Filament Spool Rewinder

This model was inspired by several spring actuated rewinders on Printables.com.  Chief among these was:

• https://www.printables.com/model/678300-compact-spool-auto-rewinder

This model is parametric allowing varying hub diameters and spool widths.  Ranges tested:

• Hub Diameter (insert_diameter):   50mm- 70mm (Default = 55mm)
• Spool Width (spool_height):          40mm - 90mm (Default = 70mm)

The .stl files in this version were generated using the defaults.  A Fusion 360 .f3d model file is also included for those wishing to vary the spool widths and lengths.

The Hub is an enclosure that contains the remainder of the parts.

At the heart of the rewinder is a coil spring taken from a retractable key ring.  I tried several badge retractors but found they lacked sufficient torque to rewind full filament spools.  See BOM for procurement.

A torsion slip clutch is incorporated to allow the retraction mechanism to slip at the connection of the Break to the Pressure Plate.  A small amount of light grease is applied to the mating surfaces to reduce the break-away force.  Without this grease the filament will playout until break-away force is reached and then the Break will allow a large percentage of stored kinetics energy to playout all at once, leaving little force to rewind the filament if it were to be unloaded immediately afterward.

The Pressure Adjuster is threaded into the Break and applies force to the Pressure Plate and in turn to the Break.  This force is adjustable.  A Tension Tool is provided to assist with the adjustment.

The Pressure Plate is coupled to the Spring Housing which contains the coil spring. The end of the coil is attached to the housing and the other is inserted into the Shaft which extends the full length on the rewinder.  See instructions below for how to load the coil spring using the Spring Loading Tool.

Both ends of the Shaft can accept a fitting that attaches the completed assembly to a stand. Mount is provided as one example of the Shaft end.

A Spring Retainer is provided to secure the coil spring to the Shaft.  This retainer extends into the Spring Housing and Spring Closeout in order to provide strain relief.

Three 608ZZ bearings support the Shaft at both ends and on the outboard side of the Spring Closeout.

The Hub tapers to a 33mm threaded tube extending to the length specified by spool_length.  spool_length is measured from the back side of the fixed Hub flange.  In the default case this is 70mm.

The Hub assembly is inserted into the spool center hole and secured by the threaded Nut.

Preparation

Note: The photos in the Gallery are ordered in sequence to assist with the following assembly.

1. Disassemble KEY_BAK Retractable Reel.  Retain only the coil spring.
2. Print all .stl parts
3. Inspect the Pressure Plate & Break and remove any seams or imperfections using 400 grit sandpaper.  The mating surfaces must be smooth to the feel.
4. Insert one Mount to the end of the Shaft closest to the printed ring on the Shaft.
5. Place the Pressure Plate into the Break.  Make sure the two mate smoothly and the bottom of the Pressure Plate is flush with the bottom of the Break.
6. Partially screw the Pressure Adjuster into the Break.  The Pressure Adjuster should be 1mm above the top on the Break.
7. Insert a 608ZZ Bearing into the Pressure Adjuster.
8. Insert the Shaft with a Mount installed through the hole in the Pressure Adjuster, long stem 1st.
9. Install the Spring Housing onto the Pressure Plate flanges that are extending through the Break.
10. Insert a few coil loops of the spring catabolized in step 1 into the Spring Housing leaving the remainder coiled outside the Spring Housing.  There is a slot in the Spring Housing that accommodates this transition.
11. Insert the coil tab into the slot in the shaft and place the Spring Retainer over the Shaft capturing the spring.  Make sure the retainer is full inserted into the 11mm hole in the center of the Spring Housing.
12. Install the Spring Loading Tool over the Spring Housing.
13. Turn the long stem of the Shaft counterclockwise until the coil is full loaded into the Spring Housing.
14. Remove the Spring Loading Tool and install the Spring Closeout.
15. Install a 608ZZ bearing into the Spring Closeout.
16. Install the M6 E Clip Ring on the slot in the shaft.  It should be just visible above the 608ZZ bearing.
17. Insert the spring/break assembly into the Hub.  The shaft should protrude 8mm out of the end of the Hub.
18. Install a 608ZZ bearing into the end of the Hub.
19. Install a E Clip Ring into the slot cut into the Shaft 7mm from its end.
20. Install the final Mount onto the end of the Shaft.
21. Screw the Nut onto the threaded portion of the Hub after inserting the Hub into the intended spool.
22. Finally adjust the tension on the Pressure Plate by tightening the Pressure Adjuster using the Tension Tool.  The Pressure Plate should smoothly slip in the Break when the spool has rotated between 4 and 6 times.  Be sure to properly lub the mating services per above.  The slip should be smooth and leave at least 3 revolutions of kinetic energy in the spring.

BOM