Cutting tools Pinpoint cooling jet lubrication

Editor: Briggette Jaya

Europe – The best cooling is useless if it doesn’t get to the blade. Therefore, tools with integrated coolant supply are increasingly used. Experts predict that the trend in cooling strategies is moving toward minimum-quantity lubrication and high-pressure cooling.

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Less is more: Targeted internal coolant supply yields very good results, both in terms of effective cooling and lubrication as well as chip removal.
Less is more: Targeted internal coolant supply yields very good results, both in terms of effective cooling and lubrication as well as chip removal.
(Bild: Horn)

They are supposed to cool, lubricate and wash away chips. Cooling lubricants (CLs) are true all-rounders with their diverse tasks in machining. Ultimately, they contribute to longer tool life, better workpiece surfaces and reliable chip removal, thus making a crucial contribution to economic machining.

Machining accuracy benefits from good cooling

Jens Thing, managing director of Haas Automation Europe, describes the task as follows: “Coolants are expected to remove heat from the processing point as quickly as possible to avoid variations in the fabric of the outer layers of tool and workpiece. The machining accuracy also benefits from good cooling, which also makes higher machining parameters possible.”

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However, according to the German Federal Statistical Office, cooling lubricant costs make up 8-16% of total machining costs. These include the provision and disposal of coolants as well as the costs during machine operation. “The percentage of cooling lubricant costs in the unit cost for the production of a component depends significantly upon the workpiece, material, machine and production concept,” explains Dr. Klaus Christoffel, Manager Product Management & Design at Sandvik Tooling Deutschland GmbH, a Sandvik Coromant Division. “In many cases, it is a substantial amount, which is above the proportionate tooling costs.”

Flood cooling probably still most common

Reason enough to look at not only the coolant itself, but also in what form and volume it is supplied to the production point. Here, one can distinguish between different concepts. In classic wet machining, tools and workpiece are flooded with cooling lubricant. “This submersion cooling appears to still be the most widespread,” says Christoffel. “That's because it is easy to implement and has no special requirements for tools and machine,” explains Markus Kannwischer, CTO and member of the executive board at Paul Horn GmbH. However, the energy demand is high and only a few percent of the used cooling lubricant would actually hit the relevant point of the blade. Jochen Nahl, sales director at Grob-Werke, names another disadvantage of the method: “The costs for supplying the machine and for the treatment and disposal of the cooling lubricant are high.”

From a cost standpoint, a strong case can be made for other cooling strategies, like minimum-quantity lubrication (MQL) with typical dosages of 5-50 ml per processing hour, high-pressure cooling from 80 bar, or dry machining. Kann-wischer's general advice for users is: “Less is more! The targeted internal coolant supply brings very good results, both in terms of effective cooling and lubrication as well as chip removal.” According to Nahl, MQL machining with its lower energy costs is used particularly in mass production. It offers benefits like cost reduction because there is no need for a cooling lubricant system (supply and removal), lower energy use (no coolant pumps required) and reduced chip disposal and recycling costs.

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