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All coolants are not created equal.

Too many of us regard coolant as an insignificant part of the production process. Companies invest in the best equipment, purchase the most expensive cutting tools in hope of achieving longer life, and then buy the cheapest fluid they can get away with on the misguided premise that all coolants are pretty much alike. Yet, my experience is that there are important differences. Selecting the right coolant can be a major factor in improving product finish and manufacturing productivity, while reducing production costs.

We manufacture an extensive line of saw blades marketed under the Sterling trademark. As an independent manufacturer, we don't dare risk selling anything less than the highest-quality blades we can make. At the same time, we must remain price competitive. I've found that the coolant we use is an important factor in achieving these goals.

As a company nearing the century mark, we have first-hand experience with developments in straight oils, soluble oils, and synthetics. We tested one after another in an effort to improve both our products and manufacturing efficiency.

Until about two years ago, we were using a good-quality soluble oil in milling our saw blades. At the time, it seemed like the best available product. But then, a coolant specialist from one of our suppliers brought to our attention a material that operates on a concept entirely different from conventional coolants.

Ionic coolant

As we learned, conventional coolants rely on one basic principle to reduce heat during machining--they contain oil or some other chemical to lubricate the surface being cut. Water in the coolant carries away some of the excess heat.

In contrast, Polar Chip ionic coolant contains no oil or organic matter. And while chemicals in its formulation do produce some lubricity at the point of contact between tool and work, the major difference is that it floods the cutting operation with a rich solution of negative ions.

Research indicates that positive ions are generated during machining. As the tool contacts the work, the cutting edge is momentarily welded to the work, only to be torn away an instant later. During this process, microscopic bits of the tool are torn from the cutting edge (dulling it), and deposited on the work surface (impairing the finish). By providing a flood of negative ions, the coolant neutralizes the positive ions, cancelling out their charge and dramatically reducing heat generation. This, in turn, provides a better finish, longer tool life, and an opportunity to increase speeds and feeds.


The most dramatic improvement we found after changing coolant was in tool life. With soluble oil, we averaged 566 cuts before a milling cutter needed regrinding. With ionic coolant, this jumped to 1815 cuts--more than three times the service before regrinding. Since each tool is worth around $3000, we are saving about $53,000/yr in the cost of cutters alone.

With ionic coolant, we also can increase table feed rate from 0.280 ipm to 0.625 ipm, reducing cycle time from 4.5 min to 2.1 min. Overall, milling machine output has increased 40 percent. This saves approximately $110,000/yr at our present labor and burden rate.

The change in coolant also resulted in a better saw blade gullet surface finish, from 250 microinches to 125 microinches, which improves blade life and cutting performance. In addition, by removing the heat-generating positive charges, we have reduced the possibility of the generated tooth being drawn to an unstable fin burr tip.

Fin burrs on a saw blade can cause deviate heat treatment, resulting in less than optimum cutting performance. Also, these burrs usually are fractured during the first contact with a workpiece, thereby reducing saw blade life. Because of these improvements, which we attribute directly to the coolant properties, we now are producing higher-performance, longer-lasting products.

Reduced sump maintenance

With soluble oil, our sumps were turning rancid at a rate that required dumping, cleaning, and refilling with fresh coolant every three weeks. Overall, we were expending an average of 8 hrs/wk on maintenance; now it's only 6 hrs/mo.

The main factor contributing to this reduction is the nature of the coolant itself. Nevertheless, as in most shops, our coolant is subject to contamination by tramp oils. These oils serve as food for microorganisms and promote their growth by floating on top of coolant in the sump, sealing the surface against air penetration.

To prevent rancidity caused by tramp oils, the ionic coolant has an ingredient to fight microorganism growth. Under all but the worst conditions, this is sufficient to prevent the problems of rancidity--foul odors, rusting, skin irritations, etc.

We have gone a step further by using an inexpensive tramp oil skimmer to remove floating oils from our sumps. This skimmer is a simple device that uses a revolving plastic wheel to lift oil from the coolant surface and deposit it in a run-off trough for collection. Since it can remove up to 8 gph, we move the skimmer from sump to sump as needed.

By eliminating the need to dump rancid coolant and replace it every three weeks, we reduced our coolant purchases from 935 gal/yr to only 385 gal/yr. We also eliminated costs and problems associated with disposing of rancid coolant.

For more information on ionic coolants and oil skimmers from Polar Chip, Irvine, CA, circle 534.
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Copyright 1985 Gale, Cengage Learning. All rights reserved.

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Author:Blakeslee, Shane M.
Publication:Tooling & Production
Date:Oct 1, 1985
Previous Article:Controlling bacterial growth in metalworking fluids.
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