I built a Greg’s Wade’s Geared Extruder for Metal Fisher. The original extruder of Metal Fisher uses a Nema 17 stepper motor which is not enough torque to overcome the internal friction inside Bowden and hotend while in printing.
When the extruder can’t push the filament forward, the hobbed gear on the stepper motor shaft starts grinding the filament.
It’s hard to do quick action when the jam occurrs. Once the nozzle start showing lack of filament, the end part of filament at the bottom of heat sink gets slightly fat due to the heat. As you see the right image, 0.2 mm to 0.3 mm of bulge prevents pulling the filament out.
It would be worst nightmare of 3D Printing because it requires complete disassembly of hotend that takes several hours.
When your 3D Printer prints most models accurately but struggles of complex models that demands heavy retraction, that is a sign of poor retraction performance of the extruder. I had played with setting of Slic3r and Cura, including firmware settings related to flow rate without a clue of the physical flaws of the Bowden extruder.
Shortening the Bowden tube’s length 80% dramatically got rid of hair-scratching tiny strings in printed models. Bulbul Junior with flying extruder upgraded printing quality to next level.
I think the minium gear ratio of extruder is at least 1:5 that makes E step number of the extruder motor over 400 with enough torque. Big E step number does finer retraction.
8 bit RAMPS 1.4 controller (Bulbul Junior) vs 32 bit Duet controller (Metal Fisher)
Duet controller board is five to seven times expensive than cheap RAMPS 1.4 not including the expansion board that enables extra stepper motors.
I didn’t aware that even I never attached LCD display to the board, the firmware was processing LCD routines in printing session that acted as overhead to the 8 bit CPU on Arduino Mega.
I suggest to get best printing quality out of RAMPS 1.4, turning off LCD support.
Greg’s Wade’s Geared Extruder
Adjustment of idler tension is tricky. I need to modify the body for mounting on the Metal Fisher’s side panel.
Parts required manual labor: Idler, M8x60 hobbed bolt, four M4 washers
M8x60 hobbed bolt