Galvo Fiber laser weaker on top half of field

Hey all,

I have an OMTech 30W Galvo fiber laser that I’ve been using for a while.

The main thing I’m having an issue with, that has always been an issue (machine is secondhand) - is the laser gets weaker the further away from the bottom left you get. About 60mm up in the Y direction (away from operator) it’s basically useless. It doesn’t mark at all, unless you’re at 100% power, in which case it makes it maybe another 20mm, but the areas below it will be much deeper engraved. The X axis (left to right) doesn’t seem to have this issue as bad, but it still is present, however only slightly.

I’m guessing it has to do with some mirror alignment? I only find ways to align the red dot though.

This issue occurs with both my F160 and F254 lenses, it seems to scale linearly with the lens.

I lined up my red dot and whatnot but it’s always had some skew/buldge issues on the edge. The red dot is correct on this (it follows the skew the laser outputs), but it still doesn’t provide a square field, so engravings get skewed on the edge. I’m working to use EZCad to get a corfile, but I can’t even get the calibration square to mark fully.

My laser also has a plate with some values on it (Galvo 1 = X, and some scale values) - but these are not consistent with what I’ve seen works in EZCad/Lightburn.

Here’s a photo of the calibration plate (can I use this for something like the skew/buldge/scale adjustments? or should I not trust it?) + the issue (although it’s not visually very interesting)


It’s not likely mirrors, but the head itself. If the head is not mounted parallel to the work surface, you’ll see the focus distance change across the work area. Using some shims between the tower and the head to adjust could help.

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Interesting! I’ll try using my precision level on it to see what I can find.

I couldn’t find my precision level, but I have another one that’s pretty good, and I’m seeing that its about 1 degree off across the head (the final box) with the farthest part from the operator being the highest, so that would explain this. I’ll try shimming it out and report back.

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Ok, I tried shimming it to neutral, and also in the opposite direction of where the issue is (by just a little bit) and had no luck. The laser fades off in intensity very quickly towards the top half, although the red dot is able to cover it. I believe it also has a much lesser intensity towards the top.

Here’s a GIF of it https://i.imgur.com/1k6bYqZ.gif

Is there something on your lens?

Nope, both lenses are clean. The mirrors in the head are also clean and don’t appear to be damaged or worn. I can’t find any information on how to align them online so maybe they are not servicable and it’s something else?

Thanks for the help on this so far btw

Very carefully with SLR camera mirror cleaning kit try cleaning the mirrors. Then double check, clean lens, unscrew lens 45 or 90 degrees, run a new focus test near center, and see if weak spot moves. As it is two different lenses probably not the lens but start from the beginning one more time to be sure. Then open up the laser path, carefully clean laser emitter lens and combiner. If you can find the model number post it please.
Numbers on the card should relate to scale bulge skew settings
image

I’ll try that, thanks. The model is a Raycus, I don’t see any model number besides a serial on it. It’s an OMTech 30W if that helps at all (probably not because I’m sure they’ve changed their emitter several times for this model)

I’m assuming the Raycus is the emitter, and then the tube is in front of it, and I know the thing sticking up at the end is the red dot emitter for tracing. Not sure which part I should unscrew or open, or where the lenses are in relation to the emitter and tube, I don’t want to knock it out of alignment any more than it already is. Do you know which ones I should take out? I know the screws around the red dot is for aligning that, so assuming it’s on either side of that. OMTech doesn’t have any kind of service manual for it that I can find.

If your table is level, the head is not

:smile_cat:

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Haha I figured someone would say something because I left the level in the photo, the table is not level at all because of the poor concrete in this building. I checked the head vs the base and everything is within 1 degree (side to side is about the same amount off as front to back, and side to side engraves fine)

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So did you try to rotate the lens 90 and check if the weak spot moved, and did you clean the mirrors and test?
The thing the red dot sticks into is the combiner, and racus is the emitter. My JPT looks similar, 4 screws for the emitter and 4 for the combiner, 4 little ones for the red dot.

The red dot adjustments is done through the software.

I tried 45 deg, 90 deg and 180 deg, no change. I cleaned the 2 mirrors in the head, however I didn’t check the optics behind that (towards the emitter) - I’ll have a look at those next. The 4 screws on the red dot I saw a video on youtube saying that’s how you adjust the actual position of it shooting out, so I was worried the emitter might be like this too.

Is there a particular part of the emitter I should remove, i.e. at the base or towards the head?

Here’s a video of the issue in action:

Very carefully remove the 4 screws and lift the whole thing. It is all one piece all the way down the fiber into the source. Look at some photos.
It may recess just a bit into the combiner.

If this issue persists after squaring the galvo head to the base, I’d presume that it’s possible that the beam path is being clipped due to misalignment between the laser source and the galvo itself. I don’t personally have any experience with adjusting this, but found this, which may help (even if it’s a different laser source type) https://www.youtube.com/watch?v=v67dSBEI7CI

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Want to be sure, the video is the laser not the red dot, correct?
So something to really check, don’t put the level on the top of the galvo, actually put it up under the lens. It is really hard to tell with sucha short video, but looks like it gets bigger at the top. If you lower your focus, does the area of good power change? Also, looks like the field is pretty large, what lens in the video?

I thought this could be the case too, I checked out that video, mine doesn’t have any adjustment screws like that one but I did notice that the tube clamp was a bit loose (end of the emitter) and that had it sagging slightly, however this may have been due to me fiddling with it trying to figure this out. I tightened it up and had no luck. The point is pretty close to bang on center, within half a mm I’d say after checking it with a compass and my caliper.

Correct, it is the emitter not the red dot. If I lower my focus, yes, the area with good power gets weaker, but going neither going higher nor lower makes the upper half of the field (where its weak) any better. The lens is a 254mm focal length. The same issue occurs (scaled to the other field size) with my 160mm.

I also tried as you suggested, the level on the bottom of the lens, I get the same result as on top of the head, so it seems square.

The optics from the emitter to the lens seem to be clean as well… this one’s a doozy, I had really hoped it would be misalignment on the emitter I could tune out.

I have one of these lenses and they have a dof of about 4.7mm, so I doubt it’s a focus issue.

:smile_cat:

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