The strategy is to encase the ToM in a nearly-airtight container and
generate a "negative pressure" inside by sucking the air out through
an activated carbon filter. The negative pressure ensures that no ABS
fumes will escape if the box through small leaks.
Encased the ToM in a plastic storage container, drilling and cutting holes for:
-power supply switch access
-USB wire to computer
-Access to SD Card Slot & Reset Button
-Fillament wires, filament, or access to buttons or card slot. These
Use duct tape to seal gaps. The airtight-ness of the container determines how easy it is to generate a "negative pressure", which ensures that no ABS fumes will escape, even at low air flow qualities.
The Activated Carbon Filter consists of a length of PVC pipe with a computer case fan at the end to draw air out of the ToM chamber through the activated carbon filter. I have chosen to use a larger diameter for the segment containing the activated carbon, because I felt that the wider diameter would mean less air resistance (less depth of carbon) and slower air flow (thus, more scrubbing time).
The activated carbon is held in up by a fine mesh sheet. In this case, I used a cut-open activated carbon aquarium pouch. This mesh sheet is simply held in place by being sandwiched between the 3" PVC
tubing (containing the carbon) and the edge of the 3" PVC elbow that is
shoved onto the PVC tube. I have made the carbon bed approx 3-4 inches
in depth.(This can later be expanded to a two-serial-column setup to maximize use of the carbon).
More or less any brand of activated carbon should do the trick.
(commonly available in aquarium stores or petsmart). In theory, a larger granule size should lead to easier air flow at the cost of lesser carbon surface area exposure to the air (thus, lesser fume-filtering). This may have to be compensated for by running the air through a deeper bed of carbon. For smaller granule sizes, the reverse of the previous lines holds true. I have used this box, just because it was the cheapest available at the local store.
A computer case fan is taped onto the opening of the 90 degree PVC
joint, and an airtight seal is reinforced using duct tape. This fan is
responsible for drawing the air through the thick layers of carbon,
thus, power is an issue. Previously, I had tried a cheap $4.00 USD,
80mm case fan, however, it did not generate enough of a pressure
gradient to suck the air through. I am currently using the Vantech
Tornado, which generates considerable flow and pressure (although,
it's quite loud. Foam packing inserts that I use to dampen the sound are
not shown). The fan can be powered from any 12 V supply, including the printer's own power supply.
The real ease-of-use comes into play with the access flap. The flap is made from a transparent report cover that is simply taped on the top edge of the surface of the box above the large access hole. An overhead transparency may also work. Keep in mind that the sheet must be clear for viewing, soft to deform and seal against the cut-out hole (unlike a plastic plate, which will leave gaps in around the edges), and firm enough to support the
"negative pressure" (unlike saran wrap, which will collapse and be
drawn in through the hole). Not shown is a metal bar inserted inside the report cover weigh it down and prevent curling over time.
It can be lifted to retrieve parts, but it also allows the ABP to eject parts.
Using this build, I have been able to have zero ABS smell without having to access and vent to a window. The Activated Carbon (small 3 inch bed) has lasted more than 4lb of ABS over 3 months.
Hope this helps everyone with ABS fume issues.