Reclaiming, recycling, and removing chips and fluids to maintain machining housekeeping.
Managing chips and cutting fluids is an age-old problem in machining. Fast forward to today’s technology that allows chips to be extracted and processed for their scrap value and fluids to be cleaned faster and reclaimed for further use or disposed of more efficiently than ever before. A mix of new technology with tried-and-true methods of scrap and waste handling techniques includes oil removal and separation technology, magnetics, and briquetting.
The goal is to reclaim scrap that can have a significant value as well as safely handle fluids and hazardous materials that can be harmful to personnel and the environment. Most important, manufacturers with the right systems in place improve machining results, improve part quality, minimize downtime due to scrap and extend tool life, guaranteeing good machining results.
When considering chip and coolant handling, you can’t avoid talking about processes like separating, skimming, filtering, shredding, crushing, briquetting, conveying, feeding and magnetically moving—in the case of ferrous metals. These processes are critical to all machining operations, including job shops, production contract manufacturers and OEMs, as well as the cadre of equipment suppliers that have raised reclaiming and recycling metals and fluids to a highly efficient science.
“The biggest advances we have made in our equipment is on the automation side and making the equipment smarter and easier to work with through our advanced controls,” said Mike Hook, director of sales and marketing, PRAB Inc. (Kalamazoo, MI).”We are taking IIoT concepts and data collection to provide our customers with information about equipment performance, as well as alerts and notifications.” Alerts can include preventative maintenance is needed, scrap bins are full, and equipment faults. “The long-term goal is to have the service technician go out with his hand-held device and know exactly what the problem is and have the right tools to resolve it,” he said.
PRAB builds its systems based on each individual customer’s needs. “Today, manufacturers of all sizes and in every industry have cradle-to-grave responsibility for their manufacturing by-products—everything from metal scrap and cutting fluids to floor scrubber and process waste water,” said Hook. “Through acquisition and R&D development, we have expanded our capabilities into four divisions that manage our expanded product offerings: conveyors; chip and turning processing systems; cutting fluid recycling equipment; and waste water treatment equipment for non-coolant fluids.”
PRAB’s chip handling and fluid processing equipment can handle the entire scrap and waste streams of the plant, even waste that is generated in plating and scrubbing, as well as process fluids and waste water. According to Hook, when evaluating the needs of its customers and designing a custom solution, there are a number of hot button questions that need to be answered about the customer’s shop.
For example, is fork lift truck traffic an issue? PRAB’s full line of conveyors can be configured to simplify transport materials. Similarly, is scrap handling causing downtime? “That’s something that should never happen.” Hook continued. “Are current scrap processes dangerous or environmentally irresponsible? Stringy turnings, especially of stainless steel, Inconel and nickel-based alloys, are razor sharp and dangerous to handle. And finally, is the shop paying too much to haul fluids and hazardous waste away?”
Basic information about the volume of scrap produced over time and fluid usage as well as what their scrap dealer values most to get the maximum return from scrap will determine how scrap should be processed, said Hook. Some scrap can be processed as a pressed brick better than loose dry chips, which are certainly better than loose wet material. “On the fluid side, what local municipalities will allow to go down the sewer will determine how non-coolant waste fluids should be handled. As to the question of how much fluid can be recycled, we can recommend how many times fluids should be recycled before being disposed of and what types of filtration work best for their fluids,” said Hook.
Coolant Cost Equation
Coolant is a significant cost to manufacturers, and should be managed as such, according to Dan Zimmerman, director-business development, Eriez (Erie, PA). Removal of solids and tramp oil from coolant and cleaning sumps is important to minimize downtime and maintain part quality while significantly reducing coolant costs and extending tool life.
Removing tramp oil, the number one cause of rancid, bacteria-laden cutting fluids in sumps, is an essential first step, said Zimmerman. Tramp oil is recognized as a major source of problems associated with water-miscible cutting and grinding fluids.
“Reducing tramp oil is a high priority for all metalworking shops. Excess tramp oil leads to smoke, mist and bacterial infestation of the metalworking fluids, adversely affects surface finish and dimensional tolerance control, shortens coolant life, and leads to inferior material removal rates as well as reduced tool and wheel life,” he said.
