As far as I remember, just for engraves (top to bottom or bottom to top). I always run bottom to top. But I could be wrong. I thought beyond that, it was just the direction of the path in the code.
I think it’s more a velocity thing. And also a turbulence thing. Though these are both essentially also volume and pressure.
The air comes off the fan in a turbulent vortex. As it moves away from the fan it spreads out, so both pressure and velocity drop. The turbulence accelerates this. So to ensure you’ve got enough airflow at the cut with an un-ducted fan, you need one that moves a lot more air. Most of what the fan is blowing is wasted, passing way off to either side of the cut where it does no good.
Jet engines and ducted fan motors for aircraft have stators to “straighten out” the vortex coming off the fan, and these significantly improve the efficiency of the fan.
Taking the air off the fan and smoothing it out and ducting it through a narrow orifice to the laser spot will essentially take all the work being done by the fan and direct it at the cut, none of what comes off the fan will be wasted. It’s got to be a big boost in the effectiveness of the fan.
I wouldn’t be hard to design and 3D print a plenum for the GF fan. I just lack the copious free time to do it… been too busy working on this project.
Static pressure for the standard air assist fan is wretched. Airflow drops like a stone if you impinge the fan.
It’s a little weird to read this, you sort of read left to right to see how much airflow drops as static pressure increases. The key thing to notice is how steep that curve is on the lower right and upper left, your airflow won’t sustain much restriction or redirection. (I am assuming the Glowforge puts ~12v to the fan so this graph is fairly indicative of our situation)
Notice that we’re talking about very small pressures here: the maximum static pressure for this fan at 12v is about a twentieth of a PSI (1.4 inches H2O is about 0.05 PSI). It’s really hard to find a fan in the same form factor that can push more pressure, check out my vacuum table thread for a deep dive into the available fans.
Add to this mix that any fan you choose to replace here needs to be about the same overall mass, or you might throw the clean corners algorithm off. If you want to use a more massive fan you’ll need to figure out how to mount it off the head assembly and use a hose to direct things (you know, like a more serious laser does)
Absolutely!! I tried to address that in the second portion but probably didn’t make it overly clear or important enough. Enough resistance and you’ll surpass what the fan will be able to handle.
I was probably making an assumption (and we know how that goes) that one of the approaches would be to essentially duct the air from existing components/fan, down to a smaller point, rather than “broadcasting” like it is now. As far as the volume/pressure comment - pumps in general go HVLP (high volume/low pressure) or the opposite. Boyle’s Law.
That’s one of the things about the in-line exhaust fans, but also applies here since the fan type is the same (axial fan). They are generally suitable for high volume/low pressure but like your chart shows, they can stall pretty quick under pressure.
I think personally, if I were to try this, I would look at something like the air curtain set up at the front of the enclosure and block off or reduce the shroud from the existing fan (IIRC, you experimented with that, right?). I have no idea how effective it is on the little Epilog, but they continue using it, so it must not be not horrible?
My feeling is that a better nozzle could do better - though experimentation required.
It occurs to me that it would not be hard to shape a fit a different nozzle out of cereal packet cardboard for a few test goes.
I reckon that nozzle that had a curve to bend the airflow would be better
I reckon a more focussed exit for the air would be better.
Also, anybody know if a more powerful fan for the same form factor is available?
There are certainly fans with much more power in that size, I have servers that have them and they are as loud (or louder!) as the GF exhaust fan when they spin up to full power, but the cables and connectors in the GF are designed for a low power fan and “upgrading” to a high power fan would almost certainly cause a failure of some type.
I think “focusing” the airflow we have to the point of laser impact would be an interesting experiment.
Give a look to my new post here:
Looking at the shape and space available below the GF laser head… there’s not much space on top (before the focus sensor? See attached picture), but plenty below and on other sides.
I believe GF could engineer an air assist module similar to the Xtool M1 i’ve linked the thread above: it works AWESOME.
Looks like an unnecessary solution to a problem that does not exist.
