I have been having some problems with my 50w Chinese laser cutter recently. Having had the cutter for 14 months and not really had many issues with it (apart from the usual Moshi problems) I originally thought the laser tube had died, after all it had lasted 14 months and not been replaced. So, I ordered two more tubes, replacement mirrors and replacement focus lens. Unfortunately I ordered the wrong size focus lens so have not replaced it yet - am going to re-order.
Anyway, the issue is that the laser beam stops cutting about halfway through jobs. The head continues to move, the laser is firing from the tube, through the mirrors just not coming out of the nozzle. I have calibrated all the mirrors at each end of the axes so I know that the beam is entering the laser head. I have posted a link to a 10 minute video below to show everyone the problem and any thoughts or ideas will be most appreciated. I am scratching my head and banging it against the wall at the moment as I really don't know what the problem could be. This video shows the job running at 85% power. I ran the same job on 20% power and it is fine - completes the job but unfortunately 20% power doesn't cut through the material. When I ran it again on 20% power and manually increased the power whilst the job was running, it stopped working shortly after I got the power back up to around 50% or more. It's almost as though the laser power is too much for the laser/lens/nozzle to handle.
I don't know whether it is the focus lens as the beam seems to dissipate just before it stops working. What I cannot understand is that it is a solid beam for a while and cuts fine, then stops. The water running through the laser is cool enough, all the power seems to be fine - I just don't get it!
Here is the link to the video:https://drive.google.com/file/d/0BwF...ew?usp=sharing
Approx. 4:06 the laser stops firing but continues moving.
Approx. 4:41 I use another piece of wood to break the laser beam - proving that the beam is actually firing up until the laser head
Approx. 6:45 - 7:32 I reposition the laser head and do a manual test
Approx. 8.18 I do another manual test and the laser stops working near to the end of the cut and there is a close up of the manual cut
Thanks in advance!