Modular Filament Spool Rack - Glueless

UPDATE: Added variants for a variety of rod sizes/materials, Metric and Imperial.

Overview
This is a highly refined remix of the original spool shelving design by @ihateu3_593067, transformed into a fully modular, user-friendly system perfect for organizing your 3D printing filament spools. Using affordable EMT conduit (like 1/2" electrical metallic tubing from your local hardware store) as the support rods, this shelving setup allows you to create customizable racks that fit snugly in closets, shelves, or workshops. It's space-efficient, sturdy, and easy to assemble—ideal for makers looking to maximize storage without wasting vertical space. Whether you're storing standard filament spools or expanding storage by adding more rows, this design delivers stability and simplicity, with ~20% space savings over ihateu3’s design by eliminating redundant components during stacking.

Key Improvements and Features
I've significantly refactored the original design to prioritize modularity, ease of use, and structural integrity:

• Enhanced Modularity: The pillars that connect each shelving row now attach directly to the rod holders via integrated dovetails, eliminating the need for separate dowel pins. This simplifies assembly—no more fiddling with extra connectors! You can easily expand or reconfigure the system by stacking rows vertically. Compared to ihateu3's design, which is technically stackable with dowel pins, mine eliminates an entire redundant rod mount section when stacking, saving valuable vertical space.
• Human-Friendly Chamfers: Added smooth chamfers to all edges and corners, making the parts safer to handle and more comfortable during installation. No sharp edges to snag your fingers or damage spools.
• Tighter Rod Tolerances: Adjusted the tolerances for the EMT conduits to ensure a snug, secure fit without sliding.
• Improved Stability: Removed the mid-pillar dovetails from the original design, which could compromise theoretical stability in taller stacks. My version focuses on clean, end-to-end connections for a more robust frame.
• No Overhangs: Eliminated all overhangs to significantly improve printability and simplicity. (Use the largest nozzle and thickest layer height preset your printer can handle! You can use fast presets because there are no forces being applied along the layerlines, so layer adhesion isn't a bottleneck.)

The result? A sleeker, more efficient system that assembles in minutes with just printed parts and cut EMT sections. Each shelf row uses two parallel EMT rods to support spools on their edges, allowing for dense packing.

Why You'll Love This Design

• Cost-Effective: EMT conduit is incredibly affordable—I personally got two 10ft rods that cost just $7 each at Home Depot, which they cut for free into 10 2ft pieces for a 5-shelf setup.
• Scalable: Print as many pillars and rod holders as needed—start small and add more rows to fit your collection. Supports standard filament spools, but remixable for custom rod sizes using the included STEP file.
• Proven Space Efficiency: Saving ~20% vertical space compared to ihateu3’s design by eliminating redundant rod mounts.

This remix builds directly on ihateu3's solid foundation while addressing pain points for a smoother experience. If you download and print this, I'd love to see your makes! 🚀

Assembly Tips

1. Determine the number of rows (R) you want for your shelving unit (e.g., R=5 for a taller setup holding 40+ spools). Print the following in PLA or PETG (20% infill recommended for strength, using gyroid or adaptive cubic infill type):
   • 2 × R rod holders (e.g., 10 for R=5).
   • 4 × (R - 1) pillars (e.g., 16 for R=5).
   • Optionally, print end caps (which can double as feet) and the big foot variant (taller for added height and stability). Print foot caps in 95A TPU for grippy, non-slip feet on smooth surfaces, or use PLA/PETG to match the frame.
2. Cut 2 × R EMT conduit segments to your desired width (e.g., 10 segments of 2ft each for R=5).
3. Snap pillars into rod holders via dovetails to build the left and right sides separately: for each side, stack R rod holders with 2 pillars per vertical connection (R-1 connections total per side). Slide in the EMT rods (2 per row) to connect the sides and form each shelf level.
4. Place freestanding—attach optional foot caps to the bottom rod holders for stability (use TPU for maximum grip or the taller big foot variant for extra height).

For folks with smaller print beds like the Prusa MINI or A1 mini, parts should still fit on the print bed if rotated.

Total Cost example:
For a 5-row rack, total filament used would be about 1.475 kg

Using Sunlu PETG, which sells on amazon for ~$14/kg, cost in filament is ~$21.

10 EMT conduit bars would be another $14. So total cost would be about $35.

Given the simplicity of the design, I'd consider making an OpenSCAD version if there's interest.