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.

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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 ! 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.

Producers often ask me whether they should feed a meal, pellet, block, or textured feed for their livestock.  The answer is that the best form of feed will depend on many factors: the type of livestock, if there is more than one species to eat the feed, the productive goals for the animals, the type of storage available, the equipment to handle the feed, the topography and size of the pastures, and the weather, to name a few.

The truth is that any form of feed can work for you.  In any given area, you can find producers that successfully using each form that feed can come in.  These  forms &#; meal, pellets, blocks, tubs, and textured &#; have pros and cons that make them unique.

Meal feeds are those that are made up of ingredients ground to about the same consistency.  If the ingredients are of different sized particles, some segregation of particles can occur.  Also, with some of the smaller species such as sheep and goats, the livestock may be able to pick out the particles they prefer, and leave the others behind, negating the &#;balance&#; of the formula.

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Generally, the ingredients are ground &#;dry&#;, meaning that no steam or moisture was added to the mix.  Some molasses may be mixed with meal mixes, but you have to be careful.  Since most meals have salt and mineral ingredients that absorb moisture, adding a moist ingredient like molasses can cause clumping.

One of the benefits of meal mixes is that you don&#;t have to worry about making the ingredients stick together as you do with a block or a pellet.  With this constraint out of the way, you don&#;t have to give up some nutrition for binding.

If the feed you are using is to be &#;salt limited&#;, then meal mixes work very well since the contact of salt on the animal&#;s tongue is how the &#;limiting&#; works.  So control of intake of meal mixes can be achieved at lower levels of salt inclusion.

Feeding meal mixes requires that you have some type of trough or tub at a designated feeding station.  However, if properly placed in the pastures, this can be turned into a positive in that it helps keep the livestock distributed through the pasture and not clustering together when they hear the &#;feed truck&#; coming.

Pelleted feeds are meal mixes that are mixed with some level of steam and molasses and forced through a pelleting die to form some size of a pellet.  The benefit of pellets over dry mixes is the steam.

Steam on carbohydrate granules in feeds breaks down the outer layer of starch in the granule.  This allows the microorganisms in the rumen to access the starch more readily, increasing the digestibility of the feed.  A general assumption is that you can get around a 10% improvement in digestibility from steaming fine particles as opposed to dry.

The drawback to pellets is that you have to keep in mind that you are forcing ingredients through a pellet die under pressure, and you have to make the pellet stick together.  This requires some level of sacrifice on the part of nutrition.  Pellet size will make some difference in this requirement in that larger pellets can have more abrasive material in them (mineral or salt ingredients), however, they must have more &#;sticky&#; ingredients, like cottonseed meal, to hold it together than smaller pellets do.

Feeding pellets is probably the best characteristic of this type of feed.  The larger pellets (greater than 3/8&#;) can be fed on the ground wherever you find your livestock.  Eliminating the need for troughs or tubs can be a cost savings.  However, if you are in very rough, or sandy country, feeding pellets may be difficult.  Also, pellets can be handled bulk, instead of sacked if you have the equipment for it, saving from $40 to $44 per ton in cost.

Blocked supplements are a unique concept of mixing and holding ingredients together in a large size.  Formulating a ration that will stick together tight enough to slow intake, but leave it soft enough to allow sufficient intake is a learned mixture of science and art.  The drawback is that in order to accomplish this some sacrifices in nutrition must be made.  In order to control intake, salt, binders, and other limiters must be added.  Because of this, the energy level of blocks is lower than other mixes that don&#;t require a limiter, such a pellets that are hand fed.

The big plus of blocks is that they can be fed anywhere.  In troughs, or on the ground, livestock can eat them free choice.  And, hopefully, they will only eat the desired amount each day.  Because they can be placed anywhere in the pasture, they can help with grazing distribution by encouraging the livestock to utilize parts of the pastures that are not used as much as others.

Tubs are a type of feed consisting of mixing ingredients into a liquid slurry, then cooking, or using a chemical binder, it until it gels.  The best characteristic of the tubs is that the surface area softens slowly, so consumption is controlled without salt.  Thus, the energy level can be higher than in the pressed blocks.  One drawback is that they are generally marketed in 250 to 500 pound sizes.  This is not a problem in itself, but producers tend to buy one tub for many head of livestock, and it&#;s questionable whether more timid animals get to eat what they need either through not enough time to get to the tub, or the material in the tub not softening up enough each day.

Textured feeds are those that have ingredients of different particle size, as are used in feedlot rations.  As mentioned before, the drawback to these type of feeds is that smaller ruminants can pick out the preferred ingredients, and leave the others in the trough.  However, the major benefit is that for rations that must contain roughage, such as feedlot rations, it allows for the roughage to be in a coarse form, which is necessary for rumen function.  Fine grinding the roughage parts of a feedlot ration can lead to a faster passage rate through the rumen, which will cause the rumen to become too acidic.  This acidic condition is called acidosis, and if allowed to get extreme, can result in death within 24 hours.

As you can see, each type of feed form has its pluses and minuses.  The form that is right for your livestock and your operation will depend on your specifications.  As I said earlier, any feed will accomplish what you need it to.  However, some will do it more economically than others.  To choose the one that is right for you, compare them for nutritional value, ease of feeding, and the equipment needed for handling it.  Comparing these characteristics among feeds will give you the answer you need.

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