3D Printing Air Filter System Does A Lot

We know we aren’t supposed to eat a lot of sugar, but we still have ice cream. We also know we probably shouldn’t be inhaling solder smoke and 3D printer fumes, but we do that too. Not [Mike Buss]. His 3D printer has a major exhaust system.

We can sympathize with his process. He mentions he started out just wanting a fan running with some filters. Then he decided to add a way to turn the fan on and off when printing. Then he added sensors to detect fumes and fire. Data collection was almost an afterhthought.

Of course, most of the system is 3D printed, alongside the electronics and some Lexan parts. We thought it was nice that [Mike’s] motivation was his newborn son, [Theodore]. There’s no word if he’s been operating the printer yet, but we sure it is just a matter of time.

We’ve seen simliar vent systems. Some of them also make the printer quieter.

29 thoughts on “3D Printing Air Filter System Does A Lot

  1. Nice case of feature creep you had there!
    Kids can be a major motivation for a lot of things.
    Speaking of feature creep, if you monitor temperature and smoke, could you also flood the box with a gas such as nitrogen if you detect any?

    1. HEPAFilter1https://www.amazon.com/gp/product/B07QM6QRJQ/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1

      It’s on the BOM

    2. As mentioned, it’s in the BOM, with working links and everything.
      I mean, how can you get a filter wrong, right?

      Actually, many ways.

      That puny little low-static-pressure fan is not designed to push air through a HEPA filter. I’d like to see the design used to come up with the filter area vs. static pressure vs. airflow. I strongly suspect that fan is pushing a very small percentage of its design airflow. A blower type fan is much more suited to this application.

      I also wonder how all that gaposis in the shell, where all the Lexan panels (don’t) meet, gets filled. I didn’t see mention of that in the writeup. Pretty tough to maintain negative pressure in there with such low fan airflow and all those gaps.

      1. Author here. All good points. The fan I had lying around definitely isn’t pulling as much air as I’d like. Sounds like my next step is to research some heavy duty blower fans.

        And, I need to fill the gaps. I had started using some heavy-duty clear tape, but that’s probably not the best long-term solution.

        1. If you take a incense stick, get it burning, and turn on the system to the preferred speed/noise level. Using the incense to search for air flow around the gaps, you might find that its drawing plenty of air in through the gaps to keep the smelly stuff flowing through the filter.

          However, as the filters get clogged, you might have issues with low static pressure. So double up the fans with a spacer between them so that they can boost the static pressure (slightly). You might even find out that you can lower the fan speed more in this situation without adding excessive noise and get better air flow through the filter for longer life too.

          Also consider rack mount server grade fans that are meant for pushing air through the confined space of a server. Many of these can be pretty quiet at lower RPM(My 200cfm 120mm delta server fans are quieter when under 25% PWM than my 1080ti’s fans while gaming, and I have 3 of them hard mounted).

          1. Doubling up fans can help, but that’s a hack and the wrong solution to a problem that would not happen if you used the correct kind of blower in the first place.

            You need a centrifugal blower, not an axial fan.

            Size it correctly and it’s quieter and more efficient than an axial fan too, though a bit more spendy.

    3. Whoops, I included the HEPA and carbon filters in the BOM but didn’t call them out in the post.

      The fan pulls air out of the chamber and through a custom-printed box that holds the two filters. As another comment pointed out, the fan probably needs an upgrade for this to be as effective as I’d like. And just like that, I’ve started sketching version 2 of all this!

      1. For V2 consider putting the filter material in between the dirty source and the fan so that the fan blades stay cleaner which can help keep airflow/pressure up, and noise down.

        Just make sure you give the fan enough space so that it doesn’t stall trying to pull air from the filter.

    1. You sure don’t need a heat exchanger. Where would you even put it?

      My rig maintains a negative pressure envelope that has a heated top chamber with the bed, motors, filament store, etc., and a cool antechamber below with all the electronics. Room air is admitted to the electronics below, and waste heat (and bad air) is exhausted outdoors through a duct to an extractor fan at the wall.

