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Picture a structural fab shop's typical band saw cutting I-beams, with fluid flooding the work zone. Of course, this makes cleanup time-consuming, with metal chips and sludge gathering at the end of the beam channel, which effectively becomes a riverbed dammed up at the end with a pile of rags, or with a carefully positioned bucket to catch the flow. The disposal costs continue to rise, along with associated handling costs. It all seems par for the course.

Or is it?

Near-dry, or minimum-quantity-lubrication (MQL), applications have made significant headway in the machining-center world. But according to industry experts, the technology has equal applicability under the saw blade.

Process Basics

In a standard sawing application using flood coolant, the water dissipates heat by evaporating. The more heat dissipates, the higher feeds and speeds can go and the more efficient the operation can become.

However, cleanup time and disposal of that sludge can take that efficiency away and then some. Yet with near-dry sawing, "you never have to clean out a sump in the saw or dispose of your coolant," says Shawn TeVelde, national sales manager for Unist (www.unist.com), Grand Rapids, Mich. For some applications, "it can actually cost more to dispose [flood] coolant than to buy it in the first place."

Unlike flood coolant, the amount of near-dry lubrication doesn't alter from material to material, explains Dennis Neuwirth, field technical representative for blade manufacturer M.K. Morse Co. (www.mkmorse.com), Canton, Ohio. The type of lubrication doesn't vary either, except with aluminum and copper applications that may require special lubricant to avoid stains from deoxidation. In near-dry sawing, a barrier of lubrication—using mere ounces during a typical eight-hour shift—is coated on the blade itself during cutting. That barrier prevents the blade from getting too hot.

According to Neuwith, the trade-off in near-dry applications occurs with surface footages. Feed and speeds generally must be reduced for near-dry sawing to work effectively. "Keep in mind," Neuwith explains, "that as far as productivity of the sawing operation itself, nothing beats flood coolant," adding that near-dry applications require manufacturers sacrifice 10 to 15 percent of surface footage (speed and feed), depending on the application.

Here, viewpoints vary. According to TeVelde, "in our experience, one does not have to sacrifice blade life or production speeds to go to near-dry machining."

Regardless, say sources, shops should look at the application from a macro-perspective. What are the fluid disposal costs? How much time do operators spend cleaning up? In certain circumstances, safety considerations may come into the picture, with pools of coolant collecting on the floor.

Fluid Application

A typical flood-coolant nozzle may be placed 12 inches away from the blade. For near-dry sawing, this must be reduced to between only a half inch and an inch away from the cutting operation. This can be a challenge for some saw designs. For installation, "we sometimes need to punch out a small space in the door so that the nozzle can fit closely and directly face the saw teeth," TeVelde explains.

Depending on the saw design, "I've sometimes had to drill holes in the saw's frame to permanently mount the nozzle" close to the blade, Neuwirth says. "Nozzle alignment is absolutely critical."