Lightobject.com Support Forum

Hi all:

I want to warn folks who own a Reci laser tube. Do NOT use CW3000 "Water Chiller" for cooling as it is NOT a chiller. It is just an Air-water cooled radiator and it won't work well for Reci tube. The manufacturer is misleading to label it as "Water chiller" and it ended up some sad story on Reci tube. Without a true water chiller, the life span of Reci tube would be dropped tremendously and Reci will not cover the warranty if they know that you don't cool it properly.

A customer of mine use a water radiator to cool a 130W laser tube bought from me and 5 months later it cracked. Lucky I was able to get a new tube replacement for him as I'm authorized to sell Reci tube and have quantity order with Reci. The Reci know me better and agreed to replace it. A folk used CW3000 to cool Reci 80W and ended up a cracked tube. Usually high water temperature won't crack a laser tube but in most case it shorten it's life-span. What it killed the tube is water bubble that couldn't escape from the tube and the differential temperature between the electrode and the glass causing the cracked. One will find that the crack always happened near to the Cathode or the Anode. If that happen, the cause was most likely caused by the water-bubble.


Marco

Hi Marco,

Thanks for clear explanation . Now I know, what was responsible of the mystery crack(near the cathode)
of my previously bad tube(now all well with the lightobject tube ) that never worked from the
beginning. I would like to add few more suggestions to help avoid the situation(apart from the real chiller as
already mentioned), is to use a pump with good flow rate(not too high to cause cavitation(results due to dissolved
air separating out due to high force of the impeller)-tiny bubbles from nowhere being the tell tale sign).
Also use a reservoir leveled just above the tube to help the existing bubbles escape.
Few drops of Wetting agent(ones used in CPU water cooling loops), should help prevent the bubbles from
sticking to the tube walls, and will help the bubbles to move gradually and coalesce into a larger bubble,
that will eventually escape in the reservoir. Also visual checking with a high power hand torch light to
confirm no bubbles are present(mostly needed the first time, if everything mentioned above is followed)
will provide the peace of mind before starting the laser.

Thanks/Regards
Raman

RECI website says coolant temp range is 0 to 40 deg C. at 2 to 5 liters per minute. Seems rather a wide temp and flow range to me but I would have thought CW3000 could meet that requirement in many climates. Not where I live.

Don't think I would let mine run that hot even if they spec it, though. By comparison, Parallax specs a range of 15 to 33 deg C and recommends you not let the temp go above 27 deg C. (80 deg F). This would definitely require a real refrigerant-and-compressor chiller.

Also, laser power drops as temp goes up even if you don't damage the tube. Don't want that either.

Think I would go with the Parallax recommendation over the RECI spec, personally...... I read elsewhere that 20 deg C was a good temp to run at. Lots of varied info out there.

With higher water temperature you won't see the 'side effect' instantly. But, it will shorter the life span of the tube gradually. If you're not not able to cool the Reci tube below the the specified temperature, chance that you won't get close to the 8000~10,000hrs. How much hrs left, we don't know. You may however get something like 3~5000hrs instead. Remember that a water evaporative cooler like the CW3000 is not a compressed type chiller. It is built by a water pump + evaporator. It is good for laser machine with 40W~60W under air-conditioned room. If you're doing job in a garage with 82'F (30'C) or above, the water temperature will go up pretty quick.

If you have a Reci tube 80W~150W, I strongly recommended water chiller. If you're running Rec W8 (150~180W) tube without a chiller, then you're running a big risk


Marco

I always run my tubes no higher than 25C, above that you start losing performance, it is best to use an active water chiller as Marco suggests if you live in a warm climate.

Also one thing to avoid, do not completely seal your water system, ALWAYS leave somewhere for air to get in and out of the system. I found out the hard way, when the tube heats the water, any left over air in the system expands, and it popped a barb right off my laser tube from the pressure. So I always drill a little hole in my water fill cap to make sure the pressure can't build up.

Yeah, I think this is true even for small lasers. And the chillers are only spec'd for max 95 deg F ambient so even they would have to be in an air conditioned space in southern US. Might be possible to use chiller that is greatly oversized to keep the head pressure down and effectively raise the max ambient limit, but that would take some further analysis. Not sure if that really would work because inlet and exchanger temps are probably still essentially the same and so is the mechanical pump load of the compressor, even with reduced laser heat load. The reservoir of coolant just gets cooled less often probably.