Extruder feeding – material bridging and ratholes

There are various forms of materials in product formulas, with different shapes, sizes, and densities.

Bridging occurs when materials interlock or bond together, forming an arch above the container outlet. There are many factors that cause the “bridging” phenomenon: particle size, shape, specific gravity, humidity, static electricity, the cohesive strength and internal friction of a single particle will all have an impact on the “bridging” phenomenon. When this happens, the arched structure holds the rest of the contents in the feeder in place, preventing the remaining material from being discharged.

Bridging prevents the powder from being fed smoothly into the screw, causing high costs and problems downstream.

In addition to powder, other additives such as plastic pellets and glass fibers can also cause bridging problems in the main feeder or side feeder.

To resolve this problem, operators often need to stop the line and intervene by hammering the outside of the feeder.

However, knocking is in vain for the “rathole” phenomenon, and knocking and vibration will only increase the stickiness of the material.

When the feeder is opened, the material does not flow. This is due to the “bridging” phenomenon.

When the feeder is opened, the material flows for a while and then stops. This is due to the “rat hole” phenomenon.

In order to solve various feeding problems, Nanjing Kairong provides various feeders, specially designed for different materials and different applications.



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