Two types of CO2 laser tube are available as DC or RF excited CO2 laser tube. Direct current (DC) lasers are made of glass. Inside this glass tube is a mixture of gases, carbon dioxide, helium, nitrogen, hydrogen and xenon. Electrical energy is sent through the tube. This energy excites the gases resulting in a direct electrical discharge. The discharge creates a laser beam that bounces back and forth until a certain level of energy is attained, then the laser beam exits at one end. This infrared beam is invisible but powerful and once focused can be used to cut or engrave various materials.
An alternative way to transfer energy into the gas is through radio frequency (RF). RF tube technology is commonly referred to as “metal” tubes. RF excitation produces a pulsed laser with an extremely quick repeatability. Unlike the parallel discharge in a DC excited tube, the RF laser discharges perpendicular to the resonator.
It is desired to understand the pros and cons of each laser when making decision.
Cost: DC lasers made of glass are roughly 10% of the price of RF lasers. This cost advantage is a result of a lower technology and manufacturing cost.
Cutting Performance: Both lasers maintain very high quality cuts. The edge quality is very similar. While, because RF lasers are pulsed, some materials may show a slightly rough edge. This is evident in acrylics. With that being said, this difference in quality is hardly noticeable to most users.
Engraving Performance: RF lasers generate a smaller spot out of the output window of the laser. The smaller the spot size, the finer the engraving detail. For high precision engraving, this smaller spot size makes a difference. There are many applications where this advantage in quality will not make itself apparent.
Longevity: RF lasers last 4-5 times longer than DC lasers. This longevity can help offset the initial higher cost of the RF laser. The gases inside RF lasers can be refilled, but this process can be more expensive than the replacement cost of new DC laser.
Laser Power: If you were to compare a 100W RF to a 100W DC tube then assuming all things are equal – the power is the same. However, RF power focuses that same energy into a more dense smaller spot. The quality and stability of that beam is better as well. For detailed etching, RF can offer that advantage. However, with cutting you can afford to buy much more cutting power compared to the cost of RF. So, determining what you will be using your laser for will help you make that decision.