I have been custom cutting art mat boards for picture framing. The mat board is a nominal 12x16” size and the original opening is 8x12”. My custom openings are typically 9.5”x13”.
To get the custom opening in the cut area, and to make it repeatable, I put in some scrap cardboard strips on the left and right and cut vertical jig lines at 2” and 18”. By lining up the bottom of the mat board with the front door of the machine, the 9.5” high rectangle can be centered in the cuttable area.
So far, so good. I was even pleased to see that the focus-checking step was being taken at the edge of the board, vs. the center where there is no material in the stock piece of mat board that comes with the frame. But when I tried to repeat the process the next day (with the same jig pieces), everything was off center. I figured out that the laser head was banging into the right wall of the machine during the focus / red laser step and throwing off the location. I didn’t notice it the first time (other than the noise it made) because I cut my pieces without having turned off the machine and losing the (incorrect) 0,0 position.
I solved the problem by making a new jig deliberately off center by a small amount. For the simple project I am working on- cutting a single rectangle out of cheap paperboard, not a big deal in terms of lost time or material. But would be a big pain on a larger project.
So… why does the machine bang the head into the limits on its own focus check, and is there any way to prevent this from happening?
I had that a couple of times. I think it became confused after doing a couple of jobs and the lid is opened.
Ever since I started pushing the gantry all the way to the back and the laser head all the way to the left, I haven’t had the issue. I don’t do massive amounts of cuts, usually a couple or three jobs at a time. I think it needs to be “reset” sometimes. If you do this first, make sure that you turn it off and on to re-calibrate before printing.
If the machine does not start from the back left corner it will wander to the right looking for the center and bump into the right side and try to keep going. I have only had that ha[pen once a year or so ago, and started with the head in the back left corner ever since.
That would be turning the machine off, then moving the head to the back left and starting the machine again. As long as the head is mot bumped you should be good.
The Glowforge often gets confused if you start up with material in the bed already.
You can usually solve that by gently moving the head under the camera before you turn the machine on. The camera will see the Glowforge logo and know where it’s starting.
It’s basically looking for straight lines and rectangles at first so rectangular cutouts can fool it into thinking the gantry is somewhere it isn’t.
If none of this works you might need to start with an empty Glowforge and cut your jig anew each day. I’d recommend using a corner jig, they’re fast and take almost no material (cardboard).
If you’re unfamiliar with that idea, I run through the procedure here:
So you think the leftover piece of alignment cardboard is tricking the machine to thinking it is the left side of the crumb tray? I haven’t had the problem since I moved my whole jig to the left a little bit instead of leaving it centered, even having left the same cardboard in there and restarted the machine each time. I guess it still could be doing what you are saying, just now there is enough slack at the far right that it doesn’t bang into the limits.
A corner jig sounds useful, but since my matboard needs to be all the way up against the front door of the machine in order for the rectangles I am cutting out to be within the cuttable envelope area, I am essentially using the door as the other corner of my jig.
In any case, moving the head to be under the camera pre-startup generally solves the issue.
And yeah if your matboard is barely fitting, it’s a bit of an issue. However, if you’re doing a 9.5" height inner cut on a 12" tall matboard, you can do it with a corner jig. Check it:
Cut the black into a corner of cardboard. The blue outline is your inner mat cut. I think your mat will fit even inside a basic, there’s a lot of room toward the back of the machine.
EDIT:
Just to clarify, this is to scale as you described in the original post.
I didn’t kerf correct this, but kerfs on cardboard are fairly small and generally at this scale 0.01" (ish) tends to not matter as much.
There is documented behavior of some misalignment and calibration when there are black squared cut outs roughly the size of the QRC of a full sheet of material in the bed and the Glowforge does its initial alignment.
Putting a full sheet of untouched Proofgrade in the machine for initial startup might help or follow the manually centering the head under the lid camera as @evansd2 suggests, when the machine is off.
I’ve been continuing to work on the project, which is custom cutting mat board for 25 framed pictures, a few at a time when I have time. I have been leaving the cardboard edge guides in the machine. I turn off the machine after each use, turn it back on, and the positioning stays the same. I tried moving the head under the camera once because I had moved it around from the back left corner after cleaning things up in the machine. That didn’t seem to affect things one way or the other.
I haven’t had any problems since I shifted everything to the left by about an inch.
