Using Shut-Off Nozzles

In a recent seminar, I was asked the following question…

We often use shut-off nozzles to prevent drooling, are there any other reasons I should use a shut-off nozzle?

My Response
Shut-off nozzles are a great resource to a technician. When processing low viscosity materials, they can reduce the need for excessive decompression. They can also improve material mixing as they may allow for the use of higher back pressures during recovery. Some molders use shut-off nozzles to improve the consistency of the melt density. Shut-off nozzles can also be used to improve cycle time in high-speed applications because the machine can build the next shot while the mold is open.
Another benefit to shut off nozzles is safety… shut off nozzles help prevent the material from exiting the barrel while the mold is open. This helps when a mold is being serviced as well as when an operator is manually removing a part from the mold.
Additional Thoughts
Shut-off nozzles can also be helpful in applications such as micro-cellular molding, liquid silicon rubber, or when using chemical foaming agents.

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