3D printer: First impressions and a DIY fume extractor

Backstory: 3D printer first impressions (pun intended)

I need to do quite a lot of round-the-house repairs, and have always fancied a 3D printer to be able to churn out custom plastic parts for replacements and custom projects. Well, as a recent birthday gift from my wife, I got one - and it proved to be one of the most versatile and good-value-for-money model on the market, thanks to a very wide community support. The learning curve was a bit steep at times but it turned out I got extremely lucky and managed to get my printer going in relatively no time without causing it major damage -- although I came quite dangerously close to it more than once, I even managed to master bed leveling without major scratches on said bed :).

An accidental find: it is more reliable to not disable steppers for bed leveling following auto homing (moving X/Y using the control panel instead). It's more cumbersome but maintaining holding current on the Z-motor ensures that the nozzle remains exactly at the same height at the beginning of the print as it was during leveling. An even better option would be to only disable X/Y steppers while holding the Z-stepper. I may end up programming some kind of manual bed leveling wizard into the firmware at some later point.

Another accidental find: it is better to not bundle the Bowden tube together with the hotend cables. It came bundled and I undid it by pure accident, then connected it, quite absent-mindedly, to the extruder (barely realizing that this is actually where the filament is going through), and only then realized that I cannot easily undo the tube connection to re-route it through the cable ties. So I just left it like that, and discovered that it makes a more natural filament path and puts less strain on the print head.

First impressions (pun intended) came out quite acceptably good, at least for my purposes (I wasn't going to set any world records in print quality or detail level or display beauty or anything line that - I simply want my parts to come out functional). Since I wanted to keep the printer busy for some time, I was mainly printing some more common accessories for the printer itself. (Yes, this kind of a 3D printer is very modular, like Lego for adults -- you can swap out and upgrade pretty much any part of it, and many upgrades come in the form of "download a model and print it yourself", so I outfitted mine with a filament guide and cleaner, extruder knob, fan cover, tool holder (a LONG almost-overnight project), etc.)

Then came the first "real-life" application: basically a custom-sized brick of plastic with a screw hole inside to serve as a spacer for mounting a hanging file frame inside a bedroom cabinet (as part of document organization project). This was an extremely simple model that came out as desired on the second try.

Then came the second "real-life" application: a holder for a Tile Sticker that would fit on the strap of a Babble Belt baby monitor. Thanks to Pavel from Dots and Brackets who introduced me to the genius idea of OpenSCAD (basically a programming language for 3D modeling), the total time from concept to printout was less that 3 hours and fit nearly perfectly.

I was ready to start conquering the 3D printing world but...

Fumes issue and extractor hood idea

...but the layout of our house left no place for the 3D printer installation other than in the basement room that doubled as gym / playroom, as well as contained one of the main HVAC returns. This basically meant that I couldn't print with anything "smelly" like ABS or, well, most materials other than PLA. Even with PLA (biodegradable / biocompatible as they claim it is) I would be a bit worried about the amount of fumes and fine particles that my prints might be generating. Especially with kids playing in the same room and the HVAC system happily blowing the basement air throughout the whole house.

So in the long run, I would totally need some kind of exhaust to vent all those pesky fumes the hell out of my house. I noticed that I had an existing 4-inch dryer exhaust in the workshop room (a small 1x2 meter closet in the far corner of the basement). Immediately I thought that I could gear up something like this (additionally outfitting the workshop itself with a functional exhaust which isn't a bad idea either). After googling around for what components I can buy cheaply I came up with the following:

From right to left: L, louver; G, grille (3D printed); ED, existing duct; BD, backdraft damper; R, 6-to-4 inch reducer; Y, 6x4x4 inch Y-connector; BG, blast gate; FD, flexible duct; V, adjustable round vent

Buyer's list

So here was my buyer's list (all prices are in Canadian dollars). Note that I got all items off Amazon with Prime delivery, which may have increased the prices compared to Ebay or Aliexpress, but I wanted to get the work started ASAP, not in a few months:

