3 things you should know about air-assisted laser cutting

A move away from nitrogen could result in cost savings and increased throughput

The FABRICATOR January 2017
January 6, 2017
By: Robert Farrell

Laser cutting with nitrogen as an assist gas is still the No. 1 choice for applications in which edge quality is critical. Air as an assist gas, however, might work in some not-so-critical applications, and its use will generate sustainable cost and time savings while boosting productivity.

Nitrogen is still the assist gas of choice when it comes to laser cutting applications in which high-quality edges are required or blemishes are not allowed on the surface area near the edge, but air as an assist gas may make sense for other applications.

If you laser-cut metal for a living, you are no doubt familiar with assist gas. You may know that nitrogen and oxygen are the most popular of these gases, and you may have even heard that air is a cost-effective alternative to those gases. But how do you know if air-assist is right for you in your laser cutting operation? Here are three things that you should know about air-assisted cutting.

1. How Does Air-assisted Laser Cutting Work?

Neither fiber nor CO2 lasers rely strictly on a light beam for cutting metal. Rather, the process includes the injection of an assist gas at the nozzle to supplement the process. This confluence initiates a process known as an exothermic reaction—a chemical reaction that releases energy by light or heat. The introduction of nitrogen, oxygen, or air helps transfer heat more effectively than the beam alone.

Initially oxygen was the most popular gas for the laser cutting process. Later it was discovered that nitrogen produced a cooler cut, resulting in cleaner edges, perfect for industries where aesthetics and edge quality were critical. While nitrogen remains the most widely used laser cutting gas, air is proving to be an effective and cost-saving alternative for a growing number of fabricators.

This is not to suggest that air-assisted cutting is a radical departure from nitrogen or oxygen. Air is, after all, approximately 80 percent nitrogen, with the rest consisting primarily of oxygen. The goal with air-assist cutting is to use this high concentration of nitrogen while at the same time leveraging the added benefits of substituting a slightly more diluted gas.

2. What Are the Advantages of Air-assist Laser Cutting?

While relatively new to some, air-assist cutting has been around for nearly 20 years. Machine tool manufacturers began researching and developing the process as early as 1998.

Since that time the use of air as an assist gas has continued its steady growth in popularity among both fiber and CO2 laser users alike. Mode quality was a major limitation when compressed air was first introduced for CO2 lasers, but that has improved significantly. Today air-assist is an efficient and popular method for cutting a variety of materials, even stainless steel and aluminum.

Air carries with it a substantial return on investment for those employing fiber lasers or those cutting stainless steel.

The intense heat of fiber lasers, combined with injected air, creates cuts without producing an oxide formation on the cut surface. This means that secondary cleanup operations are significantly reduced or even eliminated.

As any fabricator using nitrogen will tell you, it is a costly gas. In some instances, the cost of the gas alone can be as high as 90 percent of the total operating cost. Air is considerably less expensive than both nitrogen and oxygen.

Another advantage of air is the faster cutting and increased throughput it delivers. Cutting tests on the full range of materials and thicknesses prove this out.

For example, for material thicker than 10 gauge, tests have shown that nitrogen produces faster cuts, but in the mild steel range of 10 gauge (0.135 inch) and thinner, air is roughly 3 percent faster than nitrogen. In the stainless steel range from 0.750 in. down to 20 gauge (0.036 in.), air is about 22 percent faster. In the aluminum range from 0.190 in. down to 0.032 in., air is approximately 14 percent faster.

3. When Should Air be Used as an Assist Gas in Laser Cutting?

Today businesses are scrutinizing all areas of the operation to cut costs and boost productivity. For fabricators, this puts the shop floor under a microscope.

Something as common as air can deliver measurable cost and productivity improvements. While air is generally used to cut thin material, most stainless parts, especially those used in assemblies, are candidates for air-assist laser cutting.

While clearly not the best gas in all instances, generally speaking, air produces a laser-cut edge quality that is at least comparable to parts cut with oxygen or nitrogen. In fact, if one were to label nitrogen edge cut quality as a 10, then the edge quality resulting from an air-assist cut would be about an 8. Air-assist edge quality is more than satisfactory for most powder coatings to adhere to, eliminating the need for secondary cleaning operations.

Still there are times when nitrogen remains the best gas choice. Nitrogen produces a cleaner cut, and those serving customers throughout the food processing and aerospace industries should continue their use of the gas.

Additionally, some cosmetic parts cannot show any blemish whatsoever. Again, these types of parts would not be candidates for air-assist cutting.

Is It for You?

So is air the best choice for your laser cutting operation? The short answer is, of course, maybe. It all depends on the industries you serve and how important edge quality is to you and your customers.

The bottom line is that when edge quality is absolutely critical, nitrogen remains the best option. It produces cooler cuts and is an inert gas, meaning that there is no chemical reaction when cutting stainless steel. This prevents oxidization from occurring, leaving a clean, shiny edge that eliminates secondary descaling operations.

What about setup cost? Switching your laser cutting operation to air is relatively easy and cost-effective. Even most older-model lasers can be adapted to cut with air. Although an initial investment for the proper equipment is necessary, a fabricator that taps air as an assist gas should be able to generate sustainable cost savings while boosting productivity.

While air is certainly not the optimal assist gas in all cases, it is an efficient and cost-effective alternative for many. Take a look at the parts you cut, and investigate how much you are spending on assist gas. Run some tests and determine for yourself if the answer to increased productivity and profitability isn’t literally all around you.

Putting Air to Work

Doyle Equipment Manufacturing, Quincy, Ill., makes dry fertilizer blending, conveying, tending, and spreading equipment for the agricultural industry. Primarily processing stainless steel, more than 90 percent of the parts are cut on lasers. Both nitrogen and air are used, with about one-third of all cutting (both mild and stainless steels) relying on air as the assist gas.

Stuart Rumple, Doyle’s production manager, said the main concern about using air-assist during laser cutting was the weld quality of the cut part. Customers expected a nice, clean edge for a good weld.

When they saw the result of the air-assisted laser-cut edge on materials 0.105 in. and thinner, they didn’t have to worry. The fiber laser delivered edges that weld up “perfectly,” Rumple said.

“While we’ve successfully cut stainless material up to 1⁄2 in. using air, we generally find that thicker cuts are best-suited for nitrogen,” he said. “That said, we utilize air on a regular basis and have found the cost savings to be immense. Air-assist allows us to run our machines at less than $4 per hour, which equates to about a 90 percent savings over our CO2 laser and about 75 percent less cost than using nitrogen on the same machine.”

Robert Farrell

Contract Writer
Cincinnati Incorporated
Phone: 513-367-7100

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The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.

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