DON’T TRY TO CONFUSE ME WITH FACTS OR THE TRUTH!!!
(a)
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More GF hacking, what’s not to love?
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Lol you just have fun with that one.
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I remember this was supposed to be a thing. Does anyone remember if it was an original feature they backed out of, or just pre-release talk and speculation?
Well, i understand where your coming from, but this is one mod that I’m not going to be trying…
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So my opinion on this has changed a bit, as far as the risk to the fan life goes. The fan is rated for performance while totally obstructed, the datasheet specifically calls out static pressure at given airflow, even zero. I think the risk to the fan is minimal. The risk of fire etc, that’s a little less clear. Cutting cardstock on my vacuum tray last night for a total of about 1.5 hours yielded zero flareups or excess scorching, so I feel pretty confident in that use case.
As always, this is a terrible idea, don’t do it. 
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paper is probably one of the better use-cases for this. you can run high speed / low power, which generates the least fire risk.
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Yeah and given the nature of this, you want the reduced air assist to prevent things from blowing away, it’ll naturally trend toward thinner and lighter materials, which simply have less fuel even if there is a flare up. A piece of tissue catching fire is not nearly as bad as acrylic, there’s just so much more energy in acrylic or thicker woods.
So far, zero flare ups in any test, even at level 5 reduction (total blockage) cutting printer paper.
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I have to be honest with myself about this sort of mod, sooner or later I would get distracted while my GF slowly caught fire That’s why its not a mod for me.
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I’d like to see this on an engrave. As long as the exhaust is adequate and the purge air on the head is doing it’s job, the optics should stay clean, and this should reduce a lot of the build up from the system going bottom up and blowing soot into the freshly engraved areas.
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Oh that’s a good idea. I’ll do one in a bit.
OK so the bottom line: reducing the air assist does reduce engraving residue.
All of these are engraves in solid maple, 750/full/vary power/270 lpi
No reduction. This is a deep engrave, so you expect a lot of residue.
Level 4 reduction, still a bit of airflow but severely reduced. Noticeably less residue.
Level 5 reduction, completely blocked. Even less than level 4.
Side by side comparisons of the full power/no airflow engraves. Notice the reflection on the tarry residue.
Full air assist power:
No air flow:
The residue is still present but it’s far less thick. My optics seem fine, not excessively dirty at all. There was no flareup, the smoke was quickly evacuated just via normal exhaust airflow. Of course flareup and other properties may be different depending on the material, but hardwood maple presented no problem. A cleaner-engraving wood like walnut might have even better performance.
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One of the things I’ve found from going through so many lasers is that exhaust is a very significant factor in improving lots of laser processing qualities (this is why I went with dual 850 cfm fans on the Trotec). The quicker you can get that stuff out of there, the cleaner your processing will be.
The Glowforge has an advantage here with having the separate purge air on the head. A lot of systems merge the functionality of the air assist with the purge air system — the air assist provides both an area of clean air around the optics as well as directing air towards the cut. So running without air gets the lens and final mirror dirty quicker. You run with just enough air to provide that curtain.
I’d love to see someone put a significant fan on the Glowforge that would really suck. The Penn blower might suck the glass out though lol (I can feel the suction when I open the lid on the 400). But the inline Cloudline everyone goes with (which I think I was the first or one of the first to buy), stops performing as well with any introduction of static pressure.
I could almost envision someone utilizing a y-fitting off of a big fan, and running it to both the 4” outlet and making an adapter for the rear passthrough slot. The exhaust port has an area of around 12.5 sq inches. If you could utilize the pass through slot to exhaust out of, that would be another 7.5 square inches, or 160% more area to exhaust from. Plus it would be a more direct route.
One thing that your vacuum table might help with (yes, merging your topics) is pulling the smoke down and through the cut. Or, it may not have enough suction for that… hard to say. But I’ve also found that being able to pull that smoke through the cut helps with processing also. It really helps with processing acrylic.
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i did notice that the universal will pull both around the honeycomb as well as through the honeycomb, which probably does help exhaust the smoke quicker for cuts.
Covering up the unused part of the bed on the Universal will give you extra downforce also. Not sure how much but it helps. You can also get some magnetic tape, leave the paper covering on the sticky side, and cover up some of the upper slots to increase vacuum and force the top exhaust to a particular side (useful if only working on a portion of the bed). I would leave the middle open to increase exhaust towards that area.
magnetic tape won’t do much on the universal tray, since it’s aluminum. i realize it would be abnormally heavy if it was steel, but i hate the aluminum. it’s easily damaged and non-magnetic. just having the honeycomb in steel would make me happy.
Nah. Magnetic tape over the back exhaust slot - not the bed itself. I don’t think I have any pics off hand. I made a little wood piece with magnets that would attach to it, but the magnetic tape is better.
oooooohhh… i get it.
edit: since i’m in the office (first time in weeks), i actually went in an looked.
The 400 actually has 4 (I think) dampeners up there that you can slide to change the balance, which is kind of a cool feature.
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did you ever see any aftermarket vacuum beds for your universals? wondering if there are any out there. and man i’d like to swap out that honeycomb for a steel one.