ReCoreNect - connector system for spool cores

ReCoreNect – The modular connector system to connect, stack and build with empty filament spool cores.

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THE IDEA

Every spool of filament leaves behind a cardboard core. Most end up in the bin. ReCoreNect changes that — it is a modular 3D-printed connector system that turns these cores into a versatile building material.

The concept is simple: small printed rings sit between spool cores, connecting them vertically and horizontally. Stack them, link them, arrange them — into storage systems, chairs, and more.

💡 Perfect use for leftover filament. The largest connector in the set — the Cross — uses under 28g of filament. Whenever you reach the end of a spool with a little left over, print a ReCoreNect. Nothing goes to waste.

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HOW IT WORKS

Each connector ring has a groove at the top and a groove at the bottom. The cardboard wall of the spool core slides into these grooves — the cardboard itself acts as the tongue. No screws, no glue, no tools. For a more permanent structure, parts can optionally be glued together.

The optional arcs extending outward each grip into a neighboring spool core the same way. Each arc covers 85° — just under a quarter circle — so up to four arcs can connect into a single neighboring spool with a few degrees of clearance. Neighboring spool cores simply drop in from above.

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 THE PARTS

Six connector types cover every possible configuration. All share the same groove geometry and are fully compatible with each other.

Solo — 0 arcs · vertical stacking only

Use: Column building, spacer, vertical extension

Duo — 1 arc · connects 1 spool horizontally

Use: Row extensions, end of a chain, single branch

Straight — 2 arcs (opposing) · straight line connection

Use: Rails, rows, linear structures

Corner — 2 arcs (90°) · direction change

Use: Corners of frames, chairs, shelves

T-Shape — 3 arcs · branches in 3 directions

Use: Grid intersections, dividers, branching joints

Cross — 4 arcs · central grid hub

Use: Grid centers, structural hubs

FILAMENT WEIGHT PER CONNECTOR

Each ring base weighs approximately 14g. Each arc adds around 3.5g. Use this as a guide when planning how much filament you need.

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BUILD EXAMPLE – RECORENECT ARMCHAIR MINI

Just like the classic pallet lounge that has been a DIY staple for years, you can now build your own seating from something you already have: empty filament spool cores.

⚠️ Note on dimensions: This example is sized for small children (based on Bambu Lab refill core dimensions). The same building approach works for adult-sized furniture — simply stack more cores per column for height, and expand the grid for a wider seat.

The armchair is built as a 5×5 spool core grid with 5 stacking levels (4 connector layers between them). The 3×3 center block forms the seat surface. The outer frame forms the armrests, and the rear columns extend one level higher to form the backrest.

LAYER OVERVIEW

Layer 1 (Levels 1→2) — Full 5×5

5× Cross, 4× Corner, 4× T-Shape

Layer 2 (Levels 2→3) AND Layer 2 (Levels 2→3)  — Outer frame only

2× Duo, 2× Straight, 2× Corner, 3× T-Shape

Layer 4 (Levels 4→5) — Backrest only

2× Corner, 3× T-Shape

Summary

GOING FURTHER – THE RECORENECT LOUNGE

Combine the armchair with additional pieces to create a full lounge setup. A simple chair (same approach but on a 3×5 base, without armrests) pairs well alongside it. Add a low side table built from a flat spool grid, and you have a complete seating area — a modern take on the classic pallet lounge, made entirely from filament waste.

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CALIBRATION

Print a Duo first and test the fit on your spool core. The groove should grip the cardboard wall firmly with moderate hand pressure. If too tight or too loose, open the OpenSCAD file and adjust the tolerance parameter in steps of ±0.05 mm.

FILAMENT & FIT TOLERANCES

Fit can vary slightly depending on your filament — even within the same brand and material. For example, Bambu PLA Basic White and Black can behave differently. Some color variants slide in more easily, others require a bit more force. The same can apply to spool cores, which are not always perfectly identical. In general the connectors work well across these variations — sometimes with a little more pressure, sometimes with less.

PRINT BED ADHESION

Make sure your print bed is clean before printing. The contact surface of the arcs is relatively small, so good bed adhesion matters. Wipe the bed with isopropyl alcohol before each print for best results.

BUILDING TIPS

• Use Cross connectors in the center of any grid — they stabilize in all four directions simultaneously.

• At corners, position your connectors so that a full main ring grips into the corner spool — use a Corner connector if two directions meet, or a Duo if only one direction extends from the corner. A spool gripped only by arcs is significantly less stable than one held by a full ring.

• For any spool that receives arcs, try to have at least two arcs gripping into it — ideally on opposite sides. A single arc provides much less lateral stability than two opposing ones.

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PRINT PROFILES

Three ready-to-use print profiles are available alongside the individual 3MF-files.

Profile 1 – One of Each

Six print plates, one connector type per plate. Perfect for a first test print or to get familiar with each part.

Profile 2 – Full Plate

Each plate is filled to capacity with 4 copies of the same connector type. Ideal for batch printing.

Profile 3 – Armchair Mini Kit

Contains exactly the plates needed to print all 36 connectors for the ReCoreNect Armchair Mini. Simply print the plates one after another — no counting, no planning required.

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 OUTLOOK

ReCoreNect is designed to grow. If the project is well received, the following add-ons are planned:

End Cap

A simple cap that closes the open top of a spool core — for a clean finish on exposed ends, or as a base and lid.

Board Connector

Accepts a wooden board or panel — enables shelves, tabletops, and flat surfaces integrated directly into ReCoreNect structures.

Horizontal Stand

Holds a spool core on its side — unlocks new build directions, for example a wine rack where bottles rest inside the hollow cores.

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