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Liquid Nitrogen an Alternative to Traditional Coolants

Ed Sinkora
By Ed Sinkora Contributing Editor, SME Media
Ilene Wolff
By Ilene Wolff Contributing Editor, SME Media

Cryogenics offer an alternative to traditional liquid coolants when conventional cooling methods can’t or don’t do the job well enough.

For example, the Cryogenic System from 5ME LLC (Cincinnati) moves liquid nitrogen (LN2) through the machine, spindle, and cutting tool to just behind the cutting edges. This approach yields a cutting tool refrigerated to −321°F (−196°C).

This effectively raises the critical temperature of any given application (i.e., the point at which any further rise in temperature causes a dramatic increase in tool flank wear). That means a tool can be run much faster with increased material removal rates and still offer acceptable tool life.

5ME’s system includes vacuum-jacketed insulated lines that carry the liquid nitrogen from the source to the cutting tool. The lance goes through the existing spindle (including high-torque and high-speed applications) using the inner diameter of the through-coolant drawbar.

That means the machine would no longer have through-spindle coolant capability, though you can leave flood coolant capability on the machine to increase versatility.

The patented solid-carbide cutting tool technology, which 5ME brands as BlueZone, incorporates channels that radiate out from the center, following the flute pattern internally to a venting port.

The 5ME Cryogenic System moves liquid nitrogen through the machine, spindle, and cutting tool, which allows for faster turning and increased material removal while still offering acceptable tool life.

5ME has licensed Fullerton Tool Co. (Saginaw, MI) and Star SU LLC (Farmington Hills, MI) to provide BlueZone solid-carbide round tools. Additional global cutting tool OEMs are in negotiation to provide both round tools and indexable inserts, including Kennametal (Latrobe, PA), which built its first test and demonstration indexable high-feed mill in 2017.

5ME’s system also includes a sub-cooler that removes pressure-generated heat from the line, condensing dual-phase nitrogen (liquid and gas) to 100% LN2. This component ensures that there is always optimal LN2 flow to the cutting tool, regardless of the LN2 source or its distance from the machine tool.

Finally, the system comes with a programmable control that regulates the flow rate of the LN2 to the tool, with a user-friendly interface directly on the CNC.

Will Gruber, 5ME’s manager of marketing and channel sales, said that “the user controls the flow of the liquid nitrogen in the same way he would control feed rate, with programmable flow rates or manual flow rate override. Likewise, it’s the flow that determines how much heat the system can pull from the machining operation, with average flow rates of 0.25–1 L/min and the capability to increase flow as high as 6 L/min. This minimal consumption rate results in consumable costs less than $5 per hour, which is a 40% cost reduction compared to allocated coolant costs that include water, coolant and disposal.”

The 5ME Cryogenic System can be retrofitted to virtually any machining center and several OEMs have joined with 5ME to offer it as a new machine option. That group includes DMG Mori USA, FFG, Fives Machining Systems Inc., Mazak Corp., Okuma America Corp. and Doosan Machine Tools America.

The 5ME Cryogenic System includes all the mechanical components, installation, CNC interface and training.

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