Focus on 3/4” bamboo cutting board

[jim_jenkins]

Well, I guess I already learned it, by “well, don’t do that!” But would like some clarification on the GlowForge autofocus. I had the crumb tray in, and put a bamboo cutting board in that’s about 3/4” thick. I checked and it cleared the laser head and then some. Send the job, a 8 min logo, and wow it’s blurry. Canceled the job and sort of ruined my board. Sanded it down, pulled the crumb tray added spacers under the board (just less than 1” of spacer) and ran the same job. Perfect engrave. Hmmmm. How does autofocus work? Seems like it should have warned me I was too close to the head and made me over ride/cancel.

Now I am nervous about how thick something can be, I sort of ruined someone’s cutting board. I will sand it some more and see how it looks.

[Jules]

Autofocus is not enabled yet AFAIK, and you can’t use anything thicker than about 0.5 inches on top of the crumb tray.

The laser needs a certain amount of distance to focus the lens … as you discovered.

If you want to engrave on something thicker than half an inch, you need to remove the crumb tray and prop the board up so that it falls into a certain range for the laser to be able to focus on it.

There’s a really good tutorial that @henryhbk did that shows how to do it here:

Tutorial: How to cut without the Crumb Tray (Honeycomb)

Tutorial: How to cut objects too thick to have the honeycomb in place The GlowForge has a maximum material thickness it can cut through, but there is a maximum thickness you can even put on the honeycomb (crumb tray) even if you are surface engraving as the laser has a limited focus range of 0.01" - 0.4" *** above the surface of the honeycomb at the time of this tutorial. But let’s say you wanted to engrave something thicker that fits quite nicely inside the GlowForge but not with the crumb tray…

Sounds like you got lucky with the distance on your second shot though, so that was a good thing.

Sorry about that.

[markwal]

@Jules

Autofocus is not enabled yet AFAIK

It is. But it is only one spot autofocus, not continuous autofocus which is still in the “to do” category. The range of autofocus is 0-0.433 inches from the top of the tray. Clearly 3/4" is outside the range and the UI won’t let you set it to that height. If you leave the focus height unset or use Proofgrade settings it does the autofocus thing from one spot.

As for a warning when your material is too thick, seems like a good suggestion for the hopper, but my speculation would be that it will be in there a good long while.

[markwal]

Here’s the bit about autofocus.

@dan

If the focus height is left at the default, it uses autofocus instead. If you change it, it doesn’t use the autofocus. (@Tony, correct me if I’m wrong).

[markwal]

You know, a couple of things surprised me about this. One is that the air assist didn’t hit your material. I’m pretty sure there isn’t 0.75" clearance under there. The other is that the UI won’t let you enter 0.75" for your material thickness or it didn’t used to anyway and the visual alignment would have been even more off than it is normally. Maybe you didn’t use visual alignment though.

[rpegg]

@markwal

The range of autofocus is 0-0.433 inches from the top of the tray.

BTW: they have increased the material height and focus limit to 0.5" from the earlier 0.433" S/W limitation

[jim_jenkins]

Thank you so much for the detailed and thoughtful response! Seems like a little string taped to the head could help I guess.

I guess I thought the material calibration and “scanning material” was something different LOL.

very helpful, I need to be more careful about material though.

[jim_jenkins]

Look at their home page, the 12 features mentions continual auto focus.

[markwal]

Yes, but it’s still “to do”.

[markwal]

From the PRU announcement, but it’s pretty close to what my acceptance mail said more recently:

@dan

To do: Continuous autofocus to cut and engrave curved surfaces.

[rpegg]

Another tip. The 3/4" board that you tried is way higher than the air assist port just behind the laser head. On my machine that port is only 0.6" above the crumb tray. If the head had come forward a little more during the attempt the port would have hit your material. This will only ruin your engrave if you are lucky. The port could actually wedge against the material.

[Jules]

It can knock the gantry off the tracks - I did it with foamcore.
(That’ll scare the you-know-what right out of you.)

[Dan_H]

Thanks for the help here @Jules and @markwal.

It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email support@glowforge.com.