Exhaust Filter Box for Qidi Plus4

Some important notes if you're reading this:

• The deep version of this is a MOSTLY UNTESTED model. I've printed it once, determined it's dimensionally correct, and then got stuck working on something else. I haven't even tested if the back panel fits yet!
• THE DEEP VERSION DOESN'T FIT IN A STOCK CONFIGURATION. Don't print it thinking it'll just drop in place of your old filter box! See below.

tl;dr: you probably don't want the deep variant just yet. 😉

While this is an original model, it's heavily inspired by a combination of spooknik's refillable charcoal filter and James Scott's refillable filter basket. Basically, I wanted a refillable filter box without a HEPA filter integrated into it (because I use Sergej Reidel's rear-mounted HEPA filter) but didn't want to waste all the extra space hanging out in front of the exhaust fan. So, I mocked this up in OpenSCAD, and this is the result.

The stock fan, however, intrudes a bit into the area under the filter box, and so this model as-designed won't actually fit. So, to make this work, you'll need to arrange for the exhaust fan to move outboard a few millimeters. This is left as an exercise to the reader, because I haven't had a chance to revisit it yet. If you want to try this out, I'd suggest starting with Spooknik's 8038 exhaust fan modification, and play with the tunnel length and fan mounting position. The original-sized version fits just fine.

This uses Stephen Kent's honeycomb-openscad library for the rendering of the honeycomb patterns.

Included is the deep version ("deep-filter") which is, again, almost completely untested, and a version ("original-fit-filter") that I have tested that is roughly equivalent to the original box, but with a removable back and honeycomb filter openings (to allow for loose carbon to be used). This one is very externally similar to Spooknik's model that I linked above, but uses a slide-in back like James Scott's.

To print this, you'll need to split the STL into separate objects in your slicer ("split to objects" in Orcaslicer), and then you can print the back and filter housing with independent rotation and arrangement. Printing the main basket is…not ideal, right now; orienting the main basket topside-up is probably the best option, but you'll generate some pretty nasty tree supports. Cleaning this up for easier printing is also on my to-do list.

I'm uploading this mostly because I suspect there's some value in a dimensionally-correct OpenSCAD model of the stock filter box, and in the general hope that some of this might be useful/inspirational to someone, certainly more than it would be if I just left it sitting on my hard drive.

I'll try to update this later, as I'd still like to take this approach.