Why can’t we vent outside for the fine debris, etc?
Well, people do vent dust collectors outside. However, we can’t make a hole in the building’s wall. Our options are through a door- like we did for the laser exhausts- or a roof penetration. Lease prohibits us from accessing the roof, so we can’t install or maintain that ourselves, we’d need a contractor. I do wonder how much debris would make it up there and just build up on the roof.
It’s a substantial loss of HVAC airflow. Every cubic foot exhausted must be replaced immediately with a cubic foot of warm, wet outside air. If you somehow succeeded in sealed the building completely, the exhaust vent will build a pressure differential and the blower will stop moving air until someone opens a door. 600 cfm of airflow for a tool is roughly 1.5 tons of HVAC flow. Our HVAC units are 5 ton, so it’s not super overwhelmingly awful, it’s roughly one third the capacity of one unit to offset the loss through that exhaust.
I was never clear on why people don’t use the lofted polyester filter media we use on HVAC inlets for dust collector filtration. It’s high-flow (very little back pressure), effectively traps small particles, traps a LOT before being loaded down, and cheap to replace outright. HVAC rates those filters at about 300 fpm on the inlet. So, even a 20x20 filter would be close to meeting the 3 sq ft minimum for a 900 cfm flow off a dust collector. It would be easy to go twice this size, or 10x the size.
OK, now I gotta keep looking. Filters are rated by MERV number, and our “orange stuff” is MERV 8, that’s a high number for HVAC but not the highest. And it certainly traps wood dust, as is obvious in how much gets trapped in the HVAC filters.
MERV 8 is 90% efficient at 3 microns- 10 microns. But not rated for 2.5 microns, the dreaded “PM2.5” concern about breathable particles- small enough to float for a long time and be inhaled. A “premium” shaker felt bag WILL filter 1 micron. So, MERV 8 filter media as a disposable pre-filter for a large 1 micron shaker felt bag would be very little flow resistance and the bag would probably last a year between cleanings. 3 sq ft of MERV 8 media will be enough when the filter media is empty, but it’s going to spend a lot of time loaded, so maybe 2 or 3 times that, before it can go through the bag.
Hmm ok I see the design challenge there. But, wait, while PM2.5 is the particle size for respiratory concerns, it is a small minority of wood dust, the vast bulk of wood dust is larger, more easily trappable bulk particles. The huge 1 micron shaker felt bag needs to be huge because it deals with ALL the dust particles of any size. If you prefilter with 3 sq foot or more of MERV8 and change that regularly, then a large secondary MERV 11 or MERV 13 paper filter (expensive HEPA stuff that is highly effective at trapping PM2.5 and smaller) in a pleated paper box filter should last a very long time. If the filters are large enough and maintained, the net flow resistance of both filters is still minimal and can have a long maintenance cycle.
I like the new shoe more then the old one. So I guess we’ll just switch them out if we have a preference. Like james pointed out, it’s just a hex screw to swap it out, it takes less then a minute.
Whoever bought the shoe… if you see me in the shop, I’ll give you some cash to buy the next one. I agree it’s not as durable as our old one, but it works great for me.
Like I say, I’d concerned about sparking with this metal one if it shimmies off the spindle. Sparks can start a fire in the dust collector almost instantly and that’s a big problem.
So I think we should try a plastic one, like the Daedalus NL330. As I mentioned, I measured our spindle at 72.5mm so I don’t know if the 70mm or 75mm option is best.
We should add a locknut on the screw that tightens the shoe. Not where it tightens the shoe together, we leave that regular tightening nut in place. Just a locknut sitting by itself way at the end of the screw.
That’s not to keep the shoe from loosening up and falling off the spindle. Rather, reason being, you can’t lose the screw or nut when you take it off. The locknut keeps both of them captive once loose, but won’t keep you from loosening or tightening it.
Seems like we need a strategy of what to do with the 4" DC hose when not used. Sometimes it’s removed from the part of the shoe that you can remove, other times taken off it and just being hung willy-nilly and the spiral hose is taking some wear. And the Daedalus is worse to take on and off the shoe itself because it mashes the hose into an elliptical port. Like maybe we can end the hose by attaching it to a rigid coupler that can plug in and out of the shoe?
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So I’m using the CNC now, and the suction was low on power. I checked the cyclone system, and the 3 way Y that comes off the overhead PVC pipe was clogged right at the transition
. I cleared the clogged and banged the pipe around. A lot of debris came out once the clog was cleared, and the suction seems back to normal.
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thanks James
A new CNC dust shoe has been installed on the spindle. It is the red plastic shoe linked above. This shoe works incredibly well, and seems to be a great solution for the CNC. I think this should be considered the new go to shoe, and the need to swap them out should be null.
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Thanks James. I will get to printing a dock for it when it not able to be used.
I will have a student make the an aluminum plate to mount it so the dust shoe can be docked out of the way when you don’t want the dust shoe for the cut.
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New dust shoe has been installed.
I noticed some serious undercutting into the spoil board. James just installed a new board and flycut it. Please measure your material and input that into the vcarve. I’m going to order a caliper for the cnc station. The vcarve desktop is on the same kiosk so no excuses to not input the correct material thickness.
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Humm, Is there anywhere we can add more signage about checking Z height?
I saw the dust shoe dock is broken. I’m going to include the stl and design file so anyone can print or modify it. After looking at the break. I could have added a bit more support further out on the wings and more fillet in the corner.
STL: STL File
Design File: SW File
What material was it printed in? ABS?
I think pla. My abs printer was busy at the time
If someone is reprinting pieces (sorry, I can’t help here), please consider updating the top mount as well.
See my other thread on the topic:
CNC Dust Shoe loose on both the top and bottom mounts?
I think there’s a basic prob that the 2 prongs have to flex for this to work. This limits how solid they can be, and it undergoes fatigue.
Ideally I can imagine one prong fixed, the other on a metal spring. Most appropriate would be a torsion spring (think clothespin, but spreading apart) and a stop so it doesn’t overspread.
Or maybe just spring loaded detents with a linear compression spring. Again, just needs stops so it’s still pressing firmly at full extension but restrained so it doesn’t overextend.