i made a DIRECT variant of the original beltless design for 1.75mm filament. the heatsink mount is a bit tight so i'll forego the clamp for now, but i'll fix this in the final revision. requires 4 x 25mm M3 screws, L-bracket, 4mm OD bowden tube running down the length of the heatsink.. i guess the clamps will need 2 x 10mm M3's. the original (light blue) design is still running problem free but i'm going to try some direct extrusion since i'm using a moving XY plane/bed and a stationary hot end.
i'm just finishing designing the belted variant of the sliding tension block extruder. the picture does not show the 60T pulley or the 5mm drive shaft. this is one of my last projects for countersynchronized FDM as i transition to SLA/DLP resin which will use my existing table frame and a very similar Z-axis.
the belted 20T ---> 60T extruder was mainly designed for extra torque so i can finally use 2 spools of 3mm filament i bought 3 years ago... but once i perfect it, i'll include both a 3mm and 1.75 (maybe both in one) design. i have 2 sliding tension blocks in this extruder (48mm NEMA 17) but it can go up to 3 depending on how flat the M4/M5 tension block bearing screw is.
this will mount using a standard, metal, NEMA17 L-bracket and should work w/ both direct and bowden. i just have to figure out a standardized drive gear that does it all (which is unlikely).
in case you're wondering... the stepper is screwed in at the TOP and BOTTOM.
EDIT5: DO NOT print the NEMA14 extruder. besides being cute, this thing is totally useless and underpowered. the only way a NEMA14 will extrude reliably is w/ GEARS or if you can find one w/ holding torque around 30 oz-in or greater... mine at 14 oz-in is definitely not up to the task.
EDIT4: i had some parts left over and a NEMA14 that was begging for something to do, so i redesigned the extruder and posted WIP STLs. everything on it feels right so it should be OK. i'll test/reprint NEMA17 shortly thereafter. corrections to Tension Block: i think its an M4 x 12 holding the U-Groove bearing in place, but my M4 x 10 works just fine. also, NO washers above/below U-Groove bearing (if i used bridges then NO and if i printed supports then MAYBE).... i'll clean this page up soon and move on to something else. NEMA14 variant was printed too short/tall so i'll fix that later. NEMA14 height adjusted for M3 x 25mm, i just used the hex nuts as offsets in the picture, posted STL should be 1 "nut" taller (~2.4mm).
EDIT3: Tension Block rail gap is too tight. i'll adjust the gap so it slides properly.
i still have to adjust 45 degree diagonals on both extruder and tension block since most people (including me) print infill at 45. this should optimize print time by minimizing unnecessary movement.
i posted the right STLs after comparing the files i was uncertain about. the extruder now has the right hole size for tapping M6 thread. the one i originally posted was exactly 6mm which wouldn't allow the right thread for the bowden tube fitting. the test block remains the same... i just renamed the file. the confusion stemmed from not being able to fit the M4 hex bolt into the tension block, but i'm pretty sure i cleared that up. it should be fine, but let me reprint, reassemble and test it before i give you the green light--i wouldn't want you wasting filament on a zonk.
if people are finding it difficult to print M3 holes on the first layer, i might modify the extruder STL by filling in the holes on that layer.
also, if people want to modify this thing for 3mm filament or make other changes, i can post the pre-booleans BLEND file for them.
i made this thing a year ago, but only started using it recently. its heavily inspired by the Bulldog XL so i have to give credit where credit is due. i'll try to post the last STLs i exported from blender and hope that they're the right ones.
this page will be edited and revised once i figure things out. don't make this thing just yet.
here's what you'll need:
1) NEMA 17 Stepper Motor
2) 11mm MK7 Drive Gear
3) U604ZZ (604UU) Grooved Bearing (13mm OD, 4mm Height, 4mm ID)
4) M4 x 10mm Screw to secure the Grooved Bearing
5) 4 x M3 x 20mm Screw to attach Extruder to Stepper Motor
6) M4 x 25mm HEX Bolt to attach the Tension Block to the Extruder
7) M4 Flat Washer (between spring/extruder, and above/below U-Groove Bearing)
8) Spring (mine is about 8.2mm OD and 10mm Length)
9) M4 Wingnut to adjust Tension Block
Extruder and Tension Block
Screwdriver, Drill, M4 and M6 Tap, File/Sandpaper (optional--to clean up the printed parts)
M4 tap requires 3.3mm drill hole, and M6 requires 5mm.
--threading the 1.75mm filament is a challenge if its tightly wound (end of the spool)
--no practical application since i just use it the way it is, but really it should have some mounting holes to attach to a frame.
if anyone requests a different Bowden fitting, i'll post more STLs to correspond w/ your thread size.
-- print both parts (extruder and tension block)
-- clean up both parts: drill through 4 x M3 holes w/ 3mm or 1/8 bit, drill through M4 Hex Bolt w/ 4mm or slightly larger non-metric bit. drill down through tension block using 3.3mm bit or 1/8" (~3.10mm) also drill through any other holes to make em nice and round
-- tap M4 on tension block and M6 on extruder after drilling through w/ the right bit
-- assemble everything as shown BEFORE mounting it onto the stepper motor
i printed w/o supports. your printer should be able to print ~1.8cm bridges on the tension block.