Hi, Is there any way we can engrave from back to front? It seems that it would make more sense to do it that way, so the laser obliterates the soot staining, rather than soot staining the already engraved material. Is there a reason why it isn’t done that way, that I’m not seeing?
Based on the physical placement of the air assist fan for this machine, it’s always going to blow the smoke and residue forward.
If you were to engrave from the back to the front, it would still blow the residue forward, but it will build up over a larger area, and as time goes on, it might start to interfere with the engrave depth, making it harder to engrave through the material and creating more of a flame hazard. The engrave will be deeper at the back, and shallow at the front.
So that’s a no-go. 
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There was recently another thread on this very same topic…
No, we can’t change it.
Also wouldn’t really gain much since the “soot”/debris blown forward would then lay over the new material and thus start affecting the engrave/cut as it’s trying to go thru soot as well as clean material.
Also going front to back means we can see the results without the gantry & head blocking it, as well as any FLAMES and pause/shut down the job if/when needed.
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Yeah this is a weird … coincidence? Is this a cross post?
Let’s see:
Nope different topic altogether. Great minds or something.
Speaking of that, lots of previous great minds…
https://community.glowforge.com/search?q=engrave%20top%20to%20bottom
https://community.glowforge.com/search?q=engrave%20bottom%20up
https://community.glowforge.com/search?q=engrave%20direction
And a really early one (2017) from some random guy:
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Maybe I used the wrong keywords, because I didn’t find any other threads. Thanks for finding those 
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Would it really build up to such a degree that it would effect depth?
top to bottom seems to be how most folks describe it rather than front to back. Engrave direction also gets some hits as @evansd2 linked.
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One reason that came up once upon a time is that the masking could blow downstream which would impact the print.
It’s not really much of a reason, though, because that can happen with cuts as well.
Airborne particulates won’t impact it - it’s transparent to IR radiation - the beam. That’s why FLIR devices are literally life-savers in fire-fighting scenarios.
It was added to the hopper a long time ago, iirc.
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Is there an actual hopper somewhere that we can look through, or is it on their end?
All theirs, although you could search for the term and find the gazillion times it’s been mentioned. Search “by user” (dan) and you might find more interesting results.
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Probably. Maybe not in a significant way for some basic vector engraves, but for a fine photo engrave or 3d engrave where very small power variations really matter, absolutely. It’d also be dependent on the material, some things are way dirtier than others. Acrylic residue is also sticky and nasty in particular.
In any case it’d be nonzero and inconsistent.
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Cool, thanks
Debris buildup would probably make quite a difference. Don’t know why I was thinking smoke - someone mentioned it in the last couple of days.
I took a pic for another purpose…
Sorry it’s out of focus, but this is just a 16x14 uniform engrave, look how much debris collected ahead of the engrave area. In addition to the additional material to penetrate, that’s going to seriously affect the focus of the beam.
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I haven’t worked with any plastics yet, only wood and draft board. I haven’t seen a build up like that before. does that come off easily?
Here’s the result (the reason I did the test):
The vaporized debris “crazes” the surface finish. I was testing alcohol to clean up, but the right 1/3 had none applied, only water.
This is PG acrylic, by the way. SD graphic setting.
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… but it may not be an issue with wood.
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