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Fume Chamber (Negative-Pressure, Activated Carbon Filtering)

by gaerisl, published

Fume Chamber (Negative-Pressure, Activated Carbon Filtering) by gaerisl Nov 23, 2011
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Summary

Method for constructing a Negative-Pressure Activated-Carbon Fume Chamber.

Eliminate ABS fumes/smell when ventilation to the outside is not an option.

Compatible with HBP and APB.
Costs about $35 and runs at about 4 Watts.

Instructions

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.

Instructions:
Encased the ToM in a plastic storage container, drilling and cutting holes for:
-power plug
-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.

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Wow, you've actually tuppered your machine, and THAT is a good idea.

Do you think that a nozzle attached to the print head, next to the extruder could do the same job? I'm thinking small nozzle => fan => wide filter. This would allow the particles to leave the filter at low speed.

Hmm... That's one idea. It would certainly make the entire thing smaller.
Assuming the air flow isn't turbulent in a way that makes you lose control of the fumes, the only possible disadvantage is the cold air flowing past that would mess with the cooling rates of your printing... possibly an issue, or possibly not.

But sounds like something worth trying! =D

If you wanted to be really fancy you could send air past the upper part of the hot end to pick up some heat then send back across the hot end tip to create a hot air current across the tip.

The print head would probably be so big and clumsy it would never move... :(

I have a big Honeywell HEPA air purifier next to mine.

If you're concerned about the fumes, I should point out that...

From what I understand, HEPA works great for smoke (particular matter). However, volatile organic compounds are not usually filtered by HEPA.

But, if it works for you, it sure beats having to make this awful box...
Sometimes I wish I wasn't so sensitive to smells... DONT_KNOW

thanks for share this idea, in my opinion is very usefull

It would be a lot simpler to buy a 20 inch box fan and some activated charcoal 20X20 filters. Duct tape them to the fan until you made a holder with the 3d printer

Ralph, that's a great simplification, and perhaps other people could take the recommendation.

That could work, however, I needed a guarantee that I'd soak up 100% of the fumes without it leaking anything, because I basically work in a closet with no ventilation. I don't have much experience with charcoal 20x20 filters. Are they effective and/or expensive?

Just buy a regular air cleaner I think designing one yourself is probably over kill. Unless of course the goal is to screw around in which case, don't let me stop you.

I wasn't sure if your filter was a solid object or a bunch of granules. If a bunch of granules, you might find it more efficient to pump air from the bottom of the granules upward, thus "fluidizing' the granule bed.

Thanks for the suggestion!

It is indeed granules. Reversing the direction of airflow could could help reduce the pressure required of the fan.

Think I'll try that next time I do some maintenance work!

I love the smell of ABS in the morning......Smells like creativity. =-X

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