When should you consider to us hot runner system?

When:

1. The resin is sensitive to shear rate

2. The part is big or thin wall

3. The cold runner is too long

4. The part is heavy

Below is the advantage of hot runner china injection mold

1. No waist for sprue or runner, no need to grind and recycle them

The recycled material has gone through the “heat-history”, it raise the rate of material degrade, color change. Especially when the cold runner is heavier than the part. Also recycled material is easier to mix with other impurity.

2. Shorten the cycle time

The cold runner is usually thicker than the part wall and it’s closer to the injection machine nozzle so the temperature is higher, it comes to a result the runner takes more time to cold down then the part, also the opening of the runner plate is also increase the cycle time

3. Reduce the size deviation in multi-cavity mold

Multi-cavity mold will face the problem of “corner effect”, because the turning in the runner, there is a difference with the shear rate of the melt by the inner side and outer side, the cavity with same turning side are tend to be filled faster than other cavity. This will cause the difference in packing time thus cause the deviation of size

4. Reduce the rejection rate

The temperature in hot runner can be precisely controlled separately. The plastic melt goes into the cavity, the result is same quality parts.

5. Eliminate the post-process, facilitate for production automation

Hot runner eliminate the post-process such as gate trimming and runner recycling, also facilitate for automatic production

6. Widen the range of molding

Lots of molding technology is developed by the base of hot runner technology such as PET pre molding, two-color mold, multi-material injection, stack mold .etc

But hot runner also have it disadvantage:

1. If the mold is low-volume the cost may higher than cold runner mol

2. If the material stuck in the manifold and nozzle tip could degrade

3. Hard to change material color