The first line of defense against destructive tramp oil contamination is provided by Eriez Surface Oil Belt Skimmers, according to Zimmerman. Belt Skimmers are designed for use on machine tools subjected to oil contamination in the range of one to 2 gal/hr with tanks deeper than 2′ (0.61 m). Smaller models are also available for shallower sumps with lower oil removal requirements. All models feature oleophilic (oil attracting) belts that strip separated oil into an oil collection pan with drain hose connection. With long belt life and no wear items, the company says, they offer excellent performance and long service life.
For metalworking plants with multiple machines, Eriez Hydroflow portable coalescers provide a simple, effective, low-cost method for quickly and easily moving them from machine to machine or making them stationary to work on large sumps or central systems. Because of their portability, a single machine can support tramp oil removal for an entire metalworking shop, according to the company.
A larger flow-rate system can also be custom engineered to meet customer needs. The portable coalescer uses an oleophilic coalescing plate pack media that consists of over 100 ft2 (9.3 m2) of coalescing area for maximum oil removal. Eriez also offers a smaller stationary Tank-Side Coalescer to economically service individual sumps. All units operate on standard 115-V power supply with optional air pumps where required for the application.
Solids removal is the next biggest priority in maintaining coolants. Eriez offers an assortment of sump cleaners, including the Drum Top Sump Cleaner, Reversible Liquid Vacuums and the traditional high-powered industrial Sump Cleaner. The Drum Top Sump Cleaner is a vacuum unit that converts an existing open top drum into a machine tool sump cleaner. It sucks up tramp oils, used oil and waste coolant quickly and efficiently, and is a cost-effective alternative to a dedicated sump cleaner, according to Eriez.
The Reversible Liquid Vacuum offers users another option for sump cleaning or liquid removal. It connects to a closed-head drum and can remove lube or hydraulic oils from reservoirs as well. The standard Sump Cleaner (ranging from 50 to 1,000 gallon capacity) rapidly removes fluid, sludge and chips from the sump. The fluids are filtered through a mesh-lined chip basket and can be returned to the sump by quickly switching from suction to discharge mode.
Eriez SumpDoc is a portable inline fluid reclamation machine that combines both sump cleaning and tramp oil removal in one package. Recently redesigned into a more compact and lightweight unit with a smaller footprint, it serves as a cost-effective alternative to a central fluid recycling system or batch processing. The SumpDoc supplies coolant restoration and rejuvenation treatment of the metalworking fluids in the machine tool sump with minimal operator interface. There is no interruption in the production cycle or need to transport fluids. The portable SumpDoc can be wheeled next to a machine tool, parts washer or rinse tank to provide full-serve fluid reclamation in a two-step process.
Bring on the Briquettes
Briquetting is a way for shops to handle their waste streams, reducing the labor of handling chip totes and transporting them from one part of the shop to another. Compressing metals—especially higher-scrap-value materials like brass, copper and aluminum chips—into briquettes also increases their value, whether they are going back to a recycler or to re-melt, according to Neil Poissant, briquette press sales coordinator, WEIMA America (Fort Mill, SC).
“Another benefit is capturing the fluid by squeezing it out during the briquetting process. The fluid can be recycled,” said Poissant. “The benefits of briquetting are fluid recovery, labor savings, and higher resale value.”
Where the press is located depends on the size of the shop and volume of chips. “Typically, in a large aerospace plant where there are large machines making chips, the press would be located close to the machines. For smaller job shops where the volume is coming from a number of smaller machines in shorter runs, the press might be in a central location or toward the back of the shop,” he said.
For larger plants, the chip processing system can be automated. Small job shops, for example, might be able to handle their chip feeding process manually.
“For larger customers, we can automate the process with a central location, dump the chips into a bin or a hopper and use a drag conveyor or a hinged belt conveyor to convey the chips,” said Poissant. “If additional processing is required, for example for turnings and long stringy chips that may need to be shredded, we might have one conveyor to the shredder and a second conveyor from the shredder to the briquette press. Something as simple as a rare earth magnet might be used if shredding aluminum to pull out broken tooling that might go into the brick press or the bricks themselves.”
