Last month, I made a XY-plotter by Makeblock and use it to built a Drawing Robot.
This Drawing Robot was built with two Linear Motion Shaft D8x480mm, two Long Beam0824, the timing belt, two stepper motors, two stepper motor driver, and a micro-controller Arduino. You can send a picture from the phone or you can take a picture by the phone and then send it to the robot by Bluetooth. After that the robot will draw what you send.
The instruction will show you how to build a XY-plotter.
For the program process, please visit the user guide. It contains both the turtorials of how to use Android app to control XY-plotter, and how to use Gcode to control XY-plotter.
If you have any question about it, pleas visit the troubleshooting of XY-plotter to help yourself. Or you can just post your question on the forum, I will give a response in minutes.