• The hood: a mini dust hood ($17), as well as any suitable sheet to extend the hood to dimensions - I used an ABS sheet I happened to have lying around ($13) but you can use literally anything you have on hand, including cardboard from an Amazon shipping box. (Well, not quite, as it turns out. The sheet needs to be strong enough to support the curtain weight, yer lightweight enough to not bring down your mount. My ABS sheet did flex a bit so may need to replace it or to print some reinforcement beams to support it.)
• The fan: I used a 6-inch inline 250 CFM lying around ($35 a few years ago) but you could get a 4-inch 100 CFM inline fan for about $24. 
• The ductwork: blast gate ($9), backdraft damper ($13), some 4-in flexible duct ($5 for 5ft), clamps ($2 for 2), and connectors ($3.5 each). Since I used a 6-in fan, I also needed a 6-to-4 in reducer ($14), and because I designed the exhaust to also serve my workshop, I added on a 6x4x4 Y-connector ($9) and an adjustable 4-in round vent register ($13). If you decide to merge your exhaust with your existing dryer ductwork, you will instead something like a 4x4x4 T-connector ($8.5) and another blast gate. You will also need to make sure your backdraft damper is between your fan and the insertion point to your dryer ductwork, and would need to have at least some kind of lint trap or screen, compensated for by a stronger fan, so that your dryer will not rain lint onto your 3D printer. Ideally, you'd want some sensor lock-out preventing your dryer from running when the blast gate to your printer is opened, otherwise your filament won't like the warm moist air coming from your dryer. 
• The mount. I wanted it to be flexible so that I could raise my exhaust hood when not in use, therefore this part proved the most problematic. A gooseneck phone holder didn't work (way too limp); an adjustable screen arm wasn't adequate either (too heavy, not enough articulation in the needed directions, hot tight enough in other directions). But microphone mounting equipment proved quite fine just barely adequate (I ended up getting  a boom arm, a flange, a short gooseneck and a set of nuts for a total of $41, roughly the price of a monitor arm.)
• The curtains. I reused a clear plastic table covering sheet outfitting it with an abundance of Velcro strips ($10 for 5m). More on this later.

Some of the parts for the project (a few of them were returned and upgraded).

Implementation

0. Electrical wiring for the fan

This step was optional but I felt the need to do it because I had no readily available wall outlets near the fan, and did not want to mess with extension cords. So I ended up rummaging my electrical supplies box for a standard 2-outlet receptacle, a Decora switch, two 2x4 electrical boxes, two outlet covers, several oddball clamp connectors, and a bit of 14/3 cable to put in a switch-controlled plug for the fan(s). 

I decided to branch the circuit off the ceiling light as this was the closest point (behind a GFCI as are all my workshop circuits which is a bonus). The inconvenience that at least some lighting needs to be on in the workshop for the fan to run was easily offset by the ease of wiring compared to running the wire all the way to the workshop light switch. If all else fails, and if I need to run the exhaust overnight with someone sleeping in the basement next to the workshop and the 3D printer (odd as it is that the workshop light would bother that individual while the running 3D printer itself would not), I can simply temporarily unscrew the bulb.

1. Mounting the hood above the 3D printer

My idea was to make the mount without drilling any holes in the visible part of the cabinet that doubled as the printer stand. So I used some hobby 2x2 wooden stock and steel brackets from Home Depot to improvise a stand on top of the cabinet. Here goes:

[[[T, top surface of the IKEA cabinet (birch veneered particle board); PL, back of the IKEA cabinet (plywood thin MDF board); P, 2x2 poplar; O, 2x2 oak. Steel brackets and screws are self-explanatory.]]]

The resulting stand wasn't 100% solid in all directions but served my purposes. (You might as well use the nearest wall stud, though.) 

The remaining steps were to attach the microphone mount to the stand, flange then arm then gooseneck. I ended up disassembling the boom arm to be able to screw it onto the flange to avoid moving the cabinet (it is secured to the wall to avoid tipping). I fitted the hood directly to the gooseneck by drilling a carefully measured 5/8 inch hole and tightening the hood wall between two mic nuts. I may be in need of reinforcing the gooseneck in the future if it becomes limp over time.

2. Mounting the fan motor 

This step was rather straightforward. I noticed that the motor fits pretty tightly with the reducer on one side and the Y-connector on the other side (the latter needed some slight Dremel grinding to make a groove to accommodate a rivet head on the fan). The reducer, in turn, fit nicely into the backdraft damper, which could be connected to the inside of the duct with the aid of a 4-inch hose connector.

The outside of the duct needed to be replaced with a louvered vent which I had lying around from some previous projects. However I had no pest-proofing grille, so I ended up printing one:

Oddly enough, some 1/3 of the grille beams had no brim around them, and seemingly started printing in thin air, but the grille ended up acceptably good. Indeed PLA can be very forgiving. Next time I'll be reprinting those in ABS or PETG (and I might need it because PLA may not be the best material to leave exposed to the elements) I'll probably use a raft.

