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Beating the Machine Shop Heat; A Primer on Milling and Machining Coolants and Their Delivery Systems

August 9, 2022by Gerry Dillon

Thankfully, the recent COVID-19 pandemic and ensuing shutdowns are finally in our rearview mirror despite putting an enormous strain on the precision manufacturing industry. We’ll see what the future has in store however! Earlier this year, we transitioned back to a renewed sense of normalcy amidst a gradual and cautious reopening of the economy. Today, Advanced Precision Machining’s (APM) Colorado machine shop production is scaled fully back up to pre-pandemic levels although we’re still up against a faltering economy, supply chain issues, labor shortages, and shifting demand. Our facility faced down the barrel of COVID-19 and the ensuing operational slowdowns, we never lost pace, and we established new best practices as a result. As we continue to build upon our positive momentum, there is a lot at stake as we face new challenges, but we will continue to feed on our outstanding reputation for meeting our clients’ needs for high-precision parts delivered accurately and on-time. So, with summer in full swing now, the heat is upon us, both literally and figuratively!

Speaking of heat, this summer has been no stranger to high temperatures! With that being said, the staff of CNC machinists at APM thought this would be an ideal time to discuss heat in a machine shop environment, and how it’s an all too familiar foe in milling and machining operations. We’d like to provide readers with a primer on how we combat heat through the use of 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 very expensive machine tools. On the shop floor, heat is a major concern, but not in the sense of air temperature and keeping staff comfortable. Instead, 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 milling and machining equipment is at 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, types of coolant 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 introduction, we want to focus on the most commonly used coolant types: Liquids first and foremost, then paste/gels (solids) and aerosols (gasses). 

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 the preferred method. 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 blended 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. These vary 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 the 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 struggle through the dog days of summer this August, ensure that your machine shop remains cool as the temperatures rise, and look into alternative cooling methods. It’s important to 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, we wish everyone continued good health, prosperity, and safe operations as we hopefully put the COVID-19 pandemic far behind in our rearview mirror! 

Want to learn more about machine shop coolants and delivery methods, or have a question about your next milling and machining project? Contact the expert CNC machinists at Advanced Precision Machining today. 

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About the Advanced Precision Machining

APM provides comprehensive manufacturing services; from blueprint and prototyping, to machining and inspection. In our state-of-the-art machine shop, our fully certified CNC machinists offer a wide range of precision manufacturing services featuring the latest CNC mills and lathes to cut steels, composites, aluminum, plastics, and exotic metals. For additional information or to request a quote, please visit our website or call 303-776-1910.

by Gerry Dillon

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. Gerry has over 30 years of precision milling and machining experience under his belt.