I am having some trouble aligning my CO2 laser. I have the tube aligned with the first mirror. I can align the 1st mirror to the 2nd close and adjust it far, but when I come back close, the dots do not match. The only way I can get the dots to match close and far are for them to be aligned in the lower left hand portion of the mirror. When I try to adjust it to get it in the middle, it just seems to undue everything. It feels like a losing battle. I tried using the laser with the alignment in the lower left hand portion, and by the time it goes to the third mirror (which it is not hitting in the center), the laser beam is hitting the nozzle. Can anyone help?
This is one of the better videos on alignment that I have seen. Take your time with it and don’t skip any steps.
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I would suggest - and I know you aren’t going to like this - painfully, and methodically align everything from the tube towards mirror 3. As in, tape over mirror 1 and fuss with the level and alignment of the tube until it hits dead center (it will be an oval). Tape over mirror 2 and then mess with mirror 1 until the oval is precisely in the middle of mirror 2 at all distances (don’t worry, it isn’t too difficult to dial it in). Then move to the hole in from of mirror 3. Then do the lens out of the tube. I finally took all my mirrors apart after owning a few machines for a year, and I have never had a problem since, other than minor tweaks and re-alignments with age and cleanings, etc.
You’ll be glad you spent the day or so. I wish they came from the factory aligned, but no brand does. The sooner you embrace this, the happier you will be. This is the way.
Most videos work backwards from Mirror 3. I work forward from the laser, because you eliminate what your original post was about: Every change has a domino effect.
Once Mirror 1 is really precise. Now you can actually mess with the screws and see where the dot moves on Mirror 2.
Oh - one other tip. Take a Sharpie and write a line on the back of each screw - like a volume knob. Then you can SEE whether you go clockwise, counter, and how much (and what this affects).
I was dreading having to align mirrors when I ordered my first Co2, unboxed the K40 to find it arrived absolutely spot on. Uncrated my next a 50w and was a little more hopeful, again spot on. It might just be a case of our transport companies here in Australia know what and where “Fagile” is, or it could be because part of the Vevor assembly process is to align mirrors, test, then hot glue them into position. or a combination of both.
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I learned so much with my first disassemble, that it’s now the first thing I do. One of my lasers came such that I had to add spacers (I just used little washers) to the nuts so the Mirror 3 hole was in-line with the other mirror heights. That’s a design flaw. It’s a mental hurdle to take apart a brand new thing, but once you get over it, your troubleshooting days going forward are a piece of cake.
I did exactly the same thing when I changed the lens module to add air to the K40, yep firsts can be intimidating, then when it goes right, you wonder why you were nervous LOL
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I watched the video, doing each step very carefully (except for shimming the tube). I believe it’s aligned now. Thanks for your help.
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I’m glad my suggestion helped you get going. Happy lasing.
Besides about putting me to sleep, I think he’s made if a bit more complicated than it is. I’d never suggest people modify the tube mounts.
I don’t care what he says, if you change the input incidence angle to a mirror it will change it’s reflected incidence angle. That’s how mirrors work.
Scrutinize the head… My factory head - hole - mirror were not lined up… can’t use the center of the hole for the center of the mirror, in this case.
Think hard about that.
If the tube mounts have the tube parallel to the XY plane, but not coplanar and instead 3 mm too high, what happens?
You jog the gantry to the front and, by the book, adjust the angle of #1 so it hits #2 dead center. But then jog to the back of the machine and it will hit #2 almost 3mm too high. No any adjustment of any mirror can align this.
Fortunately most tube mounts have a z height adjustment. But that’s why it’s sometimes wrong.
If you only adjusted one mount’s z height, you can make it angle down slightly until it intersects with the XY plane at the #1 mirror. That’s good enough, the #1 adjustment will send it coplanar from there
It’s hard to tell if the tube is angled vs the z being too high or low anyways. The unique observable problem is hitting #2 dead center when jogged to the opposite side but off when jogged close it’s high or low on #2. Only tube.mounting z height or angle can cause this, and those are also the only way to fix it
Similarly, you initially adjust #1 and get the beam dead center on #2 when jogged to the opposite side. But the you jog to the back of the machine, close to the tube, and then it hits #2 off to the right. Well nothing about the 2 screws on #1 can fix that.
There’s 3 possible errors there, possibly a combination of 2 or all 3
- The mirror is mounted too far to the right.
- Assuming the tube exits to the left, #1 is mounted too far back relative to the #1 mirror Since it’s at 45 deg, the beam intersects the mirror to the right of the imaginary line parallel to the Y axis leading from the center of #2.
- Alternately, you could say the tube is mounted too far to the machine’s front. Pot-tay-to po-tah-to. The relative position of the tube mount vs #1 mount is wrong and you can only correct it by moving the tube or mirror or both
Often there’s no problem and the regular alignment procedures work fine. But it can and does happen, frustrating someone who repeats the “correct” procedure over and over but cannot get it right.
Oh, there’s ONE other alignment problem that is the MOST difficult to correct- the XY plane is twisted. The center of the #3 mirror is not coplanar when jogged to the 4 corners. This can result if the 4 leveling feet aren’t all that even and the frame isn’t rigid enough to avoid twisting if one foot is in the air. That case can be corrected at the leveling feet and must be redone if the machine is ever moved.
But good frames are usually stiff enough that uneven adjustment of the leveling feet doesn’t result in any twist of the gantry. In that case the 4 mounting points of the two Y axis sides need to be shimmed or otherwise adjusted to get them all 4 coplanar. It may be necessary to loosen the joints between X and Y while making this adjustment.
And I’m not sure if this should be called a fourth case or lumped in with coplanarity: say the joint in the left side of the gantry where it rides on the Y axis bearing is 1 mm higher than the other side. Actually, yes, we should consider that a different case than the XY plane being warped. The main symptom here is the focus is 1mm too close to the bed when jogged to the right. Wait, how can you tell it’s to that and not the bed’s 4x Z leadscrews being out of sync? Well, they’re almost the same thing! Adjusting the timing of the z screw can actually work and it will run fine that way. But there IS a fundamental, measurable source of the error- if you put a straightedge on the X axis rail and measure the distance to the Y axis rail, they’re not the same on both sides. Best to fix the actual problem by loosen the side joints and shifting them vertically on their holes (if there’s vertically oriented holes) or shim one side where the gantry sits on the Y axis’s bearing block. Once that’s correct, then level the z by getting the z lift screw timing right
And, theoretically, the gantry could be warped or twisted down its length. Never seen this myself, that would have to be such terrible QC you should just buy a better machine if you can