http://www.printrbottalk.com/forum/viewtopic.php?f=21&t=10161&sid=43bd6e0fb99d9607e14244c38be85f99

Printrbot Simple Maker’s Edition 1405 (aka my “PrintrBro”)
Z axis extension, X axis extension
custom designed legs
280x100x175
Octoprint/Raspberry Pi B+/Octopi Linux Distribution/Dev Branch
Custom Printrboard Case with inline LCD on/off switch for printer

The route I went for my 1405 was to upgrade the Y axis using Jon Lawrence’s No Sag 300mm Double Precision from thingiverse (which I believe is the same for the old Simple). For that all you’ll need is longer 8mm hardened rod, longer GT2 belt, some skateboard bearings and the 3d printed parts (A drill to clean up the rod/screw holes helps but I managed without). If you want to upgrade the X or Z axis then it can be even more simple (heh). For X, just get new belt and new rods and install (or go for Jon’s X axis upgrade for more stability), and for Z you’ll need a new lead rod (can be purchased through printrbot or external vendors) and hardened rods. Most of the parts you actually need to buy are really cheap on their own (to do the Y and X upgrades only costed me ~$70-$80 not including plastic). Some other options to upgrade past this are getting a heated bed, a new extruder such as the E3Dv6 (or even a dual extruder if you’re feeling adventurous), an LCD screen/Rasberri Pi (which I see you have)/Both setup for better autonomous printing, changing to a bowden style extrusion system (more preference based), or any number of cosmetic mods.

So yeah, there’s a lot of options. I’d say buying some new rod and belt and doing Jon’s axis upgrades is a great place to start, as it’s really nice to have a larger print area. Something to note is that especially if you do the X upgrade (which I recommend because double precision is great), you should also consider purchasing some 40×40 mm fans for active cooling to prevent your hot components (stepper motors, hot end, heated bed) from melting the upgrade. Along with those I would get a beefier power supply (I got a 600W ATX power supply from newegg for $30 to use with my heated bed and fans) to power any future upgrades you may need. Also, for the actual bed of your printer, look around for any metalworking shops in your area that do small orders. If you’re in the southeastern area of Michigan (I saw your remark about the detroit maker faire), there’s a place called speedy metals in Livonia that’ll cut you any size piece of 3003 aluminum for pretty cheap. The 16″ x 9″ piece I ordered took an hour before it was ready to pick up and was only like $25.

I hope this’ll help, using a machine to upgrade itself is truly something special.