Cool, Clean Cutting Coolant

Special REGO-FIX guest blog with Craig Happel, Vice President of Sales at Fusion Coolant Systems 

Liquid coolant is crucial in controlling the heat generated in metalcutting operations. Unfortunately, traditional coolant fluids contain additives that not only have adverse effects on humans, but can also present workpiece contamination issues as well.

Take for instance orthopedic implants produced by additive manufacturing (3D printing). These implants intentionally feature porous surface finishes that promote osseointegration where the bone grows into and anchors itself to the implant. A recurrent problem with these porous surfaces is that it is nearly impossible to completely clean traditional metalcutting fluids from them after machining, even with ultrasonic and other advanced washing techniques.

Metalcutting fluid or oil trapped in the porosity will cause the body to reject the implant. To ensure that the implant meets cleanliness specifications, medical component manufacturers  and others are turning to supercritical CO₂ coolant systems that use no oil or other contaminants to eliminate the need for special post-machining cleaning operations.

In operation, these systems send the supercritical CO₂ through a machine tool at temperatures and pressures similar to those of high pressure emulsion coolants. They require minimal adjustments to a shop’s machining equipment and use endmill holders, such as REGO-FIX powRgrip holders, that feature special smaller coolant holes – in the range of 100 µm to 250 µm – specifically for supercritical CO₂ applications.

The benefits come from the properties of supercritical fluids. For any fluid there is a critical point of temperature and pressure where distinct liquid and gas phases do not exist. Above that point the fluid is considered supercritical and has the density of a fluid and the viscosity of a gas. The critical point for CO₂ is roughly 88˚F (31˚ C) and 1100 psi (76 bar). Supercritical CO₂ provides cooling and lubrication for metalcutting operations, and, when desired, can also carry and disperse chilled nano droplets of oil for more powerful lubrication.

Depending on application, Fusion Coolant Systems offers two supercritical CO₂ system versions – Pure-Cut and Pure-Cut+. Pure-Cut coolant uses additive-free CO₂ in its supercritical state for dry machining and is ideal for medical manufacturing and other applications where 100 percent clean environments and excellent surface finishes are required. Chips are clean and easily recyclable. Pure-Cut + coolant adds minimal lubrication for cutting applications where faster speeds and longer tool life are desired.

Supercritical CO₂ coolant is effective in a wide variety of operations and materials. One study using Pure-Cut+ in a Vanadium steel drilling application, for instance, reported tool life gains of up to 5 times. A turning operation in titanium using Pure-Cut oil-free coolant resulted in 20 percent faster machining and 20 percent longer tool life.

Supercritical CO₂ coolant systems, such as those from Fusion Coolant Systems together with REGO-FIX tool holders, deliver performance similar to traditional flood coolants without health, safety and environment threats, workpiece contamination or machinery integration expense for a manufacturing facility. The CO₂ used in systems is reclaimed from industrial processes and no new CO₂ is generated.