Today's roller mills are an essential part of the American food production chain. Modern flour production depends on the use of grain roller mills to reduce wheat berries into flour. In addition, roller mills are vital to the processing of other grains, including the most important grain in the US today: corn.
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Understanding why roller mills have taken over the grain production industry requires an understanding of both the benefits of roller mills and the historical forces that worked together to give them an edge in the market.
Millstones: The Last Great Thing
Before roller mills, grain processing was done by millstones. Millstones were themselves a tremendous innovation and offered huge benefits when they were invented in the last millennium BCE.
Handheld grain grinder prior to the millstone.Before the invention of millstones, grain was ground using a variation on the metate: a handheld stone that was rubbed back and forth over an anvil stone. Not only was this method arduous, it resulted in the introduction of numerous rocks into the ground grain. This made the flour and any bread produced from it likely to damage a person's teeth. This is part of the reason why Egyptians needed so many dentists.
However, the Indians, Greeks, and Romans independently developed different forms of millstones. The millstone concept is similar to the metate: you have one stone that moves (often called the runner) while another remains stationary (called the sleeper or bedstone). Grain gets caught between the two stones and is ground down. At first, Olynthian runner millstones were moved by a lever over the bedstone. Later, Morgantina millstones were built in a rotary pattern. In Pompeii, relatively large mills were turned by levers pushed by slaves.
Millstone technology reached its peak when people began using wind or water power. This drove the mill better than human slaves or domestic animals could. At the same time, millstones were carved with intricate patterns of raised portions (called lands) and deep furrows, which progressed into finer channels called cracking. The pattern is divided into regular sections called harps or quarters.
Millstones could produce more flour and when the right stone was used, there was much less grit. Millstones were ideal for grinding the soft type of wheat grown in Britain and the Low Countries. Because they were so successful, millstones were used for nearly two millennia with few changes other than the motive power.
The Invention of Roller Mills
However, millstones were not as good at grinding hard wheat, AKA spring wheat, which was mostly grown in Eastern Europe and the US. This hard grain had a bran that tended to shatter in the mill, making it harder to separate from the ground flour. Retained bran tended to make the flour spoil. Not only that, but flour with too much bran had an unappealing appearance and taste. If flour made with spring wheat was to be shippable, storable, and palatable, a new method of milling was needed.
The origins of the modern roller mill begin in Europe. Swiss engineer Jacob Sulzberger began experimenting with roller mills in the s. His most successful installation was at Walzmühle, Budapest in Hungary. At this time, rollers were seen as a supplement to millstones. Stones were used for primary breaking of the grain, and the partly milled grain, called middlings or farina, then passed through rollers to be turned into flour. At Walzmühle, chilled cast-iron rolls were created in the local foundry for use in the roller mills. These rolls soon became the industry standard and were exported around the world through the 19th century. Some roller mills also used porcelain rollers, especially for processing semolina after stone grinding. By the s, corrugated iron rolls began to replace the stones at the early stages of the grinding process.
Industrialization Gives Roller Mills the Edge
As roller mills started to pop up, the ancient class of millers, who had long been prominent figures in local communities, began to see a threat to their status and livelihood. They tried to improve the effectiveness of millstones by modifying the patterns on them, but by this time the technology had largely reached its pinnacle, and they couldn't gain much productivity. However, they retained some advantage: running roller mills from water or wind sources required extensive gearing, which made them complex, noisy, and prone to failure.
With the spread of steam power and belt drives, it became easier to power roller mills. The mills themselves were also quieter, more efficient, and more reliable. The development of more advanced steel made rollers more effective and more durable. By the end of the 19th century, mills were being refitted with rollers and the millstones discarded.
The Breadbasket of Democracy
One of the major centers of milling that changed over to roller mills was Minneapolis, the flour capital of the US. As the population of the US grew through the 19th century, demand for flour skyrocketed, and mills needed to keep up. In the s, mills produced around 500 barrels of flour a day, but as the mills were changed into the much more efficient roller mills, productivity expanded dramatically. By the turn of the century, most mills produced barrels a day or more!
