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Automatic feed mill
When Matt Olmstead became
shorthanded a couple years ago, he needed a way to save time in his 6,000-head
farrow-to-finish family hog operation. Grinding 80 tons of feed a week with a
pull-behind grinder-mixer was taking about 20 hours.
“We decided to pregrind the
corn with a stationary hammer mill and store it in a bulk bin. The system is
automated, so when the bulk bin is empty, it grinds more corn. There’s always
ground corn waiting when it’s time to mix feed,” says Olmstead.
The grinding takes place in
a bank barn on the Lenhartsville, Pennsylvania, farm. Upstairs, there is a
1,000-bushel bin for holding shelled corn. Downstairs, Olmstead installed a
20-hp. hammer mill that had been sitting idle. There is also a 9-ton bulk bin
upstairs for storing the ground corn.
The mechanics of the system
are relatively simple. Two 4-inch down tubes run the shelled corn into a 4-inch
variable-speed auger. That auger feeds the hammer mill and can be set at any
speed, based on how hard the corn is. Amperage on the mill is monitored so it
won’t overload the motor.
A 6-inch auger transfers
ground corn from the mill to a 4-inch vertical auger, which carries it 32 feet
to the top of the bulk tank. Then, an 8-inch auger at the base of that bin
feeds the mixer at a rate of 1,000 pounds per minute.
Making It Automatic
The hard part, says
Olmstead, was automating the system. “We wanted it to run fully independent, so
the ground corn will be waiting in the bulk bin when we need it,” he says.
A control panel is built of
mainly used contactors and relays and used enclosures. The system starts up in
three stages with the use of timers. The phase converter and transfer augers
start first, the hammer mill starts 30 seconds later, and the feed augers and
blowers start after another 30-second delay. Delays are necessary because
neither the phase converter nor the mill will start under a load. The system
shuts down in the reverse order.
The system starts and stops
through the use of proximity sensors in the bulk bin. When the ground corn bin
gets low, a sensor starts the system. When it’s full, another one shuts it
There are also some extras
and safety features, says Olmstead. A sensor on the shelled corn bin will shut
the system down if it runs out of corn. Thermal overload protectors on all the
motors will shut down the entire system. A subpanel upstairs monitors the
system and can turn it on or shut it down. There are emergency stop buttons
both upstairs and downstairs in the barn. “We can switch to manual mode if
motors need to be reset or if a problem arises,” explains Olmstead.
Doing More With Less
A dust collector “cleans the
shelled corn before it gets to the mill if we get into some real dusty corn,”
Most of the six months it
took to build the system was spent on the control panel. “We’ve run about 350 hours
with only one breakdown – a broken auger. It saves us at least five hours a
week so we can do more with fewer people,” says Olmstead.