After going through the alignment procedure multiple times I managed to be spot on for all corners except the top right corner.
The spot on the bottom of the tape marked as (A) is the beam of the top left, bottom left, and bottom right corner. They all hit the same spot correctly. Once I go to the top right corner and do a pulse, I get the spot (B) at the top which is about 4 mm higher and to the right.
I tried shimming the top right rail by 4 mm (higher) - it made no difference, it still got me the exact same beam pattern. I checked to make sure if the cable chain was twisting the head/mirror 3 or mirror 2 - it didn’t. All the mirrors and brackets have been tightened (and I moved the height/position of the mirrors as well - didn’t change anything)
I tried Russes (SarbarMultimedia) 4th corner anomaly solution by adjusting mirror 1 to mirror 3 to account for any inaccuracies of mirror 1 to mirror 2 - this fixed the 4th corner but the misalignment then moved to the first (top left) corner. Someone in the comments had the exact same issue that the misalignment moved to corner 1 - there was no solution.
The machine is level, as well as the gantry (both checked with a level and diagonal strings to check if the rails are collinear - they are). I searched through every forum and there are quite a few people who have experienced the same thing and they didn’t find a solution.
The only thing that I can think of is my mirrors are bad - but then again I swapped them across all mirror mounts, rotated them, made them hit different parts of the mirror and nothing changed. They are slightly cloudy at some points so I will order new ones but I feel like I’m running out of solutions.
Update: From another forum I got word that it might be the tube alignment itself - how do I align the laser tube and to what do I align it to? I have a 1490 generic red&black co2 laser for reference.
Can the mirror 1 and mirror 2 mount position also affect anything here? Do they have to be perfectly aligned to a reference point such as the gantry/axis or something else? Any help is highly appreciated!
You might look at the major cause of this, which is flexing around the mirror area because of a drag chain or something else mechanical causing torque somewhere, resulting in a slight movement of m2.
The first part of this video by Russ Sadler gives you some ideas of what could be happening… maybe it will help … it might also assist with some of your questions with your alignment issues.
I checked out his videos before (there’s multiple on the 4th corner problem) but the adjustments on mirror 1 always move the problem to the top left corner.
I did check the chains on the X and Y axis after his suggestion and I tried running the laser with the chain screws loosened as well which didn’t change anything so that can’t be it.
I also tried running the alignment procedure with no belts on the Y-Axis thinking the belt is twisting mirror 2 somehow when it’s getting closer to the pulleys at the end. I moved the gantry by hand but again no difference (although since I didn’t have any belts on either side of the Y axis, they x gantry could have gone out of alignment/synchronization. This would only affect left and right movement of the dot as far as I know though, so it should have fixed the vertical offset, even if it was going out of alignment).
I do agree that this has to be a mechanical issue but I have already ruled out a lot of things so I’m not sure what I should check next. The only other thing I can think of is that one of the rails could be twisted along the length (i.e. similar to how you can untwist a rope/thread). Otherwise, I can’t think of anything else that might twist mirror 2.
Can you manually twist m2 and cause the deflection? That may be a hint in what direction it’s moving and clue you in to where you might have an issue.
Sometimes you have to think out of the box … such as how would I do this if I wanted too… Might also help in problem determination.
I’m certain it’s a mechanical issue, so I’d try physically moving m2 to try and see what’s going on.
That’s a pretty good idea, I haven’t tried that yet. If the beam of the top left corner ends up offset to the right and high on mirror 3 I guess it also twists the same way to the right and up.
I could try twisting it the opposite way and see if I can hit where the other beams land. If it fixes the problem then I know for sure that mirror 2 is causing the problem. If not then there might be an issue on the other end (top right). After some tweaking I did manage to align the beams of all corners to be within 1/3 of the “hole” of mirror 3 so I’m hoping that’s good enough for a while until I have some more time to troubleshoot.
Funnily enough, adjusting the feet (height) of the machine corners on the ground itself did change the offset as well. I will update if I can find a solution.
