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Material Handling
Wednesday | 30 April, 2014 | 2:37 pm

Moving magnets

By Corinna Petry

Above: Jim Gunter, Ridg-U-Rak plant engineering manager, checks slugs moving up an elevating conveyor.

A manufacturer, with help from a conveyor expert, figures out the best way to remove punch-outs

April 2014 - One storage rack manufacturer is so satisfied with the rugged, unfailing performance of its scrap conveyor system that it has ordered another unit and is considering additional upgrades.

Ridg-U-Rak, led by owner and chief executive officer John Pellegrino, has been in business 72 years, making storage units for industrial and commercial customers from its North East, Pa., operations.

“We make racks for Wal-mart, Lowe’s, Costco retail accounts and many others; and for distribution warehouses and industrial settings. [They are] mostly pallet racking,” plant engineering manager Jim Gunter says.

In order to produce these, the company roll forms vertical columns, welds them together to make uprights, makes horizontal sections (beams) and hooks those into the vertical uprights, and then fits cross bars between the beams for support.

MM-0414-material-image1“In order to have the beams hook into the uprights, you must punch holes for the hooks,” says Gunter. “The slugs punched out of the columns fall down through the punch press onto conveyors, moving the slugs horizontally under the machinery.” From there, the slugs are collected into scrap hoppers.

Ridg-U-Rak has seven roll forming lines at its main facility, each making a different variety of racks and shelving components.

The company has used several types of conveyors to move punch-outs in the past but found Eriez Manufacturing Co., based in Erie, Pa., to make a conveyor that requires the least amount of maintenance or worry as material is moved in various directions and into challenging environments, says Gunter.

The company starts with 4- to 18-inch-wide coils of black steel, 8- to 16-gauge, and some galvanized steel. When the steel coil enters the punch press, the press removes keyholes of 1 1⁄4-inch long and 3⁄4-inch wide, rectangles 5⁄16 inch by 2 inches and round holes, according to Gunter.

Using a series of connected horizontal and vertical conveyors from the punch presses through an exterior wall to two large hoppers outdoors, the company is scrapping 115 tons of steel slugs per month. A recycler empties the hoppers at least twice a week.

When Ridg-U-Rak began automating slug removal 25 years ago, all its conveyors were of the linked-weld variety. Slugs fell onto a horizontal, vibrating conveyor and material dropped onto other conveyors that dumped them into bins. A forklift came to each line several times a day to take the scrap bins and dump them into the recycler’s roll-off containers.

The link belts worked, says Gunter, but some slugs “start to stick or jam and then the links stop moving.” When that happened, Ridg-U-Rak would have to stop the production line “and pry out the slug that was stuck. Then the links wear out and more and more slugs want to fall into the cracks.

“So eventually, we used Eriez conveyors, where all moving mechanisms are underneath and enclosed. The slugs lie on a pan and the magnets move them at roughly 55 fpm. Now there are no moving components for slugs to fall into, greatly reducing maintenance.”

Then, instead of having a small bin at the end of each line, Ridg-U-Rak installed more Eriez magnetic conveyors to move all the slugs to a common hopper system.

“Now we don’t require fork trucks to move material outside. We just rotate a chute from one hopper to another, so there is always a fresh one in place. That way we never stop the lines,” says Gunter.

“We are much more productive after installing magnetic conveyors, and essentially eliminated breakdowns on elevating conveyors.”

Ridg-U-Rak went a step further and placed a conveyor at the end of its beam production line, where notches are removed by a hydraulic cutoff press. Just about every time it adds a piece of metal forming equipment, it adds a conveyor.

The Eriez design is what makes it so reliable in service, says Gunter, explaining, “There is no access point to the internal chain without dissection. The drive unit requires limited lubrication. The metal plates the slugs ride upon last quite a while.” Over several years, “we have replaced the sliding portion on the vertical conveyor only twice.”

More recently, he continues, “We have ordered an entirely new elevated conveyor. We are moving a lot of product with sharp edges. We have been working with Eriez on different materials and we are happy with its wear. [After testing] there’s not even a mark on it. It will probably last many years.”

When the new conveyor arrives, Ridg-U-Rak expects to pull the old assembly out, install the new one, and then rebuild the old one for future production. 

Inside the existing units, there are metal links holding the magnets and there are wear points inside, “so with the spare conveyor, there will be time to replace the interior moving parts.”

However, Gunter is not worried about that at all, given that the Eriez magnetic conveyors have worked so consistently, including a section that is completely submerged in coolant sump.

The working face is self-cleaning, and excess fluids drain easily back into the tank.

Slugs and coolant can drop right onto the conveyor, typically at the cut-off operations, and “we can pull slugs saturated with coolant—which runs off and is recirculated—out and place them right into the hoppers,” Gunter says.

The majority of the Eriez conveyors installed at Ridg-U-Rak are Model 6 units with 14 1⁄2-inch-wide slide plates. The drive chain rides within an oil-impregnated ultra-high molecular weight track, called Tuf-Trac, which is designed to operate quietly and maximize conveyor life. Tuf-Trac also eliminates the need for oil inside the conveyor housing.

MM-0414-material-image2

The Model 6 conveyors are supplied with magnets on 12-inch centers, supported by twin roller chains powered by a shaft-mounted motor reducer. The conveyors come with spring-loaded chain take-up.

 The company builds the control panels for its production lines itself, and the controls for the conveyors are hard-wired in. Each conveyor has just a small motor with an on/off power switch.

“Most companies that buy a magnetic conveyor want to move scrap or chips. In this case, it is a punch press operation,” says John Mackowski, product manager for metalworking at Eriez.

“If a customer is dealing with ferrous material, the beauty of this type of conveyor is no external moving parts. Parts can stick in hinges and can become a maintenance nightmare,” he says.

“We’ve worked with Ridg-U-Rak for several years and on several projects. They were familiar with magnetic conveyors on other applications. They told us they need to move so many tons of punch-outs per hour, so we sized the conveyor correctly and hoped it turned into an order.”

Once a magnetic conveyor goes in, “very little goes wrong. We’ve been out there and the conveyor system was running fine. If the conveyors weren’t running right, I would have heard about it,” Mackowski says.

The magnetic conveyors are made of a stainless steel sheet. The magnets move on a chain, and can convey in straight lines or up a hill. The chains are sealed so the line can enter a quench tank or a machining center with oils and coolants.

Metalworking is a huge business for Eriez, he notes. Magnetic conveyors are also able to handle cast iron fines, for example. “On almost all other conveyors, those fine grit pieces get inside the conveyors and wear out the drives. If you get the chips on our bed, there will be no internal wear of components. 

“We’ve handled parts for steering mechanisms that weigh 8 and 10 pounds,” he continues. “We’ve handled stamped-out parts and chain link for chain manufacturers.”

A typical small conveyor can cost $7,000 to $8,000 and, for large applications, can push above $100,000 depending on the physical size and length, Mackowski says.

The upfront cost for a magnetic conveyor is higher than a normal belt conveyor, “but maintenance costs much less. If a conveyor shuts down, many times the operator has to stop an entire process because there’s no way to move the material so they are losing production time.”

With the enclosed permanent magnet, the conveyor keeps running as long as the chain drive is running. 

With the right people, processes and efficient material handling in place, Ridg-U-Rak expects to durably manage and grow its business far into the foreseeable future. MM

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