Author Topic: COVID supplies - .stl patterns  (Read 831 times)

Offline awake

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COVID supplies - .stl patterns
« on: July 22, 2020, 09:03:15 PM »
Some of you live in places where the pandemic has largely been beaten back, so these files may not be of interest to you. Others of us are facing an ongoing challenge, so I am posting these files in case they will be of use.

My wife asked me to work these up to replicate commercial products that she had seen or borrowed. The "hook" is supposed to allow pressing buttons and pulling on door handles. To be honest, I am not sure that I would find these useful, but she and some of her friends have been interested. The version shown in the picture below proved to be a bit too weak - it tended to break when yanking on a car door handle, for example - so I tweaked the design to add strength. I printed the final version of this hook, which I've included .stl file below, in PETG using .2mm layer height, 5 perimeters, 4 layers top and bottom, 25% infill, and it seems to be strong enough for the intended use.

The "strap" is intended to allow a more comfortable and adjustable option for securing the elastic on face masks - rather than hooking the elastic around one's ears, this strap allows hooking the elastic around whichever "T-hook" provides the best fit and comfort. This design needs some flexibility - maybe it would work with PETG (??), but I'd think it might be a bit too stiff for comfort. Instead I designed it to print with flexible filament. The grey one in the picture below was printed using TPU-85, which turned out to be too flexible; the blue ones were printed with TPU-95, which seems to be just right.

Incidentally, I printed these straps on my home-made 3d printer with a Bowden-type extruder. Supposedly you can't print flexible filament using a Bowden-type extruder ... but in fact, you can, if you do the following: 1) use the right temperature (hot enough that minimal pressure is needed to squeeze out the molten filament); 2) increase the force on the extruder follower; 3) print slow - as slow as 15mm/s; and most important of all, set up the extruder such that the filament path is fully enclosed at every possible point, so that there is nowhere for the filament to "squish" out.
Andy