CO2 lasers generate heat as a by-product of the beam generation process. If this heat is not removed effectively it can cause the laser to overheat and at best perform unreliably and shorten the working life of the laser or in a worst scenario the laser can fail catastrophically.
An effective and efficient cooling mechanism is therefore a vital element of the laser cutting or laser engraving machine design and function.
For low power (<100w) laser cutters there are in simple term two types of laser source:
1)DC excited; generally made from glass
2) RF excited; generally made from metal with some now being made from a ceramic.
DC lasers are significantly less efficient than RF lasers and as a consequence they generate a higher heat load so they must be water-cooled. Most modern RF lasers are so efficient that air-cooling is perfectly adequate up to 100w.
Air-cooling is performed by positioning a number of fans around the laser cavity and by moving ambient temperature air over the surface of the laser the heat is removed. Air-cooling is a much tidier, lower cost method of cooling a laser, however, it can be somewhat noisy, especially for higher power lasers where the air flow must be increased to remain effective.
Water-cooling RF lasers is a more reliable and efficient cooling method, however, it adds significantly to the cost of the laser cutting machine so it’s not common to find RF lasers being water-cooled that are <100w. Higher power RF lasers generate significantly higher heat loads and so must be water-cooled.
All DC lasers require water-cooling. Some very low cost machines incorporate what is no more than an aquarium pump to recirculate a reservoir (a bucket) of water. This is a wholly inadequate and somewhat unsafe design for cooling a laser as the water temperature will consistently rise to a point where the coolant (water) is too hot to effectively remove heat from the laser. Also, it is wholly unsafe to have open containers of water close to any electrical device.
Professional, well designed laser cutting machines incorporating a DC laser will use a specifically configured recirculating water chiller. Here the coolant is pumped around the laser to pick-up the heat then returned through a cooling mechanism, which lowers the coolant to a set temperature. The function is similar to that of a radiator in a car. The coolant temperature is monitored by the unit, which self-adjusts to increase/decrease the rate of cooling and maintain the set-point.
It is important to note that devices like this require periodic maintenance, such as frequent replacement of the coolant for example. If the coolant is not changed frequently it can contaminate and in turn cause contamination of the laser itself resulting in a catastrophic failure.
Well designed water-cooled laser cutters will also incorporate a flow sensor so that the laser cannot be accidentally operated when the cooling unit is not powered-on or should the cooling unit fail.
I cannot emphasis enough just how important it is to effectively cool the laser source as significant variance in thermal load to the laser is the single biggest cause of premature laser failures.
At Lotus Laser Systems we manufacture a wide range laser, marking and engraving solutions and we have installed machines all over the World to the widest range of environments. Our experts would be happy to advise you on this or any other aspect of your laser system installation.
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