Accuracy question


Big caveat on that, though: the UI lacks any facilities for precision placement or repeatability (well ok, it has one, see below). So when it says “golly gee, something went wrong” and kicks you back to the home screen, you may have to start over with your design shoved into the upper left corner.

There’s one workaround where you make your SVG file the exact size of the bed and it will always load at 0, 0, although I can’t find the post… too much noise on this forum generated by people like me. But if you do that then you have to do your alignment by positioning the material in the right place.

I’m hoping that hopper item for just being able to type in numeric values for position and size will be done soon.



Hi Jules,
Okay but how on earth did you print that grain of rice? Last time i checked the grains are smaller than the accuracy of the machine? :grinning:



Zoomed way in. 500% (using Chrome) :grin:

I’ve always had better accuracy on the initial camera image than the secondary shot. (Basically I ignore that second one entirely.)

Every once in a while it can get a bit out of whack when they are working on it, but mostly I get pretty spot-on placement under the lens.

A lot of the alignment issues are coming and going right now. It’s going to be a different story in a few months.



Ah okay right under the camera… I really think they are going to have problems around the outer edge each lens has its own distortion level and the only way to get the software to adjust would be to create a test pattern and compensate based on what the camera sees. Thanks for the information

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I’m already trying to work out how to plot the variation so I can get precise cuts the first time. Maybe put graph paper down on the bed and run several jobs where I pew through various intersections?

But then I figure somebody at :glowforge: has already cracked a computer vision book or six and will get there before I do. :slight_smile:




(My apologies to the many folks who have seen me post this link like a million times.)



Yes. If exactly placed, should hit the exact same spot.
Just so you know, Glowforge does not use G-code.



If you start out with an art board in your design program of 20" wide by 12 " high, the design will go in the exact same spot every time in relation to the full bed of the Glowforge. If your art board is any other size, it ends up in other places.



My only problem with this approach (btw, ALL my inkscape designs are done on a 20" wide x 12" high storyboard), is that I can’t seem to place my material in the exact place needed.

The best that I’ve been able to do is to make sure the material is masked and then run the fastest and lightest score that I can to make sure that the design will land where I want it to, before doing anything that needs that level of precision.



I have marked my lower left cuttable corner with blue tape (so I can replace it every time they make an improvement in the cut height increases) on the border of the bed. Technically not precisely able to repeat placement since the bed can move in the divots but when I use a target score I almost never need to move it in the GFUI more than one or two clicks in either direction.

If if were my permanent unit, I’d have a carpenter square cut out and attached to the black bed border with double-sided sticky tape so I could really lock it in vs matching a corner to the tape.



Ah! Good to know. Probably hadn’t thought about the mechanism since late 2015 when we were all just guessing. :slight_smile:

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Do you have to draw a box around it or is just having the artboard size correct enough to trigger the magic?

Asking because in my limited playing around so far, the size of the document seems to be irrelevant and once I export an SVG and load it into the Glowforge app, it doesn’t show up as any kind of a box or boundary, it just uses the extents of the actual drawing. Maybe I’m doing it wrong.



My plan is to use a 20x12 template for everything in Illustrator, and adjust for cuttable surface using margins. Then, as it adapts, I’ll just change the template.

The fun part will be when I start slicing larger designs into 11" or so at a time and try to link them together seamlessly. (Again, if :glowforge: doesn’t get to it first. :slight_smile: )



Yeah, that makes sense. I’ll try the 20x12 trick when I get home.

I’ve made a few things where for example I know I have a 4" square object to engrave my design on, so I set the artboard to 4x4 in Illustrator and I can ensure it fits and the size and placement are good. If I want to bring that into GF and use the bounding box to align it with my material, I need to explicitly draw the box.

Nothing wrong with that, it was just non-obvious enough to me that I kept forgetting to do it.



No, the artboard is enough as @jrnelson suggests. I use the front door to register larger sheets of cardboard and then cut out a place in the cardboard as a jig to repeat or even do one offs. It’s a little setup.

Using one of the corners for registration isn’t too bad. Try it out with some cardboard and get a feel for where the designs end up.

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But doesn’t that change depending on the height of the material in the bed?



I usually call it the garage door. I hope we can settle on a name for this. Front access panel, front drop down panel, not really a doggie door, that’s the pass through slot. Well, at least a flatwork can get through. the two corners where it shuts against the case are pretty reliable registrations slots for a jig.

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Not really. I’m generally working in a relatively narrow range of materials when I’m doing this - 3mm to 3/8". The 0,0 point I’ve created is always going to be the same - the camera’s perception of material aligned with it is what is affected by the material thickness.

So my 20x12" artboard defines (effectively speaking) the 0,0 offset for my actual project. If I’m an inch up & over from the lower left corner in Corel, then the GFUI has it an inch up & over as well and every design I do will show up there as well.

The trick is getting the camera view to align close enough to drop it at the inch up & over point on the material. That’s where everyone’s challenges are coming from. GF says that we can expect what I’d now call the 1,1 location on the artboard might be .75-1.25 in either up or across position - a quarter inch off but it could be a quarter left or right so actually up to 1/2". (I’m assuming the 1/4" stated potential margin of error is + or - but it could be they mean it is really + - 1/8"…I set my expectations conservatively and have been pleasantly surprised as I achieve better accuracy :slight_smile:️ ).

So when I want precision I place a targeting reticle at the upper or lower left corner of the artboard. Then I set the GFUI to 200% magnification (after setting the material height if needed) and move the drawing so the reticle lines up with the 0,0 on the GFUI’s ruler (for an upper left reticle). I’m always pretty close - one or two clicks and that’s entirely based on whether I drop the blue artwork bounding box (Ctrl-A in the GFUI) exactly on top of the ruler line or if there’s a hair of ruler showing.

Of course once it cuts the resulting red (magenta?) lines are not precisely aligned with the cut image on the physical material. That’s when you trust your instruments and not your seat of the pants sensibilities of what it “should” be because your eyes (camera) are fooling you.



I’d propose pouring a small puddle of fast setting resin(I’d use PU ) into the divots, then drop the oiled feet of the crumb tray down onto it for a permanent fixed position.
This assumes the feet are tapered of course !

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Not sure that would help. The ability for the bed to move out of position is a relatively theoretical thing. Can it? Yeah, because it’s not locked down. Does it? Not really from my experience and I get 2 mouse (or arrow) clicks repeatability in GFUI camera view vs actual material placement pretty reliably.

I think it matters more to the people wanting thousandths of an inch repeatable accuracy of the camera vs material imaging.