I started out wanting to build a CNC/3d printer originally, but eventually realized that 3d printers and CNC machines are completely different machines. For CNC, you want strong and slow. For 3d printers you want agile and fast. These two competing objectives make a combo machine kind of impractical. Now that I have a 3d printer and feel fairly comfortable with the additive process, I've decided to design and build a CNC machine. I'm planning to go small with my first design. I'll probably end up regretting this (I wish I had gone bigger on my printer), but I just don't have the room for a big machine. I'll use this page to document the progress.
Designs
Ooznest OX CNC Machine
Seems like the OpenBuilds Ox is one of the most common DIY designs. I almost went with a similar design on my 3d printer, but eventually opted for the more streamlined corexy system instead. For a large CNC machine, though, their wheel/slot-based linear rail system makes perfect sense since it integrates the linear rails with the frame. My only concern is that it seems like dirt, debris, and chips would find their way into the slots and could affect large jobs.
The biggest challenge on the construction side will be the aluminum plates. I'm toying with the idea of 3d printing these plates and seeing how well it does. I don't see a lot of people going this way, though, so I suspect there's too much flex. Still, I wonder if I could make it work long enough to (slowly) create some replacement aluminum plates.
Root 2 CNC multitool router 3D printed parts
This is a smaller, mostly 3d printed design. I don't think it would scale to a larger, more beefy machine, but it might be a good way to get started. I might also be able to borrow some of the ideas for a larger build.
The Mostly Printed CNC
Really like this design, but unfortunately I already have some larger NEMA 23 motors I'd like to use. I'd love to borrow some of these ideas, though in order to bring the cost down on the Ox.