It occurs to me that GF could do this in software, and create a perfect map of each GF. It’d be a pretty simple process - put in a full sized piece of material (paper, draft board). GB scores a grid (or at least a known set of calibration points) on the material. Then it looks using the camera, identifies the actual scored points, and does the math to correct for the optical distortion. Might want to repeat the process to confirm that the calibration worked. This should correct for whatever the unique lens positioning is in the GF - given the extreme angles, even a slight variation in manufacturing might produce a variation in optical distortion.
I remember doing this with scanners and cameras in “the old days” - print a calibration pattern on a known good printer (or pre-printed), scan it, and the software calibrates to correct for any distortion.
Amusingly cameras in orbit, or high altitude plans, use the highways in Kansas to measure optical distortion - the state is covered by a perfect grid!
I think this is the idea that Dan has hinted at. They’ve apparently done some kind of scan like that of your machine when it was manufactured and stored it. At some point they’ll use it to do better alignment.
It should work great until you open and shut the lid so the camera is in a subtle different spot.
Actually, I think they’re hoping to be able to compare images after each shut of the lid and take that into account too.
Awesome paper, thanks for sharing it, @dan_berry! I sure hope @dan sends it to his team - looks like a clever approach to correction for optical distortion! They reported getting sub-pixel accuracy in a tiny fraction of a second!
I also noticed back in the thread a claim that Safari didn’t work well with GFUI. Based on that, I’ll also try Chrome to see how it compares.
If you calibrate at one height you should be able to calculate the correction for any height using geometry. Each pixel of the camera responds to light on a single ray. So from the calibration you work out the correspondence between pixels and angles. Simple geometry will tell you where each ray will strike a surface at arbitrary height.
Seems like GF should consider some high contrast stickers that would be just outside the cut areas so it could opticaly calibrate itself. 4 for the corners and maybe one in the center we would remove once it calibrated.
I would love it if the crumb tray had grid markers on it so you could align things exactly as you had previously when doing multi-step or batch projects. Seems like an easy add on to paint a grid on the tray during manufacturing. I MIGHT try it with acrylic paint myself if I get courageous!
I am having trouble with this method as well as the jig method. It seems as though as soon as I open the GF, the alignment is going to be different. I’ve tried the graph paper method with my object to be engraved inside at once so I don’t have to open the lid and disturb the camera. The engrave will still be off. When I created a jig and placed the object into it, on the GFUI my object was much larger and farther to the left that the trace image I used to create the jig. I also have problems with the GF engraving things larger on the left side. Any tips or do I just have a defective GF? I am growing increasingly frustrated. Engraving without cutting seems to be off the table completely for me.
If the size in the GFUI is not what you are expecting, to me that indicates that the material thickness setting is not correct. Are you measuring the thickness of your object with digital calipers and using that number? A very small error in thickness can have a large effect on alignment. Even an inexpensive set of calipers like [this one](VINCA DCLA-0605 Quality Electronic Digital Vernier Caliper Inch/Metric/Fractions Conversion 0-6 Inch/150 mm Stainless Steel Body Red/Black Extra Large LCD Screen Auto Off Featured Measuring Tool https://www.amazon.com/dp/B017KUC6XQ/ref=cm_sw_r_cp_tai_x9lhCbVQCYZP8) is better than none at all.
To use a jig: Put the cut outline and engraving in the same file. In the GFUI select the cut outline portion and ignore the engrave. Cut out your jig material (cardboard, plywood, etc). Carefully remove the cut pieces from the jig without moving the jig (holding down jig with magnets or hold down pins is recommended). Insert the pieces of material to engrave in the cut out holes. In the GFUI change the cut outline to ignore and enable your engrave settings in the engrave portion. Then DO NOT move the artwork on the GFUI. It may look like it will be off but DO NO MOVE IT. The engrave will be perfectly aligned.
Another solution to achieve near perfect positioning: a piece of tape!
open your model
put some tape inside the laser bed.
Laser something into the tape that helps you position your object. Here i lasered the outer circle that would be cut from the model, and set other layers on ignore. You could also use lines/crosses for marking. Below you can see the model and the camera offset in the outer circle.
(below, the circle lasered in tape for positioning)