Screw Feeder
A screw feeder is a feeder that introduces bulk materials into a production process in a controlled manner using a rotating feed screw.
How does a screw feeder work?
Material enters the screw area from a storage bin or hopper and is transported to the outlet by the screw's rotation. The feed rate can be controlled via the speed of the screw.
Screw feeders are suitable for a wide range of bulk materials – from free-flowing granules to powders and other demanding materials. To ensure reliable feeding, it is essential that screw geometry, material feed, and other components be matched to the properties of the specific bulk material.
What feeding methods are used with screw feeders?
The screw rotates in a screw tube, conveying a defined amount of material towards the outlet. The volume conveyed is influenced by factors like screw geometry, rotational speed, and the properties of the bulk material.
Screw feeders can be operated volumetrically or gravimetrically. In volumetric feeding, the material feed rate is determined by delivery volume and screw speed. In gravimetric feeding, the actually dispensed material is also measured. As a loss-in-weight feeder, the screw feeder can operate according to the loss-in-weight principle: Here, the current mass flow is determined based on the feeding system's weight loss, and the screw speed is adjusted accordingly in case of deviations.
Single- or twin-screw feeder?
Depending on bulk material and feeding task, single- or twin-screw feeders can be chosen. In a single-screw feeder, a single screw transports the material. Twin-screw feeders work with two screws and are particularly suitable for more demanding bulk materials, such as poor-flowing or sticky powders.
Additional components like agitators can support material flow and counteract issues like bridging in the hopper. Consistent and precise feeding depends on the interaction between hopper geometry, discharge aid, screw, and control system.