Early on, the material of choice for Pingree's frame was extruded aluminum. It is the perfect material for this application. But its not easy to prototype it as minimum orders of a custom extrusion start in 1000 pound batches. After deep thought, I decided to try and make my own small batch of extrusion in my shop. To do so, I needed a way to dimension and carve profiles in long pieces of aluminum. The solution I came up with was to make an over elaborate router/mill out of some shop scraps. In short, It worked really well, sprayed hot aluminum chips all over my shop, all while making a horrifying sound. The photo below is the finished product.
Homemade Aluminum Mill & Mandrill Bender
After a successful short run of milled aluminum I cut it to length and added an indexing hole to allow me to accurately bend the radii in a repeatable manner. The mandril I used was actually 3D printed part from shape ways. After 10-12 bends, it lost its accuracy and the profile of aluminum began to flare out. I was able to get 2 successful prototypes out of it, so I didn't leave disappointed. After the bending there was still more work to be done. Fixtures were made to accurately drill and tap the connection piece between both halves of the frame.
Above is a video I sent to my father explaining the construction of the mill. Below is a slideshow of the rest of the steps to get to the final prototype.