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Hammer Mill Application Focus: Grinding Grains for Animal Feed

Posted by Cassie Brown

Mar 29, 2013 9:37:00 AM

Producers of animal feed all know a simple truth: when processing cereal grains for animal feed, finished particle size matters.  A lot.corn before and after hammer mill processing

Blendability, and digestibility – even the economics of feed production – are all affected by the finished particle size of the grains.  But this is not a one-size-fits-all situation.¹  The ideal finished particle size varies by the grain being processed, and depending on the species, the life stage of the animal.²  With all of this in mind, selecting the proper method of size reduction is a critical decision.


Roller Mill or Hammer Mill

Unlike the angular shaped particles produced in a roller mill, the pulverizing action of the hammer mill results in particles that are more rounded. These smoother surfaces make it easier for the grains to be blended with other components of the feed.²


So Many Hammer Mills

A hammer mill is essentially a steel box surrounding a rotor. Swinging hammers attached to the rotor, flail out when the rotor spins. A screen covers the discharge opening to regulate the finished particle size.

As material enters the hammer mill, it is pulverized by a combination of hammer blows, particle on particle contact, and impact with the walls of the hammer mill. The material remains in the grinding chamber until it is able to pass through the screen covering the discharge area.

But those are just the basics. There are myriad styles of hammer mills: industrial mills, full circle screen hammer mills, horizontal grinders, tub grinders, and more.  As for size, hammer mills can range in size from 6” to more than 60” rotor widths.  Choosing the right hammer mill for your purposes depends greatly upon the material you are processing, and your production goals.


The Full Circle Solution

The design of the full circle screen hammer mill makes it the ideal method of size reduction when processing cereal grains for animal feed.  Let’s take a closer look:


With swine operations reporting that up to 75% of their budget is allocated for feed production,³  the need for energy efficiency cannot be overstated.

As its name suggests, the full circle screen hammer mill differs from the traditional industrial hammer mill because it has nearly double the screen coverage of the rotor:

 screen coverage for full circle screen hammer mill                       screen coverage for industrial hammer mills                                     

    Full Circle Screen Hammer Mill                                 Industrial Hammer Mill


The greater screen coverage of the full circle mill means that there is more area for the material to evacuate the grinding chamber. As a result, a higher throughput rate can be achieved at a lower horsepower in comparison to industrial hammer mill models.  

Particle Size Flexibility

Precision and consistency of the finished particle size has a strong effect on the digestibility of the feed.  A finished particle size that is either too large or too small will have adverse effects on animal performance.²

The primary factor determining finished particle size is the measurement of the perforations in the screen covering the discharge area. The size of these perforations is equal to the maximum finished particle size of the material processed.

The ideal particle size range of 650 to 750 microns³ can easily and consistently be achieved through proper screen selection. In addition, screens can easily be changed to accommodate the processing goals of a variety of grains using the same hammer mill.

The secondary factor in determining finished particle size if the speed of the hammer mill. When the rotor spins, the hammers flail out and impact the material with great severity causing it to break down.  As a result, the higher the rotor speed, the greater the number of hammer mill blows, and thus a finer end product.  An optional component for the full circle screen hammer mill is a variable frequency drive electrical control. This control panel allows the operator to raise or lower the rotor speed as needed for different applications.



The pulverizing action of the hammer mill produces a finished particle that is easily blendable. The nearly 360 degree screen coverage of the full circle screen hammer mill allows for the greatest throughput to horsepower ratio of all hammer mill designs. A consistent and precise finished particle size can be achieved by screen selection. Finally, the ability to change screen size, and the option of a variable speed frequency drive control, enable processing a variety of grains using the same hammer mill.



¹ Steinhart, Terry L., Iowa State University (2012). Swine Feed Efficiency: Influence of Particle Size. Retrieved from  http://www.swinefeedefficiency.com

²Pork Production in Mississippi is Particle Size Important for Swine Diets?(2013). http://www.msucares.com/livestock/swine/particle.html

³Sayler, Julie. (2012). Small Particle Size Makes a Big Difference.http://swineperformance.vitaplus.com/2012/04/small-particle-size-makes-a-big-difference/  

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Topics: finished particle size, full circle screen hammer mills, variable frequency drive, size reduction equipment, corn, animal feed, cereal grains

Hammer Mills: 5 Key Styles You Need to Know About

Posted by Cassie Brown

Apr 12, 2012 3:50:00 PM


You Need a Hammer Mill for That…

So, you have a material that you would like to make smaller for a given purpose. Sounds simple, right?  Well, in most cases it is. However, there are a number of considerations that must be made to get you to the finish line in the most efficient and  most economical way.  