An unpleasant surprise came up when it turned out that the airflow was barely enough to open the damper, limiting the exhaust functionality quite significantly. So I quickly outfitted the damper with a quick-and-very-dirty manual open/close actuator threading a piece of string through three tiny holes and tying two knots, like so:

The beauty of it is that it is simple enough to do in 20 minutes, versatile enough to allow for 3 modes of operation (as seen above), is easily outfitted with visual aids, can be secured in either open or closed position using simple loop-and-nail "mechanisms", and even lends itself to automatic actuation upgrade using some kind of solenoid electromagnet (I may do such an upgrade in the future by rigging a solenoid connected to a current sensing switch from within the switch box, as I do have a few current sensing transformers lying around.)

3. Installing the blast gate and assembling

Probably the most invasive part was installing the blast gate through the drywall. I decided to use a shuttered gate (rather than making do with something like routing a duct directly through the wall) for several reasons:

1. I wanted to be able to shut off the exhaust when not in use, so that I don't get extra cold air seeping onto my 3D printer (and into my basement). Also, to increase the efficiency of the workshop exhaust, I needed to be able to shut off the 3D printer branch. 
2. I wanted to protect the drywall from chipping near the hole. Drywall is brittle, so anything that could wiggle inside the hole would gradually cause it to chip and crack. Not only would it damage the wall, but also the resulting dust would not add to the quality of the 3D printing or the surrounding air.
3. I wanted the connection to look as aesthetically pleasing as I could make it, so that if I decide to discontinue the use of the exhaust or the 3D printer or both, I am left with a nice looking round opening with a door that can be easily closed (rather than an ugly looking protruding piece of aluminum duct, or worse, a gaping 4-inch hole). 

Cutting the hole ended up surprisingly easy with a very dull 4-inch hole saw and a handheld power drill. (Actually, the "very dull" did more good than harm. Had the saw been sharp, it would start catching in the drywall, tearing chunks off it (making a lousy looking hole), or worse, tearing the drill away from my grip and sending it flying all over the workshop. Although I might have avoided it by running the drill backwards.) I took time to carefully tape a few garbage bags with masking tape around the hole to minimize dust generation, so the hole ended up very nice. (My wife didn't welcome the idea regardless.)

Once the hole was there, it just took some silicone caulk to glue the blast gate in place

(I also reinforced the shutter stop of the gate by an M4 machine screw to prevent the door from sliding completely out if pulled too vigorously). What remained was simply attaching some 4-inch flex ducts with worm-gear clamps, sealing some joints with (insulating) duct tape, and the ductwork part was ready.

4. Making and attaching the enclosure walls

To make the enclosure itself, I re-purposed a decommissioned used clear table cloth from the dollar store, and made 4 curtains the following way:

1. Cut each curtain to size Wx2H, fold to make a double-layered curtain .
2. Use an impulse sealer to fuse the layers of the curtain at regular intervals. (Yes this was a good excuse to buy an impulse sealer.)
3. Place a small weight (I used some Home Depot brass rods I had around for 4 years but never used) into the fold; seal sideways so that the weight does not slide out.
4. Attach curtains to the hood using strips of Velcro tape.
5. Put some more Velcro tape strips on the sides (to close the enclosure) as well as in the middle (to hold the curtains rolled fully or partially up, if needed). I'll have to figure out whether to make them more continuous (to make the enclosure more airtight on the sides) or more in pieces (to make the curtain easier to roll up).

Final result

Well, a couple of pictures are worth a thousand words (This has been a long read anyways.)

Workshop side (before and after). The yellow string operates the backdraft shutter.

Basement side (also showing the printer in actual operation)

Outlook

• The gooseneck, as well as the ABS extender sheet, are just barely adequate for the weight of the structure. The hood looks a bit flimsy and will eventually shift under use, especially when (un)rolling the curtains. I will be reinforcing the gooseneck, or maybe even foregoing it entirely, opting for another articulated arm instead.  
• The curtains design just sucks in terms of fireproofing - any flame and it's curtains for the curtains, if you excuse the pun - as well as for the printer and the basement. I may, at some point in the future, upgrade the enclosure to some flame retardant (and also more easily rollable) version. So far I am investing in a smoke detector directly above the printer. And an air quality monitor to boot. 
• On the flip side, I like the transparent enclosure and easy access to the filament spool. (Most people would mount the spool outside of the enclosure anyway but I was too lazy to do so.)