Sunday 6th Dec, 2020

Automated bulk bagger boosts business

An American manufacturer attributes its growth to automation, choosing Flexicon bagging systems to help take it to the next level.

O’Fallon Casting, based in Missouri in the United States, is a major manufacturer of thin-walled, non-ferrous investment castings.

The investment casting process can be labour intensive. It begins with a wax pattern, which is identical in shape to the final casting. This pattern is dipped into a slurry, which partially drains away. Next, the slurry-coated pattern passes through rotating vessels, called drum sanders, each of which coats the pattern in a different type of sand. After the slurry hardens, the wax melts away and is replaced with a molten metal to make the casting.

As the wax patterns move through the slurry and sanding steps, they consume the fine powder used to make the slurry — called flour — and three varieties of sand.

For years, operators had replenished the slurry vessel and drum sanders by hand, carrying and emptying 23-kilogram bags into them. In 2007, O’Fallon began buying the materials in 1360-kilogram bulk bags and adding them automatically by machine.

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For this, the company chose equipment from Flexicon, which supplied four BFC bulk bag dischargers and a combination of single-run and interconnected flexible screw conveyors. One discharger-conveyor system is devoted to delivering flour to the process, while the other three deliver sand to four drum sanders.

Bulk bags are delivered to each discharger by forklift and then loaded into the frame using a hoist and trolley that travels on a cantilevered I-beam. Next, a Spout-Lock clamp ring on top of a tele-tube telescoping tube is raised pneumatically and secured to the bag spout. This contains airborne dust and maintains continual downward tension on the bag as it empties and elongates, promoting discharge from the bag.

While each sand variety flows freely from the bulk bags and hopper, the flour tends to bridge, according to Matt Cavins, metallurgical engineer. As a result, the flour discharger includes two additional mechanisms to promote flow – Flow-Flexer bag activators, which raise and lower opposite bottom edges of the bag into a V shape, and a vibrator mounted on the hopper wall.

“Those features were major considerations for us,” Cavins explains. “We wanted to make sure that it was discharging from the bulk bag smoothly and that there wasn’t a lot of dust created where the hoppers are.”

One of the benefits of receiving the sand and flour in larger bulk containers is efficiency for O’Fallon’s operation. It supplies the powders to multiple locations from a common bulk materials location.

To achieve this, flexible screw conveyors automatically transport the materials through openings in the walls to the slurry vessel and drum sanders. Since the design of the flexible screw conveyors is suited to complex equipment layouts, the series of conveyors allows the Flexicon bulk material handling system to feed the powders to varied locations. In O’Fallon’s layout, powder use points are anywhere from 2.1 metres to 13 metres away from the bulk bag dischargers.

The material conveyance is automated which helps further enhance efficiency. These additions are weight-based, with a scale beneath each vessel signalling a programmable logic controller when to start and stop the conveyors.

O’Fallon uses about two bulk bags of flour per day, and each of the sand lines consumes about two bulk bags per week. Cavins says the materials are heavy and abrasive, and the conveyors handle them well.

“We really haven’t had many issues. It’s been almost 10 years in operation now, at least on the sanders, and we’ve replaced maybe one drive, and that’s on three systems with multiple drives,”
he says.

“Two conveyor tubes have been replaced in that 10-year span. The polymer tube on the flour conveyor is more prone to wear than the steel tubes on the sand conveyors…but it’s really not enough to switch to a steel tube.

“We have more uptime and a safer working environment.”