But First a Little Background

Hammer mills are just one type of machinery among the much larger category of size reduction equipment that also includes:  shredders, jaw crushers, ram fed grinders, roll mills, ball mills, and more. Looking a bit closer, even within hammer mills, there are several styles to choose from. Among those styles, the functionality of a hammer mill remains basically the same:
  • Material is fed into a grinding chamber
  • Contact with moving hammers, and interior mill components reduce the material’s size
  • Material remains in the hammer mill’s grinding chamber until it is able to pass through a screen or grate with certain size openings.
The following is a comparison of five key styles of hammer mills:


Gravity Discharge Industrial Hammer Mills

Industrial hammer mills have the simplest and most recognizable funtionality. A rectangularindustrial hammer mill steel chamber houses a shaft to which swinging hammers are attached. As the shaft rotates at high speed, the hammers flail out impact the material. In addition to the hammers, size reduction occurs through particle on particle contact and through contact with the breaker plate inside the grinding chamber. Because of their simplicity, the industrial hammer mill is easily adaptable to different sizes and milllab scale hammer mill  designs.
Important to know: Replaceable steel liner plates protect the mill's interior from wear caused by grinding abrasive materials.
Ideal Applications: glass, coal, coke, dry chemicals, metals, resin, porcelain, aggregates, brass, ceramics.



Pneumatic Discharge Hammer Mills

The grinding mechanism of this group is quite simliar to the gravity discharge hammerhigh production industrial grindermills. However, the pneumatic mills typically use a thinner hammer and the interior wall of the grinding chamber features a ribbed liner plate. This plate has a washboard effect on the material, and works in unison with the hammers and particle on particle impact to reduce the material. finish grinding hammer mill with integral fanThe biggest difference of course is the group's the use of air assitance to evacuate material from the mill. Whether attached to the main mill shaft, or as a separate optional component in a high production model, the fan pulls the the material through the mill, and conveys it to storage.
Important to know:  Specially designed notched hammers are ideal for tearing and shredding. In addition to assisting the evacuation of  light or low density materials, the pneumatic suction can increase throughput up to 400% over gravity discharge hammer mills. 
Ideal Applications:  hogged wood scrap, wood chips, green wood, biomass, paper, carpet, meat and bone meal 


Full Circle Screen Hammer Mills         

This next group also features the same grinding mechanism as the first two, and the same thin hammers as the pneumatic hammer mills. The amount of screen coverage is what sets the full circle screen hammer mills apart.  
high production full circle screen hammer mill The nearly 300 degree coverage of the rotor translates to a greater surface area for the processed material to evacuate the grinding chamber. As a result, compared to the industrial mills, you get greater throughput per horsepower with full circle screen hammer mills.
diagram of circ-u-flow screen coverageImportant to know: To achieve the circular, nearly full coverage of the rotor requires that the screen be somewhat pliable and therefore relatively thin. Because of this, the full circle screen mill is best suited for light, easy to grind materials to that do not require initial grinding against a breakerplate.
Ideal Applications: corn, grain, spices, grasses, planer shavings, sawdust


Horizontal Infeed Hammer Mills

The unique quality of the horizontal infeed mills is that material is fed into the side of the hammer mill, instead of the top. This design makes them ideal for long, linear or horizontal trim scrap grinderotherwise large, geometric materials to be processed with out a pre-grind. This group includes trim scrap grinders and pallet grinders. As with the prior styles, the horizontal mills use heavy duty screens covering the discharge area to determine finished particle size.
Important to know:  the style and design of the hammers aggressively moves the material into the mill. Feed rolls are ideal to properly control the rate that material enters the grinding chamber.
Ideal Applications: trim scrap, truss palnt scrap, 2x4s, whole pallets, pallet scrap



The Lumpbreaker is quite different from the prior categories in both designsingle rotor lump breaker and functionality. Instead of swinging hammers attached to a shaft rotating at high speed, the lumpbreaker has stationary hammers attached to a slower moving shaft. As the shaft rotates, the hammers remain rigid, and pass between combs attached to the wall of the grinding chamber. Lumpbreakers do not use screens for sizing. Instead, the configuration of spacing between the hammers and combs, along with hammer size and RPM allows some control over the finished particle size.
Important to know: The open infeed, fixed hammers and slow shaft rotation give the lumpbreaker the ability to accept a certain amount of a headload, making it suitable for large blocky materials, de-agglomerating, de-lumping, and returning materials to a flowable consistency.
Ideal Applications: sugar, cement, dry chemicals, agglomerated powders

Broad Categories

For the purpose of this post we broadly examined five of the more common styles of hammer mills. It is important to note that each of these categories could be further broken down to highlight the scope of its variables.

