EXHAUST - dust collector vs inline fan

[Scott Shepherd]

Robert, I'm not suggesting you are doing anything wrong by any means. Simply putting it out there that in the end, you have to clear the smoke. Nothing else matters.

What's the magic combination for your setup? I have no idea. I couldn't pick it if you paid me to pick it. We use two, a 900 CFM Penn State and about a 1,300 CFM Penn State. I used the Harbor Freight red one for a while until it died. The replacement one had some wicked harmonics it would setup in my wall (our blowers are mounted above a drop ceiling), so we took it out. Sounds fine on the ground running, but mounted in the ceiling that one makes the entire office "hum".

[Chuck Stone]

I have this fan sitting beside the laser, not hooked up to anything.
I have used it now and then to clear the room of dust while sanding,
but don't have any way to hook it up to the laser.
This is fortunate, since it sounds like a 747 on taxi to the runway..
http://www.industrialfansdirect.com/...I-AX12-1V.html

[Bill George]

I have this fan sitting beside the laser, not hooked up to anything.
I have used it now and then to clear the room of dust while sanding,
but don't have any way to hook it up to the laser.
This is fortunate, since it sounds like a 747 on taxi to the runway..
http://www.industrialfansdirect.com/...I-AX12-1V.html

Good fan for exhaust in a dusty or smoky room. Or just moving some air.

[Glen Monaghan]

A HUGE part of it all has to do with the design of the intake and exhaust ports on the laser cabinet itself. [...] The motor is only one piece of it, I'd argue that the design of the cabinet, the intake and exhaust ports inside the cabinet play a much larger role than anything else.

People often recite the "don't neck down the exhaust" mantra, noting that any restriction, even a very short one, has a huge impact on the exhaust. Well, just look at the port on the back of most lasers... a 4" tube at the back-middle of a 2-3 foot wide bed. At least the inlet ports are typically spread across the front of the machine but the exhaust is just a round hole in the back. You just can't expect uniform airflow across that width with virtually no structure to smoothly guide a sheet of air from the bed into a 4" round exhaust port. And, if you think about the volume you are trying to evacuate (say an inch high, and at least 12"x24" of bed) compared to the area of the 4" port (12.6 sq inches), you find that the air has to move about 23 times faster through the exhaust port than it does across the bed. Need serious attention to port design for that to happen properly.

[David Somers]

So....I noticed a month or two ago (I think....I have zip for a sense of the passage of time) someone had a post that showed how they had installed a number of computer pancake/case fans in the front of their largish laser and were using that to help with the movement of air inside the cabinet to the exhaust port. They seemed happy with the results. Seemed like the machine had a 2ft x 3ft , or 3ft by 4ft table and were having problems originally with air being pulled well from the entire table?

Am afraid I don't have time right now to hunt for it and look at the post and thread again. Just mentioning it in this context for discussion though.

Dave

[Kev Williams]

Part of a good smoke evacuation process has to do with the airflow path. Both my old ULS and NH LS900 pull air directly out the back wall of the machine, and the air is pulled from in front of, and below the table. All the air moves right across the top of the engraving table. When I first got our ULS, the first few times I used it I just used a Rigid shop vac, and IT pulled the smoke I was creating out just fine.

I've had 2 of the HF 'green' blowers (660cfm according to HF) connected to my 2 lasers for 10 and 12 years, they run nearly all day every day, mostly because they're quiet enough I don't even notice 'em. The cooling fans on the lasers make more noise than they do. I have night-lights connected to the switch-cords that I turn them on with so I know they're on! I do try to keep them off when I'm not using 'em. One reason, the power they use, obviously. Another reason: My basement shop is 1200 sq. feet with 7' ceilings. That's 8400 cubic feet of air space. Both fans are moving a total of only 1320 cubic feet of air thru the machines per minute. Might not sound like a lot, but think about it-- they're capable of removing all of the air in my shop every 6-1/2 minutes. That's air I've paid to heat (or cool) that's being pumped outside, and it's being replaced by outside air that needs more heating or cooling...

I have enough air moving, thank you!

[Chuck Stone]

Good fan for exhaust in a dusty or smoky room. Or just moving some air.

That's actually what it was for. My dad had some smoke ejector and industrial fan samples left
They were used in halon evacuation systems years ago. These would turnover the room air
after the halon system flooded the area, and it had to do it pretty quick. It'll pull 1650 cfm
if you hold the louvers open, but those pull down quite a bit of the airflow.
did I mention it was loud?