In feed grinding systems, the correct installation of hammer mill screens is often overlooked, yet it has a direct impact on grinding efficiency, particle size distribution, and overall production stability.

Incorrect screen installation can easily lead to low output, screen blocking, excessive fines, and even moisture-related issues inside the grinding chamber. This article explains how to install perforated round screens correctly and why screen orientation matters in real production.

A standard perforated hammer mill screen has two distinct sides:

• A burr side (flared or bell-mouth side)

• A smooth flat side

The burr side is created during the punching process and features sharp micro-edges and a flared hole shape.

Correct installation rule:
The burr side should always face the rotor and hammer direction.

1. Better grinding and screening performance

When material passes through the screen, particles collide with the sharp burr edges. This creates an additional crushing effect while improving screening efficiency, resulting in higher throughput.

2. Improved material flow

The flared burr shape works similarly to the guide holes in a ring die, helping material pass through the screen more smoothly and increasing hammer mill capacity.

3. Higher cutting efficiency

The smooth side of the screen has rounded edges formed during punching. If this side faces the rotor, cutting efficiency drops and fine powder output decreases.

4. Reduced screen blocking

Installing the screen in reverse causes material to hang on the burr edges, leading to clogged holes, poor discharge, over-grinding, and excessive moisture release. This creates a negative cycle that reduces output and stability.

Due to the fan effect of the hammer mill rotor, airflow is uneven inside the grinding chamber:

• Stronger airflow near the feed inlet → coarser particles

• Weaker airflow on the rear side → finer particles and slower discharge

In practice, using a slightly larger screen size on the rear side helps balance particle size, improve discharge, and increase overall capacity.

Operators should also adjust the air compensation openings, ensuring the opened side is opposite to the guide plate direction for balanced airflow.

Correct hammer mill screen installation is a simple adjustment that delivers significant benefits. By installing the burr side toward the rotor and optimizing screen selection based on airflow, feed producers can achieve higher efficiency, more uniform particle size, and longer screen life.