Mirror alignment, Nasty Tricksy little Alignment

Mirrors 99% Aligned… or NOT.
I need a wiser head than myself on this. New 100 watt laser from China. Bed size 900 X 600.
The beam was totally out.
After the installation of my Lightburn camera and C3D board I am nearly done with setting in the laser. After much struggling, I now really know my way around accuracy, mirror settings and alignment settings.
See photo of A4 sheet.

Feel free to snigger.

Talk about a learning curve!

Right, so now my problem is : At Origin (bottom left - [yes I’m not special] ) I am on the same spot as at Home ( top left) and the same as at X900 Y0, (bottom right).
But at X900 Y600 (top Right) I am out. I tried setting it in and just reversed the problem to bottom right.

Now nothing is loose. Mirror #2 is attatched to the gantry, so it will not and does not help to raise the rail in the top right corner. (I tried and kicked myself for so being dumb afterwards!)
I am guessing that this is an issue with the tube that maybe needs to be raised or lowered at the back end of said tube.
Seriously though. I need some input please. Has anybody had a similar problem?

That’s a lot of alignment tests :wink: I can see why, though. I’d be beating my head against the thing until I got it perfect.

What it looks like is that your gantry isn’t square in Z. If you have a depth caliper i’d measure all four corners and shim the one that’s lower than the rest. Failing that, it’s beam alignment on the transverse mirror or the motive mirror. Where are you taking the measurement from? I typically do it from the beam input hole in the laser head.

I know you said you already shimmed the corner, but it can be a very tricky thing to get just right…