It’s generally not that m3 is “wrong”. M3 must send the beam through the air assist cone orifice.
First off, make sure the beam is hitting M3 in the center. If not, fix your machine alignment first.
If it’s still slanted, the whole head mount is at an angle. You’ll need to shim it into place. Slices of aluminum can works, folded over itself however many times it needs.
The best way I know to do this:
First, figure out if you’re correcting slant in X or Y. This is for X (slant goes left or right)
- Find the thickest piece of acrylic or plywood you have on hand that you can cut
- Cut a 20mm wide strip of it as long as you can, but less than 1/2 the bed width. Mark one side “bottom” all over so you don’t accidentally flip it. Actually best thing to use is acrylic with paper removed off the bottom but not the top.
- Put down something as a fixed horizontal straightedge guide, make sure it’s accurately horizontal. Just put the red dot in one corner and jog across X and make sure it stays on the edge
- Put the test bar against the straightedge, in the middle of the bed’s X width, with the bar going off to the right
- Make a vertical cut on the left side of the bar, like 1/4" from the edge. This edge is in the middle of the bed. Discard the cutoff.
- Rotate the bar 180 deg and align on the straightedge. Do not flip the bar.
- Make another cut 1/4" from the first one. That will be on the right side of the bar since it’s been rotated. SAVE this slice.
- Inspect the slice with calipers, make sure you still know which side was the bottom. If you’ve got the slant trammed out correctly, the top and bottom width will be the same. It cannot be a rhombus so you don’t need to try to measure angles! If the bottom is wider than the top, the carriage needs to have the right side lifted. If the bottom is narrower than the top, then it needs the right side lifted.
If you’re trying to correct a slant in the Y, that’s the same basic idea, but how you can adjust this is very machine-dependent. It often comes down to adjusting the XY joints on the left and right. It is possible for the gantry to be twisted, so you may need to do a slant test on the far left and far right and make adjustments to the adjacent joint independently.
Every time you make an adjustment, you want to recheck the M3 alignment so it still sends the beam straight through the AA cone orifice.