Screw Feeder

What is a screw feeder?

A screw feeder is a short screw that delivers powder and granular material from a hopper or silo outlet to the next machine at a controlled rate. It is not meant for conveying over distance but for controlling how much material is delivered, and when.

In gravimetric dosing, the screw feeder is the element that feeds each raw material from its bin into the weigh hopper. As the scale approaches the target mass the screw slows down, and it stops when the target is reached. Weighing accuracy depends largely on how the screw behaves in this final phase.

Where is it used?

• Gravimetric dosing: feeding raw materials in turn into the weigh hopper. Erk’s automatic powder dosing system works this way.
• Mixer and hopper feeding: controlled feeding from a buffer hopper to a mixer or the next hopper.
• Silo and big bag outlets: steady discharge below a big bag discharge station or a silo.
• Other industries: feeding powder and granules beyond plastics and PVC lines.

How it works

1. Hopper outlet: material flows from the hopper into the screw’s inlet section.
2. Conveying: as the screw turns, material advances along the casing and leaves through the outlet.
3. Coarse feeding: at the start of weighing the screw runs fast to approach the target quickly.
4. Fine feeding: near the target the speed drops and material is delivered in small amounts.
5. Stop: the screw stops at the target mass. The stop point is set to allow for material still in the air when feeding ends.

What to consider

• Material flow: fine, cohesive powders can bridge at the hopper outlet. The outlet and the screw’s inlet section are designed to reduce this risk.
• Rate range: where both fast (coarse) and accurate (fine) feeding are needed, screw size and speed range are chosen together.
• Flight form: flight form and pitch are chosen for the material’s flow.
• Wear: for abrasive materials such as calcium carbonate, wear-resistant options are assessed.
• Cleaning: with frequent material changes, easy removal and cleaning of the screw matters.

Common dosing problems such as bridging, flushing and overshooting are covered in powder dosing problems.

Line integration and after-sales

The screw feeder is designed in the same layout as hoppers, scales, mixers and other screw conveyors and connected to the dosing automation. Our screws are built at our factory in Ergene, Tekirdağ; installation, commissioning, operator training, remote support and spare parts are provided.

For a quotation, send us the materials to be fed, the required rate range and the hopper and equipment the screw will connect to.