Carbon Filter for Saturn 4 Ultra (3d Printed, USB Fan, Port Mounted)

This is a carbon filter for the Saturn 4 Ultra that mounts in through the rear port. It uses a USB fan (so can be powered from the printer's USB port whenever the printer is on) and includes an easily removed and refilled "cartridge" that has cheaply obtainable fish tank activated carbon inside it.

The closing seal on the Saturn 4 Ultra's lid is poor, so this doesn't do a perfect job, but it does substantially reduce the smell of running the printer.

All parts can easily be printed (supportless) on an FDM printer, but I see no reason why it should be possible to print them on the Saturn 4 Ultra itself.

For this you will need:

1. One of each of the 6 printed parts - the STL files are below. (All printable supportless on an FDM printer. Could probably be printed on the Saturn 4 Ultra - sizes are certainly suitable.)
2. M3 hex nuts x12
3. M3 bolts x12
4. (Optional - some M3 washers)
5. A USB 40mm fan. (Buying one with a USB lead is easiest, but you could buy any 5V 40mm fan and solder a lead on.) This is going to run a lot, so I suggest a ball bearing fan.
6. A little glue (I favour quick setting epoxy)
7. Some activated carbon, fairly fine
8. Some mesh to hold the carbon

The easiest way to get the carbon and some suitable mesh is to buy the carbon "tea bags" like those shown, which I think are used for some aquariums. Then you can use the mesh from the bags, which you are assured will be suitable.

First, "set" some nuts into the 8 appropriate recesses. I find squeezing with a mole grip works well for this if they are stiff. Alternatively, if they are too loose (it will depend on the tolerances of your print) a drop of glue will help to hold them in place while you do the rest of the assembly.

Use M3 bolts through the fan and mounting bracket and into the nuts you have set into the carbon holder socket to form them all into one unit.

You may need to use some washers, or cut your bolts to length, to ensure that they do not project above the "floor" of the socket, or you won't be able to plug in the carbon "cartridge" all the way.

Orient the fan so that the wire can be easily routed out through the slot in the back plate of the mounting bracket.

Ensure that you mount the fan blowing upwards. (While you would think this would work equally well either way, I've found that it works much better blowing up through the carbon cartridge - I think this is due to the direction of air flow this forms in the printer, which has a very poor seal at the top.)

Draw around the end of the carbon holder main body's octagonal end on your mesh twice (empty out the carbon from the "tea bag" into something else first, obviously) then cut these pieces out.

The mesh panels need to fit neatly into the octagonal recesses in the carbon holder top and the carbon holder base. If they are too big, trim them. If they are too small, cut new ones that ARE large enough, or you'll have bits of carbon escaping!

Put a few dots of glue into the carbon holder base and insert the carbon holder main body into it, holding the mesh in place.

Put a few dots of glue into the carbon holder top and insert the carbon holder top ring into it, again holding the mesh in place.

Leave time for both to set.

My preference for this is "5 minute epoxy", which I know works, but I'm sure many other adhesives would be fine.

Put the carbon granules into the "cartridge" you have made and put in four more bolts to seal it up.

The cartridge now "plugs" in to the socket on the bracket.

By being made this way you can easily remove the cartridge from the printer for refilling once the carbon is no longer providing sufficient filtration.

On my printer, the tolerances are such that the air goes through the carbon rather than escapes around the base of the cartridge. If yours is different, you could add a seal, or you could scale the parts slightly, or you could make a new version of the design, which is publicly available in OnShape.

Four more nuts and bolts will allow you to secure the bracket through the port in the back of the printer. Make sure that you route out the USB cable through the slot.

Once this is in place you can plug the carbon cartridge into the socket, then plug the USB lead into the printer's USB socket, so that it will be powered up whenever the printer is on. (The current draw of a small fan is well within what the port can deliver - I did check.)

As I've said, the poor seal on the printer lid means that this isn't perfect, but it does help a lot, and is an easily and cheaply maintainable system. Enjoy!

(The lid on the vat in that picture is also my design, sized for printing on an Ender 3, on Printables at https://www.printables.com/model/975938-vat-cover-split-saturn-4-ultra , should you need it.)