K40 Laser Cooling


The ideal operating temperature range for the K40 laser tube is between 10C and 24C (50F and 75F).  The laser I purchased included a small aquarium type pump, and some silicone tubing.  The most basic way to keep it cool is to put the pump in a 5 gallon bucket, pour in about 4 gallons of distilled water, and add a few frozen blue ice packs.  This provides enough cooling for a couple of hours, and I used this method for a year.

While that method works, there are some downsides.  The blue ice packs are bulky.  I would use 3 at a time, and had 6 total.  That took up a significant portion of the small freezer in my garage.  I also had a failure of a blue ice pack.  Fortunately, it happened as I was taking it out of the water bucket.  The end cap popped off, and the jelly inside came out and contaminated the water.  The laser was off at the time, and no water was flowing.  I dumped the water, cleaned the bucket, and started over.  The bigger downside to me is the time it takes to load and unload the packs into the bucket.  Sometimes I want to cut a few parts NOW, and don't want to deal with these added steps.

I already had a Engel portable fridge/freezer.  I bought this for extended road trips, and to keep food cold when the grid goes down.  We live in hurricane prone Florida, and we have experienced power outages as long as 3 weeks.  This fridge sips power, and can run indefinitely from the solar panels I have on my roof.  Very little modification was needed to make this work with the laser as well.  Depending on the temperature setting, this fridge quickly turns into a freezer.  This has a very special compressor, a single moving part (solenoid).  Don't confuse this with the cheap 12V coolers at Wallyworld.  Those use a thermoelectric chip, and lack the cooling capacity for this task.


The homebuilt thermostat keeping the water between 50F and 52F.

This is about as simple as it gets.  I put 3 in the bucket with about 4 gallons of distilled water.  The bucket will sweat in a warm shop, but lasts for a couple of hours.

Make sure you use distilled water.  Tap water is full of minerals that can contaminate the laser tube.  There can also be issues with conductivity as a high voltage is discharged in the tube.  I buy mine locally at a Publix grocery.  If you ask nice, they'll bring out a case of 6 in a nice cardboard box to transport home.

The water WILL get slimy after a week or two unless you put some algae control in the water.  Only a few drops are needed, and this doesn't interfere with the health of the laser tube.

You can buy a dedicated chiller unit for a laser cutter.  Be warned, there are a lot of them that have nothing more than a fan, and a radiator.  The expensive ones have a compressor, and actually chill the water.  But that's a one trick pony.  For a little more money (I paid $640 in 2018) you could get an Engel fridge/freezer.  I made my own digital temperature controller, details at this link.  I set the OFF temperature at 50F, and the ON temperature to 52F.  When I start cutting, the temps increase into the upper 50s, and tend to stay there.  Well below the 75F upper limit to preserve the laser tube.  I can immediately start the laser, cut for hours, and simply shut it off.  I don't have to do anything to the fridge.  It automatically runs the compressor as needed.

Rather than pour 4 gallons into the fridge directly, I bought a number of water containers for hurricane preps.  This Jerry Can shape fit into the cooler nicely.  I cut the top portion off, and dropped the submergible water pump inside.  This allows the lid to close most of the way, only cracked open enough for the water lines.  It will operate fine like this, but I'm going to modify mine a step further by drilling the lid, and adding two 1/4" copper tubes.  That way I can fully close the lid.  Especially useful when I create clouds of sawdust as I sacrifice a piece of lumber to the wood gods.

Now you can see how well this jug fits into the cooler.  I used an oscillating cutter to slice the top section off.  Filled it with water, dropped in the pump, and the temperature sensor line for the fridge thermostat I built.

For now, I have it sitting on the workbench beside the laser cutter.  The lid isn't completely closed, but it has so much insulation, the small air gap doesn't seem to matter much.  I'll fix that shortly.
Update coming soon...


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Last updated 03/08/22    All rights reserved.