Stand-Alone Auto-Rewinder

This Stand-Alone Auto-Rewinder allows my Auto-Rewinder for Ultimate Filament Drybox design to be used without a drybox OR with a drybox other than the cereal container used with @GunplaMark's The Ultimate Cereal Container Filament Drybox.

This design provides automatic filament spool rewinding to help eliminate tangled filament due to MMU or BMCU retraction during filament changes - without requiring a filament buffer! You can use it for a single spool of filament OR use the included Snap-On Clamps to join any number of spools together side-by-side! It can also be used without a filament changing system to help ensure tangle free spools whenever you unload filament from your 3D printer; if used in this way, be sure to secure the end of the filament to the spool to prevent filament unwinding during storage.

This design supports 1kg filament spools that are up to 68mm (~2.68") wide with a diameter up to about 204mm (~8.03") and a center hole diameter of at least 50mm (~1.97"). Most 1kg filament spools should work as long as they are within these size constraints.

1kg spools of Bambu Lab PETG and PLA, Prusament PETG and PLA, Sunlu PETG, FilaCube PLA, Yxpolyer Nylon (PA), and several other filament brands/types are known to work well. Prusament ASA and PC Blend spools are a bit too wide for this design.

You typically don't want or need to use this or any other Auto-Rewinder with TPU (Flex) filament, since it usually won't push back onto the spool and cause tangles when it's unloaded. If you do want to use a Stand-Alone Auto-Rewinder with TPU spools for uniformity, then I recommend that you disable the rewind feature by leaving out the piece of the spring that has the gears; this will allow smooth rotation without rewinding the spool!

Except for the optional TPU (Flex) Drum Sleeve, all of these parts are intended to be printed in PETG, though PLA should work as well. The TPU Drum Sleeve is recommended to provide more friction when using plastic filament spools. This version has a lip at each end to keep the spool from slipping off the edge of the drum, so it's hard to slip Prusament spools on due to the small center hole size on Prusament spools.

A complete Stand-Alone Auto-Rewinder requires two 608RS bearings and the following 3D-printed parts:

1 - Drum Assembly - consists of a Drum and a Drum Cap - included here in the 3MF file, but if you wish to make changes to these parts, then you'll find the remixed design file in my Auto-Rewinder for Ultimate Filament Drybox.

2 - Spring Assembly - consists of a 7-part 3D-printed Spring - included here in the 3MF file, but if you wish to make changes to these parts, then you'll find the remixed design file in my Auto-Rewinder for Ultimate Filament Drybox.

3 - Saddle - two (identical and interchangeable) saddles - included here in the 3MF file, but if you wish to make changes to this part, then you'll find the remixed design file in my Auto-Rewinder for Ultimate Filament Drybox.

4 - Axle Assembly - consists of an Axle and two (identical and interchangeable) Axle Flanges - included here in the 3MF file, but if you wish to make changes to this part, then you'll find the original design file in my Auto-Rewinder for Ultimate Filament Drybox.

5 - Base - new part that is placed on a flat surface and has openings for a Saddle on each side to allow use of the Stand-Alone Auto-Rewinder without a drybox OR with a drybox other than the cereal container used with @GunplaMark's The Ultimate Cereal Container Filament Drybox. You can use the included Snap-On Clamps to join any number of spools together side-by-side! Note that the Saddles fit very tightly in the Base to ensure solid, reliable operation; carefully press the Saddles into the Base until fully inserted as per the following photo, and feel free to apply a thin coating of clear RTV silicone to the bottom of the Saddles if desired to make assembly easier.

6 - TPU Drum Sleeve - optional - a TPU (Flex) sleeve may be used to provide suitable grip on plastic filament spools. When used properly, a spool with a drum sleeve should be centered on the Drum and be able to wind the Spring on the Drum but still allow slippage when the Spring has been wound more than a few full turns. It is designed for spools with a center hole diameter of 54mm (~2.13") or more and a maximum spool thickness of 62mm (~2.44"). This sleeve remains on the Drum at all times. I recommend TPU 95A filament - since softer TPU (like 85A) will likely be hard to install on the drum and have too much grip on the spool.

7 - Clamps - new optional part that can be snapped onto Bases to join two Bases together side-by-side - repeated as many times as desired. Two Clamps are needed for each pair of Bases to be joined.

The non-3D-printed parts that I used are:

608 RS Bearings - two required - https://www.amazon.com/dp/B09PKD8QZZ - pressed into each end of the Drum Assembly

You can use the parts linked above or any equivalent parts.

The following photo shows all parts included with this Stand-Alone Auto-Rewinder:

The following photo shows a single assembled Stand-Alone Auto-Rewinder ready for use:

The following photo shows a single Stand-Alone Auto-Rewinder in use with a spool of filament:

The following photos show four joined Stand-Alone Auto-Rewinders as might be used with an MMU or a BMCU:

The following video shows the Auto-Rewinder in operation. The video shows the cereal box version, but the rewinder parts are identical to the standalone design. The important thing is that the spool must slip when the spring is wound the full 4 or so turns - since there is no internal clutch.  The video begins with the spring already fully wound and the spool slipping (as intended) on the drum. At the end, the spool rewinds as the filament is retracted from the MMU:

https://youtu.be/BG8dOWd7sr8

Please refer to the Auto-Rewinder for Ultimate Filament Drybox design on which this Stand-Alone Auto-Rewinder is based if you need further details on how to assemble the Drum and Spring Assemblies, the Axle Assembly, or any other part that isn't new with this design.

To allow modifications, I have provided STEP (.stp) files for te new Base, Clamps, and TPU Drum Sleeve.

PrusaSlicer 3MF files have been provided for ALL parts as well as for the new individual parts and the TPU Drum Sleeve; I used transparent Giantarm 95A TPU for all my TPU Drum Sleeves.

None of the parts should require supports or brims. All parts are designed for a 0.4mm nozzle at 0.2mm layer height. Default settings for walls and infill should be fine - no special values for these settings are required.

Be sure to check out my other designs - including honeycomb storage wall (HSW) accessories, universal key covers, and a diverse collection of household accessories and 3D printing tools - on Printables at https://www.printables.com/@PhilCaruso/models