Experimental Powered Air Purifying Respirator (PAPR)

thingiverse

This is an experimental Powered Air Purifying Respirator designed for customization based on available motors, electronics, and filters. The build is intricate, but it allows users to tailor the design according to their preferences. My test implementation uses a 775 DC motor from a hand drill, a PWM motor speed controller purchased on Amazon, and filters from my Eufy 11+ robotic vacuum. The print resolution used was 0.30 mm, which resulted in tight tolerances that may require deburring. The blower wheel is secured to the 5mm motor shaft using a small hose clamp. I employed 3/4" #6 sheet metal screws for most of the assembly except for the corners near the hose, where 1/2" #6 screws were used instead. The motor plate attaches with 5mm flat head screws, while the 775 mount uses 5mm bolts to allow for adjustable blower wheel placement in the fan box. The filter cover is secured using 5mm screws in heat set inserts placed in 6mm holes. To facilitate easier setting, I used a counter sink post print with a slight bevel. I experimented with M5x10mm long x 7mm wide Hilitchi inserts from Amazon but found that shorter inserts would have been more suitable as the over-melt at 10mm did not leave enough clearance. Applying food safe silicone grease to the hose adapter proved helpful in smooth operation. Two versions of the blower wheel were created, with the original being heavier and featuring thicker blades. The lighter version, although not pictured, has worked well so far and may be a better option for some users. Balancing the blower wheel is recommended for optimal performance. A 32mm hose adapter was designed to fit 1 1/4" ID pool discharge hose from Ace Hardware, while a 34mm pinch adapter accommodates hose from my local vacuum supply. However, the collar on this adapter interferes with the screw mounting point. The motor box's battery compartment has an area for perfboard installation. Consider splitting the battery plate in two to have a fixed and removable portion. Adding an on-off switch on the switch plate is also envisioned. To prevent motor slippage, I strongly recommend slow motor ramp up using PWM or other methods. This design was a large print, resulting in several problems during the process. As a result, not all parts have been printed with final modifications. Changes include: - Motor box: added strap mounts and fillets on corners - Fan box: added heat set screw - Motor cover - changed the heat set insert for the battery plate from 8mm to 6mm - Battery plate - not yet printed - Switch plate - not yet printed Things to consider when building this device include: - Silicon or glue between motor box, fan box, and filter box - Thermal control - I've not run the unit long enough to know if heat will build up in the motor box. Perforations in the motor cover could be an option but would allow increased leak around the motor with possible unfiltered air contamination - Gasket between motor mount and fan box - Vibration dampening: slight widening of 775 motor hole and placement of rubber dampener around motor - Engineered blower wheel - I just eyeballed something that looked reasonable, and it seems to work ok - PAPR hood - the next project - Eufy 11s filter box - I didn't realize there was a difference in size between the 11s and 11+ (what I own) so now I have a bunch of 11s filters, and I might make another filter box for them Disclaimer: I've done my best to consider real-world use for this device. However, I cannot tell you that it would be effective at filtering in any situation. The consequences of its use are strictly your responsibility. Note: Photos show one filter. Videos were taken with both filters in place. YouTube water test: https://youtu.be/g4K87gPUxf4 YouTube assembled: https://youtu.be/8Wv7aYr8OZ8