Dust Collection

This weekend I installed the shop dust collection system. The system consists of several parts:

Fan/Motor: I repurposed a portable dust collector fan I’ve had for a while that’s been underutilized (collecting dust, but not as intended). Space is limited in the mechanical room so since the fan won’t need easy access I mounted it high up above the air compressor near where the dust collector pipe enters the mechanical room.
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Pipes: 4″ PVC DWV pipes; there are a few branches leading to the different tools. I tried to keep the overall length as short as possible and the bend radius’s large.

Blast Gates: The blast gates control the air flow though the system by blocking off unused branches. I made these with 1/2″ plywood and 1/4″ hardboard. Circle cutouts were made on the lathe to match the pipe outside diameter exactly.
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Filter and Collection Bin: The portable dust collector came with a light canvas bag that restricted the air flow massively while still allowing fine particles to escape. To improve this I replaced the bag with a semi truck air filter mounted to a trash can. The theory is that air will exit the filter and larger dust/chips should fall into the trash can below. There are purpose-built dust collection filters available, but the costs are much higher for these and the semi truck filter has the same specs; different economies of scale. To mount the filter to the bin I made a plywood ring, for now they’re just taped together but I may add latches at some point. The design may need some tweaking; I’ll know more after it gets further use, but for now the airflow is excellent.
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Return Vent:  Having the collection bin in the mechanical room created a problem; the mechanical room is well sealed for noise reduction, so there was nowhere for the air exhausted from the filter to go. For heat/air to be retained in the shop, the exhaust air needed to return to the shop via a vent. Since I also wanted to keep the mechanical room noise level as low as possible this meant the vent needed to be sound proof. I built a sound proof vent by creating a 3ft long box and offsetting baffle plates inside of it. The sound has to reflect a dozen or more times off of the baffle plates; at each reflection it gets absorbed some by a fiberglass lining. The air, however, is able to snake around the baffles and find its way out. The inlet to this vent also points directly at the floor away from the sound sources. Somehow after adding this vent the mechanical room noise is actually noticeably quieter than when it was completely sealed. I think this may have had to do with the air pressure changes resonating in the previously sealed room, whereas now any fluctuations are equalized through the vent.
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Control: For now control of the system is via a remote control outlet (repurposed from controlling the vacuum at the old shop), at some point I may integrate some low voltage switches with the blast gates so the motor will turn on as soon as any gate is opened.

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