JAK ZUŽITKOVAT TŘÍSKY
January 05, 2016
Move it, shred it, or pack it—chip management doesn’t have to be hard work
My first shop job was shoveling brass chips from the tail end of an Acme Gridley screw machine. Each afternoon I went home with my pants reeking of sulfur-based oil, my legs covered in rashes and my 16-year old back afire from hauling 55-gallon drums of oily swarf. I lasted two weeks.
Of course, that wasn’t the last time I shoveled out a chip pan. In a machine shop, dealing with chips is part of the job. But chip management shouldn’t mean oily clothes and cut fingers. Manufacturers of material handling equipment offer a number of solutions designed to tame pesky chips, preserve the environment, and improve profitability.
There are many reasons to invest in a chip management system. The first is uptime. Every minute an operator spends with a shovel in her hand is a minute she isn’t checking tools or loading parts. The first line of defense in this case a scrap conveyor, which lifts machining waste out of the machine tool and moves it to a drum or wheeled bin for transport away from the machine tool. It also gives the shovel an early retirement.
Don Suderman, material handling product manager for Bunting Magnetics Co., Newton, Kan., said scrap conveyors today aren’t an option—they’re a necessity. “Unless you need the exercise or you have extra manpower, there are easier and more economical ways of handling scrap steel than moving it with a shovel.”
For shops that primarily machine ferrous materials such as steel and iron, magnetic conveyors are a common method of chip disposal. They use a series of rare earth or ceramic magnets mounted beneath a stainless steel conveyor belt, which pull the scrap materials up an incline. At the top, the magnets retract to release the scrap, where it falls into a waste bin or into another conveyor system.
Suderman said magnetic conveyors have no external moving parts, so are fairly jam-proof and work well for moving sharp scrap steel. And by running the conveyor at a slow speed, much of the cutting fluid that would otherwise be hauled off with the chips is allowed to drain back into the machine. A basic magnetic conveying system starts at around $10,000.
Some might say, “Why bother?” Scrap steel and iron isn’t worth much—a ton of clean, dry chips fetches no more than a few hundred dollars from a scrap dealer. But in today’s green world, keeping waste out of the landfill is important. According to the American Iron and Steel Institute, steel is the most recycled material on the planet, and suffers no degradation with repeated processing.
Hinged for Success
Machine protection provider Hennig Inc., Machesney Park, Ill., is another company that makes and sells conveyor systems. Chip conveyor and filtration system business manager Scott Cooley said the company offers several flavors of chip removal equipment, including magnetic conveyors, scraper-type conveyors for cast iron, bronze, and brass machining, and general-purpose hinge-style systems. Of these, hinged conveyors are by far the most popular.
“Job shops might cut Inconel one day, brass or aluminum the next,” Cooley said. “In this situation, a hinged conveyor works best. It can handle long, stringy chips as seen with stainless steel, very fine chips such as those produced in cast iron machining, and anything in between. They are very universal.”
Cooley said 90 percent of the conveyors produced by Hennig are hinge-style conveyors, and are sold to end users and OEMs alike. As the name implies, they use a cleated steel belt that looks somewhat like the tread on a battle tank to grab chips and carry them up and away from the machining area. Like a tank, the belt is rugged and capable of carrying heavy loads.
Conveyors do more than move chips. Small metal fines can plug high-pressure coolant systems and damage pumps, while tramp oils eventually turn even the most pristine machine sump into a swampy mess. To combat this problem, Cooley recommends a chip disc filtration (CDF) system, an integrated hinged or scraper belt conveyor solution that includes disk-style permanent media filters, high and low pressure pumps, and an inline oil skimmer. The price? Around $15,000-$35,000, depending on the configuration.
Spinning wheel, got to go round
That may seem like a lot of money, but without clean cutting fluid, tool life and part quality suffer. Mike Hook, responsible for North American sales at chip and fluid management provider Prab Inc., Kalamazoo, Mich., said the cutting fluid aspect of chip management is frequently overlooked. “With just about any machining process, you’re dealing with cutting fluids. So before you send a dumpster full of wet or oily chips down the road, you have to consider the cost of those cutting fluids as well as the environmental impact of not recycling them.”
