Summary

3D prints can fail due to filament misfeeds - which is a problem if a print takes several hours and stops part way. This project combines a physical filament monitor, some simple electronics and a Twine to create a monitor that emails you with the printer status; fully operational, filament feed stopped and printer stopped.

Instructions

The monitor has 3 components:

1 Filament movement monitor
The photo shows the filament movement monitor, which is a small cylinder mounted on small ball bearings. (3mm, 8mm ID, 12mm OD, available from hobby shops). There is a small rare earth magnet in the rotor which triggers a small reed switch twice every rotation. The filament contact area of the rotor has a thin layer of blue-tack to make it sticky... There are STL's for both a single and dual extruder Replicator. There is also a Rhino3D file of the model. The monitor attaches to the filament feed tubes and is quite stable in this position as you can see from the photo.

2 Interface circuit
The attached schematic provides the information you need for the electronic interface. The circuit is powered from the Twin'e breakout interface, which provides 3V DC. The circuit draws less that 20 microamps, so is not really a consideration in the scheme of things... The rotor movement is sensed using reed switches, that open and close twice per rotation. The circuit uses a CMOS 4030 XOR to create pulses on switch open and close and combine them into a single (slow) pulse stream. A CMOS 4047 Astable device is configured as a retriggerable monostable circuit, providing a high output as long as there is some rotation detected every 40 seconds or so. This covers filament movement for all practical feed rates. This output signal is passed to the Twine through the latters breakout circuit. The circuit schematic is attached as an image and an EAGLE design file.

3 Twine email messaging
The Twine offers a range of useful sensing options; temperature, breakout status, Twine orientation and vibration. For this application I set up rules so that the monitoring function would be activated when the Twine was set on its side, on the printer top. (Exposing it to as much printer vibration as possible!) The Twine emails me when the printer is fully operational (vibration sensed and filament in motion), when the printer is stopped (vibration ceases) and when the filament feed is disturbed (vibration sensed, but no filament feed).

Sourcing materials:
In Australia, www.jaycar.com has all the electronic materials, magnets and reed switches. The Twine comes from www. supermechanical.com. I found the ball bearings at www.hearnshobbies.com. The total cost of the materials was less than $20.

Filament monitor for Replicator 3D printer