ERCF EREC Encoder Mounted Filament Cutter

2024-05-25 Repositioned Blade on Cutter Gear (V2) to afford additional clearance mounting screw head to Encoder housing.  Replaced Fusion 360 file and added [a] Cutter Gear v2.stl.

The original design was well thought through but lacked a few features that I needed for my Voron 2.4R2 with ERCF V2:

1. Power Cutter directly from BTT MMB board without the need for a buck converter,
2. Contain filament cutoff so that the filament does not fly off the cutter to places unknown,
3. Improve cut operation by providing a hard surface for the blade to travel over when cutting the filament,
4. Improve the Gear geometry/resolution,
5. Improve the blade recess to better fit the X-ACTO blade profile.

The cutter operation, including lowering the servo peak current, was accomplished by changing the gear ratio, increasing the distance the blade would travel before encountering the filament (acceleration distance), and adding a M3 Hex Nut to the modified Encoder body in a manner similar to Filametrix.  

A boss was added to the cut off slot to capture the cut off portion of the filament and to allow it to drop into a tray located below the EREC cutter.

The drive Gear is designed to accept standard MG996 Servo round accessory adapter which is secured to the Drive Gear with M2 SHCS screws.  See Fusion 360 model for detail.

With the revised gear ratio, Open to Close range is approximately 10° to 170°.  This affords some ability to change the Closed position to align the filament path if necessary.

The Cutting surface was hardened to improve the filament cutoff:

1. This affects both halves of the encoder housings,
2. The Encoder cutout for the hex nut is slightly smaller than the nut and is intended to capture the nut without the need for adhesives,
3. The Hex nut is reamed using a 3mm drill in order to remove any threads which may restrict the filament passage,
4. A 3MM ID PTFE tube was installed between the Nut and the Encoder to ensure low drag filament path.  The Encoder end of the tube was chamfered so as not to present a protruding surface that might catch the filament,

The Gear geometry was generated by Fusion 360 macro GF Gear Generator using the following criteria: