1️⃣ What Are Cohesive Powders?
Some powders in manufacturing are extremely cohesive and difficult to handle. These are referred to as cohesive powders, such as carbon black, titanium dioxide, and silica.
They tend to form clumps because fine particles experience strong inter-particle forces like van der Waals forces or static electricity.Even powders that appear free-flowing can clog hoppers or stick inside screw feeders.
For stable transport and precise feeding, special handling techniques are required.
2️⃣ Why Cohesive Powders Are Difficult to Handle
Poor flowability is primarily caused by:
- Very fine particle size, resulting in high surface area and strong cohesion
- High moisture absorption, which makes particles stick together
- Static electricity causing particle adhesion
- Compaction from external vibration or long storage
Such powders can easily form bridges or rat-holes in hoppers, disrupting uniform flow.
3️⃣ Problems When Handling Cohesive Powders
Using standard feeding systems with cohesive powders can lead to:
- Screw rotation becoming heavy due to material buildup
- Hopper outlet bridging, stopping the flow entirely
- Inconsistent feed rates affecting downstream processes like mixing or reactions
- Manual intervention by operators, creating safety hazards
Thus, cohesive powders can impact production efficiency, quality, and safety.
4️⃣ Design Tips for Stable Feeding
Stable handling requires both equipment design and operation control:
- Agitator-equipped hopper to keep the powder loose
- Smooth hopper surfaces (e.g., stainless steel or fluorine coating)
- Optimized screw geometry to prevent compaction and promote flow
- Air vibrators near the outlet to reduce sticking
Operational measures:
- Start the feeder at low speed and gradually increase flow
- Control humidity during storage to prevent cohesion
- Regular cleaning and calibration of screws and hopper interiors
5️⃣ Practical Examples
For materials like metal oxides in lithium-ion batteries or pigments, cohesion is significant.
Using a screw feeder with an agitator-equipped hopper ensures a stable, continuous feed.
Adjusting screw diameter and pitch allows precise feeding even for fine or micro powders.
6️⃣ Seiwa Giken’s Solutions
Seiwa Giken provides screw feeders tailored for cohesive powder handling:
- Mini Screw Feeder – Compact, for small-quantity feeding. Hopper includes an agitator for smooth flow of cohesive powders, ideal for R&D and pilot trials.
- Standard Screw Feeder – Standard 20L hopper model with agitator and variable-speed motor, ensuring stable feeding even for highly cohesive powders.
Both models can be customized in screw design and rotation speed to optimize flow for specific powders.
👉 Learn more about Seiwa Giken’s Screw Feeders↓↓
