The hidden costs of laser cutting gases

Eliminating inefficient gas delivery can boost the bottom line

By John Gabris

July 6, 2009

Gases for laser operations can be a significant factor in keeping costs down.

A well-designed and -installed lasing gas delivery system will ensure the gas remains pure when traveling from the cylinders, through the plumbing, and into the laser system.

Operations managers are always on the line for costs. Whenever the economy takes a dip, the microscope comes out for a closer look at how an operation can be more efficient. Gases for laser operations can be a significant factor in keeping costs down and, in some cases, can make the difference between survival and closing the doors.

Lasing Gases

Lasing gases must meet the stringent purity specifications found in the OEM manual for each machine. Note that while the manual may indeed mention certain gas vendors, fabricators aren't required to buy from them. Indeed, some vendors listed as "approved" may no longer exist. As with any purchase, fabricators are free to choose an approved vendor that best fits their needs. At the end of the day, it's the service and gas quality that really matter.

Laser equipment OEMs approve gases from various vendors—both independent suppliers and national chains—as long as they obtain a certificate of analysis proving they meet the OEMs' standards for quality. Also know that OEMs are continually approving new vendors.

Purchasing lasing gases from an unapproved vendor usually voids the equipment warranty, and for good reason. Gases that do not meet purity specifications can damage a laser machine's mirror and lenses, which can lead to lost production and repair costs. Mirrors cost up to $500 each, and some lasers have 10 or more mirrors. Lenses can run $1,000 apiece. And all this can require a certified technician who sometimes needs to be flown in, often costing $1,500 a day.

Getting high-quality gases in the door is the easy part; preventing gas contamination is the tricky part. High-purity regulators are designed with high leak integrity, because only a few parts per million of oxygen or moisture from the atmosphere in your shop can damage the laser or cause poor-quality cuts. Standard industrial-grade regulators are not sealed as well and are not made with high-quality materials. Over time their internal components can break down, sending destructive particles into your laser system.

Running out of gas completely can cause similar harm. If you starve your machine of gas, you may also damage it or incur significant maintenance costs. How much production time will be lost each time you stop to change out a cylinder? Automatic switchover devices do this for you and help maintain gas purity.

Gas delivery involves more than just the cylinders, regulators, and manifolds. The actual piping from the tanks to your system need to enter the equation. The piping contractor must understand the tremendous importance of purity when installing the pipes feeding gas to a laser cutting system. Small particles left in the pipes from installation can damage the mirrors and other internal laser components. For this reason, all pipes purchased for the installation must be cleaned and capped.

If you can't find a local gas vendor experienced in such laser installations, it might be a good idea to consider packages from OEMs that include not only the machine but a gas delivery system as well. Note, though, that some of these start-up kits may not suit your operation, particularly if you operate multiple lasers.

Assist Gases

Assist gases use a completely different delivery system. They require high-flow regulators, and just as with lasing gases, regulator quality also is very important.

Because assist gases are used in high volumes, the source tanks will be larger too. Here, be sure you install tanks that are large enough to plan for growth, but not too large. Some may start with a cylinder bank or liquid cans, but many shops soon find this inadequate when they bring another laser onto the floor.

You don't necessarily need bulk tanks either. It's common to see bulk assist-gas tanks at many companies, large and small, but are these really needed? True, choosing this option allows a fabricator to get the lowest gas price per unit, but rarely are these bulk tanks really the best option for small or medium-sized laser operations. Bulk tanks traditionally start at 1,500 gallons and go all the way up to 13,000 gallons. They require heavy, reinforced concrete pads and have large rental fees. They also require a separate booster system to attain required assist-gas flow rates for laser operations.

As an alternative, consider microbulk tanks as a happy medium. These tanks start at 450 liters and go up to 2,000, can be placed on existing pavement or a light pad, and are available with output pressures up to 500 PSI—essential for the high flow rates laser assist gases require. Ferrous metals require oxygen flows of about 400 standard cubic feet per hour (SCFH), while nonferrous metal requires nitrogen assist gas to flow at about 3,000 SCFH. These tanks are also modular, so additional tanks can be added as the business grows.

Uninterrupted Supply

This is essential for high-volume operations. It is easy to lose track of your gas inventory when you get caught up in the daily grind of production. Uninterrupted supply requires good service from a gas supplier. At times judging customer service can be subjective—but geography isn't. Where is your gas vendor located? A St. Louis metal fabricator buying gas from a supplier in Michigan doesn't make much sense. No matter how good that Michigan gas supplier is, freight costs to deliver cylinders several hundred miles can add $30 to $50 to the cost of each cylinder. The farther away a supplier is, the more expensive and time-consuming gas delivery becomes.

Some of the newest technology involves satellite transmitter systems attached to bulk or microbulk tank gauges. This sends daily tank readings to the gas vendor, which collects the data to build a detailed history of gas usage. When the gas level reaches a predetermined point—usually between 25 and 30 percent full—the system automatically triggers an order for the gas vendor to fill up the tank.

A satellite transmitter about the size of a toaster is mounted near the tank. It transmits volume readings, normally once a day, to a low-earth-orbit satellite. The information bounces off the satellite to a ground earth station, and the data is uploaded into a database. The gas vendor monitors the usage data and schedules deliveries as required.

Paying More, Costing Less

Just as a shop floor can be lean, so can your gas supply system. Admittedly, it's counterintuitive. But paying more upfront for high-purity gas, associated regulators, high-quality plumbing, and other elements that help deliver the gas into your laser actually costs less in the end.