One Bad Apple Cylinder Spoils the Whole Bunch
Metal fabricators began reaping the benefits of laser cutting technology as far back as 1965 when they started using it to drill holes in diamond dies. Because of its cutting precision and energy efficiency, laser cutting has many advantages over plasma cutting when cutting sheet metal. And through numerous technical advancements, newer laser machines operating at higher power (6000 watts versus the 1500 watt ratings of early laser cutting machines) have approached plasma machines in their ability to cut through thick materials.
But to realize these benefits, laser cutting machine owners and operators must adopt some key processes and procedures. One set of key processes and procedures involves "assist gas" management. Following sections describe key do's and don'ts about laser assist gas management...including how the old saying One Bad Apple Spoils the Whole Bunch is something to worry about...but can be easily addressed.
No Matter Which Laser Cutting Gas You Use
Your choice of a laser cutting gas mixture hinges on an analysis of manufacturing-cycle-time versus the cost-of-the-gas. Since it's a exothermic reaction, oxygen cutting lets the laser efficiently cut thick material with relatively low laser power and low gas flow. But the oxide edge needs to be removed if the parts are headed for welding and painting. Cutting with nitrogen produces no oxide edge, but with its high pressure and flow, clean cutting with nitrogen requires a lot of assist gas. And cutting with air often requires costly upfront expenses for specialty equipment to ensure that air is delivered as clean as possible and with sufficient pressure.
Laser cutting gases delivered in cylinders must meet the stringent purity specifications found in the manual for each machine. Because if left unmanged, one bad apple cylinder of laser gas in you gas cylinder inventory can lead to severe damage to your laser cutting system. 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. Some lasers have 10 or more mirrors where each mirror can cost up to $500. Lenses can cost $1,000 apiece. In addition, a certified technician costing $1,500 a day may be required to make the repairs.
Demand Bottle-certified Laser Gases for Higher Quality
For a variety of reasons, you probably keep an inventory of laser gases on hand. Lost production time because you ran out of gas is often unacceptable.
But you need to make sure that your laser gas supplier has the equipment and procedures in place to ensure that the cylinders you receive deliver gases that meet the laser cutter manufacturer's purity specifications. You need to know that the gas you receive has a COA (Certificate-of-Analysis) stating that the gas complies with the manufacturers requirements. And, you can reduce risks of non-compliant gases if your gas vendor bottle-certifies their lasing gas cylinders. A vendor that bottle-certifies their lasing gases tests each-and-every-one of their gas cylinders containing laser gases.
WestAir clients have seen how high-quality bottle-certified gases has improved laser cutting machine performance, and reduced machine wear-and-tear between scheduled maintenance periods.
Some vendors simply batch-certify their laser gas cylinders. Batch-certifying involves testing a sample, not all, of their cylinders. While a statistically-valid sample can be calculated, you don't want to be on the receiving end of a cylinder that was not tested. As mentioned earlier, gases that do not meet purity specifications can damage a laser machine's mirror and lenses...leading to costly repairs and lost production time. WestAir has helped customers who have been victims of non-compliant batch-certified gas cylinders.
Manage the Transition to Bottle-certified Laser Gases
You may need to exhaust your supply of laser gases before you can purchase and benefit from bottle-certified gases.
During this period, you can protect your laser cutting equipment (and reduce downtime) by running an equipment diagnostic each time you attach a cylinder of laser gas. The gas-coefficiency metric will quickly identify whether or not you should use that cylinder of laser gas. The greater the gas-cofficiency number...the dirtier the gas...the greater chance the gas can damage your laser cutter...more likely it is that you should NOT use that cylinder of gas.
Lesson learned: run a system diagnostic each time you attach a cylinder of laser gas to your cutting equipment.
Also, remember that gas delivery involves more than just the cylinders, regulators, and manifolds. You must also consider the piping from the tanks to your system. The piping contractor must understand the 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.
Bottle-certified laser gases are a form of simple insurance to improve the performance and availability of your laser cutting equipment.
Look to a gas vendor with the financial resources and management philosophy to test each and every cylinder of laser gas mixtures. By eliminating this area of concern, you can put your time, effort, and money into other important issues.