominent in multi-cavity molds;

5. The mold temperature is too low and the water transportation design is unreasonable.

analyze:

1. Insufficient filling is generally determined by the shape of the mold and the fluidity of the material. When the material shortage is caused by the setting of molding conditions, the molding conditions should be set in the direction of good material fluidity, that is, increase the mold temperature, barrel temperature, injection speed, and injection pressure.

2. When the design of the exhaust groove in the mold cavity is unreasonable, it will be difficult to discharge the air in the mold.

3. Pay attention to check whether the flow length ratio of the plastic material is reasonable. The flow length ratio is the ratio of the maximum filling length to the glue level thickness.

Solution:

1. Appropriately increase the mold temperature, increase the barrel temperature, and increase the injection pressure;

2. Add an exhaust groove to the parting surface; increase the number and size of the exhaust ports

3. Appropriately enlarge the gate and increase the flow channel; increase the size of the flow channel and reduce the flow resistance.

4. Avoid uneven thickness of the glue on the product, and try to pour in the thicker position of the glue. The position of the exhaust port should be set appropriately to avoid poor exhaust (check whether the under-injection area is burnt)

5. The position of the gate is designed to ensure that it is filled with thick walls first to avoid retention, which may lead to premature hardening of the polymer melt.

6. Increase the number of gates and reduce the process ratio.

7. Add cold material well design to discharge cold material

8. The distribution of cooling water channels should be reasonable to avoid causing local low temperatures in the mold.