Can the travel direction of the gantry be reversed? So that the engraving proceeds from the back of the bed to the front, and the direction of the engraving is the same as the airflow of the fan?
Nope. It’s controlled by Glowforge.
That’s what I figured. Had to ask, though.
There’s been some discussion about this if you search around. I’m not sure GF has ever officially commented on why it’s this way, but I always assumed it was to make more consistent engraves. Seems like if you go the other way, you will be powering through an unknown amount of laser residue (aka goop) and that will probably throw off the engrave. Thus, they will always prefer that the air assist blows the opposite direction of the engrave.
It’s just a guess, but it doesn’t take much to throw it off – PG labels will do it. I can only assume that goop will too, and especially since the amount of goop is dependent on materials and power settings, it gets really hard to plan for it.
I think Dan once mentioned that Bailey suggested it be front to back so it photographs better
Might have been tongue-in-cheek.
I always thought it was to keep the maximum resinous remnants out of the fans so we didn’t have to clean them as often, and to facilitate cleaning the stuff off of the machines.
It’s easier to clean it off of the front of the machine than the back, (easier to reach), and by depositing some of the residue on the material, which still has the masking, it’s not carried to the front of the exhaust fan, which is damned hard to reach for cleaning.
Might be wrong though, and they’ve never said.
Here’s one of the more informative previous threads on this topic:
I have been annoyed by this very often as well when doing a deep engrave it often burns the front end to a char as the fan makes the heat of the cut like a blowtorch, where if it were cutting forward that would not be an issue.
For the record, and now that it’s been over a month since the last reply, I was reading on Inventables website, and they suggested when engraving on acrylic, specifically the two-color acrylic, that reversing the direction of the engraving can reduce the possibility of having engraved areas be stained or marked by the residue blowing across them, as the engraved acrylic can be softened by the laser as it passes. At least until the material cools. If the residue is blowing over an area that has not yet been engraved, that would be eliminated.
However, I don’t have a ton of experience with engraving two-color acrylic, or even clear acrylic, yet. So I don’t know how much of an issue this is.