heat in the carriage

[agron zeka]

Recently I've refurbished the tube in my mercury 25w it's all good, but after a while the carriage is getting very hot and the cutting power is decreasing, I've checked from the cooling of the tube the alignment and mirrors, but everything seems ok. All this is happening in cutting mode not while engraving.The heat is only the carriage not in other parts like mirror 1,2,3. After a while it will not cut not even the half of the material. Thank you in advance.

[Bill George]

I'd check your lens for dirt and is it installed the correct way? Curved side up as I recall.

[agron zeka]

I've checked it looks ok, even I've changed the lens to the 2" for but still the same.

[agron zeka]

Any help...

[Ron Gosnell]

Start at the beginning again. Start at mirror 1 and tape it or paper it and make sure it's center. Go to mirror 2. Go to mirror 3.
I think it has to be a beam problem. Maybe even a split beam on a new tube. Unusual from what I've read on smaller tubes though.
It could the beam bouncing off the head of the lens holder too from not being centered.

Gozzie

[Richard Rumancik]

Agron, since the carriage is getting hot it would seem that the laser energy is not passing through the optics properly - the mirror holder will heat a small amount but you should never have a situation where the carriage gets hot or even warm. So I have to believe like others that the beam energy is hitting the aluminum carriage housing somehow.

I would take out the lens and put a piece of masking paper over the nose cone. Then do a short-duration beam test (using the diagnostic procedure to test the laser source.) The burn mark should be ideally right in the center of the nose cone hole. If it is a bit off that's fine but if you are getting a partial burn at the edge then you might have the beam hitting the inside of the nose cone. Does the nose cone seem to get hot? Can you tell what is the warmest point on the carriage assembly?

[agron zeka]

Thank you all for your help. I've checked the mirrors from 1 to 3 they are OK center beam everything, as for the cone I've suspected that too so to make a test I've removed the cone for a test a again is getting hot, really hot and i think that some of the heat is being transferred into the material also, because the other day i did some acrylic cutting it seems very hot, which was not the case before.

[Bill George]

Thank you all for your help. I've checked the mirrors from 1 to 3 they are OK center beam everything, as for the cone I've suspected that too so to make a test I've removed the cone for a test a again is getting hot, really hot and i think that some of the heat is being transferred into the material also, because the other day i did some acrylic cutting it seems very hot, which was not the case before.
Did you remove the lens and clean? Is it installed correctly and have you by any chance replaced that lens with a new one?

[Mike Null]

Agron

Have you tried running a job with zero power to see if the carriage gets hot? I'm trying to determine if it is a mechanical issue with the carriage.

Are you doing the alignment with the laser beam or the red dot pointer? Sorry if that seems to be a silly question.

You say you refurbished the tube. I'm wondering if Ron hasn't suggested an answer with his split beam comment.

[agron zeka]

Well yes as I mentioned in the beginning of the thread I've changed the lens to a different one, no issues while engraving only cutting, it can engrave for days and not get hot. The problem starts after maybe 10 minutes of cutting the carriage gets hot, and the laser losses power I know it's an issues with beam or somehow the radiation from the beam is hitting the carriage but any solution, and Mike Null can you explain a bit more on split beam or is any thread on this issue. Thank you all.

[Mike Null]

Agron

I'm sorry but my technical expertise is just about zero. I am only an operator. I recently had my tube re-manufactured and they replaced the optics in the tube enclosure so I'm guessing that there may be something to the split beam theory.

[agron zeka]

Today I'll get another carriage mirror and do a test as the only suspicion is on that particular mirror I will let you know. Thank you all.

[agron zeka]

Changed the carriage mirror still the same thing, its not the mirror, nor the lens any suggestions.

[Bill George]

Changed the carriage mirror still the same thing, its not the mirror, nor the lens any suggestions.


So did the problem start after you had the tube recharged, and have you vector cut successfully before without heat? Either before or after the tube work.

[agron zeka]

Before it was OK, the problem started after it was refurbished, I didn't noticed it earlier because it cuts very good for 10 to 15 minutes, but recently I had to cut small pieces on acrylic for long period and then I've noticed the problem.

[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.
317498317497317499317500

[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.:confused:


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.

[Richard Rumancik]

Kev, I'm not sure there is an extra burn from mirror 1 or that is just dirt on the test card.

Agron, I believe that mirrors 2 and mirror 3 are identical. (If I remember correctly mirrors 1 and 4 have heat sinks on the back of the mirror plate.) Maybe you could interchange mirrors 2 and 3 and retest? (Or swap in different mirrors if you have any.)


If you are in a pinch and don't have spare mirrors you might be able to cut some "mirrors" from an old disk drive platter just to test the optics. They don't have to be circles - you could shear rectangles from the aluminum disk platter. I am not recommending this permanently, but just as a low-cost test if you don't have a budget to buy parts to diagnose the problem. Tradeoff between time and money. Using old disk drive platters to make mirrors has been discussed in separate threads.

Also, when you test, perhaps you could reduce the power and/or burn time. Set the power to maybe 10 or 20% and turn the laser on for a second or less (whatever it takes to make a tiny clean burn mark.)

It seems like there is a thermal issue going on during vector cutting - the heating effect seems to be causing shifting of optical alignment. So maybe mirror 2 or mirror 3 is heating up too much and warping the mounting system. Have you checked if either of these mirrors and mounts are getting hot? You might have to pull them out of the mount and touch the back to tell, unless you have some other way. (But keep in mind that removing and replacing mirrors can affect alignment.) You could also try to feel the back of mirror mount #1 to see if it is overheating.

I suspect that raster engraving isn't heating the mounts up as much so you seem to be able to get away with it.

[Dan Hintz]

I will step in and put a large sum of currency on a split beam heating the carriage...

[Gary Hair]

I will step in and put a large sum of currency on a split beam heating the carriage...

I'll take some of that action...

I have about $1.50

[Dave Sheldrake]

I will step in and put a large sum of currency on a split beam heating the carriage...

yup, pretty much the only way it can get hot is from action of the beam

[Bill George]

And since it all started with a tube replace/recharge.....

[agron zeka]

Well I did all sorts of tests but the the only thing left is split beam (as you are mentioning) how can I fix it when i don't see it in any of the tests. No sign of it. The Synrad company in Germany are not replying to any of my emails, which is very suspicious.

[Bill George]

Well I did all sorts of tests but the the only thing left is split beam (as you are mentioning) how can I fix it when i don't see it in any of the tests. No sign of it. The Synrad company in Germany are not replying to any of my emails, which is very suspicious.

I think its been covered but removing the tube cartridge and taking a close look at the lens or glass and then the next mirror up.

[Dan Hintz]

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.
317498317497317499317500


the the only thing left is split beam... how can I fix it when i don't see it in any of the tests. No sign of it.

I'm not sure if the question was ever answered... are those multiple burn spots on the third and fourth cards the same test or separate? If it's the same test, the beam is splitting.

Also, you mention the beam axis is off-center... it drops visibly from the center on the latter mirrors? Where are you running these tests? Have you run the same tests at (0,0) and at the far extents of the bed? If the beam is shifting off-axis slightly at (0,0), it's going to be WAY off at the far extents... which means the beam is hitting the carriage.

[Mike Null]

Agron

At least two highly competent engineers here have suggested that the source of the issue is the tube itself. You say you refurbished it. I think you should send it out and have it professionally done or try it again yourself to see if the problem persists. It seems to me that you've exhausted your options with the mirrors.