MultiCore: Multi-Filament Spool Accessory

💡 The "Why": Solving the Leftover Filament Problem:
We all know the struggle: you finish a project and are left with 30g or 50g of filament. It’s too little to justify taking up a whole slot on your shelf, but too much to throw away.

I designed this Modular Spool System for the Bambu Lab Reusable Spools to solve this exact problem. Instead of having multiple nearly empty spools cluttering your workspace, this system allows you to consolidate your leftover filaments into compact "slices" that seamlessly stack together to form the width of a single standard Bambu Lab Reusable Spool.

⚙️ Engineering & Design Considerations
This isn't just a scaled-down spool; it was designed entirely from scratch in CAD with strict Design for Manufacturing (DFM) principles and polymer physics in mind.

🧩 Fractional Modularity: The mini-spools are designed in fractional widths (e.g., 1/2, 1/3, 1/4). You can mix and match them! Put four 1/4 spools together, or one 1/2 and two 1/4s. Their combined width precisely matches the internal width of the Bambu Lab spool so the master spool clicks shut perfectly.

🛠️ Print-in-Place Compliant Filament Clip: This is the core innovation of the design. I integrated a flush compliant zigzag spring directly into the spool wall.

The spring remains in a state of rest while holding the filament via geometric interference. You only compress the spring momentarily to release or insert the filament. This guarantees the PLA won't deform permanently over months of storage.

🔒 Bambu Lab Ecosystem Integration: The center core exactly replicates the Bambu Lab bayonet locking mechanism and anti-rotation keyway. It locks in smoothly with a satisfying "click" and is fully compatible with standard setups.

🖨️ Printing Guidelines
Material: Highly recommended to print in PLA. PLA offers the best dimensional accuracy for the bayonet tolerances and prevents stringing inside the print-in-place sliding mechanism.

Supports: None required! The design is 100% support-free.

Layer Height: Standard 0.2mm works perfectly.

Wait before moving: Let the build plate cool down completely before removing the print to avoid warping the flat walls or deform the bayonet locking mechanism . Once removed, simply swipe the integrated clip block  up an down a few times to break it free and get the spring moving smoothly.

It should be noted that there is currently no version that fits on the Bambulab A1 printing plate

⚠️ A Note on Filament Dryers:
This design is optimized for PLA. However, PLA has a low glass transition temperature (~60°C). If you plan to put these mini-spools inside an active heated filament dryer, please print these models in PETG, ABS, or ASA to prevent the tension of the wound filament from warping the plastic.