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 down.
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.