Chinese 40w laser power output not consistent

[kwiktsi]

I recently purchased one of the cheap 40w lasers and while it works very well for the money, I have noticed that it's cutting power seems to vary. I can have a sheet of 1/8" birch and with max power, speed of 10, the first few pieces will just fall out at the end of the cut, the others are still very much attached and need at least one more pass to cut them. I was thinking mirror alignment, but check that to the best of my knowledge and all seems well. It also doesn't seem position dependent, it can be anywhere along it's path, even areas that cut clean on the last pass now will need a second pass. It is very hit or miss and I have yet to figure it out. I tried moving the focal point around, cleaning the lens and mirrors, etc, and if it all works fine after I'm done, and I think I got it, it will act up again shortly after .

A couple things to point out- when I took the mirrors and lens out to clean them, I noticed a chip on the back side edge of one of the mirrors and the focal lens has a nice chip in the edge as well. I don't see it being a problem as the chips are outside of the lasers path and I can't see that making it inconsistent.

Another is after using it for a few hours when I first bought it, their water pump screwed up and output got very week- assuming it overheated the tube. After a cool down period and putting their pump back together, it seemed to be working fine, but I don't know if overheating the tube once can cause permanent damage or not (no visible cracks or anything). Last problem was one day the meter started flaking out, then stopped working followed by the laser shortly after. Upon inspection, the blue wire that goes from the resistor to the end of the laser tube was pinched in the case during assembly, eventually shorted and completely burned through. It burned the wire in half and was arcing to the case pretty good too...

The seller has been OK for communication but has no real answers. Any thoughts from those in the know here ?

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[Tweakie]

I could be that the shorted blue wire in some way injured your power supply. Does the mA meter slightly reduce in value when the power falls off ??

When a glass tube overheats the epoxy (I assume it is epoxy) bonding the rear mirror and output coupler will soften and allow small movement to take place. This affects the efficiency of the optical cavity and laser beam generation will suffer. In most instances it will return to it's original position when cold so check that you are not still overheating (no air bubbles and adequate flow rate etc etc ).

Tweakie.

[jadran60]

Hello, I had this problem that continues to go lower laser cut, laser beams easily escape from the center and does not complete in the middle of the mirror. Here's a link and see how it should do to work ok. Sorry for my bad English.
http://www.youtube.com/watch?v=pBZYO5-Iec8]Mini Laser Stamp Engraving Machine Adjustment Ray Path - YouTube

[kwiktsi]

Thanks for the replies guys. I went over it again and did find some things misaligned- mirrors, x axis was cutting on an angle, etc. and I straightened that out. It seems better so far, but I haven't been using it often enough to see if it still acts up or not. Time will tell...

[Exsecratio]

Love the size of the bubble in the lens end of the tube in that video

best wishes

Dave

[Tweakie]

Love the size of the bubble in the lens end of the tube in that video

best wishes

Dave

It is not all bubbles Dave, I am sure he has some water in there somewhere.

Tweakie.

[Exsecratio]

Yup sure does Tweaks, just not for long

[BrinkH]

I am aware that this is an old thread. I thought I would answer anyway, in case it helps someone who has the same question.

The OP is describing a situation where at the start of a run power is higher than at the end of a run. He is describing a tube that is warmer at the end of the run than at the beginning. Sounds like better cooling would help.