mzettl
06-29-2008, 06:35 PM
Per Paco's request, I'm posting some photos of my dust skirt, such as it is. This is certainly a topic that has seen a lot of traffic over the 2+ years I've been following these forums, so I may as well give my thoughts.
The idea (not original with me) to get as much air flow coming as close to the bit as possible is what made me try this. The skirt that came with the machine seemed to me to be too restrictive. A 4" hose stepped down to a 3" hose, which was then squashed together to fit into the back of the skirt. the net effect was that the cross sectional area of the original 4" duct was considerably reduced.
My thought was to maintain the same, or even slightly more, cross sectional area all the way to the outlet, as near to the bit as possible. To achieve this, I constructed a two tube configuration out of Lexan, with each tube coming down alongside the spindle. The tubes join together above the spindle in a plenum that attaches to the 4" flex hose, and then to my Oneida cyclone. The sum of the cross sectional areas of the two tubes is just a shade more than that of the 4" hose as I recall. Part of the problem is that there isn't much room on either side of the spindle, and the fit of the tubes is snug to say the least.
Attaching to the bottom of the tubes is the actual skirt, and this is held in place by the original ShopBot hardware as the photos show. I'm not happy with this arrangement, as removing it for bit changes is fussy, but I've done it so much now, that it only takes a few seconds. Bit changes take me about two minutes, similar to what others here have reported. Still, a more elegant solution would be desirable. I've considered various rare earth magnet solutions, but haven't really set my mind to the task.
The other problem is that the twin tube arrangement necessarily creates a wider skirt, so when cutting close to the table edge along the x axis, half the skirt may hang over, decreasing the effectiveness of the dust collection.
Finally, I think I would be better served for my own applications to have the skirt fixed to the gantry and not the Z axis. Then I could just adjust the skirt to the level of the material, and cut away with it at the ideal height. I'm sometimes cutting mortises 2" deep, and with the way it's set up now, the skirt is well above the material when the cut starts, not at all effective.
A number of other minor improvements are in order, but I'm just busy with other things. I think the blue painter's tape is a nice touch for that "quick repair!!!"
-Matt
5386
5387
5388
5389
The idea (not original with me) to get as much air flow coming as close to the bit as possible is what made me try this. The skirt that came with the machine seemed to me to be too restrictive. A 4" hose stepped down to a 3" hose, which was then squashed together to fit into the back of the skirt. the net effect was that the cross sectional area of the original 4" duct was considerably reduced.
My thought was to maintain the same, or even slightly more, cross sectional area all the way to the outlet, as near to the bit as possible. To achieve this, I constructed a two tube configuration out of Lexan, with each tube coming down alongside the spindle. The tubes join together above the spindle in a plenum that attaches to the 4" flex hose, and then to my Oneida cyclone. The sum of the cross sectional areas of the two tubes is just a shade more than that of the 4" hose as I recall. Part of the problem is that there isn't much room on either side of the spindle, and the fit of the tubes is snug to say the least.
Attaching to the bottom of the tubes is the actual skirt, and this is held in place by the original ShopBot hardware as the photos show. I'm not happy with this arrangement, as removing it for bit changes is fussy, but I've done it so much now, that it only takes a few seconds. Bit changes take me about two minutes, similar to what others here have reported. Still, a more elegant solution would be desirable. I've considered various rare earth magnet solutions, but haven't really set my mind to the task.
The other problem is that the twin tube arrangement necessarily creates a wider skirt, so when cutting close to the table edge along the x axis, half the skirt may hang over, decreasing the effectiveness of the dust collection.
Finally, I think I would be better served for my own applications to have the skirt fixed to the gantry and not the Z axis. Then I could just adjust the skirt to the level of the material, and cut away with it at the ideal height. I'm sometimes cutting mortises 2" deep, and with the way it's set up now, the skirt is well above the material when the cut starts, not at all effective.
A number of other minor improvements are in order, but I'm just busy with other things. I think the blue painter's tape is a nice touch for that "quick repair!!!"
-Matt
5386
5387
5388
5389