This first drawing is a proof of concept. 3 hours to complete. A cheap 0.7mm HB mechanical pencil. An Arduino Nano to control the contact force between the pencil and paper and to dispense pencil graphite as needed. An Arduino Uno running GRBL and GRBL shield to control the 2 axes. G-code file generated using LaserGRBL. CNCjs as the g-code sender software. About 12 hours of troubleshooting and system tuning before achieving this level of drawing quality. 

Next step is to achieve sharper transitions and higher contrast by increasing the speed of the pencil control response and/or increasing the duration between movements to match or exceed the pencil control response. I can start to play around with different pencils and multiple passes after that.