Power degradation during a long job

[Mike Lysov]

Hi guys,

I have a Laser Pro 100W with a Synrad tube and it is loosing power if I run a 20-30 minutes job on it. I do not believe it is a beam alignment or dirty lens/mirror issue because I check them regularly and clean them. Even the ones that located at the bottom under cover where it is combined with a red beam. I have checked all fans that cool the tube and found that one was not working. But there are a lot of them and that one does not even blow at the tube, more like above it. I cleaned it but I do not believe it will fix the problem.
What else could it be?

I do not think it is a tube problem as the laser is only 5 years old and I do not think it's been made more than 2000-3000 hours. Power level was checked a year ago during some maintenance by a distributor tech. He told me it is still strong. I am going to check it myself once I receive a power meter but I do not think I will find something considering that power degrades only after a long job.

To get an idea how it degrades, when I turn it on in the morning I can cut 6mm MDF with 2% speed and 100% power, then if I run 20 mins job after 4-7 mins of cutting it stops cutting through. Then I have to drop the speed to 1.8% and the same happens again after just a short run. Even if I drop it to 1.5% after that it will cut through 15 minutes out of a 30 minutes job. Small jobs do not seem to be a problem at all. So it seems to me that for some reason the tube is not properly cooled. Can a hotter than required tube behave in such a way?

[Dan Hintz]

You are losing power most likely due to heat... a failed fan is not a good sign and was probably not doing you any favors. You may have slowly cooked the caps in the RF section, so it may be time for a replacement.

BTW, a 6-month old tube can fail just as easily as a 5-year old one, especially if it is a refurb.

[Mike Null]

It might well be that your tube is failing. Your symptoms are similar to what I experienced with my Synrad tube after just 3 years on my old ULS machine.

[Mike Lassiter]

laser tube or cartridge going bad. This was exactly how my 60 watt cartridge did. Replacing it cured the problem. Thermal imaging camera showed it hotter than the 75 watt cartridge was. After replacing my cartridge the laser is much quiter both on but not cutting and while cutting. The cooling fan was running wide open all the time I think in the failed cartridge.

[Mike Lysov]

Thank you guys. The fan I have mentioned is not on the tube, there are no fans on it at all except the one that cools read beam combiner. The tube is sitting inside a heat sink and all fans are installed on a laser case and blowing toward the heat sink. One did not work but I fixed it. And it still drops the power after long run. The strange thing that I cannot see any degradation if I cut 3mm MDF at 4% of speed. It still cuts through after 20mins. Does anybody know how much it costs to refill/repair 100W Synrad tube?