Mixers: Considering durability and power
May 9, 2016
by Joanie Spencer
When considering a mixer, or even evaluating the process in general, bakers and manufacturers first discuss the most basic element: what is being mixed. In that context, the focus remains on how the mixer and its process affect the batter or dough.
But the conversation shouldn’t end there. To mix the best possible product while putting the least possible stress on the machine, bakers need to expand their thinking and dive a bit deeper early on into the equipment manufacturer’s design stage.
“The first thing you have to look at is throughput — that’s the starting point for any equipment manufacturer,” said Terry Bartsch, vice-president, sales, Shaffer, a Bundy Baking Solution. Once bakers determine what they’re mixing — and how much of it — a host of important questions should follow in order for the choice of design to fall into place.
Mixing is a punishing process, especially when it comes to dough, so a well-designed mixer must be ready for the fight. “There’s a certain amount of energy that’s required to properly mix a dough,” said Jim Warren, vice-president, Exact Mixing, Reading Bakery Systems. “So you have to think about the dough that’s being mixed and what kind of stress the mixer will see based on that.” For example, a nice, soft bun dough is going to be a much easier opponent than, say, a cracker or bagel dough that has a significantly lower moisture level.
The stiffer the dough is, the harder the mixer will have to work. So when bakers consider the amount and type of dough in relation to mixer specs, they can work with a supplier to determine the proper horsepower to fit their needs. “Different doughs have different resistances, thus different strain on the mixer,” said Patricia Kennedy, president, WP Bakery Group USA. “Artisan doughs need to be treated gently, high-speed bun doughs need high-energy input, and stiff doughs require more mixing energy, thus stronger mixing tools.”
The last thing a baker wants is an under-powered mixer. “For example, to mix 1,000 lb of bun dough, you need a 60-hp motor; to mix 1,000 lb of bagel dough, you need a 150-hp motor,” Mr. Bartsch explained. “Everything changes. The components and the structure, everything, changes because we design around torque.”
Damian Morabito, president, Topos Mondial Corp., also placed a heavy emphasis on the type of dough when designing a mixer. “The absorption of the dough and how much water is in it are important for mixer design and what we call the ‘drive train’ — the motor, gear boxes and timing belts,” he said. “When you work with a stiffer dough, it puts a harder load on the mixer, so you want to make sure the drive train is sized properly.”
And when in doubt, overestimating is the safest bet, especially when it comes to the frame, according to Bill Grutter, vice-president, BakeRite Systems. Regardless of whether a customer is going to buy a 30- or 40-hp mixer, if the frame was designed for 30 hp, and a 40-hp motor goes in, it’s a recipe for disaster. “However, if the frame was designed for 40 hp, and we put on a 30-hp motor, you have a brute mixer with the required horsepower, and it can withstand much more.”
Mr. Morabito agreed, going back to the role played by the dough’s water absorption in determining how powerful the mixer needs to be. “We never like to size a mixer on the edge,” he said. “If we know it’s a 1,000-lb bagel dough, we want to give the customer a 1,400-lb mixer that has ample capacity upwards in case any type of dough happens to accidentally get dryer for any reason.”
In an effort to put less load on the machine, Topos Mondial designs its mixers to mix with a lower final speed. “We configure the bowl so that we effectively knead, not mix, at a lower RPM to get the proper action,” Mr. Morabito said. The result puts less strain on the motor, requires fewer horsepower and takes less cooling.
Batch volume must also be considered. Christine Banaszek, application engineer for Charles Ross & Son Co., explained how this applies when considering a ribbon blender for mixing dry ingredients. “Batch volume, not mass, defines the size of the ribbon blender, but bulk density determines the right horsepower,” she said. “Heavy-duty blenders are typically required for denser products. Running an overweight batch on a light-duty ribbon blender, even when the product level (volume) is below maximum, could overload the motor or lead to more serious mechanical failure.”
This is something that bakers need to consider when looking toward the future, especially when exploring the possibility of expanding product offerings. As bakers start preparing their wish lists for the International Baking Industry Exposition taking place Oct. 8-11 in Las Vegas, they must consider what’s to come. If there’s a chance that lower-moisture products will be made in the future, a mixer’s strength and durability must be prepared for that.
“Every baker will come knowing they’re going to mix something different in the future,” Mr. Grutter noted. “When they buy a mixer for a product today, they must consider if it will still work for them down the road; flexibility has to be there,” he said.
“Getting proper upgrades on bowl and frame, and proper agitator sizing will ensure the mixer can be reused in new applications if the bakery needs to drastically change the product line,” said Alain Lemieux, director of engineering, dough processing, AMF Bakery Systems.
Strength is not just a factor when mixing dough. It should also be considered in the design of a batter mixer, as well. “When we design these frames, even special frames, we do dynamic load calculations to check for any kind of bending moments, or deflections, to be sure that under load, the frame will not deflect,” said Bob Peck, vice-president of engineering, E.T. Oakes Corp.