Developing a dust collection boot for deep relief carving
CNC machines create a huge amount of debris very quickly. I make kayak seats out of solid wood, sometimes taking a 10 pound block of material down to less than a pound. This means that 90% of the material is cut away and turned into chips. Without some efficient means of collecting the dust my shop would soon be over run.
My table saw not withstanding, dust is likely one of the more dangerous things in the shop. While it won't kill you right away, breathing fine dust into your lungs is seriously bad for you. I make a point of collecting as much of the dust as close to the source as possible to minimize the risk of breathing it in.
The standard dust boot for CNC machines is fairly low, wide and flat. It is intended to be placed directly above the material surface to efficiently capture the chips as soon as they are made by the bit.
The rapidly spinning bit spits the chips out at high speed, with centrifugal force flinging them away from the tool. They are often moving with sufficient momentum that even a really powerful dust collection system can not stop them from flying past the edge of the boot. It is important to have the skirt hang down at least as far as the bottom end of the bit to block the chips and redirect them into the collection system.
With deep relief carving the boot must be sufficiently high as to not hit the work material while the router moves, but it must be low enough to catch the debris. One solution is to just have a realy long skirt or brush with really long bristles. But if the bristles are too long they will just get sucked up into the vacuum intake tube and they won't do their job. Alternately you can extend the side of the boot down farther to allow for shorter bristles, but then the boot may hit your work piece.
I tried to develop a boot that balanced long enough bristle with a compact boot wrapped close to the router so the boot would be less likely to hit the high sides of the seats I am carving.
I created a boot with a suction gallery that wraps all the way around the router base and keeps the skirt close to the cutting bit.
This carving boot is made from laminated pieces of 1/2" thick acrylic glued together with CA glue. The brush is nylon 3" bristle that is press fit into a groove in the acylic. I'm using 1/2" diameter by 1/8" thick rare earth magnets to hold on the brush ring.
I've been using this boot for quite a while. It is quite effective even on some fairly deep relief carving. How well it does will depend on the shape of the object you are cutting. Concave shapes that naturally contain the chips will work better than convex shapes with lots of room for chips to escape.
The magnets releasing the brush are a great convenience.
This boot can be used in conjunction with the ShopBot presser foot when cutting thin materials.
The long bristles will get sucked into the intake a bit, particularly on the vacuum source side of the boot. I have restricted the width of the intake a bit on that side to reduce the issue some. Overall this boot will restrict the suction of your dust collection system just due the amount of resistance created by the small intake relative to the 4" hose size.
Vcarve Pro files for cutting the acrylic parts are included below. Please let me know if you make any improvements.