I just recently had to relevel my cut bed and going through realigning my laser afterwards, I encountered a seemingly counter intuitive alignment issue.
bottom left in this pic I’m showing that I am aligned at position 3 after going through my normal process of aligning at positions 1 and 2. When I move the laser back to positions 2 and 1 however I find that they are off and drifting down and to the right. I’ve realigned a few more times and this difference was uniform. I also found an odd U shaped drift as I moved the laser toward the back of the machine.
I’ve puzzled through it myself for a while now and I cannot really see anything obvious that might be causing this. My laser is dual headed but I don’t think that really affect it. ( I mostly only use the one side.)
The alignment on those mirrors 1 and 2 are spot on across the board.
I did run a few more checks and from corners B to C the laser moves up and to the left ⇖.
The over all scatter across the whole table and all four corners is a bout a centimeter.
Did the machine get moved that maybe the laser motion rails are no longer square? The most suspect would be the Y axis where on side leads or lags the other a small amount.
Even with the issues you are seeing, seems the beam will still make it the focus lens, just maybe not at full power.
Try putting a big piece of poster board or similar down and etch a big rectangle. See if it’s dimensions are right and if the corners are really 90 degrees.
