Summary

NOTE: This is for the AMZ version 1, the new Mega Zero v2 seems to need the mounting point resized a bit before this will fit. The FreeCAD project is included if someone else would care to remix things to fit that version, or I may try to come back and update this later myself if I have the opportunity.

After seeing variations of the filament guide, I decided to make my first "from scratch" freecad project. This filament sensor for the Anycubic Mega Zero re-uses the "go big" filament guide wheels from [https://www.thingiverse.com/thing:4683505](https://www.thingiverse.com/thing:4683505) that I had already printed. I also copied some of the dimensions for the screw less mounting bracket slot from that same project to ensure a similar perfect fit of my design.

The sensors are inspired by the idea behind [https://www.thingiverse.com/thing:3319350](https://www.thingiverse.com/thing:3319350) and the wiring and configuration should be similar.

Switches should be wired in series, in their normally open positions, so that they are "closed" when the filament sensor is depressed and the tangle arm is in it's relaxed position. The circuit should be connected when in a printing-ready state. Switches should be connected between signal and ground on the filament sensor plug on your board. Marlin can then be set to read them in the same manner as the endstop, where either switch being triggered will activate a pause in marlin while awaiting user intervention.

My Marlin/Configuration.h contains the following changes:

#define FILAMENT_RUNOUT_SENSOR

#define FIL_RUNOUT_STATE HIGH
#define FIL_RUNOUT_PULLUP

I used these amazon microswitches and modified them by pulling the metal arm off with pliers as required. These are also conveniently compatible with this excellent allen key bed probe that is also designed for the Mega Zero.

4/10/21 v1.1b

Repaired the missing filament guide tube that should have been present in v1.1

4/9/21 v1.1

Updated to allow reverse feeding of filament through the runout sensor, allowing for direct mechanical attachment to the extruder intake tube without jamming on runout. Also add a zip-tie loop to remove strain from the electrical connections.

3/29/21 v1.0

Initial public version

Print Settings

Rafts:

                                            Supports:                      
Yes

Resolution:

0.20 mm

                                            Infill:                      
20

Filament: Hatchbox PETG

                    
                        Notes:                     
Supports are required around the mounting nut cut out, as well as the bearing "fingers" on the arm if you print flat. Alternatively, if you print on supports in a mostly "upright" position you might find the part easier to prepare after printing at the expense of using more time and plastic.
PETG is basically required as a material, due to the extreme flex requirement for the jam sensor. You might be able to reverse the switch to make it more sensitive, but testing any other material is left as an exercise to the reader.

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