      When the heated build chamber above is too warm, its heater turns off, and at a degree warmer its exhaust fan starts exchanging air with the cool chamber below, which promptly joins the flow outside. It only takes about 10 CFM to do all this, so it’s fine to leave that exhaust running all the time.

      There’s a second circulating fan on the heater in the build chamber that runs all the time (heating or not). It has a dust and carbon filter, but that only sees the small amount of air circulating around the chamber: it does not see the much greater volume of air that passes through the rest of the system all day, so it lasts thousands of hours.

      The only other filter is the screen on the exhaust outside to keep critters out :-).

        1. The writeup? That’s it, up there. I keep bare minimum documentation for my own use, and hardly any at all for one-off ‘functional’ (as contrasted with ‘expositional’) builds like that. It takes me (really) ten times longer to create and maintain documentation for public consumption, so I generally just don’t — I’d never get anything done. Selfish, maybe. I’m sorry I’m finite.

    2. I use a recirculating hepa+carbon filter in my heated enclosure. I suppose that the circulation probably improves temperature regulation a little bit, and it does a Good Enough Job that i can work all day in the same room while printing ABS and not smell it much let alone get woozy from the fumes.

      FYI, I have a friend who is a retired chemistry professor who also spent some time running a plastic injection molding company, made things like combs and marital aides. He said they vaporized so much plastic that even after installing 300cfm exhaust fans over the molding stations that forced the fumes through a cubic meter of activated charcoal, little spiderweb-like whisps of plastic would still accumulate on all of the equipment.

      He tells me that Butadiene, the B in ABS, is a really crappy central nervous system stimulant with a really short “upper” cycle followed by a long, drawn-out, awful comedown. And that Styrene, the S in ABS, although not particularly toxic, causes nausea because humans have specific styrene receptors that trigger a nausea response. This is why extended exposure to ABS fumes makes you feel edgy and crappy at the same time.

      I’m not aware of similar issues with PLA, PETG, PA (Nylon), PC (Polycarbonate), or TPU fumes, but all of them can probably result in airborne particles that you don’t need to expose a baby’s lungs to. ASA (Acrylonitrile Styrene Acrylate) most likely has the same styrene nausea issue.

  2. Nice looking build.

    I’m running through my PAPR design iterations that I plan to use a HEPA and carbon filter with at least for welding and most likely a pre-filter to extend life and a post filter just in case. One design will use a 5v USB fan and the other a 4.5V mattress inflator. I’ll have to test the performance eventually with the filters installed. https://hackaday.io/project/176773-diy-cost-effective-papr-design

    Will be interesting putting together the test equipment as I’m super confident will not be suitable with any of my other pneumatic or hydraulic gauges. Will be interesting to see what can be made cost effectively also since I’m guessing there are science fair projects that will most likely be suitable or at least improvable and test able to verify performance with a primary standard someone owns already.

    Still using PLA with my MPMS V2, though planning to have to make an enclosure to better control performance as well as deal with the toxic effusia and effluant with my PET strip goal that is turning into a grinder auger feed extrusion corrupted potential future goal.

    This seems like a nice localized design as I was thinking connecting with the honking 6″ old grow fan exhaust system circuit to get more utility out of that. Will definitely keep in mind so the portability capability is easier.

  3. 3D printing people really need to get a clue about how much they’re polluting their homes. Decent ventilation is good, but a multi-stage air scrubber should not be optional IMO. I’ve got an Austin Air Healthmate Plus Jr. (small one) for my 1-room workshop and the difference is really remarkable. They’re not cheap, but how much are your lungs?

    1. Not disputing the notion (and I built a sealed enclosures for mine that exhaust directly outside) but I’m mindful of Akin’s Law #1: “Engineering is done with numbers. Analysis without numbers is only an opinion. ”

      So, can you put some numbers on that? How do you quantify “polluting their homes”? How much does your little fan filter actually reduce “pollution”?

      Or, at the very least, how does such pollution compare to a stir fry cooking, or a candle burning, or “air freshener” spray or plug-ins, or fabric softener sheets, or even human exhaust?

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