Compact ventilation for Creality K2 Plus (parametric) (updated!)

This ventilation system was designed with the following priorities in mind:
- space saving, you only need about 7cm of space behind the machine
- don't interfere with poop chutes which respect airflow, I chose shay's variant also because it's space effective and also has a bin, some other compatibles: one, two, three… (also see note at end)
- don't interfere with PTFE piping and still be able to use the CFE buffer, moreover, help with placement of a Y splitter if needed
- no need any modification to the machine (except using two longer screws)

It's composed of:
- two back attachments with TPU rings 
- straight pipes upwards
- a Y coupler to a 75mm ventilation pipe
- a holder bracket to fix it to the machine

If you worry about the pipe sizes, don't. The cross sections of the pipes are matched with the cross section of the grilles on the back of the machine, you simply don't need any bigger pipes as more air wouldn't go through anyway. A 75mm flexible pipe (see note about pipes at the end) having 64mm internal diameter, in this use case causes a 0.001 bar pressure loss on a 5m long section, it's completely negligible.

Doing prints regularly in smelly materials like ASA, the printer is in my office room and have zero smells near me, it's very efficient. The exhaust goes into the house attic.

I recommend PETG for printing (I had the cheapest one at hand and went with “Generic PETG” profile in Creality Print), set Wall Loops to 3 and 33% infill. The Y coupler doesn't need supports, but using both inner and outer 5mm brim is recommended. The the back attachments need supports, use Zig Zag pattern (.3mf file included below). At least for the holder bracket I recommend using the adhesion stick glue that came with the printer. I included some 3mf project with settings for the back attachments, the Y coupler and the rings with TPU filament PolyFlex TPU95. 

Assembly (also see the photos in the gallery:
- push in every component firmly. Watch for the Y coupler arrangement, should orient the bolder part towards the front of the machine so you can push it up to the wall. Don't forget the holder bracket.
- Insert the TPU rings into the back attachments. These are optional, but recommended to have an airtight connection with the surface. Can be printed easily on the K2 if you follow Creality's tips.
- remove the back cover of the machine, and use two 2.5x15mm woodscrews and washers to fasten the back attachments though the center holes of the vent grilles, from the inside.
- re-attach the back of the machine together with the vent piping in place. For the topholder bracket, you'd need two 22mm M3 screws to be used in place of the original factory screws which fasten it together with the back cover at the top.
- re-attach the poop chute parts as needed, snap in the PTFE pipe into the hoding grip of the bracket.
- if you have the CFS I'd suggest to attach the filament buffer to the back of the CFS (it's provided with factory supports) instead of the machine, you just need to change the order of the tubing and the cabling. But if you insist on still having the buffer on the back of the machine, use just one screw and mount it vertically.
- put the machine back to the location, place firmly against the wall.
- attach the top exhaust ventilation duct by firmly pushing it in the Y coupler.

You can use my remixed pipe holder for the 75 duct fixation, and my grilled cap at the other end, to prevent insects from entering, or even mount an additional extraction fan if you want to.

Designed in FreeCAD, parametric project files included.

Notes: 

• 75mm flexible pipes are usually used for two things: the ones similar to this, often go in heat recovery ventilation systems, they are coated on the inside with an antibacterial layer, and the ones like this which are technically the same, only without antibacterial coating, these are intended to be used for cable or gas piping protection, or drainage in the ground or concrete. I have samples of 3 such types with 75mm external diameter, the internal diameter is around 64-65mm. It's perfectly suitable for the ventilation of a 3D printer.
• There are many poop chutes designed which you can print out. Make sure you only use one which doesn't obstruct in any way any ventilation holes on the back. This is especially true regarding the center fan, which is the inlet for fresh air and air to be heated when a hot chamber is required. Failing to draw sufficient air due to obstruction of the holes may cause overheating of the heat element and could result in accidents with tragic outcomes. This ventilation system takes care of the possibility to place an appropriate poop chute in respect to the above.