Hot ABS plastic gives off a characteristic stink odor smell aroma that’s hard on the nose and probably not particularly good for the lungs. Even in the basement, it seems like a Bad Idea to stink up the place, so I added an exhaust fan and charcoal filter to blot up the odor.
The key step is to add the fan provided with the TOM (which they recommend you don’t use!): outside the box, oriented backwards, and running on +5 V instead of +12 V. The general concept: free up some precious space inside the box, shove the exhaust through a filter, and do it with a gentle breeze rather than a mighty blast.
Although it’s not a part of this sub-project, the heatsink holds a 2 Ω 25 W resistor that serves as a 12.5 W dummy / minimum load on the +5 V supply to keep it within tolerance. Right now, the heatsink is just jammed between the screws, because I’m probably going to add a similar dummy load to the +12 V supply when I move to a stepper extruder.
In case you’re hypersensitive to overheated resistors: the heatsink runs at 65 °C, the resistor at 75 °C, and the specs give a permissible dissipation of 20 W. You could work it out…
The first step is to route the 4-pin ATX power connector (which popped off the big connector block plugged into the Motherboard) out the left-rear hole in the acrylic floor under the XY stage. I don’t have a mating connector, so I conjured up something from the same square pins as I used in the Extruder power supply modification and some wire harvested from a dead ATX supply. The black heatshrink tubing holds the four wires and their pins in the proper configuration. Obviously, you want matching colored wires, because the “connector” isn’t polarized!
On the other end, a four-pin screw terminal block provides a convenient way to attach a variety of gadgetry. At last count, it serves the exhaust fan, +5 V dummy load, LED platform light, and a cooling fan. More details on those later…
The fan frame required a small gouge to route the wire inward through the vent hole in the side of the TOM case:
Four nuts secure the fan to the frame. Fortunately, the fan’s motor housing sits on the exhaust end, so the filter material rests against the hub support and spider. Here’s what the whole arrangement looks like, with the filters pried away from the fan.
A trip to the local Big Box home warehouse produced a $10 20×25-inch activated charcoal air filter intended for a whole-house air conditioner. I now have a large plastic grid, a sheet of open-cell foam air filter, plus a generous supply of charcoal filter material. I cut a 4-3/4-inch strip from one side, chopped it into 4-3/4-inch squares (that’s 120 mm everywhere else in the world), trimmed off the corners, tucked two layers behind the TOM filter holder frame, and added four more nuts-and-washers.
The spare filter material goes in a sealed plastic bag, because activated carbon has a limited lifetime when exposed to free air. That’s what it does for a living: adsorb smelly molecules from passing air!
The final step is to close off all the TOM’s openings, thus restricting air flow through the case. This has the happy side effect of warming the build area and reducing drafts, both quite important in a wintery 50-ish °F basement. Taking pictures of clear acrylic sheet is essentially impossible, but you can see the front piece there and the paper seals around the filament spool there. I make no apology for the masking tape; after everything’s working, I’ll formalize the arrangements.
Incidentally, don’t get too secure with the front window, because the ABP pokes through the opening to disgorge finished parts. In fact, the front of the ABP whacks the window when the nozzle reaches the back of the ABP, so you don’t want a mechanical latch holding the window closed.
I’m thinking a magnetic latch is in order.
There’s enough leakage around the windows to keep the fan happy, although it sucks the last one closed. Those four square cable holes in the acrylic sheet between the upper and lower chambers provide the only air channels, so the exhaust fan probably doesn’t compete with the ATX supply’s cooling fan.
While the filter doesn’t kill off all the stink, the TOM is a much better companion now…
The Smell of Molten Projects in the Morning 
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