From the inception of the laser until March 2016, the laser cutter was cooled with a CW-3000 radiative / forced air cooling unit (50W/C cooling capacity). This was insufficient to keep a 80W tube at a nominal cutting temperature (which we estimate needs ~600-700W cooling capacity). Consensus suggests an ideal cooling water temperature of 15C should be maintained for consistent operation. With the CW-3000, the laser cutter cooling water would always run 3 or more Celsius hotter than room temperature (20-30 Celcius was common)
An AC unit water chiller was fabricated to replace the CW-3000 and provide consistent water temperatures year round. The AC unit was a 5000 BTU (1800W cooling power) air conditioner purchased on craigslist for $20. The evaporator (cold) side of the AC unit was relocated to the interior of an insulated chest cooler and the holes made in the cooler were sealed with expanding foam and silicone sealant. A temperature controller was then installed to turn the AC unit on / off based on the water temperature in the cooler. The water in the chest cooler is then pumped through the laser cutter tube using a submersible pump. A second submersible pump keeps the water moving in the chest cooler (it could be argued that this pump is not needed, but in times of heavy use, this keeps the evaporator coil from icing up)
Similar build thread - AC glycol chiller http://www.homebrewtalk.com/showthread.php?t=103280
The pumps used were replacement water pumps for the original CW-3000 chiller. This ensures we have the same flow rate as the laser cutter was designed for. http://www.rabbitlaserusa.com/WebShop/Chillers.html
A ESP8266 was installed in June 2016 to monitor the chilling water supply and return temperatures. A live feed of these temperatures are available below on the VHS network http://172.16.0.161:3000/dashboard/db/laser-cutter
The chiller should be checked for water volume at least every month. At time of this check, water can be added to the chiller to refill. For every gallon of water added, be sure add 1 tsp bleach to keep nasties from growing.
The chiller was rebuilt after 10 months service and was re-sealed. PL Premium polyurethane adhesive was used to seal the slot cut into the cooler in January 2017. Time will tell how long this seal lasts. CLR was used to scrub the evaporator and was flushed through the laser tube for a few hours to clean out the lines.