Chips Away: Turning Performance

Central conveyor systems provide benefits, but not everyone needs one

The chip collection bin at a shop’s turning center is full, so a worker grudgingly begins the mundane task of moving the bin via a forklift to the chip collection station at the opposite end of the plant. Unfortunately, the bin leaks and coolant drips on the shop floor, causing the shop’s biggest customer to slip and fall while visiting to check on his latest order. There’s got to be a better way.

Fortunately, there is: a central conveyor system transports chips from individual machine tools to a chip processing site, eliminating the need for individual bins at each machine.

An Eriez magnetic conveyor moves punch-press scrap. Image courtesy of Eriez.

The benefits for a shop begin with a facility that projects cleanliness, sophistication and automation, according to Dan Baumbach, president of Titan Conveyors Inc., New London, Wis. “The appearance of a facility with a central collection system is dramatically different and catches the eye immediately upon entering. The value of a clean, organized shop with a top safety record should not be underestimated when presenting it to customers—it’s huge!”

A central system also reduces labor, fork truck traffic, safety hazards and housekeeping messes, added Mike Hook, North American system sales manager for PRAB, Kalamazoo, Mich. The company manufactures systems for processing turnings, chips and coolants, and conveyors for automated material handling.

Nonetheless, a central conveyor system can pose problems if a parts manufacturer doesn’t appropriately predict company growth. Conveyors tend to have a long service life, and a shop can outgrow its system in a few years.

Therefore, customers must look at the big picture and plan for future expansion, emphasized John Mackowski, metalworking product manager for Eriez, an Erie, Pa., manufacturer of magnetic conveyors for transporting ferrous chips and parts. “That’s what most customers tend not to do,” he said. “They don’t think far enough into the future.”

Although determining future requirements can be a daunting task, inadequate planning is especially problematic for an end user with a magnetic conveyor system. Mackowski explained that magnets move inside the housing and each magnet grabs a certain volume of chips or parts. As more chips or parts are produced—for example, transitioning from five machines generating a total of 1,000 lbs. (454 kg) of chips an hour to 10 machines producing twice that much—the magnets are unable to accommodate the increased capacity.

It’s different with belt-style conveyors, Mackowski said. “If you keep piling stuff on top of a belt conveyor, you can increase capacity fairly easily.”

In addition, the width of a magnetic conveyor might need to change as it progresses along its route to where it discharges at the central collection zone. At the beginning of the line, where the conveyor is only being fed by one or two machines, “you might only need a conveyor that’s 8″ or 10″ wide,” Mackowski said. “Conceivably, you can get to the other end of the building and be handling material from 20 machines, so the conveyor is handling substantially more material than it did at the beginning. It’s not a problem, but people just have to understand why you start with an 8″-wide conveyor and, at the end, have a 28″-wide conveyor.”

System Selection

The types of central systems available include in-floor, on-floor and overhead conveyors. An in-floor conveyor is the ideal scenario, according to Titan’s Baumbach, because it can be plated over to make it practically invisible and requires the least conveyor footage because machines typically discharge material close to floor level. However, installing an in-floor conveyor in an existing plant is challenging because a trough must be dug beneath the floor, which requires a significant upfront investment and causes disruption and downtime. It’s also not suitable for a facility that frequently reconfigures its machines.

An in-floor harpoon conveyor automatically feeds a screw conveyor. Image courtesy PRAB.

“When facilities are being [designed], customers want to automate and improve their chip handling process,” said Mike Weckerle, OEM sales manager for Jorgensen Conveyors Inc., Mequon, Wis. “The cleanest way to start is before concrete is poured.”

It’s even better when a parts manufacturer requests feedback about how a conveyor can best be integrated in a facility while it is still being planned, Weckerle noted. “We love it when customers call before the building is fully designed.”

However, Hook pointed out that while the company works with customers as their plants are being built, a majority of the company’s work involves retrofitting existing factories. This might involve installing a simple conveyor system for a production cell with six or eight machines. However, because there is no preexisting pit, the project requires expertise in conveyor and equipment layout to make it cost-effective.

Weckerle added that the larger the shop, the more likely it will opt for centralized chip management.Such shops mainly serve the automotive and aerospace industries.

Although aerospace applications often have a high “buy-to-fly ratio,” where a large percentage of a workpiece becomes chips, Hook said those parts are usually milled and, therefore, the chips are a consistent size, material and solid-to-liquid ratio. This makes an in-floor or aboveground conveyor fairly straightforward. Turned workpieces, on the other hand, tend to generate long, stringy bundles of chips, complicating the conveyance process and requiring the conveyor design to account for all operating conditions and material variances. In addition, the plant may need a chip shredder, mill or crusher to reduce chip volume by converting the bushy wads of turnings into a manageable “shovel-grade” size.

Prab’s in-floor harpoon conveyor is engineered to move volumes of metal chips, fines and turnings from the source. The free-floating ram pushes material down the length of the conveyor, and a liquid-tight trough prevents coolant spillage and allows metal and fluid to be recycled. Image courtesy PRAB.