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Beating the Heat with Machine Shop Coolants and Their Delivery Systems

[6/18/2020] COVID-19 and the ensuing shutdowns have put an enormous strain on the precision manufacturing industry, but as we transition back to a sense of new normalcy amidst a gradual and cautious reopening of the economy, machine shops are doing everything they can to scale up their production in spite of breaking supply chains, labor limitations, and rapidly shifting demand. The good news moving forward is that there have been some recent signs of slight economic improvement now that states and businesses are tentatively resuming operations. At Advanced Precision Machining’s (APM) Colorado machine shop, we have faced down the barrel of operational slowdowns, disruptions to our supply chains, and reduced demand for the parts we manufacture. Now with strict health and safety guidelines in place and weeks of careful planning, we’ve established new best practices within our rearranged milling and machining facility and are ready to ramp up to full speed. As we build our momentum back to pre-pandemic levels, there is a lot at stake, and we will continue to feed on our reputation for meeting our clients’ needs for high-precision parts delivered accurately and on-time. So, with the official start to summer soon upon us, the heat will be on us, both literally and figuratively!

Speaking of the returning high temperatures with the approach of summer, our staff of CNC machinists at APM thought this would be an ideal time to discuss heat, and provide readers with a primer on machine shop coolants, also known as cutting fluids, and introduce some common methods of coolant delivery. To put heat into proper perspective, one must look at the heart of most machine shops; its investment in expensive machining equipment. On the shop floor, heat is a major concern, but not in the sense of air temperature and keeping staff comfortable. Instead, throughout milling and machining operations, high speed machine 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 workpieces and the cutting tools being used. In short, there is perhaps no greater obstacle to producing a quality and accurate end product than heat. 

If machine tools are the heart of a machine shop, second only to its CNC machinists of course, then coolant can be thought of as its lifeblood. Consisting primarily of lubrication fluids, coolant types and their delivery methods vary widely. They have been developed and incorporated into nearly all CNC machining operations, and they work exclusively to lubricate and remove the heat produced at the point of origin between the tool and workpiece. This results in less damage to finished parts and/or equipment, lower operating costs, and increased efficiency on the floor. For purposes of our brief primer, we want to focus on the most commonly used coolant types: Liquids first and foremost, then Paste/Gels (solids) and Aerosols (gases). In a precision manufacturing environment, the most heavily relied upon coolant application is via a liquid medium. An emulsification combining water, oil, and often a chemical component is ideal. Water by itself has poor lubricating properties and causes rust, while oil alone is a poor coolant and is flammable. An optimal coolant is created by combining proper amounts of oil, water and an emulsifier together into a semi-synthetic concentration. Certain chemicals can be added to the mix to enhance rust and corrosion resistance, improve lubrication, and control bacterial growth for example. Some machine shop services do require the use of a solid or gel-based coolant, while others benefit from an aerosol or misting application, although these are far less commonly used and don’t warrant much discussion for our purposes.

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. Properly delivering coolant to a CNC machine and the workpiece in and of itself is a complex task and comes with different techniques and applications, varying in both properties and pressure. The most common forms include air, mist, flood coolant, and high pressure (aka through-tool). Cooling with air clears chips but has no lubrication purpose. Misting with coolant is a low-pressure method utilized where removing chips and heat are not a real concern. So, for the sake of simplicity, we will limit our discussion again to the most widely utilized techniques; traditional flood cooling and more advanced high-pressure delivery systems. Advanced Precision Machining relies on both methods, and we’d like to provide a comparison between the two highlighting some key advantages and disadvantages.

Flood cooling, an umbrella term, dates back some 150 years. Relying mostly on lower pressures, it describes the flooding, spraying, or dripping of coolant directly into the tool/workpiece interface. For use with smaller CNC machining centers, slower speed operations, or short production runs, it’s 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 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 steel, resulting in faster cycle times, better cut quality and greater throughput. Even chip management is improved as shorter shear zones create thinner chips.

So, as we move into the heat of summer, be sure that your machine shop remains cool as temperatures rise, and look into alternative cooling methods. Keep the lifeblood of your milling and machining operation pumping! We’ll do the same at APM as we continue to turn out the quality machined parts our customers rely on. Moving forward post-pandemic, it is our hope that all of us come out on the back end of this stronger than when we went in. And of course, we wish everyone continued good health and safety as we get back to business!

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 and a partner began 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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