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20. Project development

Going into this week, I had several of my parts already fabricated. I decided to begin this week by outlining the main components of my project. Mr. Dubick suggested this to help us rationalize the parts of our projects that were completed and the parts of out projects that were not complete.

Here is my outline.

  • CPR Dummy Body (Done!) (Here is the baby doll that I used to create my mold.)

While most of my components have already been fabricated in previous weeks, I still had a lot of work to do (i.e. my circuitry container, general assembly, final touches). Unfortunately, I was on an exchange trip in Germany during weeks 19 and 20. While on the trip, I tried my best to organize my final project page and documentation. I also began brainstorming my circuitry container.

Circuitry Container

The last component that I wanted for my final project was a container for my force sensor circuit. After talking to Dr. Harris, I decided to create a “head” for my CPR dummy body that could house the circuitry. I wanted to 3D print this piece, so I began by designing it in Fusion.

The design consisted of two separate parts. The first part (“spinal cord”) would house the force sensor within the CPR dummy mold. It would also contain the force sensor circuit board. The second part {“head”) would cover the circuit board containment area.

Here is the sketch that Dr. Harris helped me develop.

Spinal Cord

I began developing this part of my circuitry container by taking the measurements of my circuit board, force sensor, and check valve. (Side note: Early on in my final project development, I planned to include a check valve which I had developed in week 6. I wanted to include this component to simulate both the compression and breathing aspects of CPR. Sadly, the implementation of this component with my force sensor attachment would not cooperate. I found this out when molding all my components, so the larger circle, meant for the check valve, is still included in my design.)

Here is my check valve for reference.

After taking the measurements of the relevant pieces, I started drawing the shape of the force sensor in Fusion. I also created a rectangle with the dimensions of my circuit board (plus 1 millimeter of clearance). I added some extra material under the area where the force sensor would sit to give more structure to my silicone dummy. I extruded all of these components and created a gap for the wires to run through. I also created an attachment “mechanism”. For the spinal cord component, I created a 2.25 mm cylinder hole in the box which would be filled by a 2 mm cylinder on the head cover.

I created the head piece in the same file as my spinal cord. I did this by making a copy of the file and adjusting my head design according to the dimensions of my circuitry container box. I created a 90 mm sphere around my box and hollowed it out so that it would be 4 mm thick. I added to 2 mm cylinders to the top of the dome directly over the holes on the circuitry box. (This design aspect would eventually fail as I designed my box to be too large to fit completely under my dome.)

Here is my force sensor attachment.

Here is my baby head cover.

Here is a photo of both of my 3D printed parts. (I printed a matching grey head cover, but I accidentally ripped a hole in the top when removing the supports.)

This photo shows my circuitry inside my circuitry container.

Mold Adjustments

Once I completed my spinal cord attachment and head cover, I worked on editing my mold to fit my new components. To do this, I used the bandsaw to cut away the top portion of my mold so that the spinal cord would lay flat.

Here is how my spinal cord attachment fit inside my mold.

Unfortunately, I did not clog the hole I created with enough duct tape so the casting materials leaked. Luckily, Will grabbed me a hot glue gun to clog the leak.

I let my CPR dummy body cure and begun the long journey of documentation.

After 6 hours, I popped my dummy out of the mold and connected it to an FTDI header. It worked!

This is my final project!

This is a video of my project working!

Here is my final project slide.

Here is my final project video.

(See my final project page for an overall view of my project development.)