Make sure your water is running. If you notice that it hasn't been running don't just flip the cooler on. If you run the laser cutter for 90 seconds and then flip the cooler on you could easily crack your tube. The better option is to turn off the machine and allow it to naturally cool down for up to a half hour. Also it is far better to go with a closed system that actually uses coolant. What this essentially means is don't use the water chiller CW 3000 or run it off of a bucket. Neither of these options will adequately work for you in fact you could actually damaging machine without knowing it!