A friend of mine was talking about his latest rep-rap project and he mentioned that the stepper motor controller was the most expensive part.
Hmmm...are we not makers? There should be no "expensive" parts. We have the whole chinese continent churning out inexpensive components at our ebay fingertips.
So, I was thinking: 3 hbridges to control 3 stepper motors and an mcp23017 attached by I2c to an arduino to handle any other stop switch/sensor thingies. The hbridges were cheap only a buck or so. Iteadstudio kicked out a pcb after a few weeks, but testing showed that the hridge I selected couldn't provide enough power to drive a NEMA-17 ($15 ebay stepper motor suitable for 3D printer).
So that idea went on the shelf for awhile and then I saw this $4 hbridge on ebay: http://www.ebay.com/itm/L298N-DC-Stepper-Motor-Dual-H-Bridge-Drive-Controller-Board-Module-for-Arduino-/380520063503?
I used them before to drive some rc tanks. They have plenty of power.
And so the idea was reborn. I'll created a github repo to open source the improved schematic and source codes to handle g-codes here: https://github.com/Paulware/3DPrinterController/
. Here is a crappy video: