Can anyone point out the simple mistake? I was just setting up for my first attempt at cutting out pre-printed items and set up a flat board for alignment, drawing the size of the cut area on it. IT ISN’T SQUARE! The A4 the laser cut into the board goes off anywhere from -3 to +3 mm. Given how small the items I wanted to cut are this is too big a margin of error. Where do I start sorting this? Head alignment? Level of table? Adjustments somewhere else?
Is it off in both X and Y directions or just X or Y? I would check belt tension first.
it seems to be most out at top left and bottom right, coming in OK around the middles.
I linked to a video that helps with making sure the software is set correctly for your machine.
Corrected an error on mine over a larger area.
Can only help.
Ooh a new option, software. This gets deeper!
Oh one comment “RDworks won’t work on the type of controllers that come stock with k40’s.” so that’s out then.
few ideas for diagonal issue:
Lens in holder is well in the center and not up side down.
Check if laser head ok, I mean Z is vertical.
See as well if bed is horizontal at equal distance of focus point.-
finally alignement (everything should be as closed as 90°, no mirror chasing the next one to the hit center), check tube parrallel with bed & X, …
Sorry I’ve the K50
Check that the Y-axis rail is square. There have been cases where people’s K40s have arrived with the rail significantly closer to the back on one side of the Y-axis rail than the other.
Yes Yusuuf while the cutting area appears square the whole rig is off 3-4 mil from the case at one end. No idea how to adjust but would also solve the air duct being similarly angled across the top. Does look like the simple mistake I am looking for 
but how to fix?
@Frank_Fisher You’ll probably have to unmount the whole rig & possibly redrill the holes in the base (4 bolts if I recall correct, 2 each side) on the side that is out of square. I’d consider just elongating the existing holes, then you can put the bolts in on that side & slide rig to square position & then tighten in place.
OK got the tools, but does sound like a lost day including realigning the lens as well? Still can maybe move the awful vent back a bit at the same time.
Thanks.
@Frank_Fisher Yeah I think it will probably be a decent job to square it all up. Hopefully all goes well.
My k40 was out of square when cutting and it ended up being the belts on the left and right. I loosened the screws that held the extension on the motor and carefully adjusted the left and right sides until they were equal distance from the front of the rail. After doing this I tested a 280 x 180mm rectangle and it’s less than 1mm off diagonally where before this it was off by more than 3mm and horizontal lines were slanted a little. So far, with the items I create, this hasn’t been an issue, even with boxes.