Relocate exhaust fan from back to side?

[Ryan Fancher]

Hey guys! I'm getting a bit frustrated with how much room my laser is taking up with the exhaust fan, hoses etc at the back of the machine. I'm thinking I could save a ton of space by relocating it to the left side (50w blue/white) so I could push it back towards the wall. It doesnt appear to have anything in the way, so physically relocating it wouldnt be terribly difficult. Is there any reason why that would be an issue?
(I have an external exhaust fan doing the bulk of the work if that makes a difference).

[Tim Mellor]

Look at the actual Fan itself and see if you can reduce the depth by hacking it. My little one got some 3D printer love and some hack sawing to the body viewtopic.php?f=133&t=4570&p=24792&hilit=airflow#p24792

Cross Bed Airflow is a weak point of some Lasers in particular. Mine initially came with ZERO air intake from the front meaning I had to block the door open Before that the air intake was from Random Speed holes in the main body so lets just say the Airflow Sucked and Blowed all at once.

Enter my Fix/Block the Speedholes with a fancy option. Magnetic Sign material would be a good choice too but I didn't have any. The dirty option is Gaffer Tape viewtopic.php?f=123&t=3905&p=21890#p21890

That then led me to the Door Jacking fix. This post and a few more just after it. The final result was this which fixed the door issue.

20200616_110336_resized.jpg

Where this is leading is I now had vastly better and LINEAR/EVEN cross bed flow than I had initially. So in your case if your door doesn't suck where does the Air come from? The reality is while Air doesn't travel in straight lines what we have is still not linear but more like the second as we try and cram width into a relatively small diameter. So we are starting to get pools of air with reduced flow at the back Left and Right.

Ideal but False.jpg

Closer to reality.jpg

If you then want to take that flow and turn it at 90 degrees to the Left of this example sketch then the entire Back Right will be getting near Zero Flow and most of the Right Side will be getting vastly reduced airflow as the Air will take the path of least resistance. I haven't drawn this but it would take more than the one coffee it took to draw the previous two

[Ryan Fancher]

See now this is the type of reply I needed! haha

reducing the fan wouldn't really help much with spacing issues, its more the hose out the back that is hindering it.

Left side would reduce the airflow significantly, i'm seeing that now.

but... what about out the bottom? if i were to cut a hole in the bottom and in the stand i've built, drawing everything from top to bottom, i'm guessing it would perform better than simply exiting left side... its possible to do without hindering the bed, as i don't think i've ever lowered the bed far enough to get close.

[Jeffrey Aley]

See now this is the type of reply I needed! haha

reducing the fan wouldn't really help much with spacing issues, its more the hose out the back that is hindering it.

Left side would reduce the airflow significantly, i'm seeing that now.

but... what about out the bottom? if i were to cut a hole in the bottom and in the stand i've built, drawing everything from top to bottom, i'm guessing it would perform better than simply exiting left side... its possible to do without hindering the bed, as i don't think i've ever lowered the bed far enough to get close.

Smoke rises...

Ideally, you want laminar flow across the cutting plane. That means an exhaust at approximately the focal plane of the laser. Most of our lasers have unusually deep cabinets (handy for laser carving jack-o-lanterns, but not much else), so putting the exhaust at the bottom would put it pretty far away from where you need it.

It's also important to ensure you understand where your make-up-air is coming from. The builders of my blue & white didn't, so for some materials, I have to operate with the lid ajar.

[Tim Mellor]

As Jeffrey has put you want cross bed flow. If you try downdraft then areas not covered by the material is where all the air will go bypassing the cut/engrave area. The Cut width is insignificant so can be ignored. If you fill the cutting bed area then you trap the smoke/debris up top so it is still a loser.

I haven't added this to my current CAD design for my larger format Laser viewtopic.php?f=159&t=4710 but this is in essence what I will be doing. Taking the cross bed airflow and bending it down into a collector tube below the bed then off to the extraction fan.

As an idea of scale the virtual bed shown is 600x400 and the above bed elbows are 80mm (roughly 3") If you can't find a Cross in your local plumbing supplies then use two Tees side by side one up and one down to the expansion coupling. This does work on the theory you have 4-5" behind your bed in the cabinet and the center of the elbows should be around nozzle level. The virtual model is here if you want to spin it around for a better look https://a360.co/2N9BaNb