Manufacturing News

Sustainable cutting fluids

WITH the awareness that climate change is not going away, many companies are working hard to reduce their impact on the environment and improve their green image.

While there are many ways businesses can minimise their carbon footprint, since being green has become en vogue, there’s been a flood of products and solutions to hit the market claiming to be the answer to this problem.

It can be confusing to know which are ‘the real deal’ and what is just part of the green wash, and this is never more so the case than when it comes to cutting tool lubricants and coolants for metalworking applications.

Biodegradable lubricants and coolants, for example, have been offered as a viable alternative to petroleum and chemical based products and often deliver the same benefits but can, contrary to popular belief, also encounter some of the same issues.

The idea behind biodegradable lubricants is that they are derived from natural renewable sources (usually vegetable based) and are formulated in such a way to as to eventually break down after use for easy disposal.

In machining situations however, cross contamination between the different machining lubricants can occur, often rendering biodegradable lubricants as chemical waste.

Geoff Mahoney, technical manager with ITW Polymers and Fluids, says while many manufacturers want to use more environmentally friendly products in their operations, depending on the application, using biodegradable lubricants can be a false economy.

“Because there are often other fluids involved in the machining process such as gearbox oils, hydraulic oils and mill oils from the workpeice itself, biodegradable coolants can quickly be contaminated by these fugitive oils.

“This means the biodegradable lubricant can no longer be disposed of in sewage treatment plants or released into the environment in a controlled manner, so people expecting it to be disposed of less expensively as other lubricants often find this is not the case,” he told Manufacturers Monthly.

However the recent trend for formulators to develop ‘bio balanced or bio stable’ lubricants and coolants which are designed to last longer, means that solutions can now be recycled rather than disposed of in landfill etc.

Mahoney says with bacterial growth one of the main causes of reduced cutting fluid life, these solutions allow improved resistance to bacterial and fungal degradation.

“Manufacturers want a fluid that will last longer in their machines, reduce the downtime required to change the fluid, and which will not corrode the equipment or workpiece they are machining.

“A good quality, extreme pressure cutting fluid that provides effective cooling and lubrication can achieve this,” he said.

Less is more

Regardless of what solution is used in cutting fluids, there is no doubt that using less coolant is infinitely better not only economically but environmentally as well.

Robert Resch, MD of ProTUBE says bio-balanced machining coolant (cutting tool) formulations are enabling a lower consumption of fluids in machining and cutting operations.

“The emulsion droplet size does not change substantially over time, which provides a number of benefits including maximum coolant flow at the cutting edge for efficient cooling and extended tool life.

“Excellent coolant run-off capabilities avoids deposition of sticky residues on CNC machine windows, fixtures and components, and draining of coolant in chip disposal systems also reduces consumption,” he said.

According to Resch, bio-balanced coolants are healthier, safer and last longer with extremely good performance levels.

“Because the fluids are designed to have a low pH value (8.6-9.0), they cause less skin irritation and are less aggressive to materials susceptible to attack by alkaline solutions.

“Therefore, little or no staining on aluminium and little or no attack on painted surfaces. The pH level never needs to be increased as with some solutions to slow bacteria growth,” he said.

Recycling is also made easier because of the unique formulation of the solution.

“Due to demulsifying properties of less than 1%; a very small amount (less than 1%) of tramp oil emulsifies in the coolant. The tramp oil easily separates from the coolant and may be skimmed off.”

“Synthetic ester based cutting oils are providing high cutting performance at an economical cost, saving tool life and providing higher productivity as heavier cuts are possible than with mineral oils or soluble coolant,” he said.

Advances in cutting tool and machining techniques and developments in cutting tool materials such as the introduction of ceramic tips in cutting tools, are said to reduce the need for cutting fluids altogether, though both Mahoney and Resch do see a need for lubricants in the future.

“To get a good finish on the end product, the use of a cutting fluid can help to prevent metal build-up or damage to the surface of the workpiece, giving a better quality finish,” Mahoney said.

Both men also say there is a place for biodegradable lubricants in manufacturing operations particularly in situations where they can be pumped directly onto equipment and can be lost directly to the environment after use, such as in mining or railway applications.

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