How to cool a CO2 laser cutter?

Cooling a CO2 laser cutter basically boils (no pun intended) down to cooling a laser cutter tube which is crucial for maintaining its efficiency and longevity. Whether you’re a hobbyist or a professional, understanding the right cooling methods can prevent overheating, extend the lifespan of your machine, and ensure consistent cutting quality. Operating your CO2 laser tube at optimal temperatures will greatly increase performance and tube longevity as the cooling system is one of the crucial components of every laser cutter, but what are the common types of cooling systems you can get to cool down your laser tube?

Bucket and a water pump

Yes, that’s right, a bucket.
If you are really short of cash and you are comfortable using DIY solutions with your laser cutter then a bucket and a water pump with some hoses are everything you need. And some cooling liquid of course.

If you are using your laser sparingly (like for small home projects)  and the temperature in your workshop is within optimal limits then you can probably get by with just this way of cooling. But if you plan to use your laser for some kind of small production or any other time consuming work then you should really look for a more effective and permanent solution since there are 2 major problems with this cooling method:

1. Lack of any laser tube protection. If at some point your water circulation stops (for different reasons –  from pump failure to clogged hose) your tube will overheat.
2. Water in the bucket will heat up quickly since there is no active way of cooling. You can combat this by replacing warm water with cold one periodically, or by adding ice to your water bucket but you will then have big water temperature fluctuation and that’s not good for your laser tube. You want to keep the temperature of the water circulating through the tube as consistent as possible. Besides changing water bottles and adding ice can get pretty tiring pretty fast.

So with that in mind, let’s look at some more permanent cooling systems – industrial water chillers. They are essentially bucket-pump with some form of cooling and additional features depending on the specific chiller model.

Here you can compare basic specification for chillers used in CO2 lasers with recommendations.

CW 3000 “water chiller”

The  water chiller part is in quotes because CW 3000 in not actually a chiller even though it is often advertised as such.It only has a fan assisted radiator and no cooling compressor (like the ones you find in refrigerators and water cooling machines) so you cannot control the water temperature with it. Meaning the lowest temperature you will get from this is the room temperature.

It’s still a lot better than a bucket+pump solution since with CW 3000 you get at least some cooling with a vent and a radiator as opposed to no cooling at all. Other than that, you also get real time temperature monitoring (which is essential), tube protection in the form of flow sensor that alerts you of any blockages or when the water temperature exceeds safe limits, enclosed water tank so there is a less chance of water contamination…

It comes with 9l water tank and is usually rated at 50 W/°C radiating capacity which is the cooling energy you will get per 1°C of difference between water and ambient temperature. So if, for example, your chiller measures water temperature to be 10°C higher than your ambient temperature then you should get (in theory) 500 W of cooling energy.

This is not an ideal solution and this “chiller” is not recommended for anything above 50-60W laser tubes, but if your workshop has good air condition that can keep ambient temperature low enough and you don’t use your laser for a few hours straight you can get by with it even for 80w laser. In fact we used CW 3000 with a 80w laser in our  (small, well air conditioned) workshop and managed to keep water temperature below 25 degrees Celsius for the most part. The key is not to overpower your laser tube (link).

CW 5000/CW 5200 Water chillers

Now onto some chillers that can actually chill. CW 5000/5200 are industrial water chillers with refrigeration compressor and a fluid stored inside a closed loop (like in refrigerators). This allows you to control water temperature and keep it at a fixed point. Laser tubes power output varies with temperature, so keeping it at steady temperature will get you more consistent results when cutting and engraving.
It’s worth noting that CW 5000/5200 sometimes come preconfigured to use so called “intelligent mode” which is programed to take a room temperature and add or subtract a fixed value (like 2 or 3 degrees). Now, depending on you ambient temperature that might be fine for some, but not for others who are better of switching to ”fixed” mode in which you chiller will keep the same predefined temperature regardless of room temperature. If you want to reconfigure your chiller and set it to fixed mode here is a good video explaining how to do that:

CW 5300, CW 6000, CW 6100, CW 6200

Other CO2 chiller models are working on the same principle as CW 5200 chiller with key differences being increased cooling capacity and some additional features like water pressure gauge, service port for cooling fluid recharging,  dual water outlets and inlets for additional laser tube, wheels… basically nothing you can’t live without. So unless you really want to know the water pressure in your system or you need wheels to move your chiller around, you should just pick the one recommended for your laser tube wattage.

Recommended cooling liquid

Tap water has a good thermal properties but a high mineral content which increases fluids conductivity. It also contains chloride which can be corrosive. Distilled water on the other hand has very low levels of minerals and much lower conductivity which is why it is most commonly used and recommended cooling fluid for CO2 laser tubes.

You will often hear recommendations for different additives like antifreeze to prevent freezing or algicides to prevent bacterial growth. These are not necessary because adding anything to distilled water will increase its conductivity and can sometimes do more harm than good.

If you live in an area with harsh winters and below freezing temperatures you can just get a storage heaters or leave the chiller running (flowing water can’t freeze). If you really want to use antifreeze, please use RV antifreeze instead of your regular automobile antifreeze which is not suitable due to its toxicity in the presence of silicon hoses and sensitive gaskets in chillers.

And if you are concerned about algies – the key to prevent them from forming is using closed container and limiting water exposure to sunlight. If you still have problems with algae you can add a little bleach or a single silver coil in the reservoar. You will need to flush the algae first with distilled water + ¼ cup of bleach mixture and then rinse it and refill again.

Summary

While bucket & water pump DIY solution may be good enough for some “light” users, most of the laser cutter owners will need some type of industrial chiller to cool down their laser tubes. While there are many different specs and features for different chillers, the most important thing is picking the right one for your laser tube wattage.