Creating your own assistive technology with the Bambu P1S and Onshape
Cholesteatoma
The past 10 years, I have been dealing with a pretty persistent cholesteatoma which has required surgery three times now. While the surgery is pretty long, recovery has gone quite smooth and is mostly just really boring.
As far as restrictions in daily life during recovery go, the biggest one is that absolutely no water can enter your ear canal. The official solution from the hospital was to have someone place a cup or something over your ear while rinsing your hair, but given the fact that I do not have such a someone living with me and my love for (over)engineering a solution, it was time to fire up Onshape and to build a solution for this.
The idea
The idea was already given by my doctor: a simple cup over your ear. For added waterproofness and comfort, I wanted to add a flexible ring made out of TPU. For keeping it fixed on my head, something stretchy would be required.
The cup
First some measurements were needed. Using my trusty mitutoyo digimatic calipers, with the following result:
This was turned into a base, which can be used for extrusion and some lugs for attaching the stretchy stuff were added. The 30mm width for the lugs was chosen because that was the size of the elastic band I could get my hands on.
This then was extruded 25 mm and a cover was added to make it a fully functioning "cup"
And the last step was adding some fillets to break any hard edges
The ring
Then, the TPU ring needed to be designed. Here, the idea was to inset the start of the ring a bit so that it would "overhang" a bit, so that it would bend to create a flat seal.
This was realized by again creating a base, creating a sketch perpendicular to it and sweeping this using the inner base as path.
Which yields the following result:
Since I only had shore 95A TPU around, the thickness of the ring needed to be adjusted. The initial width chosen was 2 millimeters, but this turned out to be too stiff, so it has been reduced to 1 mm.
Printing
The cup
To properly print the fillets, printing the cup face down is necessary. Using the P1S' filament swap ability, PETG was used as a support interface layer when printing with PLA for clean separation. For the rest, the default Bambu 0.2mm profile was used
The ring
The TPU was a bit more tricky to print. While it might seem obvious to print it with the big flat part on the build plate, the flexible nature of TPU disallows this when the part is thinner than 2 mm.
Other parts
To keep everything in place, about half a meter of 30 mm wide sewing elastic is needed. I don't know if there are any specifications to this, but I went to my local sewing store and got something that looked and felt about right.
For adjusting everything, a simple buckle was needed. This one was perfect, but made for 26 mm belts, so that needs to be scaled in the slicer.
Assembly
The first step is to glue the ring and the cup together. I used regular CA glue, but there are probably multiple glues that will work. Next, take one end of the elastic band and loop it around the middle part of the buckle. Sew those two pieces together. Then, thread the elastic band through the first lug of the cup, weave the elastic band through the buckle and then through the second lug. Finally, sew the two ends together and you're done! The final result should look as follows:
Making your own
The onshape project can be found here. Feel free to make any modifications or use it for any non-commercial purposes.
If you don't have a printer yourself, please send me an e-mail at my first name at happytechnology.nl