CO2 Lens Failure Causes Part 3: Gas Pressure, Improper Nozzle Selection & Lens Issues

As discussed in the last two laser blogs, there are several reasons for lens failure. Still, many contributing factors often makes diagnosis difficult, especially after-the-fact. The March 2019 blog covered lens failures due to problems associated with machine power and cooling system problems. This is the last blog in the series.

Gas Pressure Issues
Optimum Gas Pressure is important to edge quality and lens life. The gas delivery system must be adequate to flow sufficient gas volumes consistently, even at lower gas tank levels or additional equipment demands. If the gas pressure is inadequate, contaminants may build up more easily on the lens, resulting in premature lens failure.

Improper Nozzle Selection
Adequate Pressure must be combined with the proper nozzle to enable to cut to “blow clean” and still allow an adequate standoff distance. In general, longer tapered and high-pressure nozzles will better protect lenses from contaminants. Two-piece (double) nozzles also provide additional protection for aluminum and stainless cutting.

Lens Issues
Stressed lenses: Over time, the heating and cooling cycles can set up stresses in the lenses, causing them to become unstable and subject to thermal breakage.

Improper Lens Mounting: If a lens is mounted incorrectly, thermal expansion can cause damage or breakage because the lens and the mounts expand at different rates.

Faulty Material/Coating: Some competitive low absorption coatings absorb moisture, which can provide thermal variations as the lens heats up. Mate’s Black Magic™ lens avoids this problem by providing a more stable low absorption coating.

Many lens failures can be traced to poor maintenance. Other causes result from machine or material variables. Finally, a small percentage may result from problems with the lens itself. Only a complete analysis of the laser operating conditions and lens characteristics will allow you to determine a meaningful solution.