Totally disagree @eflyguy…
Please try, with our Glowforge, to obtain such a clean cut (just layered with my “cheap” M1 with some very cheap amazon not-masked wood)
I paid more than 8500€ to have a GF Pro in Italy and I’m getting crazy to (non) obtaining (expensive) proofgrade materials delivered locally…
And cannot obtain any clean cut out of non-masked materials… If you’re able to, please share and make me happy (not painting the wood and not sanding it…).
But you same wrote “I think “focusing” the airflow we have to the point of laser impact would be an interesting experiment”. This is exactly what the xTool M1 does. With these EXCELLENT results (useful even on foam materials to avoid melting out).
How thick is the wood? How many passes did you require to cut it?
This is a simple 2mm plywood. With the M1 (10 optical Watt) you have no problems in cutting 1.5, 2, 3 and some 5mm in a single pass. For 2mm I use 100% power, 8mm/s, 1 pass.
But the air assist is needed (not only cleaner cut, but even more powerful cuts, as there’s no smoke to disturb the laser beam, and all the dust/soot are immediately removed.
If you tied in an 800 CFM exhaust to the far end of the exhaust hose you would be removing so much smoke so fast it would not have time to dirty anything. Even the 190 CFM Vivo fan plus the built in exhaust makes a big difference from just the built in exhaust alone.
At the moment the new place where I need moving the GF has no close windows, therefore I’ll need using a smoke purifier (that - in any case - has a strong air suction).
Nonetheless… I’m sure that a little compressor blowing air just on the laser spot might turn far more effective.
I already added an external inline fan to my home-based xTool M1 (AC Infinity S4, 205CFM), but the results I obtain with the air assist mod, and a little compressor, are fa better.
You are painting yourself into a corner I think. The Hepa filters are very expensive and if they get filled they move air even worse. I have a Blu-Dri for industrial use that is 500CFM but it has a 12" intake and as I was able to use a window it gets rather minor use as much for kitchen smells and smoke as Glowforge room smoke (now rare)
Anything less than 200 CFM and you will need to change the filter so even 500 CFM to start will fill fairly fast. There are games to play with cheaper prefilters etc but that is a deep rabbit hole. There are some here who run their hose 30 feet (and really need a high CFM just for that) to avoid needing an indoor filter.
I expect that the Glowforge air volume needs will be far higher than the x-tool also.
At the moment I did already buy an HEPA filter… not the GF original one, but the XTool one (that seems equal or better - same shape too, maybe same producer).
Unluckily at the moment I’ll have to keep the GF in my garage, that has no windows, so… I’m not lucky with a close access to “free exhaust”.
In the future I’ll try to move it in another place. Thanks!
I would think of your Glowforge as an indoor family pet. It can die if too cold or too humid even if you are not using it, and it will collapse if working while it is too warm. If the pet would not be happy, you will not be happy. The main working part is a glass tube full of water, and like freezing a glass bottle full of water it is not very useful after that.
Luckily is an heated garage, and even when not heated, has never gone below 7ºC in full winter, sort of bat cave
Just to know… in this case do you add an 800cfm inline fan without removing the internal one (that spins at different speed). Might you have counter currents when you switch on the super external fan and provoke the glowforge one spinning? Or spinning more rapidly than expected?
And overspinning a brushless motor can destroy it.
* I haven’t heard or seen anyone who has destroyed their builtin exhaust fan this way.
Cue someone who will interject with “just remove the inline fan, it works better and you’ll be happy you did”. Yeah, yeah, Mr/Ms I-have-a-basic-machine. Not as simple if you have a pro.
Removing my broken fan in my Pro was a PIA, but worth the effort. Knowing what I learned about airflow over unpowered fans and propellers from my RC days, I felt it had to be done. I was running a 4" inline duct fan at the time, and the difference in debris build-up was quite noticeable.
I’ll admit it’s not a simple task, and beyond what many GF owners should attempt. I wouldn’t put you in that category.
Cutting out the old-style grate also made a visible difference. Switching to a 6" fan, despite the 25’ of 4" ducting leading to it, made the biggest difference. I never ran a 6" fan with the failed built-in fan and stock grate, so I can’t comment on that.