Hammer Mill or Roller Mill: Advantages & Disadvantages

Hammer mills and roller mills have been at the center of many debates in recent years. Although roller mills often seem to get the better of these debates, both systems have different supporters because both have their own advantages and disadvantages under different conditions. Wayne Cooper, Feed Mill and Machinery Expert from Anderson Feed Technology, evaluates these two systems and classifies their usage areas.

Wayne Cooper
Feed Mill and Machinery Expert
Anderson Feed Technology

So the topic of the month is hammer mills vs roller mills. Not much of a question for me because I am highly prejudiced about this particular subject. In short, look at hammer mills like this: “Let’s toss a piece of corn up in the air and try to hit it with a hammer and make little pieces.”

Yes, you can quote me any time to anyone. The following discussion would be fun. All sarcasm aside, (sorry for that) the hammer mill is a brute force instrument. Yes, you have breaker plates and hammers at high speed. But the essentials are still the same. Hammers hitting corn in the air… Man, that eats up a lot of energy. The other part of the problem is complacency. That hammer mill has been here for 50 years and it’s still running! Why should I replace it? Well, one reason would be your electric bill but we will come back to that.

Roller mills: Roller mills are at least a bit more refined. They control the corn kernels and literally squeeze them into smaller particles with a bit of counter revolution movement to help out. The rolls effectively grab the kernels and pull them through, which is not a pretty sight when it is fingers involved instead of corn. So do utilize the lock out/tag system, PLEASE! The rolls are huge and solid metal. If they aren’t operated properly, the maintenance bill goes up in a hurry. Some managers prefer to operate hammer mills simply because they can perform maintenance in house, without outside venders. And they don’t like seeing the bill. Automated controls for roller mills are not cheap but pay for themselves rapidly in time, maintenance, and parts wear. The level of adjustment down to .1 mm and the ability to stay perfectly parallel are impressive. A side benefit is the auto-adjustment for control of micron size as the incoming grain changes.

Although you have some large bills when changing rolls, overall your cost to grind grain will be significantly lower when using roller mills. An added benefit is particle sizes that are consistent, mash feed with less dust, and less kilowatts. Those are my reasons for the prejudice towards grinders. Roller mills work well, as most of you know, down to a certain particle size. Then your roller mill simply operates with the rolls too close together and maintenance issues rear their ugly head. That dictates when to utilize hammer mills. So my guidelines are as follows:

Use roller mills:
• For mash feed down to 500 microns.
• For large volumes of feed.
• To effectively control particles of all sizes.
• To reduce energy costs.
• In front of hammer mills when doing large volumes.

Use hammer mills:
• For particle sizes under 500.
• For pelleting. We need some of the fine dust for “glue”.
• When you need multiple particle sizes but volume dictates only one machine.
• For multiple ingredients. (Some of us have had to grind ingredients other than just corn.)

We recently designed a grinding system for a fair amount of volume but they needed both hammer mill and roller mill feeds. The triple roller mill was placed over the grinder with bypass options. The system could use any or all of the rolls then go through the hammer mill or bypass it for rolled corn. We could roll corn to any specified micron size before entering the hammer mill. If doing volume, it will pay for itself.

I will (sort of) apologize for the sarcasm in this article but it was done to get your attention. Too many mills are complacent about using hammer mills and it costs them money. Now one last item, if you have a better method to grind corn than either of the two methods discussed, my number is 712 346 8308! Thanks for reading. ‘Til next time!

About Wayne Cooper
Wayne Cooper operated and supervised feed mills in Iowa for 23 years before taking on the job of Director of Feed Technology for the Cherkizovo Group, Russia’s largest feed manufacturer. This production had an extreme focus on pelleting as every ton from all seven mills was pelleted. Those years allowed him to see an international version of the feed industry and the technology on both sides of the Atlantic. His problem solving experience is now used to optimize feed mill production for the clients of Anderson Feed Technology.