Laser & Router combined exhaust

[Re Wood]

Ahoy hoy!

This is my first post and I'm super excited about it. I've had a Shopbot 8'x4' CNC router for a couple years and my Trotec Speedy 400 is scheduled to be delivered tomorrow. When I first got the router I purchased a harbor freight dust collector which was very noisy and ineffective. I think it blew as much dust around my shop as it collected, so I got rid of it and have been using no dust collection with my router.

Well, the laser must be vented outside. So my thoughts are that this is a good time to get a cyclone (http://www.oneida-air.com/inventoryD.asp?item_no=AXD002030&CatId={17F46883-40BB-471E-982F-E5F28583241B}) for the router and connect the two machines exhaust together with one blower and a little ducting. The router would be blowing out only the tiniest particles left over from routing, and the laser will be spitting out wonderfully toxic fumes. The only place the two lines will meet is a Y-connector right in front of the blower and then the few feet of ducting out of the building. Is this a terrible idea? Anyone ever tried it?

[Mike Troncalli]

This could get complicated.. And there will be more than one opinion on this I'll bet as well.. So here is mine... You are combining two very dangerous items.. Fine dust and a machine that vents possible sparks... Chances of the laser sending a spark down the tube is going to be pretty remote, but I would think twice about it though..

[Scott Shepherd]

I'm with Mike, it's not something I would do.

[Re Wood]

I doubt very seriously I'll ever need to run both at the same time. Additionally, I was thinking I may have to put backdraft dampers on both lines in front of the blower, like this:
(laser - damper - y-connector (w/ blast gate) - blower - outside)
(router - cyclone - damper - y-connector (w/ blast gate) - blower - outside)

But ya.. I knew it would be a little risky.

What about a separate exhaust & blower for each machine. How far apart do the holes in the wall need to be for safe operation?

Thanks for the input.

[Mike Troncalli]

Cost of second blower ~$250.00
Cost of new building ????
Cost of piece of mind. Priceless

Do what you feel comfortable with, but why take a chance... Both in fire hazard and dust hazard back to your machine.. damper / blast gate or not... I run a lot of wood working machines with a dust collection system and I can tell you from experience that a lot of fine dust gets into places that it shouldn't.. I don't care how tight the connections are...

[Re Wood]

You're right. Peace of mind is priceless. Thank you all.

[Keith Outten]

My system is just as you describe. Both my CNC Router and my Laser Engraver connect at a "Y" connector right in front of my dust collector pump. Its been this way for ten years without incident. FWIW I don't have bags or filters as my pump exhausts directly to the exterior of my shop into a large tank or chip-box. I don't run both machines at the same time as my 1.5 hp DC pump is too small to provide the necessary suction for both machines. If I did have a larger dust collector I would not hesitate to run both machines concurrently, I don't believe there is a fire hazard from the level of dust commonly found in small shops. The machines that produce the most dust are sanders, saws and routers produce mostly chips. Laser Engravers produce mostly smoke and at times very low levels of dust.

I should note that 75% of my laser engraving work is done with Dupont Corian. When you engrave Corian at high power levels there is a constant stream of sparks at the surface but they have never been a problem as the high rate of air movement cools and extinguishes the sparks immediately.

[Gary Hair]

I wouldn't worry at all about combining the two, there is really no danger in doing this. There are myths all over the internet about dust collector explosions and fires caused by sparks, but I ask anyone to provide concrete evidence that any of them actually happened. I did demolition in the Army, and I can tell you that the perfect mix of and airborne accelerant and the timing of the ignition are so critical that it is virtually impossible to happen unplanned. What I would worry about, however, is the environment that a CNC creates is nothing I would consider for a laser. Keith does it with success, but I would worry about the dust getting sucked into the laser and causing all kinds of problems.

[Dan Hintz]

I see no issue... as long as the blower is as close as feasible to the outside to prevent toxic fume blowback into the environment.