Inline exhaust fan question

Hey all

Does anyone have experience of an inline fan 300cfm.

The enclosure should be around 10.5 cubic ft and the pipe-6" round, to the fan about 2.5ft draw and 16 inches the the final vent.

Would such a fan have a good draw?..in general.

The open area of the tube is 17,543 sq mm

The fluted cutting base for SM Ray is…shaped like (UUUUUU…) x 35 U’s, is 4,140 sq mm. The cutting base is going sub foor with jig to form cover, and fed by air intake at Left side of enclosure.

The enclosure will be pretty much air tight to give partial vacuum…So the air will be drawn in and along the ‘flutes’ of the cutting base toward vent side.

I can then introduce air intake above the subfloor (main enclosure area) to remove bulk smoke/fumes with the remaining 13,403 sq mm draw area, toward same 6" out vent, and try to find the sweet spot to keep the cutting deck/work piece smoke free as well as the main area above it.

I do realise there will be a leaking & mixing of air in areas but I’m idealising the concept…for sanity sake!

The main thing is the frame is chunky at 50mm x 70mm and there could be dead spots etc blocking airflow…So does 300cfm seem powerful enough…or too much!

You are asking a question that needs an engineer’s input. Even with all your measurements, I cannot visualize your system. So I will reply with what works for me.

  1. 300 CFM is free flow, expect 1/2 to 1/3 of that in practice.
  2. The openings into the box in square inches should exceed the area of a 6" circle by 50%. That would be about 8" or so.
  3. I have a 300 CFM on my SF-A9 laser and it provides decent smoke clearing ability.
  4. On both my S30 and SF-A9 lasers, I added 3 each 12v 1" cooling fans to help with air movement. They provide a gentle breeze to help move smoke towards the duct in the back wall.
  5. Both of the enclosures on my lasers are about the same size as yours. I keep the enclosure closed for a minute or two to give the smoke time to clear. My Laser Room is inside of my house.
  6. Both of my outlets are at or below the laser frame. I did not want to suck creosote laden smoke through the laser frame. Hence the little fans to assist.
  7. Consider the effect of prevailing winds against the outdoor exhaust opening. You may need to add a domed vent or wind powered turbine to aid in the draft.

Unfortunately, sometimes field engineering means you have to buy more parts.

Hi Mike

Hope all are well in FL.
Some interesting points you made on the fan. Firstly I’m thinking the 300cfm will quite happily draw smoke…Once its in the pipe, but you have to assist it getting there, which suggests the draw drops off rapidly at a number of inches away from the enclosure exhaust out point.
I’m surprised by the clean air in ratio as I had thought equal in/out would get the best velocity, but I guess more free air in is less stress on the fan…We’re gonna need a bigger fan!

I roast coffee and would expect the same oily problems when cleaning, filtering & venting with woodsmoke etc, Would/do draw fans need a regular clean?

I’ve got 360 degree prevailing winds…I’ll think of something, like alternate between north and south facing…gonna need some wheel’s.

You’re outlet is at or below frame level, does that mean your outside vent is at or below also…gravity helps.

My frame is 600mm x 825, probably 400-450mm for enclosure (H) and I’m going to bracket the two Y axis (with legs removed) to the enclosure frame with four brackets and not certain about overall length but probably 900mm-ish.

Considering I clogged the filter on my new iCube in a week of piddling, I am positive it should be considered.

Yes. A 3" and a 4" duct to a board in the window. Visualize air going out one duct and makeup air + smoke coming back in the other. I had to add air gates to both boxes to stop that.

I am in NY. Neighbor said my place is fine. I have a 40’ tall Amateur Radio antenna I was worried about, but got lucky. Thanks for mentioning!

HAM!!..International/Jumbo with halfwave silver rod.

Just bought the Xtool 410 variable speed 6".

My first one was variable speed too. Found I did not vary it much.

I have a 12"x12" to 3" duct for sawdust I used on my original 3018 Pro setup. Did not have room behind my current enclosures. I wanted to put a 12"x12" disposable paper filter in front of it. Should have because I have spotted soot particles in the clear flex duct.

I think your right about field Exploration and the gathering of parts, I hit the buy button to get it done. I’m actually looking forward to the tuning of the system as much as the making stuff and thats not so good cause I have a tendancy to get lost in the weeds. But even if its not optimal I’ll be able to calibrate and go from there which is cool.
The draw to outside will be super short like aprox 1m with everything accessible so cleaning will be less of a chor.

ps If the variablespeedalizer is not up to the job…Can better a one be wired in.

Mine was a variable 12v supply to the blower. Discovered at full power the blower would overheat and go into thermal shutdown. Pretty sure the power supply was capable for the load.