Dust collection system
Last update: Oct 18, 2011
Just an outline of the shop's dust collection system, I'll be expanding and updating as time goes on
NOTE: Yes, I use PVC ducts. No, I don't ground them. No, I'm not worried about a static-induced dust explosion. Here's why ...
Click on any picture to see a larger version. You can then use your arrow keys to move between all the images in that group.
The core of the system is a Grizzly G0441 3HP cyclone separator. Although it can be mounted on the wall, that would transfer all the vibration to the walls and potentially act as an amplifier. Grizzly sells a stand for the unit, but I decided to build my own isolation stand. The hardest part was lifting the assembled uppper section onto the deck.
As you can see, the stand was designed so that it could be easily lifted and moved using a pallet jack. More on that later.
The stand also incorporates a pair of hinged arms that attach to the collection bin lid. This allows me to lift the lid and hook it to a bungee cord, then roll the bin out.
One other "enhancement" I've made to the collection bin is a bag retainer. It's just a plywood ring with ten wooden dowel rods to hold a liner bag. Without something to hold the bag down, the cyclone will quickly suck the bag up into the cyclone. Any sort of ring or weight at the bottom will get buried, but rods hold the bag while being very easy to slide out when I'm ready to empty the bag.
A large cyclone is not a quiet beast. To keep it livable, I decided to sacrifice a corner of the shop and build a sound deadening closet. It's made from OSB, which (because of its random internal structure) dampens rather than transfers noise. It's also lined with accoustic ceiling tiles. Note the exit duct, placing the exit at the top forces air around the motor, keeping it cool. It also bends, preventing any straight sound path from the unit to the shop space.
The front wall is easily removed. If (God forbid) something on the unit fails, I just have to remove a few screws and unhook the intake and power, then I can wheel the entire thing back out into the shop.
The closet has proven to be quite effective. I measured the sound level near the filter (the loudest point) at 87 dB @ 5 feet away. Measuring from the same distance after the closet was in place, I got a reading of only 74 dB. To put that in perspective, 74 dB is just a little louder than a typical home vacuum cleaner, while 87 dB is more than twice as loud and can cause hearing damage with prolonged exposure.
My ductwork is 6" PVC sewer & drain (S&D) and 6" flex hose. One of the challenges in building a ductwork system can be interfacing the main ducts and the flex hose. I've found that the 6" hose I got from McMaster-Carr (Economical Clear Duct for Dust, part # 56355K34) fits perfectly inside S&D fittings and bell ends, as you can see in this connection between two sections. (The wood strip keeps the flex section from collapsing under suction)
I recommend including these small sections throughout your duct design, it allow you a little bit of room to disassemble small segments for rearrangment, insertion of new drops, etc. If you build the duct system solid and you want to add a new wye, you might find yourself disassembling entire runs to remove one small section of duct.
I also used the same sort of transition with a standard 6"->8" HVAC adapter to connect to the cyclone's 8" inlet.
For holding the duct on horizontal runs, I use this simple bracket made from plywood. The single screw into the roof truss is plenty to hold duct and gives me the ability to turn the bracket on angled runs. And if I need to remove a section of duct, I can just back out one of the bottom screws and pivot the bottom of the bracket out of the way to drop the duct out, instead of sliding the duct out lengthwise. (The duct is held 4" off the ceiling to clear lighting fixtures)
Another problem can be getting the flex hose to stay in when the hose is hanging from the connector, the weight will slowly pull the hose out. However, a simple HVAC duct connector can be used to make a strong connection, as you can see here on the blast gate leading to my lathe. Just put a bit of caulk on the connector and slide it up into the PVC, then run a couple short screws through both, making sure you get all the way through the metal and at least 1/8" inside. Pre-drilling helps a lot.
Coming soon: more details on my shop-made blast gates and automatic starting system
So far, the most intricate collection setup I have is on the bandsaw. The cross sectional area of a 6" duct equals two 4" ducts plus a 2", which is what I've split into. One 4" goes to the standard dust port while the other is pointed up just below the lower guides. A flexible hose is used for the 2" inlet.
I experimented a lot with different intakes, positions, and mounts for the 2" line. I finally hit on using a vacuum hose with a pair of 1" rare earth magnets. One goes on the bandsaw and the other goes inside the hose. The steel reinforcing wire in the hose holds the magnet in place while getting it into position. The hose ends up sandwiched between the two magnets, which locks it into place wherever I want it.
I usually stick it on the side of the blade guard, but as you can see it also works quite nicely on the front when a blade is throwing chips forward. Sometimes, however, the best spot is on the table off to the side. The blade tension quick-release make a great hose-holder!
I didn't want to spend $45 on another 6x6x4 wye plus the adapters to get the 2" outlet, so I made my own 2" inlet. I drilled an appropriately sized hole into the upper duct segement and inserted some 2" PVC. I then heated the 6" duct with a small heat gun to soften it while pulling down on the 2" part. In just a few minutes, I had an angled hole. After trimming the 2" piece to a proper angle, I attached it with two small screws (one inside). The edges of the hole leak a bit and someday I'll probably put some silicone caulk on it.
Update: I kept having issues with long parts where I was trying to make an angled cut, the back end would run into the wall next to the bandsaw. So I made longer horizontal ducts to allow me to move the bandsaw out a couple feet. A nice side benefit is that it's now much easier to reach the blast gate. The flexible hose I've been using for the above-the-table pickup is now a bit too short, but I've been planning to try out a new hose anyway. It's flexible, but "snaps" into position so that it tends to hold its shape so it'll potentially eliminate the magnet.
The hood on my mitersaw station has a trapezoidal duct in the back. The shape is to keep approximately the same cross-sectional size as it transitions from the round duct to the narrow entrance at the base. The hose connects the blade shroud exit directly into the duct. View the video to see it in action!