Research and Reviews: Swine 2001

Special Circular 185-01

Particle-Size Evaluation of Grain Fed on Ohio Swine Operations

Results and Discussion

Roller Mills

Roller mills accomplish size reduction through a combination of forces and design features. If the rolls rotate at the same speed, compression is the primary force used. If the rolls rotate at different speeds, shearing and compression are the primary forces that reduces particle size. If the rolls are grooved, a tearing or grinding component is introduced. Course grooves provide less size reduction than fine grooves. One advantage of roller mills is that little noise or dust pollution occurs with properly designed, operated and maintained roller mills. Also, slower operating speeds do not generate heat, there is very little moisture loss, and particles produced tend to be uniform in size with very little fine material compared to hammer mills.

Roller mills provide a very energy efficient grinding or rolling process that has potential to produce uniform particle sizes. All roller mills share the following design features, but come in various sizes.

• A delivery device to supply a constant and uniform amount of corn to be ground.
• A pair of rolls mounted horizontally in a rigid frame, with one roll in a fixed in position and the other in a movable position with respect to the fixed roll.
• The rolls counter rotate either at the same speed or different rates.
• Roll surfaces may be smooth or have various grooves or corrugations.
• Pairs of rolls may be placed on top of one another in a frame.

Micron sizes achieved for 13 corn samples obtained form commercial feed mills and on-farm roller mills are shown in Table 2. The low, average, and high particle sizes were all within the acceptable range and possibly even smaller than typically desired for ground corn.