Below is a sketch of a typical vented barrel configuration. The longer screw will facilitate producing a homogeneous melt. In addition, a hood placed above the vent is recommended to remove the volatiles from the molding facility. However, in cases where the material contains a very high level of moisture, the vented barrel process is not capable of removing all of the volatiles. Below are advantages and disadvantages of using a vented barrel.
Advantages Possibly eliminate pre-drying of the material.
Assists in reducing air entrapment in the tool cavity. Possibly avoid the cost of drying equipment for most Capron nylon products, but may require a starve feeder. Easier and quicker material changes. Disadvantages Potentially greater variation in part quality due to inconsistent levels of moisture in the material. Risk of partially clogged vent ports resulting in poor part quality.