OMTech CO2 Laser Coolant

Plain distilled water is fine in a heated room and dangerous anywhere that drops below freezing. The coolant also carries corrosion inhibitors, which protect the pump and the chiller's metal parts from slow erosion.

Do not reach for car antifreeze. OMTech warns that automotive antifreeze has higher viscosity and pH, and both hurt a laser: thick fluid moves less heat through the jacket, and the additives change how the water conducts. The result is lower output power and a shorter tube life.

• Freezing: protected to -31F, so the jacket survives a cold snap.
• Heat: the fluid carries heat away from the tube to the chiller or tank.
• Corrosion: inhibitors guard the pump, fittings and chiller.
• Oxidation and dust: OMTech says the fluid reduces both, helping tube life.

Heat matters as much as cold. A glycol mix still has to carry the tube's waste heat away, so the tank or chiller has to be sized for the job. If you run the K40 year-round in a space that freezes, coolant is not optional. Lay out the rest of the cooling loop with the K40 setup guide, which covers the pump, hoses and the water check before every job.

1. Unplug the laser and the pump. Never drain a system with the tube's power supply live.
2. Drain the tank or bucket completely, and blow or siphon water out of the hoses.
3. Flush with distilled water. Fill, run the pump for a few minutes, and drain again. Repeat if the old water was cloudy.
4. Fill with coolant straight from the jug. It is prediluted, so do not add water.
5. Purge the bubbles. Run the pump and watch the tube. An air bubble trapped at the top of the water jacket creates a hot spot; tilt the machine gently or pinch the outlet hose until it clears.
6. Check the flow at the return hose before firing the tube.

Keep the return hose below the fluid line in the tank. A return that splashes from above whips air into the coolant and sends bubbles back into the tube.

Look at the whole loop while it is empty:

• hoses that are stiff, cracked or stained inside
• hose clamps that have loosened on the tube's glass nipples
• a water-flow switch, if your K40 has one, and whether it trips
• algae or slime in the tank from past water

Read up on the tube, its water jacket and the safe current range in the K40 tube and power supply guide.

A CW-3000's tank alone holds 9 litres, more than two jugs, and the hoses and tube jacket add a little more. Plan on three jugs to fill it and have some left for top-ups. The OMTech CW-3000 and Cloudray CW-3000 both use a 9-litre tank.

Stock K40s often come with a submersible pump and a bucket. Filling a big bucket with coolant takes several jugs, so many owners switch to a smaller sealed reservoir. That cuts the volume, keeps dust out and slows evaporation.

Resist the urge to stretch one jug with tap or distilled water. Diluting a prediluted fluid raises its freezing point and thins the corrosion protection, which defeats the reason you bought it. If the budget only covers one jug, run a smaller reservoir.

• Measure your loop by draining it into a marked container.
• Round up, since you need spare for top-ups.
• Keep unopened jugs sealed; the warranty drops to 3 months once opened.

If you are buying the machine now, OMTech sells the K40+ with laser coolant in the box, which covers the first fill.

Coolant does not last forever. As it ages, it picks up dust, metal from fittings and growth from the tank, and its conductivity climbs. Change it before that happens, not after the tube starts to struggle.

Signs the coolant is due:

• the blue has faded, gone green or turned murky
• slime or specks in the tank or on the hose walls
• the tube runs hotter at the same power and speed
• cut depth drops with clean mirrors and a well-aligned beam

A routine that works for most home shops:

1. Check the colour and level every session through the tank window or lid.
2. Top up only with the same OMTech coolant.
3. Flush and refill on a set schedule, and sooner if any sign above appears.
4. Keep the tank lid closed to keep dust out.

Keep a note of the fill date on a strip of tape on the tank. Coolant ages quietly, and a written date settles the question of when it was last changed.

Dispose of old coolant as your local rules require for glycol. Never pour it on the ground or down a storm drain; it is toxic to animals and waterways.

Cooling is one of the upgrades that protects every other part. The K40 upgrade order puts a proper cooling loop near the top, ahead of cosmetic add-ons.