This is especially true with cutting oils, which can easily cost $20 or more per gallon, 10 to 20 times the cost of water-soluble cutting fluids. For heavy users of cutting oil—Swiss-style CNC shops and screw machine houses—this can mean big bucks. Recycling a ton of brass chips containing just 5 percent by weight of oil could mean a loss of $5000. Likewise, shops that generate a dumpster’s worth of aluminum chips each week may lose comparable amounts of money in water-based cutting fluid.
The solution is spinning. Centrifuge systems are the metal equivalent of salad spinners, and quickly turn wet chips into dry ones. Hook said some shops keep it simple: fill up the chip carts on a regular schedule, pull them over to a standalone centrifuge, dump them in the hopper, and push the button. “There’s some manual labor involved to this approach, but it’s pretty minimal. The alternative is an automated system that carries the chips to the processing unit through a series of conveyors. Depending on the shop, this can cost anywhere from $100,000 up to a million dollars or more.”
Again, that may seem like a big price tag for a system that doesn’t actually produce anything, but for shops with a few dozen machines running round the clock, payback can be relatively quick. Aside from eliminating coolant loss, clean, dry chips bring a premium price. And coming from someone who started a manufacturing career shoveling out six-spindle screw machines, anything a shop can do to automate the tedium of chip handling is money well spent.
“If you truly look at what chip management costs in terms of labor and down time, it doesn't take long to justify some version of an automated system,” Hook said. “Every minute spent doing manual clean out of a chip tank, or wrangling chips into a scrap bin, you’re losing money. Also, the cost of fluid handling can quickly add up. That’s why it’s important to select a chip management system that not only dries the chips but recovers and recycles cutting fluids to like new condition.”
Throw on a couple briquettes
It’s much easier to design a shop for an automated scrap handling system than it is to retrofit one after the walls are up. Trough-style conveyors in the shop floor are an effective way to carry the chips to processing equipment, but may require extensive concrete cutting and remodeling. And environmental concerns over leaks and groundwater contamination are making some companies look towards the ceiling rather than down at the floor for chip management. “In-floor systems seem to be getting fewer and farther between,” said Ed Zeitz, sales engineer at Mayfran International Inc., Cleveland, Ohio.
Instead, many shops opt for vacuum systems that suck chips to a central location, or “pump backs” that use coolant to flush the chips to a holding tank for processing. Whichever way you go, stringy chips can spell problems. Cutting tools equipped with chipbreakers go far to bust material into manageable pieces, but still some chips don’t behave. For this situation, shredders are often needed. “Automakers use these on their crank and camshaft lines,” Zeitz said. “The other option is a cutter pump, which can break up small strings and allow them to be move through the system.”
Another consideration is volume, especially for light fluffy chips such as aluminum and zinc, or for shops in rural areas where the scrap man has to drive long distances compared to urban locations. For these chip producers, minimizing the size of their machining waste brings maximum value. Said Zeitz, “We have a customer in Iowa that machines a lot of aluminum. Due to their large chip volumes, and because the scrap hauler was charging a fee for every pickup, the company invested in a system the shreds and compacts the material into briquettes.”
Depending on the equipment manufacturer, aluminum briquettes weigh around 125 lb./cu. ft., nearly ten times denser than loose chips, saving considerable storage space compared to the “throw it in the dumpster” approach. Briquettes also bring premium prices, sometimes 2 to 3 times that of material that has not been compacted. For shops with substantial chip volumes, briquetting makes a lot of sense.
Mixing it up
All of this is good news for the shop making millions of aluminum aircraft components annually, or the Tier-II automotive supplier cutting trainloads of engine blocks. But for the typical job shop, there’s little joy here. High-tech automated systems are designed to process a single material and do so very efficiently. Switching a chip management system from one material to another means extensive cleaning to prevent cross-contamination. Yet many Mom and Pop shops machine dozens of different materials every week, and no one has yet invented a cost effective way to separate stainless steel chips from those of brass or aluminum.
That’s not to say chip management is a lost cause for smaller shops. Chip conveyors are still a good investment, reducing the time needed to shovel out the chip pan, improving efficiency and worker disposition. Clever job scheduling and dedicating machines to certain materials minimizes contamination, thus increasing the price received from the scrap man. And mid-size shops with a dozen or so machines running common materials may benefit from centrifuges and briquetting systems. Whatever the solution, it’s time to get rid of those shovels. They’re a real back breaker.
Bunting Magnetics Co.
Mayfran International Inc.