The Precious Plastic machines are on Orchard, which is like Github for open source hardware ( https://3DOrchard.com ). On Orchard, we can collaborate on the design of the machines from right within the platform (with the free, built-in CAD), or if you have your preferred CAD you can just upload revisions.
Here’s the Shredder: https://3dorchard.com/app/single/5939b97b98473c0d2e723eb5/593a1ffb98473c0d2e7240fa
On the right, you’ll see the Orchard tree. Next to that tab are the comments and finally the list of parts (pictured below). You can copy the components from any of the machines to remix and add to the other machines (and the tree will grow).
There are written tutorials here: http://learn.3dorchard.com/tutorials/beginner/getting-oriented-with-objects-on-orchard-part-1-of-2
If videos are your thing, there are quick searchable video overviews in the top-right help (“?”) button.
Orchard is still clunky in some areas (it’s still in Beta and there are just three of us), but hopefully, it can grow into a helpful location to collab on the designs!