J-Struder : 1.75mm Bowden Extruder For NEMA 17 Motor

Update 2019-08-21 :
Version 4 guide: use collet and clip to secure bowden to guide, use genuine E3D 4mm bowden collet for 1.75mm filament, the clones are too big and will not fit

Update 2019-02-02 :
Version 3 guides : enlarged fitting hole radius by 0.1mm for easier mounting and to prevent cracking, added tensioner to guides to allow for spring tension adjustment, use 15mm or the stock 20mm spring, 2 tensioner length provided. If you prefer the fixed tension, continue using version 2

Update 2019-01-27 :
Version 2 base : minor tweak, use 8mm m3 lock bolt, added base with tube support

Update 2018-11-04 :
Version 2 guides : improvements to guides: minimize gap to optimize for flexible materials, use M4 nut to secure bearing

Update 2018-09-14 :
Version 1 : improvements on the base (retraction stabilizer and reinforcement) and guides (more room for gear, plunger, rounded edges)

This design is inspired by SeeMeCMC EZR Struder, I had been using it for over a year on my CR-10 until it finally broke on me. This is designed for the NEMA 17 motor. The head of the knob when inserted between the spring base and the guide will hold the spring compressed when assembling and feeding/removing the filament.

3 options for the filament feed end:

1. Direct
2. Fitting
3. Bowden
4. Collet

The bearing, M4 lock washer and spring are from the stock CR-10 extruder.

Bearing is U604zz available here:
https://www.reprap.me/creality-3d-cr-10-extruder-bearing-filament-pulley.html
https://www.3dprima.com/parts/spare-parts/creality-3d/a-22668
https://www.spool3d.ca/u604z-bearing
... also available from aliexpress

Alternative bearing is 694zz, 11mm od x 4mm id x 4mm thick.

Other hardware:
2x M3 20mm socket head cap hex bolt (through 3mm plate on CR-10)
2x M3 10mm socket head cap hex bolt (through 3mm plate on CR-10)
1x M3 8mm socket head cap hex bolt (for version 2 base)
1x M3 6mm socket head cap hex bolt (for version 1 base)
1x M3 nut
1x M4 10mm
1x M4 nut (for version 2+ guides)
1x PC4-M6 fitting, 2x when using "fitting" end

Print the base and guide at 0.12mm or higher, this requires your printer to be properly tuned, the gaps are 0.15mm on each side. Use ABS or PETG, PLA will work if you are not using an enclosure. 100% infill recommended for printing base

Assembly:

1. Insert M3 nut in base and screw in the M3 6mm bolt, don't tighten
2. Screw fitting(s) to the guide, push in a piece of bowden tube where applicable
3. Using the 10mm M4 bolt and lock washer, secure bearing to the guide
4. Slide assembled guide into base
5. Insert spring
6. Insert knob head between the spring base and guide to compress spring for easy assembly
7. Attach to motor/printer

Usage:

1. Loosen the M3 6mm lock bolt before pressing the spring
2. Press spring and insert the knob head between the spring base and guide gap
3. Unload or load filament
4. After loading filament, remove knob head between the spring base and guide
5. Tighten the M3 6mm lock bolt

https://youtu.be/GqlBTxhC-ZU