Dual feed extruder by rcmonitor by rcmonitor

Last crawled date: 3 years ago

Developed to extrude 3mm (2.85mm) filament via E3D hotend.
Can be modified to use 1.75mm filament by making appropriate hobbed axles.
X carriage mounting bolts offset 24mm

Design goals:
improve extrusion accuracy;
improve extrusion stability;
improve filament reaction;
increase filament pressure;
decrease filament slipping possibility;
increase retraction accuracy;
increase X-axis available print length;
provide easier maintenance;
improve attachement to X-carriage;
achieve low weight;
provide cable management;
Pros:
extrusion is very accurate (+/- 1mm calibration on 100mm extrusion);
very stable results even under pressure (important for first layer on non-planar heatbeds);
very accurate retraction due to almost no backlash;
high maximum filament pressure due to bigger hobbed axle diameter and two hobbed axles;
filament is more responsive due to reduction of length between hobbed axle and nozzle;
extruder stepper motor not crossing Z threaded rod on the left side, so X homing point can be moved to the left (I was able to reach 216mm X by 206 mm Y print area after some heatbed modification);
designed to be easily opened to change filament / cleanup;
remembers filament hold-down tension setting;
gears and hobbed axles can be removed with no tools (nuts can be placed, but are redundant);
places for zip-ties to get cables in place.
really lightweight (for dual extruder) due to hk1210 bearing usage for hobbed axles. With aluminium axles only 90 grams heavier than Wade's extruder;
no need to center drive gear;
more steadily attached to X-carriage due to bigger attachment plane.
Cons:
parts are not easily-printed, especially extruder body and clamp plate;
lots of work to remove supportive structures from body and clamp plate;
lathe required to craft hobbed axles;
some parts are not easy to obtain (M3x50 bolts, M2 threaded rod);
Y axis print area moves 10-15mm towards Ymax (can be fixed by Y-axis calibration).
BOM
printables:
extruder body 1pc
drive gear 1pc
big driven gear 1pc
small driven gear 1pc
clamp plate 1pc
latch 1pc
latch fixer axle 1pc
latch fixer axle knob 1pc
hardware:
DIN 618 hk1210 bearings 4pcs
DIN 625 skf 608 bearings 2pcs
bolt DIN 912 M3x50 3pcs
bolt DIN 912 M3x45 2pcs
bolt DIN 912 M3x14 4pcs
setup screw DIN 913 M8x30 2pcs
setup screw DIN 914 M3x6 1pc
screw DIN 84 M2x12 1pc
nut DIN 934 M3 4pcs
nut DIN 934 M2 5pcs
washer DIN 125 M3 6pcs
either
bolt DIN 931 M12x80 1pc
bolt DIN 931 M12x100 1pc
or
hobbed axle 12x72 1pc
hobbed axle 12x94 1pc
nut DIN 439 M12 2pcs