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Dust collection issues Options
johnm
Posted: Monday, December 1, 2014 11:43:50 AM
Rank: Newbie
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Joined: 5/19/2007
Posts: 0
Location: Lakeport, CA
Folks -

The maintenance guys are getting surly with me for the "snow" I've been getting out of the cyclones. The school and shop were built in 1966 - I went to High School here. The tablesaws have very poor dust collection, and are the farthest from the cyclones.

The dust collection works *okay* on the other tools, but no matter how I have the blast gates set up, I am getting a significant stream of sawdust and wood chips discharged out of the top of the cyclones out into the back parking lot. It does this whether the dust bins are full or empty. The system is sealed well, but we've always had this problem with varying degrees chip discharge. When we use the planer it makes the back lot look like a snow globe.

So, I have two issues - one is less than optimal suction at the farthest (furthest?) leg of the DC conduits, and the second is the chronic chip discharge out the stack instead of into the DC barrels. I'd appreciate any feedback.
klandin
Posted: Monday, December 1, 2014 6:21:47 PM
Rank: Newbie
Groups: Member

Joined: 6/1/2006
Posts: 0
Location: Connecticut
Speaking from experience I'd say that if your cyclone is blowing sawdust out the top, then that almost certainly indicates a serious leak between the cyclone and your collection bin. In order for the cyclonic separator to function properly there must be no air being drawn up through the cyclone from your collection bin. When this happens it creates an updraft that prevents the sawdust from settling into the bin as its meant to do. Instead the sawdust gets ejected out the system's exhaust port. In order for the cyclone to work properly the seal between the the lower part of the cyclone and your collection bin must be absolutely air tight. By the way, you will probably find that this fixes your other problem as well. If you seal up your bottom end leak then it will force the fan to draw all of its air from the other end of the system, resulting in more suck where you want it.

Keith Landin
Woodshop instructor, Woodstock Academy
"Mens tua sit implementum acerrium in fabrica"
tbockman
Posted: Tuesday, December 2, 2014 6:41:03 AM
Rank: Newbie
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Joined: 11/17/2006
Posts: 0
Check the motor direction. My last school was almost an identical situation as you describe with the same build date (1966) and everything. Running in reverse oddly only makes a dust collector inefficient. It will still work, but not nearly like it should. We figured that one out a few years back because the school had replaced the entire electrical system and the utility hooked it up differently... maybe the way it should have been at the start (?). The belt disc sander began running in reverse. I had to get the electricians over to see what it was doing so they would believe me. As silly as this sounds, there had to also be blockage in the dust collector that you couldn't see because when they got it all set up the right way, it just made the chips fly further. We finally resorted to getting a long thin (flexible enough) stick pushed up into the unit. We used it to prod and poke around until a shower of chips let loose. I couldn't see that blockage before, but it came down none the less and we never had the "snow" issue again as long as we kept it cleared out. Auto shop loved getting those chips as they work so well to absorb oil spills, and students sometimes would take bags of it home for their pets.
johnm
Posted: Tuesday, December 2, 2014 12:52:21 PM
Rank: Newbie
Groups: Member

Joined: 5/19/2007
Posts: 0
Location: Lakeport, CA
The seals at the top of the dust bins were all shot. I did replace all of them and renewed the closures, so that is all air-tight. I did think that this was the problem when I first started, but I'm still getting snow, even though the volume is reduced.

It doesn't matter which kind of wood debris is being collected. Big chips from the jointer blow out just as readily as MDF dust. If the system is airtight, and the motors are spinning correctly, what else might be the cause of the snowfall?
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