Filament-Holding Drybox Cap

This Filament Holding Drybox Coupler Cap Gen 3 is a perfect companion to any drybox with (or without) a filament spool rewinding system - such as my Auto-Rewinder for Ultimate Filament Drybox - holding on to the filament so it doesn't get pulled into your drybox when it's not being used for printing AND then sliding on to the PC4-M10 coupler to seal the opening. It works great with any filament type that you might have in your dryboxes - even TPU!

This Third generation of my improved Coupler Cap for the Ultimate Filament Drybox is a complete redo of the original design. It's a 2-part design consisting of all Bambu Lab "TPU for AMS" filament or a flexible TPU 95A Base with a PLA or PETG Knob that snaps on to the Base. You twist the Knob to engage a clutch that firmly grasps the end of your filament, then you slide the Coupler Cap onto the PC4-M10 coupler on your drybox. This Gen 3 version grips the filament very firmly, and it has much smoother operation than earlier versions.

This Filament Holding Drybox Coupler Cap Gen 3 replaces the Coupler Cap from my original Coupler Cap + Adaptor for Ultimate Filament Drybox and my Coupler Cap Gen 2 with TPU Filament Clutch.

This Coupler Cap Gen 3 consists of two parts that are snapped together after printing:

1 - Base - printed in Bambu Lab "TPU for AMS" or similar in 1 or 2 colors OR printed in 1 color with 95A TPU

2 - Knob - printed in Bambu Lab "TPU for AMS" or similar in 1 or 2 colors OR printed in PLA or PETG (or any other hard filament type) - in 1 or 2 colors

The strongest grip on the filament is provided by a Coupler Cap with both the Base and the Knob printed in Bambu Lab "TPU for AMS" - which has a Shore 68D hardness. Other brands and hardness levels of TPU have not been tested - except for TPU 95A - which works nearly as well, but requires the Knob to be printed in PLA or PETG and TPU 85A - which is too soft for this design. The Base must be printed in fairly hard TPU for this design. Multiple colors are not required, but having the raised bumps a different color than the bodies helps make it easier to see when the Coupler Cap is clamped onto the end of the filament.

The following illustration shows the process for assembling a Coupler Cap Gen 3:

If some of your TPU Bases don't print with a smooth internal hole - making it difficult to insert filament - insert a 1.5mm allen wrench and twist a few times to provide smoother entry for the filament - as seen in the following photo:

If some of your Coupler Caps are hard to twist when inserting and removing filament - you can either twist the Knob multiple times after assembly to loosen them up OR you can add a TINY amount of Silicone Grease (not oil) to the shoulder of the Base before assembly - as seen in the following photo:

To use the Filament Holding Drybox Coupler Cap Gen 3:

1 - twist the Knob so that the raised bumps on the side of the Knob are about halfway between the raised bumps on the Base (to release filament clutch)

2 - push the loose end of the filament all the way into the Coupler Cap

3 - twist the Knob so that the raised bumps on the side of the Knob are aligned with the raised bumps on the Base (to engage filament clutch)

4 - push the Coupler Cap onto the PC4-M10 coupler on the drybox

The following illustration shows the process for securing filament with the Filament Holding Drybox Coupler Cap Gen 3:

To remove the Filament Holding Drybox Coupler Cap Gen 3:

1 - pull the Coupler Cap off of the PC4-M10 coupler (the filament should be attached!)

2 - while holding on to the filament and the Base, twist the Knob so that the raised bumps on the side of the Knob are about halfway between the raised bumps on the Base (to release filament clutch)

3 - pull the filament out of the Coupler Cap

4 - load the filament into your printer (or otherwise secure the filament)

The following photo shows a Filament Holding Drybox Coupler Cap holding filament:

The following photo shows a Filament Holding Drybox Coupler Cap holding filament and sealing a drybox:

The following photo shows multiple Filament Holding Drybox Coupler Caps (holding filament) attached to dryboxes using my Auto-Rewinder for Ultimate Filament Drybox:

The following render shows a Filament Holding Drybox Coupler Cap holding filament and about to be pushed onto a PC4-M10 coupler on a drybox:

The following photo shows a collection of Filament Holding Drybox Coupler Caps - some assembled and others not yet snapped together:

To allow modifications, I have provided STEP (.stp) files. The raised bumps on both the Base and the Knob are separate objects to make it easy to colorize parts of your Coupler Cap.

3MF files have been provided for Prusa Slicer (has "-Prusa" in the filename) and for Bambu Studio (has "-Bambu" in the filename). Versions are provided for a single Coupler Cap and for 6 Coupler Caps (since the cereal boxes are usually sold in sets of six). All the provided 3MF files are set up to print the raised bumps in a different color than the part bodies; if you have a single-color 3D printer, then selecting that printer should remap both colors to one filament. The 3MF files with "TPUALL" in the filename include both the Base and the Knob and are intended to be printed entirely in Bambu Lab "TPU for AMS" filament (Shore 68D hardness) - which can be used in an AMS, MMU, or BMCU to print the entire Coupler Cap in 1 color or in 2 (or more) colors. Alternatively, the Coupler Cap can be printed with a single Bambu Lab TPU for AMS filament on any single-color printer.

The Filament Holding Drybox Coupler Caps seen in the photos were printed with White and Red Bambu Lab TPU for AMS (68D) with a 0.4mm nozzle at 0.2mm layer height with concentric top and bottom layers (purely for the visual effect) and a 0% infill density - on a Textured PEI build plate with Kores glue stick applied to allow easy removal from the build plate. Supports and brims are not needed and must be avoided due to TPU's stickiness. The TPU Bases must be printed mostly hollow to provided the required flexibility, so preferably use the provided 3MF files OR be sure that you specify 0% infill density in your slicer settings.

The following illustration shows the hollow interior of the Base prongs when correct slicer settings are used. If your slicer preview shows any additional filament being deposited inside these prongs, then you need to verify the slicer settings to get the desired print:

Be sure to check out my other designs - including universal key covers and a diverse collection of household accessories and 3D printing tools - on Printables at https://www.printables.com/@PhilCaruso/models AND on MakerWorld at https://makerworld.com/en/@PhilCaruso