K40 Repair - No output to mirrors - Laser tube cut a hole in water hose near tube?
I got a strange one here I would appreciate if anyone could chime in if they seen something like this or have a idea what to look for to find the exact problem to repair.
My k40 has worked for a year fine since I got it. I use it sparingly but never had a issue. I have a water pump going to a chiller that has always worked fine. Started working on something a few days ago, and I cut for 20 minutes without trouble. Then I noticed the last cutting out mid cut and I was looking for a issue. I was checking water flow and it did seem like one hose may of been slightly kinked. When I unkinked it and got full flow back water outlet stream was very hot, so I thought maybe the tube overheated. I left it off for awhile giving it time to cool. Made sure water flow was good and cool before trying again and I could not get any output from my laser on the material and immediately had water everywhere. I quickly powered all down and found that some how the tube, in the back housing, cut a hole through the water hose. Very strange to me, but I could see the laser tube was not outputting through the tube now and just lighting up at the beginning of the laser.
After cleaning, drying, and replacing house I tried the laser a few more times on very low settings and I have no output to material, but almost instantly I had a new pinhole size hole in the new hose next to the tube in the back. So somehow at least a partial laser must be coming out of the side of my tube hitting the waterline next to it. Very strange so I wanted to see if anyone has seen something like this, and if my tube is fried or if their is a possible cause I could look for.
@donkjr I made this picture to show were I am at with this. You will notice a few things. The black scorching is were the water line originally melted through and where the pinhole appeared within 10 seconds of attempted use after repairing water line. I am assuming this was caused by a HV arc?
HV wire appears in tact and I wouldn’t think this arc originated at the terminal connection due to the location of the black scorching being over 6 inches away and a bit around the housing as you can see.
The tube does not fully light up anymore then I energize it I can just see the high voltage sparks inside the tube in the first 2 inches or so where it is a small diameter right next to the HV wire as shown in the picture.
Any suggestions on what I should try or test to determine the state of this? Any way to test if my tube is fried now? I will add that this tube has about 2hrs of run time since I got it about 2 years ago.
Sounds like a fried tube to me, and that the power is finding less resistance to that part of the chassis over through the gas in the tube. Plus most laser tubes have a maximum life span thats more in the 1-1.5 year range so 2 years on a tube isn’t all that bad. Only way I know to test a tube is to either hook up a new one or to hook it up to another laser PSU and see if it works. Personally I’d try replacing the tube first since you know it had a critical temp issue.
LPS will arc violently when there is no load (bad tube). They can easily arc across a 2" gap. Usually this means the tube is bad and is providing no load.
I would think that you could see this arc if you “pulse test” with the rear cover off in a dark room. Use safety procedures and stay well away.
Isolating bad tube vs LPS is tough. If the LPS has a strong arc it is usually ok and the tube is bad. If not its usually the LPS.
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You can try cutting those tie wraps and routing the HV wire away from the coolant tube to see if it arc’s to a different place.
You can also try putting a thick piece of Plexiglas/acrylic between the HV lead and the coolant tube. I would use a min of 1/4" thick.
All this will prove is that the LPS is probably good and the source of the water line damage.
… what coolant are you using??
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LPS are not that expensive these days I have seen them for $40. My guess is that you will replace it in a year anyway. Depending on your budget getting one with the new tube may save you some grief.
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Notes:
… its best to install a tube flow meter and temp monitor into the interlock circuit to prevent tube damage from overheat.
… tubes have a shelf life as well as an operating life as @Domm434 has suggested.