With MQL, less is more

It might seem counterintuitive that a cutting tool doesn’t need to be flooded with coolant to prevent it from overheating during a metalcutting operation, but minimum quantity lubrication has a long history of effectiveness.

“It’s difficult to break from the myth that more is better,” said PCA Products Inc.’s Don Yates. “If there was a better understanding that a minimal application of lubricant will get you more life in your tool and less cleanup, it would be worth someone taking a shot.”

Although his title is marketing manager at the Sevierville, Tennessee-based manufacturer of sliding screen doors, he said he also manages custom tool manufacturing and designs aluminum extrusions.

“I am kind of the IT department, the engineering department and the marketing department,” Yates said. “I wear a lot of hats.”

Presented here are the MQL applications at a couple of U.S. manufacturers and a look at what the technology offers.

Put Down the Bottle

PCA Products is a family-owned company that started producing screen doors with heavy aluminum frames 35 years ago in Florida, where it still does some light manufacturing in Punta Gorda.

“We do our own proprietary extrusion designs, and we powder-coat instead of wet-paint,” Yates said. “From the standpoint of durability and longevity, it’s a great combination. It makes them last much longer, even in a heavy salt environment like the Florida coast.”

Elite Trailer Manufacturing machines aluminum using MQL. Image courtesy of Elite Trailer Manufacturing

The company began its MQL journey 15 years ago when it installed an MQL applicator from Unist Inc. in Grand Rapids, Michigan, on a double-miter saw. At the time, machine operators manually sprayed lubricant on a tool using a spray bottle prior to cutting, he said. However, shielding around the saw prevented that approach, so PCA Products tested a couple of MQL systems and selected the one from Unist because it applied the least amount of lubricant.

Bottle spraying continued for the other machining operations, but the process was far from ideal. Yates said manual spraying deposits an inconsistent amount of lubricant on a tool, and any excess remaining on the tool causes chips to stick to it, making the cleaning process difficult and time-consuming.

“There is no portion control when it comes to a spray bottle,” he said.

In addition, Yates said Occupational Safety and Health Administration regulations require that bottles of chemicals, such as metalcutting lubricants, be labeled properly with warnings and other information, but labels don’t tend to adhere well to a bottle with lubricant on its surface.

“You can hardly keep a sticker on it,” he said.

Another consideration was cleaning, which Yates said is a three-stage dip process involving cleaning, rinsing and sealing before powder coating. Reducing the amount of coolant left on parts would reduce the requirements of time and money to maintain each of the three 3,028-L (800-gal.) tanks.

“Every time we dump a tank,” he said, “$200 in chemicals goes in the tank.”

To keep up with demand, Yates said PCA Products added a couple of product lines over the past several years in which aluminum is powder-coated prior to cutting and assembly.

“You need to keep lubrication to an absolute minimum,” he said, “or you are transferring it to all your materials, and you are spending more time cleaning the doors. As we evolved in our production, the need for MQL became more apparent.”

Yates said PCA Products has stayed busy during the pandemic. As with toilet paper, demand is strong for screen doors when people spend more time at home, he quipped. The company expected to process more than 317,515 kg (700,000 lbs.) of 6063 and 6065 aluminum alloys in 2020.

About four years ago, PCA Products started to build computer-controlled cutting tools and added Unist applicators that could be triggered from a programmable logic controller or from software, he said. In addition, the company put MQL systems on equipment that it initially didn’t consider suitable for a Unist oiler, such as two- and six-gang drill heads, chop saws, flywheel presses and a pneumatic punch. When equipment is oiled manually, PCA Products has developed methods to prompt the Unist oiler.

“If we are using a pneumatic tool or a chop saw that only has air to it but no power,” Yates said, “we will use a pneumatic roller switch and just trigger the Unist (oiler) from the pneumatic trigger.”

The six-gang drill at PCA Products is equipped with a Unist MQL system with three pumps that are PLC-triggered to three split nozzles. Image courtesy of PCA Products

He said when PCA Products first used MQL on its double-miter saw, it applied lubricants that were designed for cutting steel and aluminum and weren’t from Unist.

“They were so thick,” Yates said. “We were seeing them all over everything.”

He said after the company expanded its use of MQL, it switched to a Unist Coolube lubricant designed for the aluminum alloys that PCA Products processes.

According to Unist, Coolube’s polar molecules have opposing charges at each end that cause the molecules to align and create strong bonds, providing a thin, low-friction barrier between a cutting tool and a workpiece.

Yates said PCA Products uses the same base MQL applicator with usually either a single-pump oil unit or a dual pump for machines with multiple nozzles.

“We use a triple pump on the six-gang drill to get all six nozzles lubricated,” he said. “We use split nozzles on the drills, drill presses and punches. It allows us to get two nozzles out of a single pump.”

With MQL, a tool remains dry enough to blow chips off it with an air hose, Yates said. In addition, tool life nearly has doubled compared with manual spraying, depending on the application. For example, a drill on a six-gang drill unit now produces 2,000 to 3,000 holes before needing replacement.