Once the bricks are made and the fluid recovered, WEIMA typically provides some way to discharge the bricks to transfer piping or channels to transport them into a bin or hopper so they are easily loaded onto trucks. WEIMA presses make bricks in varying sizes from 2″ [50 mm] diameter rounds up to large rectangular bricks that are 60 x 150 mm from a few pounds up to 10 lb (4.5 kg) in copper. Size depends on density of the metal, output required, and what the scrap dealer or re-melt shop requires.
It’s important for shops to separate tramp oil from cutting fluid. This oil may come from multiple sources, such as the conveyor, tooling, fixturing, or the manufacturing of the part itself. An additional filter to remove the fines and small chips that escaped the initial processing may also be added to the system.
Aerospace is a big market for aluminum brick pressing. “The rule of thumb is that if you are producing 100 lb/hr [45 kg/hr] of aluminum chips, using a brick press is almost a no-brainer. At 50 lb/hr [22 kg/hr], there are other considerations, including recycling and reclaiming cutting fluid and labor reduction. The auto industry’s increased use of aluminum for lightweighting makes it a good opportunity. Of course, titanium, copper and brass command the highest scrap values and are good candidates for briquetting,” Poissant said.
Attacking Rising Disposal Costs
Chips can be tough to process so the chip handling equipment must be tougher. When Hennig Inc. (Machesney Park, IL) introduced its Chip Disc Filtration (CDF) technology, the patented stainless-steel disc system demonstrated that it could withstand day-to-day wear and heavy volumes of chips, which would destroy weaker nylon and other synthetic fiber drums.
The CDF system tackled the problem of rising coolant and chip disposal costs with a reliable, effective and economical way to deal with the increasing volume of chips and coolant produced by cutting tools and the machines, according to Hennig. The benefit of the system is that it not only removes chips from the operation, but also filters the dirty coolant. By cutting disposal and replenishment costs and ensuring that only a clean coolant is returned to the machine for re-use, tool breakage, workpiece damage and machine downtime and repair are reduced.
The Hennig CDF system works in three stages: For coarse chip removal, a hinged scraper belt collects larger chips and particles for discharge into the chip hopper. Removing coarse chips before they reach the disc filter keeps them from bundling and jamming the system, which fosters extremely efficient fine particle filtration.
Fine particle filtration is achieved when small particles escape the belt naturally and migrate with the coolant flow to the rotating disc filter. The collected particles rotate with the disc filter and are lifted out of the coolant, towards the backwash spray. There, the particles are blasted onto the belt with a backwash spray and removed along with the coarse chips. The particles down to 25 µm are collected and the cleaned coolant flows back to the tank.
Cast iron microfiltration is achieved by collecting and discarding cast iron fines. The addition of a solid rotating magnetic drum allows for cast iron fines to be collected and removed from the coolant. When enough particles have collected on the magnetic drum to form a heavy sludge, the sludge drops onto the dry conveyor incline and is discarded along with the coarse chips and particles that have been collected on the disc filter into the chip hopper.
While the general principles of operation are similar between drum-type filters and CDF, in practical application CDF is considerably more economical and effective over the life of the machine, according to the company. First, the Hennig CDF system can be used with either a hinge or scraper belt. Many drum manufacturers use a more expensive dual conveyor system, with one hinge belt and one scraper belt design. This design is much larger, more expensive and uses additional real estate.
Next, the stainless-steel media can handle a continuous heavy chip load compared to mesh or drum-type filters. In addition, because of the way the mesh media is attached to the drum, it can take hours to replace. In comparison, it takes 10-20 minutes to replace the stainless-steel disc on the CDF, requiring only the removal of a single clamp nut. Also, maintaining the spray nozzles, used for the filter backwash, is considerably easier with CDF. These nozzles are externally mounted and easily accessible, compared to the drum-type filters mounted to the pipe inside the drum, making maintenance difficult.
Finally, CDF requires only one drive system for all types of machining operations and chips. End users can benefit from lower equipment cost and reduced maintenance with the unit that will pay for itself in a few months, according to Hennig.