This is the ultimate refillable charcoal chamber filter for the P1S, P1P and X1C - in my opinion of course.

I've tried numerous designs, from the ones just for charcoal to the ones with multiple sections. I felt that the designs were not sufficiently robust, and in some cases just impossible to remove. HEPA + charcoal hybrid designs either required an extra tool for removal, gluing back the filter tab or a flimsy pull tab which I've snapped off numerous times. This led to frustration and ultimately motivation to design my own - with several goals in mind:

• Easy insertion and removal
• Robust design, able to withstand multiple reuse cycles
• Proper air flow and filter order (air passes through HEPA filter first, then carbon to maximize air velocity)
• Tight fit with HEPA filter module for maximum effectiveness

Thus, after multiple revisions and rounds of prototyping, I arrived at this final design. Using the brilliant idea of using 1.75mm filament as hinges, a design feature commonly seen on mechanically functional designs, I've integrated two hinged doors that act as pull tabs for easy removal. The doors close flush and allow for the stock cover panel to close without any obstruction, keeping the filter out of sight and streamlining airflow. Other design highlights include a snug fit with the HEPA filter thanks to thin yet strong reinforced 0.8mm side walls, and a small indent to indicate where the plastic tab keeping the filter in place resides. To aid removal, simply push the area below the indent to make it easier to pull out the filter.

For assembly, just print the design as-is, then cut two strands of 1.75mm filament, around 23mm to 25mm each. The depth of the slot for the filament is exactly 25mm, thus if you want a flush look be accurate with the cutting. Once done, just fill in your carbon pellets to the lip, making sure the distribution is even. Lastly, pop on the HEPA filter and you're all set.

The list of required components is as below:

• -Activated carbon pellets (acid free please)
• HEPA filter for iLife robot vacuums, same type as for the BentoBox
• 2x 25mm long 1.75mm diameter filament strands

I recommend printing the filter in PETG at least, more heat resistant materials such as ABS and ASA would be ideal. If you only print PLA, PLA+ should suffice but is not recommended for longevity. With all that being said, I hope that you enjoy this design, and find it useful.

Cheers,
-K