FDM 3D Printer Flow Manager (1 nanometer sensitivity)

https://github.com/TimIsabella/FDM_3D_Printer_FlowManager
(see GitHub for Arduino code used in this project)

FDM 3D Printer Flow Manager (1 nanometer sensitivity):
Possibly the biggest issue in FDM 3D printing is flow control, and the reasons for this are as follows:

- Inconsistent filament diameter
- Improperly calibrated flow rate
- Extruder skipping

Any one of these can cause bad prints or failed prints, which is both costly in material and time.

Flow Manager is an attempt to control all three of these critical parameters, and in addition will yield consistent layers which means better looking and better performing prints.

How?
By measuring the filament diameter as it is fed, an exact flow rate can be calculated to ensure a consistent flow. Flow Manager measures this filament diameter by two points offset around the circumference of the filament (offset as a triangle), and averaging those points with a precision of up to 6 digits beyond the decimal, which results