Our CO2 glass tubes used in our CO2 lasers such as the Muse, Muse Titan, and Pro-series are consumable items. They work in a similar fashion to a fluorescent light bulb- there is a high voltage initial strike that creates a plasma, followed by a lower voltage closed loop current.
Once the plasma is generated, much less voltage is needed to sustain the current as the plasma is conductive.
CO2 tubes, while referred to as just CO2 are actually a mix of Nitrogen, Helium, and CO2. The Helium balances while electricity excites the Nitrogen which gives it that pinkish-purple glow and resonates with the CO2 to produce the 10.6 um laser beam.
Just like the light bulbs we compared them to earlier, the electrodes used to create the plasma wear out when being sparked. The sparking itself can also cause debris to be generated in the tube such as as carbon ash which can impede the internal optics or even get into the chamber containing the gas which would reduce power.
If you spark the laser tube and leave it constantly running with proper cooling, it can last for 10,000+ hrs for gold catalyst type CO2 laser tubes and an average of 2000-3000 hrs for non-gold catalyst tubes.
Signs of a failing tube:
1) The tube shows signs of arcing. This will result in all sorts of electrical interference noise which may cause the laser to pause/reset. A sure tell sign is if the job runs no problem with the lid open (motors move but no laser firing) but pauses/resets with the lid closed (laser firing).
2) The laser tube has very weak brightness or glows white instead of pink.
3) Even when aligned, it has a hard time cutting acrylic at 100% power at 15% speed. Acrylic is a very consistent material and if you can't cut it at these settings. If it cuts better in the left position than the right side, you are simply out of alignment and not a tube problem.
4) You test the laser with a laser power meter and it shows 50% of it's rated power or less.
5) You performed the tests here: https://fsl3d.zendesk.com/hc/en-us/articles/13227434933147-No-laser-firing-testing-procedures
Reasons a tube fails early: Too many on/off cycles
As mentioned above, constant arcing of the tube causes the electrodes to wear out. If you do a lot of rastering then the tube can turn on/off 500 times per inch if rastering at 1000 dpi. At 20 inches a second speed, you will have 10,000 potential on/off strikes a second. However, it's well known the glass tubes have an upper limit of around 2000 on/off durations per second which is why we recommend rastering at 250 dpi with a CO2 glass tube laser. If you're vector cutting however,
To prolong the lifetime of your tube, raster more solid fills rather than dithered images and do vector cutting / vector fill instead of rastering.
When vector cutting, RE3 has two settings, power and current. Power pulses the laser on/off at high speed to achieve fine control over the laser power. Using these fine power settings, RE3 can allow users to only score but not cut through paper. Using laser current, the feedback loop of the power supply is adjusted to reduce laser output. However, below around 20% laser current the laser will not fire at all. Thus it is not possible to achieve ultra low power settings using laser current alone. However to prolong the live of your tube, use 100% power and adjust only the laser current setting as the laser will turn on and stay on instead of striking multiple times to achieve lower average power.
Inadequate water supply/dirty water:
Dirty water can cause the tube to spark to the water causing premature electrode wear. In adequate water or kinks in the water caused by dirty water can cause the glass to overheat and crack. This cracking is most common near the left laser exit side in the inner neck. There are actually 3 glass chambers. The thin inner most tube contains the gas to be excited and is directly aligned with the internal laser mirrors, The second middle tube is actually a water cooling jacket and you can see the water nipples fill and empty in this section. The third chamber is a large glass outer gas exchange chamber which exchanges hot gas with new gas. Breaks/cracks in the inner tube are most common as it's the thinnest part and the most fragile.
Just like light bulbs the laser tubes wear out. We expect 10,000hrs of continuous use but your tube may only last a few months if you do a lot of high density rastering. However, the tubes are relatively inexpensive but do to be replaced as consumable item from time to time.
Our fiber lasers, UV, and RF excited ceramic core laser tubes do not have these electrode issues and are not considered consumable items so are fully covered under warranty.