Me and my friends mechatronics company EDM OÜ cooperated. The result - automated drilling machine for a factory. Machine uses stepper motors to move aluminium rails and drills holes in them. Then it uses a saw to cut it necessary length. The machine is controlled from touchscreen connected to raspberry pi. Software gets in files with drill and cutting information and sends commands to low end. In the low end there is an Arduino Mega that controls bunch of stepper drivers. As necessary for such devices - everything is optically isolated.
EDM made all the mechanics and integration. I designed and made the control electronics and wrote the software. The most interesting part was writing stepper pulse generator with acceleration and deceleration. Also we found out that rotary encoders need interrupts to give proper feedback, because of small vibrations.