Low Friction Dual Bearing Spool Hub - Bambu Lab A1

Ultra-Low Friction Dual-Bearing Spool Hub for Bambu Lab A1

This uniquely engineered spool holder extension is designed to replace the standard friction-based spool rolling mechanism on the Bambu Lab A1. By utilizing dual, precisely toleranced ball bearings, this hub virtually eliminates rotational drag.

While standard PLA or PETG filaments can handle the drag of stock spool holders, this upgrade is strictly necessary for flexible filaments like TPU and TPU 95A HF. Flexible materials are prone to stretching under tension. When the extruder has to pull against a high-friction spool, the filament stretches before entering the hotend, leading to severe under-extrusion, inconsistent layer lines, or the extruder gears completely slipping and stripping the filament. This bearing mod ensures the spool unspools smoothly at the slightest pull, entirely mitigating these feed-path issues.

Technical Specifications

Hardware Required: 2x 6907RS Ball Bearings (Brand used in design: KBS LLC)
Bearing Dimensions: 35mm Inner Diameter (ID) x 55mm Outer Diameter (OD) x 10mm Width
Spool Compatibility: Designed specifically for filament spools with a standard ~55mm central hub diameter (perfectly fits standard Bambu Lab reusable spools and many aftermarket brands).

Design Features

True Concentric Rotation: The 35mm inner races of the bearings sit securely on the 3D-printed central shaft, while the 55mm outer races interface directly with the inner wall of the filament spool. This transfers all rotational movement directly to the steel ball bearings.
Threaded Retention: The assembly features a custom-threaded end-cap that locks the bearings and spool securely in place, preventing lateral walking or wobble during fast Y-axis bed movements.
Direct-Fit A1 Integration: The core shaft is engineered with a slotted, locking base to interface perfectly with the stock Bambu Lab A1 spool holder arm, ensuring a rigid mount that won't sag under the weight of a full 1KG spool.

Assembly Instructions

Insert the two 6907RS bearings onto the main 3D-printed cylindrical shaft. They should press-fit snugly onto the 35mm sections.
Mount the shaft assembly onto your Bambu Lab A1 spool holder arm.
Slide your filament spool over the assembly. The 55mm outer diameter of the bearings will act as the new perfectly sized hub for the spool.
Screw on the threaded end-cap to secure the spool on the bearings.

Recommended Print Settings

To ensure dimensional accuracy for the bearing press-fits and the threaded cap, please observe the following:

Material: BambuLab PLA Basic, PETG, ABS/ASA, or PLA+ (High rigidity is required to prevent shaft deflection over time; standard PLA may creep under the load of a heavy spool).
Layer Height: 0.16mm or 0.20mm (Important for the smooth printing of the threaded sections).
Wall Loops / Perimeters: 4 to 6 perimeters (Crucial for the structural integrity of the bearing mounts and the A1 arm interface).
Infill: 25% Gyroid or Cubic.
Supports: no support needed

Designed by Ádám Pálvölgyi, text me if you have any questions.