Should you adapt an air knife to your bar feeder? When do you need an air knife?

First, an air knife comes standard on our Patriot 338. It can also be added to a Ranger 120 or retrofitted in the field or in-house on an FMB Turbo 3-38, FMB Turbo 5-65, FMB Turbo 8-80 and FMB Turbo 20-100.

Why do you need an air knife?

In high-speed CNC lathe operations, 12 and 6 ft bar feeders use hydraulic oil to achieve the hydrodynamic effect (sometimes called the hydrostatic effect). The hydrodynamic bearing effect keeps the bar stock spinning smoothly. A thin layer of oil forms a pliable barrier between the bar and the guide channel, which reduces friction, cuts down on vibration, and cushions the bar as it rotates. You can read all about it here.

However, depending on a shop’s setup, longer parts are coated in oil, but may not have enough time to spin all the oil off before going into the lathe. For shorter parts at higher RPMs, the oil usually has time to whip off the bar before it reaches the spindle, so it’s less of an issue. On long parts, however, the oil can travel into the spindle before the material even starts spinning.

We’ve seen shops losing a significant amount of oil from their bar feeder, which (depending on the model) holds 15 to 22 gallons.

This creates two issues: we lose a small amount of circulating oil with each bar, and the coolant can become contaminated.

The air knife helps reduce both problems by blowing air around the bar to remove excess oil before it enters the lathe. Generally, it’s good for applications that involve long parts.

How does the air knife function?

The air knife functions in automatic mode any time the collet is open or material is moving forward, so that it can cut oil from material as the material moves into the spindle of the lathe. You can adjust how much pressure the air knife uses. Too little air pressure, and it won’t cut the oil properly. Too high, and you force air toward the spindle. Make sure you use the proper amount of pressure to cut the oil down and into the bar feeder, not forcing it forward or not cutting at all.

An air knife is an easy solution to avoid cross-contamination and minimize oil loss. It doesn’t need to be adjusted per bar diameter; one size fits all. Because it’s a blast of air, and the machine already has the provisions for it, it requires no additional maintenance either.

This way, you don’t have to skim so much oil from the lathe side!

To see the air knife in action, watch the video below.