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[April 27, 2015] The heat is on! With the approach of summer and returning high temperatures, the staff of CNC machinists at APM’s precision machine facility thought this would be an ideal time to provide readers with a primer on machine shop coolants, also known as cutting fluids, and introduce some common methods of coolant delivery. Throughout the milling and machining process, there is perhaps no greater obstacle to producing a quality and accurate end product than heat. Today’s high speed machining tools generate a lot of friction resulting in heat, which if left unchecked, can damage both the workpiece and the equipment being used. Coolants, primarily fluids, have been developed and incorporated into CNC machining operations to both remove heat from the process and lubricate the interface between tool and workpiece. This results in less damage to finished parts and/or equipment, lower operating costs and increased efficiency on the machine shop floor. For purposes of our brief introduction, we want to focus on the most commonly used coolants and delivery methods.
In generic terms, coolants/cutting fluids can be lumped into three basic categories: liquids, paste/gels (solids) and aerosols (gases). In a precision manufacturing environment, the most heavily relied upon method for reducing heat and improving lubrication is through the application of a liquid medium. An emulsification combining water, oil and often a chemical component are most often utilized. Water by itself has poor lubricating properties and causes rust, while oil alone is a poor coolant and is flammable. Optimal cutting fluids are 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. Certain machine shop services 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.
When it comes to CNC milling and machining parts, the coolant delivery process is as varied as the task at hand and the equipment used. For the sake of simplicity, we will limit our discussion again to widely utilized methods; traditional flood cooling and more advanced high-pressure delivery systems. Flood cooling is an umbrella term, and describes more low-pressure applications of coolant to the machining equipment and workpiece. This can include truly flooding the work area (although messy), spraying it, using a slow drip or misting it. These methods of applying cutting fluid benefit precision machine parts that are turned out with smaller CNC machining centers, or stand alone equipment, often operating at slower speeds or for shorter production runs. More complex, larger and technologically advanced CNC mills, lathes and routers require high-pressure and high volumes of coolant to keep up. High-pressure delivery eliminates the vapor buildup common with flood cooling as the coolant reaches its boiling point rendering it less effective. In addition, it has better ability penetrate into the interface between tool and workpiece. As a result, cycle times are decreased, tool life and chip management is improved, and the final part is a smoother, more accurate and high quality result.
So, keep cool this summer, and we’ll do the same as we turn out quality machined parts. 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.
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.