Feed Throats

The feed throat is an extension of the barrel and can be one of the most often overlooked parts in your injection and extrusion process. It needs to be the same ID as the barrel or it will not feed properly. It's the area at the rear of the screw and barrel where the plastic pellets feed into the plasticating screw. It is very important that adequate provision is made to cool the barrel in this region, otherwise the extruder will not feed properly. The hopper or magnet box sits directly on the feed throat. 

A properly functioning feed throat:

• Provides a clear, free-flowing path for plastic granules, powders, and liquids (i.e. liquid color) into the feed section of the screw.
• A bridged feed throat prevents the free flow of pellets into your extruder. Avoiding bridging saves time spent clearing the feed throat and, more importantly, prevents a potentially dangerous safety issue. We have seen the feed throat get choked up, where someone tries to remedy with a crowbar, usually resulting in the tool getting sucked into the extruder and serious issues occur.
• A bridged feed throat allows pressure to build up so high it can blow the plastic and even the hopper to the ceiling.
• Provides for venting of volatiles without providing a condensation area for these gasses.

With a feed throat out of OEM Spec (the ID is worn):

• Slippage
• Production Loss
• Lack of Feeding
• Decrease in ability for polymer to feed
• Energy Cost Increases