To make a 3DP I needed to not only automate the "reset" but also, precisely control the movement of 2 bins, switch a dc motor on an off, and be able to tell the printing computer to "wait" and not send the next page until the printer is ready. I could have built a dedicated circuit to do all this but as I stated earlier, My knowledge of electronics is limited and I don't have a clue how to program a PIC. I decided instead to go with a CNC setup. The inkjet still does all the actual printing then the CNC takes over and re setts the gantry, adjusts the powder bins,spreads the powder, and then tells the printing computer that it can send the next page. You can see in the diagram that PC 2 has replaced the pulse generator and a relay has replaced switch 2. Additionally, 2 more steppers and a 2 axis stepper driver have been added. Switch 4 gives feedback to the control program and signals the change from the print to the recharge cycle. Relay 2 breaks the connection on pin #11 of the inkjet's parallel port. this tells the PC that the printer is "busy" so it wont send another page until the printer is ready. Relay 3 is connected to the motor that runs the powder roller. The breakout board is a convenient place to make all the connections to the parallel cable and PC 2. Note that the parallel port of the PC doesn't output enough current to drive a relay directly so I used the outputs to switch transistors that supply 5v to the relays.
For the CNC control I use TurboCNC and a G-code program. The program is a step by step set of instructions which can be used to set the logic state (high/low) of the parallel port pins. Also, pins can be monitored and step pulses can be sent to the stepper drivers.
Hopefully this helps clarify what I've done. If I haven't answered your questions feel free to ask.