I have started building a Prusa I3. Purchased the plactics off ebay and planned to cut the plates on my G704. I could not get TurboCAD to open the DXF files for the original designs. Found where thainfamousnate posted his version with aluminum upgrades. His files opened no problem.
prusa i3 aluminum frame w/ aluminum upgrades by thainfamousnate - Thingiverse
Once I started looking at dimensions, I realized my G704 was not going to have enough travel in the Y axis. I split the frame into two pieces with a spacer bar between the halves to get the width needed. The design of the frame, braces, and brackets by thainfamousnate is well done. I used a 1/8" 2 flute solid carbid endmill. At 6" a minute, it took 1.5 hrs to cut one half. Slow, but results are very good.
So far, I have cut the main frame, the brackets for the motor mounts, and the brackets for the top mounts. I discovered .25" aluminum may not be .25" thick. Mine is .258". This made assembly a bit of a challenge as the holes for the brackets are all laid out for .25". A small file and a rubber mallet persuaded the pieces into place.
Still need to cut the back braces and the deck.
I order a rod kit off ebay. The Y axis assemble easily. Still need to purchase electronics.
I will try to keep this updated as I assemble parts.