A way to improve object placement

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.

What an amazing community!


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.

Agreed. I did an analysis a while back that predicted how much cutting error would happen given the amount of warp. All just geometry.

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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.


Thanks for this, @Jules–I just used this method on Longclaw and it worked perfectly.

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This one is @cynd11 's brainstorm! :wink:

So helpful thank you!

It would be great to have a software save for this alignment trick!

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!

You could make your own crumb tray ruler using this design generously donated by @jbmanning5:

Crumbtray Rulers


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.

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We aren’t using them but still have placement problems on proof grade materials. I’ll pick up a set today and try it out though. Thank you!

Use the Snapmark feature if available. I use it on everything that’s not on a full sheet now.


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!

  1. open your model
  2. put some tape inside the laser bed.
  3. 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)
  4. position your plank/whatever to the markings made on the tape. Do not move the model in the web interface.
  5. Start lasering.
  6. PROFIT???

Nice and simple tape trick. Good one.

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Not new but the clearest description of this to date so thanks.


You don’t happen to forecast stock prices too, do you?


No, but long ago in my career I did write software to calibrate scanners by scanning a reference grid and generating a correction map so that future scans came out correctly. Correcting for optical distortion by using a reference grid is a very old technique, and very well understood.

Just read https://app.glowforge.com/maintenance/camera-recalibrator ! Yay!