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.