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This was due in part to the use of a series of rollers that created a gradual reduction of wheat berries into flour. Not only was the process more efficient, it produced a higher quality flour that could sell for much higher prices. This drove the expansion of mills to improve profitability.
Wheat production was in high demand during WW1The improvements were timely. They let US wheat production compete on the world stage. Soon, exports of US wheat made the country an essential trading partner around the world. The wheat was especially in demand during the World Wars when grain production in Europe was dramatically disrupted. It was around this time that Automatic Equipment Manufacturing entered the picture. By WWII, our mills were helping grind the flour that fed the soldiers who won the war.
Rolled wheat had been plagued by one disadvantage: it was less nutritious than stone-ground wheat. This is because the processes of rolling grain led to a better separation of the nutritious bran and germ from the wheat, processing the less nutritious endosperm into flour. This eliminates most of the iron, vitamin A, and vitamin B1 from flour. However, fortification of the flour made the rolled flour comparable to ground flour.
Roller Mills and the Rise of King Corn
But roller mills can process all types and sizes of grain, and the growth of roller mills is intertwined with the most important crop in the US today: corn (maize).
Corn is a grain native to the Americas, but it remained a relatively under-cultivated crop for centuries. In part, this was because it was an inefficient crop to grow. Corn yields per acre remained stagnant until the s when productivity per acre began to increase dramatically. This was due to two innovations: the hybridization of corn to make larger ears, and the development of industrial fertilizers that could satisfy corn's tremendous demand for nitrogen. Once corn productivity per acre began to soar, corn became more and more important as an animal feed.
Just in time, too, because by the time Americans returned from WWII and enjoyed the prosperity associated with their newly-won superpower status, they demanded more meat in their daily diet. As a result, corn demand also grew. From to , corn production grew about 8%. From to , corn production soared by 59%!
The spread of corn as animal feed was also facilitated by the development of highly efficient roller mills for cracking. These mills let farmers produce their own feed for a wide variety of animals, from chickens to cows.
Automatic high-capacity roller mill using PTO power.Roller mills became standard equipment at most farms. They were produced in small sizes for use by small family farms and in high-capacity models that helped farmers develop larger-scale operations so America could enjoy the plentiful supply of meat that made it the model of a prosperous democracy, leading to victory in the Cold War. The widespread use of electricity and the development of PTO systems with tractors helped make roller mills even more flexible and useful.
Today, corn is the most important agricultural product in the US. American farmers grow about 8 times more corn than wheat.
The History of Roller Mills Continues
An early Automatic Roller Mill, nearly 100 years ago.Today, Automatic Equipment Manufacturing continues to produce innovative roller mills. We draw on the extensive history of roller mills, including our own history that approaches a century of experience to make mills that incorporate the lessons of history to be efficient and durable. But we are also innovative, constantly seeking to make our mills produce better products, while becoming more efficient and easier to operate.
If you are looking for a roller mill to improve your farming or feedlot operation, we can help. Please contact Automatic Equipment Manufacturing today.
When deciding on the right milling equipment for your operations, its essential to understand your options. Two primary types of machinery available are roller mills and hammer mills. Now, RMS also offers the VersaMill, a direct-drive roller mill that allows for even greater control.
Many people have questions about the difference between a roller mill vs. a hammer mill. Here, we dig deeper into the most commonly asked questions, including what is a hammer mill, what is a roller mill, what are their common benefits and applications, and what machine owners can expect in regard to maintenance for each type of equipment.
A hammer mill acts like the name implies, milling grain with a smashing motion. If you took a kernel of corn and smashed it, you would have multiple pieces with variation in size.
A roller mill acts more like a cutting knife. As one roller spins against another, it creates a shearing effect. Roller mill particle size generally sees lower variance than hammer mills, which results in a more consistent grind.