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Topics: full circle screen hammer mills, particle on particle contact, size reduction equipment, industrial hammer mill, hammer mills, hammer mill design styles, gravity discharge industrial hammer mill, liner plates, pneumatic discharge hammer mills, ribbed liner plates, air assist, low density materials, abrasive materials, horizontal infeed hammer mills, trim scrap grinder, pallet grinders, feed rolls, stationary hammers, hammers and combs, deagglomeration, delumping

The Industrial Hammer Mill: A Versatile Workhorse

Posted by Cassie Brown

Mar 7, 2012 8:56:00 AM

One Design,  Many Applications

The basic design of the industrial hammer mill is really quite simple:

  • A steel chamber containing a shaft to which rectangular steel hammers are affixed.
  • Replaceable plates lining the mill's interior to reduce wear caused from grinding abrasive materials.
  • Steel screens or bar grates cover the mill's discharge opening.
Material is fed in through the top of the mill. Once in the grinding chamber, it is reduced by a combination of repeated hammer blows, particle on particle impact, and contact with the walls of the mill. The material will remain in the grinding chamber until it is reduced to a size that is able to pass through the screen covering the mill's discharge opening.
The simplicity of this design makes it a very versatile hammer mill, one that can be adapted to suit a wide variety of materials, such as:

 industrial hammer mill applicationsr

 Similar, Yet Different

The same hammer mill for fishmeal and coal?  Well, yes and no. The basic framework of the mill is the same. However, the configuration of the variable components is how they differ. That determination is based on the following criteria:

  • Material being processed -  Material characteristics such as: friability, flowability, moisture content, and infeed size
  • Desired finished particle size  - Gravel, granules, powder?
  • Desired production rate - 10 lbs/hr, 10 tph, etc.

With this information, the following can then be determined:

  • Hammer mill size - Rotor diameters between 6" and 44", and internal mill widths of 6" to 72".
  • Hammer size and style - Number of hammers, size, style and metallurgy.
  • Screens or bar grates - Style and thickness of screen or bar grates, and size of openings.
  • Choice of proper RPM
It's Optional
Finally, once the the mill is configured, the last determination is whether or not any optional peripheral equipment is needed. For this, the following questions must be answered:
  • How will the material be fed into the mill? By hand, auger, or belt conveyor?
  • How will the material be taken from the mill? Heavy materials such as stone or metal may evacuate via gravity, while light or low density materials will require pneumatic suction.
  • Is dust a concern?

Answers to these questions will help to determine the best types of optional equipment such as belt conveyors, augers, rotary feeders, and dust collection, as well as the most efficient design of the infeed and discharge chutes.  

And that's about it...If you would like more information, please click below to download our free eBook!

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Topics: finished particle size, hammer mill, hammer configuration, bar grates, moisture content, hammers, internal liner plates, size reduction equipment

Laboratory Scale Hammer Mills - Top Five FAQs

Posted by Cassie Brown

Feb 14, 2012 9:50:00 AM

Whether it is space constraints or small production, a laboratory scale hammer mill is often the right choice for size reduction.  Often used for testing and batch sampling, common installations include: colleges and universities, government testing facilities, and pilot plants.

laboratory scale hammer mill dimensions

Below are answers to the top five questions we receive about our laboratory scale hammer mills:

1. Can my material be processed in a lab scale hammer mill?

The laboratory scale hammer mill has the same full range of capabilities as larger industrial hammer mills.  Applications include: chemicals, glass, food waste, biomass, lathe turnings, metal powders and much more.  Material infeed size and production goals are the ultimate determining factors on whether or not a lab scale hammer mill is suitable for your operation.

2. How durable is the lab scale hammer mill?

The lab scale mills are constructed based on customer specification. The options include carbon steel and 304 or 316 stainless steel. Stainless steel models feature all stainless steel contact surfaces. Replaceable internal liner plates are also an option, The liner plates protect the grinding chamber from wear that results from processing abrasive  materials.

