The ins and outs of mixers

by Joanie Spencer
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A mixer has a job to do. From the loading of ingredients to the discharge of dough or batter, it must do that job quickly and efficiently to keep everything moving down the line.

“From tricky ingredient input to multiple mixing phases to successful automated discharge sequences, all factors need to be considered for any specific application,” said Alain Lemieux, director of engineering,  dough processing, AMF Bakery Systems. And this applies regardless of mixer size or level of automation. “Small machines using a lot of manual interactions are very different than high-speed lines in enclosed automated environments.”

While many larger operations may have a completely automated feeding system, many small to mid-size bakeries still manually load minor and micro ingredients. “A bakery that is hand-loading ingredients needs to consider the best way to get that done — is it with a platform in back with an ingredient door, or are they going to tip the bowl down and toss ingredients through the front?” asked to Bill Grutter, vice-president, BakeRite Systems.

Bob Peck, vice-president of engineering, E.T. Oakes Corp., also indicated that E.T. Oakes takes ingredient loading into consideration when designing a mixer. “Sometimes customers will want a platform, or mezzanine, with a couple steps up to get height advantage for hand-loading of ingredients,” he said. “They’ll want the machine designed where the control box is at a certain height up from the floor to accommodate that platform and maintain a certain HMI height for the operator.”

In some cases, premixing can streamline the process, which introduces another set of design considerations. Zeppelin Systems USA manufactures a pre-hydration device that can be incorporated into either a batch or continuous mixing operation between the scale hopper and the mixer itself. By eliminating the blending stage in the mixer, stress can be reduced, according to Stephen Marquardt, sales director, food, Zeppelin Systems USA. “That saves the power you needed for the blending stage; the mixer can go directly into the kneading stage, and you can run more batches on your lines,” he explained.

And of course, what goes in must come out, so discharge is also a key factor in mixer design.

“Dough discharge is usually achieved by tilting the bowl, and structural considerations play a big part in determining how efficient this is,” said Keith Graham, marketing manager, Baker Perkins. “The bowl should tilt far enough to invoke gravity assistance and ensure that full discharge can be achieved with no operator intervention,” he said.

The amount of tilt will often be determined by the type of dough being mixed and discharged. “In the old days, 95° mixer was pretty much the standard mixer, and you’d watch the bakers having to cut the dough out. They would take a large knife and slice the dough, then make the mixer back-spin to try and kick it out.”

Today, mixers can be designed with not only 95° tilt but also 120° or 140°, explained Tim McCalip, general manager, Oshikiri. “Now with automated processes, dough comes out of the mixer into an auger-type device that will feed it automatically to the lines,” he said. “With mixers designed all the way up to a 140° tilt, the dough will discharge out of the mixer without the operators having to interfere with it.”

After all, the less the operators need to tangle with the mixer, the safer they will be.       

Although a mixer has to be strong enough to handle the batter or dough, it also has to be safe enough for the workers to operate it. This is a challenge that Topos Mondial faced, especially in designing mixer frames. “You want to build a strong structural frame that is sanitary in its design, but you have to eliminate pinch points for personnel safety,” said Damian Morabito, president, Topos Mondial Corp. “It’s an engineering challenge, but it can be done. It just needs to be really well thought out. We figured it out on ours, how to keep the pinch points away.”

The challenge is in striking the balance among strong, safe and sanitary — no baker is willing to sacrifice any of the three.
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