Engravable Area and Limit Switches

I am considering making an alignment grid for my wasteboard. I have secured the laser (an Atomstack A5 M50 40W) into a set position on the wasteboard, and was getting ready to engrave a 410 x 400 mm grid to use for aligning engraving targets.

And then I realized that I might not be able to actually do this, since the engraver has limit switches that set the 0,0 machine origin. When starting Lightburn, the machine goes to the limit switches, then backs off by 1mm in both the x and y directions, ending up at coordinates 1.000, 1.000. If I were to try engraving a line along the x or y axis, I think the gantry would hit those limit switches, creating an error condition, and halt any engraving that was ongoing.

If I do make an alignment grid for my wasteboard, do I need to make it smaller than the maximum machine work area to get around the limit switch conflict?

Try actually going to 0,0 to see if it triggers the switch. It’s possible that the pull-off is sufficient that the switches won’t be activated.

Have you confirmed that $27 is set to 1? Not all machines are configured to end-up at 1,1 after homing. They’re typically 0,0 after pull-off, assuming home and origin is same corner.

Alternatively, disable hard limits temporarily to create the grid ($21=0).

Thanks for the feedback…

Yes, $27 set to a 1mm pull-off, and if queried the machine will report that it is at (1.000,1.000) after homing. That surprised me a little when I saw it, as I had previously assumed that it would set machine origin at the pull-off position and not the homing switch position.

Silly me!!! I should have tried an actual engraving that includes positions right on the x and y axes. I was focused on not messing up the wasteboard grid after all the trouble of fixing the engraver to a solid and repeatable position on the wasteboard. (the “feet” on my Atomstack are almost exactly the width of my table saw kerf, and fit in there nice and tight).

And thanks for the idea of temporarily disabling the hard limits. I hadn’t considered that approach.

Well, it looks like I’ve been overthinking the possible problem. As a first test, after homing the laser head, I checked the position, and it was at (1.000, 1.000). I then used the move window to send the laser head to (0.000, 0.000). It moved appropriately, and when queried the machine showed it was at (0.000, 0.000).

I then set up a simple test burn of a rectangle located at (0.000, 0.000). The laser burned that rectangle perfectly! I should have no problems setting up a reference grid on the wasteboard.

Nice. I’m curious how close you would need to get to trigger the limit. It’s also possible that limit switches are disabled after homing. Can’t quite recall but I remember some counterintuitive behavior there. You may want to experiment.

Not sure about how far the physical (limit-switch) limits will allow you to go, but with soft-limits set, any object that extends even .01 mm over the boundary will be flagged, and if you go ahead with the engraving, it will not be sent to the machine to be burned.

Yeah, the hard limits really only come into play when steps have been lost or when soft limits are not enabled.