12 solutions for under injection molding

Undershot is when the injected material does not fill the mold cavity, resulting in an incomplete part, usually in thin-walled areas or areas away from the gate. Some minor keys that are not important on the inside and do not affect the appearance need not be adjusted. If it were to be adjusted, it could result in a positive appearance.

There are many reasons for insufficient injection, mainly in the following situations:

1.Insufficient Materials Or Garbage.

Adjust as appropriate until the part is filled.

2.The Barrel Temperature Is Too Low.

When the material temperature is low, the viscosity of the melt is relatively large, and the resistance during mold filling is also significant. Appropriately increasing the material temperature can enhance the fluidity of the melt.

3.The Injection Pressure Or Speed Is Too Low.

The filling process of the melt in the cavity lacks sufficient driving force to continue to flow to the distal end. Increase the injection pressure so that the molten material in the cavity can always obtain sufficient pressure and replenishment before it freezes and hardens.

4.Insufficient injection time.

It takes a certain amount of time to inject a whole portion of a certain weight. If the time is insufficient, the injection volume is insufficient. Increase the injection time until the part is filled.

5.Improper pressure keeping.

The main reason is that the pressure regulation is too early. The pressure holding switching point is adjusted too large. The remaining material is supplemented by the holding pressure, which will inevitably lead to a low weight of the parts and insufficient injection. Should readjust the packing switch position to the optimum point to complete the part.

6.The mold temperature is too low.

When the shape and thickness of the parts vary greatly, too low mold temperature will consume too much injection pressure, so appropriately increase the mold temperature or reset the mold water channel.

7.The nozzle and the mold gate do not cooperate reasonably.

When injecting, the nozzle overflows, and part of the material is lost. Readjust the mold to fit the nozzle well.

8.The nozzle hole is damaged or partially blocked.

When choosing backrest production, the continuous impact of the nozzle and the mold for a long time will quickly make the injection hole gradually smaller. The material flow channel will become smaller, and the area-specific volume of the material strip will become smaller. If it increases, it will cause the cold material to block the nozzle hole. Or consume excessive injection pressure. The nozzle should be removed for repair or cleaning, properly reset the front end of the nozzle, and reduce the impact force to a reasonable value.

9.The rubber ring is worn.

The wear gap between the non-return ring and the thrust ring on the screw head is large. Cannot effectively cut off the injection, the molten material measured at the front end will flow back and lose the injection weight resulting in incomplete parts. The wearing method of the rubber ring has been verified: after the last cycle of injection is completed, switch to the manual operation mode, lower the injection pressure and speed, and complete the storage. The degree of leakage of the apron has been checked—minor blockage and the more significant the leak. For the rubber ring with a significant degree of wear, should replace it as soon as possible. Otherwise, we Cannot guarantee the production quality.

10.Poor mold exhaust.

During the injection process, the air in the mold cavity is too late to be discharged from the parting surface or the gap between the ejector pins, so that the final molten material is blocked by the high-pressure air that is continuously compressed in the mold cavity, leaving the end material flow blocked and unable to fuse defects. Appropriate exhaust passages are provided on the parting surface corresponding to the throttle position. Suppose the air choke position is not on the parting surface. In that case, Can use the original sleeve or thimble to change the internal exhaust, or the gate position can be re-selected so that the air is discharged in the expected position.

11.Ribs are too thin or too deep.

These are dead spots where the air is easy to store, and it is also difficult to fill the mold.  Should thicken, The reinforcing rib glue or the root arc angle increased. The most radical approach is to increase exhaust measures.

12.The runner or gate channel is not flat.

Due to the continuous improvement of mold manufacturing technology and design level, most of the runner designs of single-head mold materials are reasonable and meet the molding requirements—the distribution of multi-lumen flow channels. There are often subtle differences in each gate, resulting in uneven flow composition injected into each cavity so that some cavities are filled while others remain under-filled.

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