Tour De Force: High Pressure Coolant Machining

Tour De Force: High Pressure Coolant Machining Colibri Spindles

High pressure coolant machining can avoid heat problems, poor chip control and low lubricity. By Sharon Weiss, chief executive officer, Colibri Spindles

High Pressure Coolant (HPC) has proven itself in many dedicated turning and milling applications and on difficult-to-machine materials at removal rates up to three times more than conventional flood coolant systems. Users report elimination of chip jamming, faster cutting and much longer edge life in outer and inner diameter turning as well as grooving, parting and hole-making.

The coolant is delivered with enough force (pressure of up to 80 bars) and fast enough to reach the cutting zone as a liquid, not a vapour. In the liquid phase, it lubricates the cutting process, as it cools the molten chip; shattering it into smaller, more manageable pieces. It also helps keep tool, insert and workpiece temperatures lower, resulting in significantly extended tool life—especially under high speed conditions.

The Flood Effect

Ordinarily, jets of high pressure coolant are delivered through two or three high precision nozzles creating a high pressure flood effect. However when using the flood method, coolant may be repelled from the cutting edge because the chips themselves create a pressurised area around the cutting zone that acts like a shield; deflecting coolant away from where it is needed most.

A way around this problem is to ensure the high pressure coolant is delivered as close as possible to the cut zone, to keep it well-lubricated and cooled.

HPC Applications

For that reason, the benefits of HPC machining can really only be achieved by using tools and holders specially developed for high pressure coolant applications. This includes tools that enable a more focussed coolant delivery such as through-the-tool coolant systems designed to work with HPC. An example would be Colibri’s HPC coolant-driven auxiliary high speed spindle, which is engineered to utilise a high pressure coolant pump for high speed operations of up to 60,000 rpm.

It is applicable for a broad range of turning, milling and drilling operations on an equally broad range of machines. It is also suitable for machining challenging materials as well, such as titanium and various stainless steels. Selecting the right tools and pump (pressure and flow) for each application, correctly applied, will ultimately improve your bottom line, by providing a quicker return on investment through increased machine utilisation and optimised metal cutting efficiency.

Implementing HPC

If HPC is implemented at the time of a new machine investment, the payback can be realised in just a few months. High-pressure capability is increasingly becoming available as standard on new machines.

However, retrofitting still offers benefits. So whether you are thinking of purchasing a new machine equipped with a high pressure coolant pump or retrofitting your existing machine, be sure you have got the right tools best suited for HPC machining operations—especially at high speeds.

APMEN Machine Tools, September 2017

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