The Technology Explained
NOT ALL CO2 LASERS ARE THE SAME
Learn more about a CO2 Laser
A CO2 laser is otherwise known as a gas laser. As the name suggests it is created by harnessing the reaction of a mixture of gases within a sealed tube under vacuum. These gasses are known collectively as the gain medium. The wavelength of this laser is from 9.3µm to typically 10.6µm, which reacts well with most organic materials such as wood and leather, many forms of plastic, paper and card, stone, glass and rubber to name but a few.
Despite what some may claim the 10.6µm laser is not a good wavelength to mark metals but at high power (>600w) and coupled with a gas assist it is suitable for cutting some metals.
At Lotus we supply systems incorporating low power CO2 lasers from 30w up to 400w
G GGGGlass or Metal?
For almost all low power CO2 lasers the tube, or cartridge as it is otherwise known, is sealed and does not consume any gas from an external source. It can be made of glass or metal.
Glass tubes are designed for cutting applications. Metal tubes are suitable for cutting, marking or engraving applications primarily because they are able to be pulsed with higher frequency than glass tubes.
Glass tubes require frequent monitoring for performance fluctuations and often user hardware adjustment (voltage fluctuation) during operation whereas metal tubes do not.
Replacement of a glass tube can be required as often as every 3 months with average useage. Metal tubes can perform consistently for many years even when operated 24/7 and we have experience of some designs of metal tubes working perfectly well even after 9 years of constant operation.
The glass tube is excited by very high levels of DC voltage, typically 20kV for a laser outputting around 40w. Radio Frequency (RF) is used to excite the metal CO2 laser.
Glass tubes can only be cooled by recirculating water. Metal tubes can be cooled by air or water.
Glass tubes by their very nature are fragile and being connected by a hard wire solder joint they are somewhat high risk during replacement. Metal tubes use quick release connectors and are low risk to exchange.
Glass lasers offer little in the way of any performance benefit as in short they are unreliable and are very unstable. Their only advantage is one of very low cost. Typically, comparing an almost like for like power, the glass laser will cost approximately 1/30th the price of an alternative metal RF CO2 laser.
The initial cost differences are somewhat misleading. Considering all factors, using a glass tube will ultimately be more costly for most installations
We have extensively tested both forms of CO2 laser and, as explained above, have found without any doubt that metal tubes offer greater efficiency, performance, stability and have a significantly longer working lifetime.
Therefore, the entire range of CO2 laser systems supplied by Lotus use all-metal tube technology.
What's happening inside the tube?
LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.
The process starts by applying electricity to creat RF, which is used to excite the gas molecules and so create the laser.
The main gas within the tube is CO2 hence the title; CO2 laser. Other gases are Helium, Xenon and Nitrogen. Each of these gases plays a specific role during the creation of the beam for which the process is called population inversion.
Within the tube are a number of optical elements. At one end of the tube is a 100% reflector. At the other end is a partial reflector through which some energy reflects and some escapes. With some designs of tube there are additional internal mirrors. Upon excitation by RF the gas molecules are Stimulated and react to create a population inversion.The optical elements are used to pass the resulting stimilated Light through the gain medium over and over again, Amplifying it with each pass until the desired wavelength is achieved and so allowed to pass through the partial reflector as an Emission of Radiation.
Modern RF metal lasers are relatively efficient, however, as a byproduct of the process heat is generated.
It is vital to remove this heat effectively before it has time to alter the structure and state of the laser tube. Inadequate cooling of of a laser is the single biggest factor that influences stable operation and longevity of working life
There are two methods of cooling a laser:
1) By flowing air across cooling veins
2) By flowing chilled water around cooling channels
Water-cooling the laser offers the best form of heat removal from the tube, however, water-cooling adds significantly to the price, overall footprint and running costs of the system.
Water-cooling is best suited to:
- harsh, industrial environments
- where the system will be operated at a high duty cycle for long periods of time
- where the ambient room temperature varies significantly
- where highly consistent results are critical
- where minimising the noise level of the equipment is a significant consideration
Air-cooling is well suited to:
- stable, office type environments
- where the system will be operated with a medium to low duty cycle
- where the ambient room temperature is relatively stable
- where higher noise levels can be tollerated in the work environment
For most installations air-cooling the laser is adequately efficient and offers significant savings in terms of system cost and footprint.
How is the laser power controlled?
Laser power is controlled via the software as a percentage of maximum potential output (0-100%). To increase effective power the laser is pulsed. Pulsing is controlled by frequency in kHz (how many pulses are fired per second). For most common applications this is typically between 500Hz and 10kHz.
Laser power and frequency as well as motion control settings can be varied to provide for a wide variety of cutting and marking applications.
The beam exits the laser tube with a diameter of approximately 2.5mm (depending on model) where optical components further enhance and deliver its effective energy at the workpiece.
Where are our CO2 lasers made?
The majority of our CO2 systems incorporate a laser that is manufactured by Synrad (USA). Synrad was one of the originators of all-metal sealed tube technology and have made tens of thousands of lasers
Some of our higher powered CO2 systems incorporate a laser that is manufactured by Rofin (UK). Rofin has an enviable pedegree for high-performance CO2 lasers
Both companies have a reputation for outstanding products that are more than proven over 20 years of of manufacturing sealed tube all metal RF laser technology.