It´s all about air flow and air dynamics, how the air behaves and what the fans we are using really can do.
Most fans are good at sucking, moving the smoke past the turbine/wings in a pretty good way.
Most fans sucks at pushing the smoke in the hose out of the room you have the machine in.
This is where the optimized exhaust comes in.
Seen posts on groups and forums where people are buying fans they could fly hot air balloons with, not sure what they were thinking 😛
But this is the danger of Facebook and forums, someone seen one doing it and it spreads like a fact, without anyone really know why they are buying a big ass fan.
Fans are mostly made for two purposes, pushing or pulling, and you wont find a pushing fan without visiting a ventilation expert store.
Why small fans directly at the machine doesnt work
Having the fan directly at the back of your machine put alot of pressure on the fan.
It has to do two things. Both creating a negative pressure inside the machine to suck the smoke up, and creating a static positive pressure, to push the air in the 4-5 meter hose.
Positive and negative pressure works against each other, moving the fan to the end of the fan will almost be 100% effect on sucking (negative pressure) as there is no positive pressure built up.
Tips for having a optimized exhaust.
1: Buy a in-line fan matching the hose you are using, 100-150cfm is enough
2: Put the fan at the END of the hose, where you evacuate the smoke (window sill for example)
3: Seal your machine to prevent smoke creeping in to your room.
4: Have a good working smoke assist in your machine
Taking advantage of how air behaves and how fan works gives you more effect for the money, better working exhaust and less noise in your room.
I can run my laser on full power while taking a phone call, no problems, they won´t even hear it.
There is always some situations where people are reusing fans or exhausts they already own, well go ahead, if you have a big fan, use it, it does the job. But don´t pass it on as a fact that you need 800cfm to move the air, just because you have it close to the machine and that fan is less capable of creating static pressure than grandma´s fart is.
There is always theese “i have one, it works, you are wrong” posts when i try to explain why their fan could be working so much better.
My intention is not to piss of anyone, my articles are written with a pinch of humor sometimes and some people can´t just stand that.
If you bought a big fan, and it´s working – good, you are set, no problems.
What i wan´t is to give the best solution to maximize the function of what the end user wan´t to do, in this case exhaust the air. A hot air balloon fan is not the most effective solution for that.
Report below if you have a nice working setup, no matter how big fan you have, does it work good, found any fan you want to suggest to others? comment below!