I spent last night dialing settings for the 3D printer, and was finally able to extrude my first multi-layer object. There's still a lot of improvements to be made, but this is a huge step forward! The final part is light and flexible, and so strong you can't pull it apart or break it no matter how hard you try.
This was made with #5 polypropylene plastic, which used to be trash food containers, which were washed and shredded with the Precious Plastic shredder into fine flakes, and then fed directly into the print head.
The next step is to see what kind of low-resolution objects I can make with this. I'm also interested in trying to make a part with 100% infill to see how solid an object I can make. Stay tuned!