heat in the carriage

[Jeff Body]

When your aligning the mirrors how big is the circle on the test paper before it goes through the lens?

[Dave Sheldrake]

I'm thinking same as Mike, the output coupler is causing a split beam (or REALLY bad transverse mode), there isn't much in a laser machine that will heat the metal structures up other than the beam itself (there are others but the machine would have gone bang almost right away)

Have a look at the lens in the end of the main laser tube, even a tiny scratch (almost invisible to the eye) will split a beam or cause bad beam modes.

[Bill George]

Would of saved a bit of time, it that info was presented in the first post. Can you install the tube so its not lined up correctly? On my ULS you would really have to try hard to install wrong.

[agron zeka]

Thank you very much, this is the area where I need your help as Dave mentioned maybe it is the coupler that is causing it (which I don't know what it is) or the beam shape. While aligning it i don't see any flaws but maybe it is there but i don't see it. How to fix the shape of the beam. And I know it's not a physical thing because it can engrave all day long without heating. I can install the tube no problems and it is not that difficult. I did clean the lens at the end of the tube and there is no problem because the other mirrors are not getting any heat only the end one.

[Dave Sheldrake]

The coupler is the lens in the end of the tube, if the beam is splitting from there then the divergence it causes may only start having an effect at the final mirror. Put a piece of white card in front of the tube and fire the beam for a split second. That will show the beam rough profile, then do the same in front of each mirror.

If you can post pics of the test it will help (it will give an idea if the beam is diverging)

It's not possible to test the actual Mode without a beam profiler but a white card test is better than nothing

[agron zeka]

Well I did tests all day today and what I've managed to find is that after some time of cutting, the laser beam starts to fall from the center towards bottom of the carriage hole, even in mirror three, so the falling of the laser starts from mirror two to three. When it cools it goes up again. This is so far. And I will do the card test and send some pics. Thank you.
DSC_0111.jpgDSC_0112.jpgDSC_0113.jpgDSC_0114.jpg

[Dave Sheldrake]

On M3 and M4 are those other dots from a different test or are they from the single firing of the beam?

[Scott Shepherd]

Maybe there's a loose mirror. You shouldn't be seeing that at all.

[Dave Sheldrake]

I have a feeling from the pics Mirror 2 is either surface cracked or scratched

[Bill George]

I think you need to go back to the laser cartridge and see what is going on like Dave suggested earlier. It could be matter of its not being seated correctly or scratch on the lens of the tube. Did you have anything else loose or removed when replacing the tube?

I have been known at times, not very often where I re-installed something with parts missing and wondering why its not working right!

[Kev Williams]

Look hard, there's a faint second dot in M1 too... I think the only reason it's not in M2 is because that pic appears to be more of a closeup, or enlarged...dot is out of the picture

[Bert Kemp]

Where do we get 4 mirrors? and as Dave asked in mirror 3 & 4 why is there 2 burn marks?

[Bert Kemp]

Are you looking lower right in mirror 1? or straight across like 3 & 4

Look hard, there's a faint second dot in M1 too... I think the only reason it's not in M2 is because that pic appears to be more of a closeup, or enlarged...dot is out of the picture

[Chuck Stone]

almost looks like the beam is bouncing off the wall of the tube between mirrors 1 and 2. (only because I've seen it before)

Bert .. the Mercury has the tube down underneath, so mirror 1 is a few inches form the tube bouncing the beam up,
then mirror 2 is in the back left corner. Mirror 3 is on the X rail to the left, and mirror 4 is in the carriage.

[Bert Kemp]

Thanks Chuck I didn't understand the 4th mirror.

almost looks like the beam is bouncing off the wall of the tube between mirrors 1 and 2. (only because I've seen it before)

Bert .. the Mercury has the tube down underneath, so mirror 1 is a few inches form the tube bouncing the beam up,
then mirror 2 is in the back left corner. Mirror 3 is on the X rail to the left, and mirror 4 is in the carriage.