Advanced Precision Machining

Flood vs. Through-Tool Coolant Delivery Systems

[5/12/2016] With the approach of Spring and rising temperatures again, the heat will soon be back upon us. On the machine shop floor, heat is a concern to milling and machining operations, but not in the sense of air temperature. Instead, high speed machining tools such as CNC mills and lathes generate a tremendous amount of friction during the process of removing material from machined parts, resulting in heat, which can damage both parts and cutting tools. Second to its staff of dedicated CNC machinists, at the heart of most machine shops is its investment in expensive machining equipment, and coolant can be thought of as the lifeblood. Consisting primarily of lubrication fluids, coolant types and their delivery methods vary, but they work to remove the heat produced at the point of origin; between the tool and workpiece.

Today’s technologically advanced CNC machine tools all come outfitted with a standard coolant delivery system, resulting in less damage to finished parts and/or equipment, lower costs and improved efficiency. The most common techniques of delivering coolant to where it’s needed include traditional flood cooling, and newer, through-tool coolant systems. Advanced Precision Machining’s Colorado machine shop relies on both methods, and for the sake of discussion, we’d like to provide our readers with a comparison between the two highlighting some key advantages and disadvantages.

Flood cooling, an umbrella term, is perhaps the oldest and most traditional standard for coolant delivery dating back some 150 years. Relying mostly on lower pressures, flood cooling describes the flooding, spraying, dripping or misting of cutting fluid (coolant) directly into the tool/workpiece interface. For use with smaller or stand alone CNC machining centers, or for slower speed operations or short production runs, it has long been considered effective to simply splash fluid around the work area to obtain the desired result. Flood coolant does draw heat out of the machining process, but not very effectively on today’s faster, more complex and advanced CNC mills, lathes and routers. Vapor buildup becomes common with flood cooling as the coolant reaches its boiling point rendering it less effective. Simply put, flooding the interface does not direct the coolant to where it’s needed most; directly under where the tool is shearing through metal. Flood coolant is effective however at improving tool life and surface finishes, reducing friction, corrosion prevention and moving larger chips or swarf out of the way.

The higher speeds, faster feed rates and extreme temperatures produced by today’s more advanced CNC milling and machining centers have led to more innovative cooling methods. Newer machines require higher pressure, more volume and better directed coolant to keep pace and the flooding paradigm is no longer the clear winner. Delivering coolant into the cutting edge or point of the tool directly through tool or spindle has proven much more effective. Known as through-tool or through-spindle coolant systems, they are plumbed to create a rotating union between the spindle or tool and the coolant supply, resulting in a host of benefits. Higher pressures and velocities eliminate the vapor barrier problem and heat is removed more effectively. More efficient cooling allows for the utilization of carbide cutting tools over high speed steel (HSS), resulting in faster cycle times, better cut quality and greater throughput. Even chip/swarf management is improved as shorter shear zones create thinner chips/swarf.

 Compared with traditional flood coolant systems, the trend today towards through-tool coolant delivery satisfies ROI in terms of lowered operating costs for coolant, increased tool life, faster speeds and feeds, more accurate parts and reduced secondary operations. So, keep cool as temperatures rise, and look into alternative cooling methods. Be sure to keep the lifeblood of your milling and machining operation pumping!

Want to learn more, or have a question about our range of services? Contact the expert CNC machinists at APM’s Colorado machine shop for all of your milling and machining needs.

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About the Author

Gerry Dillon is a co-founder, current owner and certified CNC machinist at Advanced Precision Machining (APM), a full-service machine shop located in Longmont, Colorado. Before making his home in the United States in 2000, Gerry was born and raised on the emerald isle of Ireland and took an interest in milling and machining from an early age, ranking #1 in the Irish National Apprenticeship Program. In 2005, he partnered with his friend and colleague, Kirk Tuesburg, currently APM’s machine shop manager, together launching what’s grown into a leading Colorado machine shop. Gerry brings over 30 years of machining experience to the shop floor, and is certified in all aspects of geometric dimensioning and tolerancing. 


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