Coolant Considerations

For effective metal cutting there is no escaping the use of machine tool coolants, and as an essential element in a metalworking process it’s necessary to maximize the efficiency of the fluids while also maintaining a healthy work environment for machine operators.

Metalworking fluids typically fulfill two important cutting functions, cooling and lubrication. The cooling effect is necessary to remove heat from the tool, chip, and workpiece. It ultimately helps to extend cutting tool life while also helping keep the metal, part thermally stable.

Of course coolant also flushes away chips from the tool and cutting zone, and with such large volumes of liquid sloshing around it’s advisable to ensure that it’s safe to be around.

“Most people want to give their employees something that is safe,” says Brett Reynolds, senior applications engineer with Blaser Swisslube. “But I think as people are becoming more aware that metalworking fluid costs keep going up. They’re becoming even more conscious that they should be taking better care of the fluids they have so they can get the most out of them.”

When it comes to making productivity enhancements through the use of coolant, some fluid companies are promoting vegetable-emulsion coolants as a solution over traditional mineral oil based fluids.

“We’ve actually been marketing vegetable-based metalworking fluids as long as I’ve been associated with Blaser (as far back as 1999),” says Reynolds. “We’ve gone to market with these products, not so much from an environmental aspect, but because performance aspects of those fluids are substantially higher when compared to traditional metalworking fluids,” he explains.

Blaser’s vegetable ester-based products include its Vasco series. “Once people understand how that base oil interacts with the metal surface and delivers the additives more effectively, then they realize that it makes sense to move to a more expensive fluid that’s ester based because of the performance.”

Condat Corporation recently released its new MECAGREEN product line made with a blend of synthetic vegetable esters. In promoting the products, Condat points to benefits including extended tool life (as much as 20 per cent), reduced consumption (as high as 30 to 40 per cent compared with mineral-based coolants), improved cleanliness with less residue left on parts, tool holders and windows, and overall improved operator friendliness with no skin sensitivity issues.

The knock on vegetable-based products in the past has been the unpredictable bio-stability of the fluid, because it is essentially biodegradable and bacteria feed off of the base oil in the product. But as is the case with the Condat product, today companies are using synthetic esters. The early natural ester-based fluids didn’t last long and smelled bad, giving the products a bad reputation. “In my opinion that’s a moot point now,” says Reynolds, explaining that because the natural esters are now chemically altered it’s a lot harder for bacteria to break them down, making the new synthetic esters essentially bio-resistant.

While the upfront price of ester-based fluid will usually be higher than mineral-based products, according to Reynolds price has little to do with the overall cost of a metalworking fluid.

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“What you pay for and what it costs you to use it are two different things,” he says. “A lot of people only look at up-front price. The benefits of using ester-based metalworking fluids include the run-off rate which is substantially higher, so you actually use less product, and a lot of times the decreased usage offsets the higher price.”

From a health and safety point of view, he points to the problems of misting or fumes that are also greatly reduced with the use of the ester-based fluids.

For shops locked into using mineral-based coolants there may be an environmental change coming very soon anyway. Unless legislators in the U.S. have a change of heart, the Environmental Protection Agency (EPA) is banning the use of medium- and long-chain chlorinated paraffins in metalworking cutting fluids beginning in May, 2016.

Already, even in Canada, some fluid suppliers are encouraging shops to switch to chlorine-free solutions. According to Barry Gothard, sales representative with Fuchs Lubricants in Canada, word has come down from the top to begin educating metalworking customers about the change.

“We’re here to help customers comply,” says Gothard. “We want to be looked at as the chlorine-free alternative,” he says.

Unlike the chlorine in a swimming pool, the use of chlorinated paraffins in coolant has nothing to do with controlling bacteria. Instead, the chlorinated paraffin is an extreme pressure (EP) additive that is carried by the oil and interacts with a metal surface forming a metal chloride under heat and pressure. This bond provides a lubricating film that can withstand higher temperatures than mineral-based oil on its own, so in essence, the chlorinated paraffins provide lubrication to protect cutting tools when working at higher temperatures.

“They’re extremely effective on stainless steel and nickel-based alloys, just because of the way they interact with the surface of the metal,” says Reynolds.

There are EP additive alternatives to chlorine, namely sulphur or phosphorous, but one of the reasons chlorine has been favoured is because it is the least expensive option of the three. So according to Gothard there will be an incremental increase in the purchase price of the chlorine-free fluids.

There are still other ways to improve coolant productivity in a shop and keep an environmentally-sensitive approach. A common refrain from all the coolant suppliers is that as metalworking fluids continue to increase in price companies will become more proactive in recycling their fluids.

Looking to extend the longevity of coolants through proper filtration and incorporating maintenance procedures, shops will be able to reduce their costs.

“The biggest step a shop can take is to check its coolant concentration, that’s a key factor in metalworking fluids success,” says Reynolds.

Gothard agrees, noticing that some customers will try to push their concentrations lower and lower to save on fluids. “But if they run only water they’ll have rusty parts, rusty machinery and broken tools, so they need to keep the concentrations between five and 10 per cent,” suggests Gothard, insisting that chemists formulate their products to work best at a certain percentage, and it’s up to the customers to run it at those percentages. The productivity benefits in production will outperform the savings from skimping on fluids.

There are many companies on the market that are promoting or selling coolant recycling systems, including PRAB, Eriez or Custom Coolant Equipment of Lynden, Ontario. These suppliers are all helping shops maintain their systems and reduce their costs.

PRAB for example recently introduced a new feature for monitoring and controlling coolant concentration within its Guardian coolant recycling system.

The Automatic Coolant Concentration Control (AC3), continually monitors coolant concentration levels and adjusts automatically to maintain ratios within a plus/minus 0.5 per cent accuracy.

The monitoring system takes continuous measurements using an automatic refractometer. The readings are analyzed and the system automatically determines action; opening and closing valves, and turning on and off a pump delivery system.

“The industry has long sought an economical solution for automatic concentration control. We developed the AC3 for those customers seeking to improve the performance of their coolant chemicals, which in turn improves tool life and lowers operational costs,” states Tim Hanna, managing director of PRAB’s fluid filtration division in a company release.

Their company’s coolant recycling system uses a coalescing filtration process removing mechanically dispersed tramp oils to 0.1 per cent or less, and according to the company has demonstrated a reduction in haul-away costs by 90 per cent, and has lowered new coolant purchase up to 75 per cent, noting that payback on the equipment is typically six to nine months.

From vegetable-based options to recycling systems with automated concentration options, there are many ways shops can be improving their operations with new coolant solutions.