This is extremely correct. A very small vertical distance will create a very large horizontal offset in the preview.
We’ve never seen this happen. Given the way the hardware works, I believe it’s unlikely - if it moves at all, it’s going to fall off.
In manufacturing, ever part has a tolerance. Machine-to-machine variation is calibrated out at the factory, though.
Indeed. It’s easy to obtain much larger or smaller values depending on the height error. (There are other sources of error, but that’s the biggest).
The nonobvious piece of the puzzle is that the height of the material has an enormous impact on the final image accuracy, and that depends on:
The flatness of the surface your Glowforge rests on
Whether the tray feet sit properly in their grooves, or if there’s a tiny bit of debris in there
Whether the metal grate is dead flat
Whether your material is dead flat
The material thickness, which is the only one on the list that we actually know and can compensate for.
Any tiny variation in those factors will cause a big change in your positioning accuracy.
In the future, we plan to dramatically improve this by allowing you to scan the material with the autofocus system to get a very accurate read on the material height (not thickness - the height, which is what actually matters). We also have some improvements (especially around the edges) coming from a new calibration system.
They’re easy to miss with such low contrast. I hate them as they are.
I was zoomed in to 150% for these pics. I should have made it easier by going 100% or 200%, but oh well.
I think it is a 4" square that Tom_A placed in each corner of the bed in turn and added one engrave in the corresponding corner of the small square. A clever way to avoid wasting big sheet.
Well, it’s semi-consistent. I mean, the shift appears to always be to the left. In the upper-right and lower-left it also shifts down. As you can see in my previous post, center-bed appears pretty darn close to spot-on.
Exactly. When Rita asked that I test on my first thought was “Sure. If I get store credit for it.” Then my seconds thought was “Oh, hey! I kept that failed box for scrap if I needed it. Guess I need it.”
For those keeping score… Still working with Support on this. Which I’m happy to do. They’re really very wonderful people to deal with!
They haven’t asked for anything new, but I offered a couple of center-bed images because I’ve basically found that, on my unit, there appears to be no place on the entire bed where it’s actually accurate (unlike my first unit that was accurate throughout the majority of the bed). I figured to get a better view of this, I’d try a Score instead. Here’s that. As you can see, with the center of the object at ~8.5" x ~5.25" it’s pretty close to center-bed, where one would expect the highest accuracy.
Heh. No. But if the crumb tray were warped, I’d be able to tell pretty quickly as I lay un-warped material on it. All materials I have laid on it have laid perfectly flat. I’ve laid sheets as small as 4" x 4" and as large as 20" x 12". No indication of warping.
I guess I should also note that I’ve touched the camera housing and found that it appears to be completely fastened securely. I sense 0 movement, and it appears to be properly fixed to the unit.
Since the head position is calibrated dead centre it seems that either the camera or the laser beam don’t point straight downwards. I.e. when the logo is dead centre relative to the camera the beam is striking the material in a different place to what the camera sees directly below. Or it could be a software bug.
. I decided to do the extreme corners of the available workspace. Here are my results:
In the upper-right and lower-left it also shifts down. As you can see in my previous post, center-bed appears pretty darn close to spot-on.
my first thought was “Sure. If I get store credit for it.” Then my seconds thought was “Oh, hey! I kept that failed box for scrap if I needed it. Guess I need it.”