3. Can a lab scale hammer mill produce multiple particle sizes?

Yes. In an earlier post we discussed the factors determining particle size. In short: the screen size, shaft speed and hammer configuration selected give you the ability to steer the particle size in any direction you require. This principle holds true with the lab scale hammer mill as well.

Hammer configuration is determined by the material and processing goals, and is generally not changed once mill construction is complete. However, shaft speed and screen size are quite flexible. Screens can be purchased in multiple sizes and are easily interchanged. The smaller the opendings in the screen, the finer the product that is produced.  An optional Variable Frequency Drive (VFD) control allows the operator the ability to control the rotor speed. Faster rotor speed results in harder and more frequent blows, where as a slower speed allows for a tighter particle size distribution.

lab scale hammer mill variable frequency drive

4. Is the lab scale hammer mill scalable?

Absolutely. The lab scale hammer mill is, quite simply a miniature version of larger production models. Thus, the lab scale hammer mill production results can be extrapolated to that of its larger counterparts.


5. What can I expect in terms of set-up and maintenance?

The lab scale hammer mill is fully assembled upon delivery. The operator simply needs to connect the mill's motor or control panel to the main building power source. The top of the hammer mill hinges open to allow easy access for cleaning, screen changes and hammer rotation. As with larger hammer mills, optional dust collection systems can be integrated if needed.


Download our eBook: Industrial Hammer Mills- A Versatile Workhorse


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Topics: finished particle size, particle size, hammer configuration, variable frequency drive, internal liner plates, laboratory scale, size reduction equipment

Welcome to Shop Talk

Posted by Cassie Brown

Feb 14, 2012 8:26:00 AM

Crush, grind, pulverize, shred... Size reduction is fascinating!

Welcome to Shop Talk, the official blog of Schutte-Buffalo Hammermill, LLC. We are a Buffalo, NY based manufacturer of custom engineered size reduction equipment, and we aim to become your trusted resource on its design, manufacture and usage. But first, a little background...


Yeah. It is a mouthful. Frequently misspelled and often mispronounced, but our verbose trade name has an interesting origin.

Back in the late 1920s two size reduction equipment manufacturing companies emerged in Buffalo, NY; each with their own distinct focus.

Schutte (pronounced shoot-ee) Pulverizer Company focused on processing organic materials, building an extensive line of gravity and pneumatic discharge hammer mills, earning them a leadership role in the fields of wood waste reduction and feed and grain processing.  Across town, Buffalo Hammermill Corporation was applying similar principles to more industrial applications such as mining, metals recycling and dry chemical processing.

Fast forward to 2001 and the two companies have merged. The result was Schutte-Buffalo Hammermill, but bigger changes were still ahead. In 2004, company President Tom Warne and General Manager Jim Guarino joined forces to purchase the company from retiring owner, Harry D. Schutte.

Small but Mighty

Post merger and now post acquisition, the new incarnation of Schutte-Buffalo Hammermill is still a company small in size, but one with an ever growing impact.  Even today the staff numbers just under 30, and 90% of the equipment fabrication takes place in "The Shop" adjacent to our corporate headquarters here in Buffalo.  However, we have seen tremendous growth in recent years.  Presently, our installations number more than 16,000 worldwide, serving a wider variety of industries and applications than any other size reduction machinery manufacturer.

Continued Innovation

A key component in this growth and the overriding theme of the Warne / Guarino era has been innovation. Building on the success of Schutte-Pulverizer Co. and Buffalo Hammermill Corp, the time proven principles of size reduction technology and manufacturing have been applied to new and burgeoning applications.

Industrial hammer mill technology originally used to process coal and bulk chemicals has been adapted to de-manufacturing electronics for recycling, and for dismantling spent military munitions.  Similarly, machinery developed for processing wood for mulch production or animal bedding has been applied to processing wood for a myriad of bio-fuel applications.

Just to name a few...

Stay Tuned

Size reduction is amazing! And the application possibilities are virtually endless. In future posts we will share our knowledge about the principles of size reduction and our experiences in greater detail. Some of the general topics will include:

    • The basic principles of size reduction

    • An in-depth look at different hammer mill components and their functions

    • Applications: from the commonplace to the very, um.. unique materials processed in hammer mills.

    • A comparison of the different types of size reduction equipment and their uses.

And much more!

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Topics: hammer mill, bio-fuel applications, processing wood, size reduction equipment, Schutte Pulverizer Company, mulch production, de-manufacturing electronics, Buffalo Hammermill Corporation, Schutte-Buffalo Hammermill

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