1️⃣ Why Powder Segregation Happens
Although powders often appear uniform, they are actually a mixture of particles with different sizes, shapes, and densities.
When vibration, shaking, or free fall occurs during conveying or feeding, larger particles tend to separate from smaller ones, leading to what is known as powder segregation.
This segregation can have serious effects on product consistency and process stability.
In industries such as food, pharmaceuticals, ceramics, or plastics, maintaining uniform mixing ratios is essential for quality control — making segregation prevention a key engineering issue.
2️⃣ Mechanisms of Powder Segregation
Powder segregation occurs through several mechanisms:
- Percolation (size segregation): Larger particles roll down or fall faster, while smaller ones remain on top.
- Density segregation: Heavier particles settle to the bottom due to gravity, while lighter particles rise.
- Air entrainment (aerodynamic segregation): Fine particles become airborne and are carried away by air currents.
- Flow pattern segregation: During hopper discharge, powders can form core-flow or funnel-flow patterns that cause uneven layering.
In other words, the conveying and feeding process itself can trigger separation if the equipment or operating conditions are not properly controlled.
3️⃣ Problems Caused by Powder Segregation
Once segregation occurs, it’s very difficult to reverse. The impact can be significant:
- The ratio of components changes, resulting in inconsistent product quality.
- Particle size distribution shifts, leading to unstable reactions or sintering.
- Process reproducibility declines, causing yield losses.
- In critical applications such as pharmaceuticals or battery materials, segregation can even lead to quality complaints or product failures.
Because the phenomenon is subtle yet cumulative, segregation prevention should be addressed at the equipment design stage, not only during operation.
4️⃣ Design and Operational Tips to Prevent Segregation
① Keep powder movement gentle
Reduce drop height and avoid strong vibration or impact that can cause particles to stratify.
A screw feeder can provide steady, low-speed transfer that minimizes turbulence.
② Optimize hopper design and discharge method
Segregation is often caused by uneven flow in the hopper.
Using a central discharge design or an agitator-equipped hopper helps maintain a uniform flow and prevent funneling or bridging.
Adjusting the outlet shape can also help equalize the flow pattern.
③ Integrate mixing and feeding into a continuous process
Segregation often occurs during storage.
If mixing and feeding are performed in a continuous process, the powder stays homogeneous from mixing to dosing, reducing segregation risks.
④ Select a screw geometry suitable for the powder characteristics
Even for powders with mixed particle sizes or densities, stable feeding can be achieved by adjusting screw pitch, diameter, or rotational speed.
The right screw design ensures consistent flow without particle fractionation.
5️⃣ Real-World Example
A ceramic powder manufacturer faced segregation issues when using a gravity-fed hopper system.
Larger particles accumulated at the bottom of the hopper, while fine particles stayed on top, leading to uneven compositions during mixing.
After switching to a screw feeder with an agitator-equipped hopper, the powder was discharged uniformly and continuously.
As a result, the composition deviation was reduced dramatically, improving product quality and yield.
The change also reduced operator intervention and eliminated the need for frequent remixing.
6️⃣ Seiwa Giken’s Solutions
At Seiwa Giken, we provide screw feeders designed to maintain powder uniformity and prevent segregation during conveying and feeding.
- Mini Screw Feeder – A compact, laboratory-scale model ideal for precise feeding of small quantities.
Even fine or lightweight powders can be fed stably thanks to the agitator-equipped hopper. - Standard Screw Feeder – A 20L hopper model designed for stable, continuous feeding in production environments.
Equipped with a built-in agitator and variable-speed control, it minimizes segregation and ensures a uniform flow of materials.
Both models can be customized with different screw geometries and rotational settings to match the specific flow behavior of your powders.nd rotation speed to optimize flow for specific powders.
👉 Learn more about Seiwa Giken’s Screw Feeders↓↓
