Coolant has long been a critical element in machining operations and its importance continues to grow. The increased speeds and higher metal removal rates of today's newer machines create more chips, placing increased demands on the coolant and on associated chip removal and coolant filtration equipment. Many machining operations have moved to high-pressure coolant systems for faster chip removal and greater precision. This puts increased stress on the fluid, magnifying the adverse effects of chips or other contaminants.
The stress on coolant is compounded when cast iron is machined, as an Ohio contract manufacturer that produces parts for the energy and solar power industries on a five-axis Makino a61 horizontal machining center recently discovered. That's because in addition to chips, cast iron machining creates fine particles in the range of 25 microns which can quickly become suspended in the coolant to create sludge. And today's high performance CNC lathes and machining centers with high cutting speeds, like the Makino a61, can produce a lot of cast iron fines in a short time period.
For example, a 30 hp machining center can produce up to 25 ft³ of chips and 150 in³ of sludge in a 24 hour time period. Chips and sludge on typical machine installations can migrate through to the "clean side" of the coolant system resulting in increased wear on tools, machine components and workholding fixtures, necessitating more frequent and costly maintenance and lost production time. This also causes part quality problems and shortens coolant life translating into higher coolant disposal and replacement costs.
This problem of chips and fines migrating back into the machining process is a critical element in the performance equation. Consider the blockage of coolant distribution channels including the system's pump, reducing coolant flow to tools and parts. This can result in chips not being properly flushed from parts and workholding, premature tool wear, inaccurate tool compensations, and higher heat that can work harden areas of the part. Eventually, the pump will cavitate, potentially burning out motors or wearing seals. Also, when chips and fines accumulate in the reservoir, to the point where their volume displaces too much of the fluid, the coolant temperatures begin to rise, resulting in evaporation and further quality issues.
The picture for this manufacturer was further complicated by the existing chip conveyor and coolant filter attached to the a61. Clogged with cast iron sludge, the drum screen on the coolant filter would break and the company would only find out when the coolant nozzles plugged or broke. This caused extensive downtime for cleaning. The time between cleanings was every three months, and each time the drum screen had to be replaced.
For a solution they turned to Mayfran International (Cleveland). Mayfran supplied a MagSep® Conveyor for the dedicated cast iron application. With the MagSep magnetic drag (or scraper) conveyor, coolant and chips are directed to the magnetic surface before exiting the conveyor. The magnetic bottom pan attracts ferrous chips and fines and the conveyor flights continually remove chips from the bottom pan while clean coolant exits the tank.
This action results in coolant clean enough for many machining operations at moderate costs, but for this application Mayfran upped the ante with the addition of an AT-Cleaner Coolant Cleaning system. The AT-Cleaner, a media-free unit, further cleans the coolant, removing fines and maintaining a 10-15 nominal micron level in the coolant, which in turn promotes longer tool life, less maintenance on machines and workholding devices, and greater part quality. Plus, the AT-Cleaner is maintenance-free, requiring no media filters to change and dispose of, resulting in lower costs and more spindle uptime. An easy-to-clean holding tank, separate from the clean tank reservoir, accumulates the sludge deposits discharged by the AT unit.
The benefits of the Mayfran MagSep/AT-Cleaner approach quickly became obvious: The company eliminated eight days of downtime totaling 320 labor hours, and eliminated $8000 in drum screen replacement costs every three months, achieving rapid payback. Understandably pleased with these results, they plan to add a Mayfran MagSep with AT-Cleaner to their next machine.
In today's unforgiving competitive environment machining facilities are constantly striving to optimize all aspects of their operation. Time and energy are expended on questions of machine tool design, control technology, material handling and process improvement strategies like Lean Manufacturing. Rarely do questions of chip disposal and coolant management receive the same degree of attention. They should. Chip and coolant management impact cost, quality and productivity - in other words, they impact survival.
An Ohio contract manufacturer turned to Mayfran International who supplied a MagSep® Conveyor for a dedicated cast iron application on its a61 Makino HMC.
For further editorial information or electronic files contact: Rol Kracoe - Kracoe Szykula & Townsend, Inc. PH 248-641-7500 - FAX 248-641-4779 Email: rkracoe@ksthip.com
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