CTR Lasers - Types Of CO2 Lasers

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Types of CO2 Lasers

Types of CO2 Lasers (DC and RF)

There are two main CO2 laser types used in small to medium size laser machines. These are commonly referred to as DC (or ‘glass’ tubes) and RF (also called ‘metal’ or ‘ceramic’ lasers).

The price difference between the two is significant; the DC laser being a low cost disposable item and the RF representing a high quality, long life product. The actual cost per watt/hour of the two types is very similar. However, the quoted power output of the RF laser will remain virtually constant over their long life; whereas the DC laser output will gradually decline. This decline in power means the operator will need to reduce the cutting speed as the laser ages, resulting in longer job processing times.

There are other differences which impact on productivity such as the kerf width when cutting (width of slit made by the laser). This will normally be narrower from the RF laser because the optical quality of the beam is better, giving a finer focus spot. This increases the power density (watts per mm2) resulting in a possible increase in cut speed. For example, it may be that a 60w RF laser could cut at the same speed as an 80W DC laser.

The full power life expectancy for an RF laser is typically over 20,000 hours. This represents more than 12 years of single shift working. They can also be refurbished, giving many more years of life.

DC lasers on the other hand may give one to two years under the same conditions; although the manufacturers quote from 8-10,000 hours but only when used at low power settings.

The RF laser switching time is faster than DC lasers. This results in sharper definition when engraving fine detail, and the ability to increase the engraving speed without detriment to the quality of result.

Synrad Laser Powers

The materials used to make the laser cavity in the two types are very different. The RF lasers are constructed from metal or ceramicore within an aluminium extruded outer body.  This results in a robust construction with good optical alignment. The DC tubes are predominantly glass consisting of three concentric tubes with metal ends bonded on which contain the optical elements. These tubes are relatively fragile and need correct support to ensure alignment and effective operation.

The DC tubes are always liquid cooled. This makes them prone to frost damage so care should be taken regarding the environment the machine is kept in. Also they typically use 20kV DC power to excite the lase gas (hence the name ‘DC’). 20kV is quite capable of jumping across air gaps and tracking along surfaces, especially if the air is humid. Because of this, it is important to ensure the laser machine is not colder than its surroundings as this gives rise to condensation, promoting the chance of failure.

RF lasers, especially those of less than 100W are commonly air cooled, presenting no freezing problems, however it is still prudent to ensure a non-condensing environment, as with any electronic product. RF are powered by low voltage DC (30v to 100v) which is used to generate the radio frequency energy to excite the lase gas (hence the name ‘RF’). These low voltages will not jump or track except in extreme conditions.

An RF laser offers you:

  • Finer line width (kerf width) when cutting, or finer detail for engraving.
  • A longer laser life and 24 months warranty.
  • Continuous high power operation over their lifetime.
  • A more robust build quality and lower operating voltage.