I have attached a motor to the front roller. This task contained two components: Physically attaching the motor to the axle and implementing a controller for the motor.

I upcycled the motor from an old robotic vacuum. The motor is a simple 12 V DC motor. The motor had an integrated optical sensor, but I was too lazy too incorporate this into my mechanism. 

[Figure 1: Motor Salvaged from bObsweep Robotics Vacuum]

I designed a simple adapter that connects the motor to the front axle. I connected the motor to the axle and then I designed the mount that connects the motor to the bed. This order ensures that the motor axle is concentric to the roller axle.

[Figure 2: Axle Adapter Attached to Motor-]

[Figure 3: 8-32 Hole for Adapter]

[Figure 4: Motor Connected to Front Roller]

[Figure 5: Motor Secured to Bed with Motor Mount]

I powered the motor with an upcycled 120V computer power supply. Before adding logic to the circuit, I ran a few tests with the motor.

[Figure 6: Testing Printing on Conveyor Belt]

[Figure 7: Testing Ejection System]

It is important to note that the skirt of the print is not ejected by the conveyor in the shown example. After adding the shear, the skirt is also removed consistently.