Hammer mills also use different screen sizes to adjust the particle size for either a coarser or finer grain. Often, they have to shut down their entire mill to change a screen.
On the other hand, roller mills can alter the grind simply by changing the roll position. If you want to achieve a finer grind, you can move the rolls in. If youre looking for a coarser grind, you do the opposite and back the rolls out.
The VersaMill can also control the speed of each roller. Differential roll speeds allow for greater sheer, and an even finer grind than with a traditional roller mill.
Target particle size is a leading factor in determining if a roller mill vs. hammer mill is better for your application. If the material has high moisture, then a roller mill is also generally better. With a hammer mill, you run the risk of the temperature of the product rising as it runs through the machine, which can lead to plugging and increased fire risk.
If a coarse grind is desired, a roller mill can generate coarser particle sizes at a much higher consistency. The pulverizing motion of a hammer mill often leads to more waste in the form of fines than grinding with a roller mill.
Simply put, roller mills are used for particle size reduction, taking raw material and reducing it into a usable size for a given application. They are used to execute consistent, high-quality particle reduction in non-fibrous materials such as grains, fertilizers, coffee beans, and other biomasses.
One key benefit of a roller mill is its ability to produce a consistent grind profile. Due to its grinding process, the distribution of particles sizes is far more predictable than a hammer mill. Another main benefit of a roller mill vs. hammer mill is that it uses substantially less energy. The roller milling process does not produce excess heat and other energy-consuming effects like hammer milling does.
Energy efficiency is becoming a top priority for many mill owners, and roller mills are typically around 25 to 30% more energy efficient than their hammer mill counterparts. The VersaMill is even more efficient than a traditional roller mill because it does not use belts. Its a higher end machine than your typical roller mill, but the energy savings pay dividends down the line.
Many industries rely on roller mills for their operations. Many are upgrading directly from hammer mills to the VersaMill:
This industry relies heavily on roller mills for feed applications where it previously relied on grain hammer mills. Integrators and toll mills that feed cows, chickens, and pigs are implementing roller mills because the machines are an efficient way to achieve the appropriate feed particle sizes for different animals. A feed hammer mill generally cannot compete with the benefits of a roller mill.
These industries depend on a consistent crush profile for the different grains they use to create their products. Because of their reputation for a consistent crush, roller mills are becoming the mill equipment of choice for breweries and distilleries in the United States and overseas.
Many companies and farms on the West Coast are looking to reduce the amount of unabsorbed materials in their products to create a more even application. They need a consistent, fine grind to increase the absorption rate into the water because theyre looking to spray the liquid through a fertilizing unit. A better grind not only allows for better coverage, it also prevents blocking in the application units.
Some businesses in the coffee industry have been employing roller mills to grind up coffee beans for larger companies. For those businesses, the coffee grounds must be a consistent grind, and the roller mill is an optimal way for them to do that.
This is a newer industry integrating roller mills. One example is biochar. This is used as a fertilizer and as a filter to clean out contaminants in water sources and other applications. Biochar comes from wood thats been burned in a vacuum chamber. Often, this wood has to be sized at a consistent output before it can be utilized.
Both roller mills and hammer mills use tooling to reduce the particle size. Like most tools, the hammers used in a hammer mill will wear out and will need to be replaced.
Roller mills use corrugated rollers to reduce the particle size. Those will also eventually become dull over time. How often the rollers will need to be replaced depends on the target particle size, how often the machines are running, and the cleanliness of the grain or product.
Foreign materials such as rocks, cobs, sand, and metal material will reduce the life expectancy of the rollers, in addition to adversely affecting the hammer and screens of the hammer mill. Fortunately, when the rolls become dull, they can be easily taken out and replaced with sharp ones.
To help alleviate some of the maintenance costs of replacing and sharpening rolls, RMS offers a comprehensive Endurance Roll Program to qualified customers.
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