Enough cooling to keep your cooling water bucket under 20C/68F and enough pumping to keep about one liter of water per minute flowing through your laser tube.
The laser tube makers recommend water at 18-20C (64-68F) and about 1 liter per minute. Actually, the laser tube designers for the K40 laser tube didn’t say a word about it, because no one knows who exactly they are. The 18-20C temp is a common recommendation from other laser tube makers, and the 1 L/m is based on commercially available 80-100W tubes. But they’re really good guesses.
Letting the tube cooling water get to 30° can damage the tube (accelerates irreversible CO accumulation) and using tap water can increase the rate of LPS failure.
Both the tubes and the laser power supply are essentially consumables. Gradual partial loss of power is most likely the tube.
However, there are a few other simple, cheap things to check first.
Make sure that your mirror alignment is still good, and that your mirrors and lens are clean. Dirty lenses and mirrors, and poor alignment, can both reduce cutting performance. Air assist, properly implemented, can reduce lens fouling.
Almost all K40 owners who replace their tubes report better than new performance. You do have to be careful to buy a tube that will fit in the case you have, or be ready to modify your case to fit a longer tube.
Thanks again, i read the links you recomend
I will be carefull about the temperature
I bought this machine second hand like I said, but the seller is an importer from china… And it cost me too much… then I found out that the machine is a chinese style machine K40
At this point i don’t now if that makes me happy, because i can found a lot of info about k40 on the internet or makes me sad sabe by the price i paid for this
But the support of this seller told me that 30ºC is good for usage
But now i will be more carefull about the temperature
The laser is powered at about 20,000 volts and there is no safe test you can do of the laser power supply’s “business end” with a voltmeter.
An analog ammeter is important for actually measuring current through the tube. But it’s most useful when you start with a good tube and then keep track of the amount of power it takes to make a known cut; as the necessary power goes up for a known cut, you know the tube is wearing out.
Read all the pages in Getting Started with CO2 Lasers — there’s a lot of information in there, but it’s more expensive not to know. That includes installing an analog ammeter.
I’ll let others chime in on what tests you might be able to do, but losing cutting power is a classic dying tube symptom.
I do not recommend getting near a live anode on the tube. It is dangerous and should only be performed by someone with training and experience dealing with high voltages. High voltages require special measuring procedures and safety precautions.
The health of your laser system can be measured without the expense and exposure of direct anode measurements. After installing the 30 ma meter you can tell all you need about the behavior of the tube and supply.
Check the output of the tube at m1… it must resonate in TEM00 mode to be useful. When a tube goes south, it will sometimes show up first with a failure to resonate or lase properly…
I use this type of setup to align mine… that allows the TEM00 check at m1.
The less power the better… You want a Gaussian power distribution across the beam… A light outer area getting darker towards the center… A hole or solid black spot on the target is not helpful.
