Evolutiv hexagonal race caster bearing — assembled face view
◆ Working Prototype — First Generation
Evolutiv Filament Construction System

Hex Race
Caster
Bearing

Load-adaptive.
All printed.

A heavy-duty caster bearing built entirely from printed geometry and 1.75mm nylon filament. No purchased bearing inserts. No metal races. The hexagonal intermediate race geometry distributes load across defined contact flats — growing stronger under the loads it is designed to carry.

4
Filament torus rows
3
Printed components
1.75mm
Only external input
Caster bearing fully disassembled — outer race, hex inner race, outer housing with blue filament entry
Three components. One filament entry. ——
Outer housing · Hexagonal race · Inner shaft insert
The blue stub is the filament before sealing
Assembled caster bearing face-on — hexagonal geometry visible through gray outer race
System Anatomy

Three components.
One torus.

  • 01

    Outer Race — The Wheel

    Printed in gray PLA, the outer race is the rolling surface that contacts the floor. Its interior bore is octagonal or decagonal — not circular. This polygon profile is the defining geometric choice: under radial load, the flat faces of the polygon press against the filament torus, distributing contact force across a flat area rather than concentrating it at a point as a circular bore would.

  • 02

    Intermediate Hex Race — The Load Distributor

    The black intermediate element sits between the outer race and the inner shaft insert. Its exterior is hexagonal, presenting six defined contact flats to the filament torus rows. Its interior carries the hexagonal shaft bore. This is the element that makes the bearing load-adaptive: as radial force increases, the flat contacts widen in engagement, increasing contact area proportionally rather than inducing stress concentration.

  • 03

    Filament Torus Rows — The Bearing Element

    Four rows of 1.75mm nylon filament are loaded tangentially through four independent entry ports in the outer housing. Each forms a continuous closed torus running the full circumference between the housing race and the intermediate hex element. Four rows provide axial load distribution across the bearing width, enabling the assembly to carry loads that a single-row configuration could not sustain without lateral tipping.

  • 04

    Assembly — Topology-Locked, Tool-Free

    Once all four filament tori are inserted and their entry ports sealed with printed plugs, the bearing is permanently assembled. No adhesive. No screws. No press fit that relies on material interference. The filament tori physically cannot exit their closed channels without destroying the channel geometry. Disassembly is impossible — which is precisely the correct design criterion for a load-bearing caster.

Assembled caster — hex geometry face view
Assembled — Face View
Three components exploded — housing, hex race, outer race
Exploded — Three Components
Miniature 25mm bearing showing filament entry principle
Miniature — ⌀25mm Scale
Why the Hex Race Matters

Every advantage is
geometric, not
material.

⬡

Polygonal Contact Is Load-Adaptive

A circular race contacts a rolling element at a single point. Under increasing load that point becomes a stress concentration. A hexagonal race presents flat faces to the rolling element — faces whose engagement width grows with load. The bearing becomes more stable under the conditions it is most stressed by. This is the opposite of how conventional bearings behave under overload.

Hex Race Geometry
⬤

Four Rows for Axial Stability

A single filament torus row can carry radial load but is vulnerable to axial tipping under offset or eccentric loading — exactly the conditions a caster wheel encounters when changing direction or running over an obstacle. Four rows spaced axially across the bearing width provide moment resistance, keeping the wheel axis stable regardless of the direction of the applied force.

Multi-Row Configuration
◎

Filament Precision, Not Print Precision

Commercial 1.75mm nylon filament is produced to diameter tolerances of ±0.02–0.05mm — tighter than typical FDM surface resolution. The torus geometry derives its roundness from the filament, not from the printed channel. The channel only needs to be round enough to guide the filament; the filament provides the precision rolling surface. This is why the bearing runs smoothly without post-machining.

Dimensional Source
◈

Topology Lock: Stronger Than Assembly

The assembled bearing is not held together by friction, adhesive, or fasteners — it is held by topology. The filament tori exist inside closed channels that form only when the components are correctly assembled. The strength of the joint is the shear strength of the housing material around the channel, not the friction or bond strength of any interface. Separation requires destruction.

Assembly Lock Principle
Filament Loading Process

One port.
One filament.
Permanent.

The red miniature bearing at right shows the loading principle at its most visible scale — 25mm OD, the filament entering tangentially at the three o'clock position, the blue torus already seated in its channel, the inner race insert sitting beside it not yet assembled.

At caster scale the same sequence is executed four times — once per torus row — each through its own tangential entry port cut into the outer housing wall. The filament is pushed through until it completes the full circumference and the tail is visible at the entry point. The entry is then sealed with a printed plug. The torus is trapped permanently inside a geometry that has no opening large enough to let it exit.

1

Assemble the three-component stack

Inner shaft insert inside hex race inside outer housing. Components align axially — no fasteners yet.

2

Insert filament tangentially

Standard 1.75mm nylon pushed through the entry port. Follows the circular channel by geometry — no threading tool required.

3

Complete all four rows

Each row loaded independently through its own port. Each torus is self-contained — failure of one row does not affect the others.

4

Seal entry ports

Printed press-fit plugs close all four entry points. Bearing is now permanently assembled and ready for load.

Miniature red bearing 25mm OD — filament entry visible
Scale Range

⌀25mm to
caster scale.
Same principle.

The red bearing at right demonstrates the minimum viable implementation of the torus bearing principle — 25mm outer diameter, 6mm bore, 6mm height. This is smaller than a standard 608 steel bearing (22mm OD). The geometry, loading process, and mechanical principle are identical to the full-scale caster. Only the dimensions change.

This range — from instrument-scale to load-bearing wheel — with no change in construction method or material requirements is what distinguishes the Evolutiv bearing system from specialised solutions. One design language, any scale.

⌀25mm
Miniature variant
⌀16mm
Smallest demonstrated
4 rows
Caster configuration
1.75mm
All scales, same filament
Miniature 25mm bearing — red outer race, blue filament entry stub, inner race beside it
Technical Specifications

First generation.
Proven geometry.

Parameter Value / Description
Bearing type Filament torus rolling bearing with polygonal intermediate race — multi-row caster configuration
Filament torus rows 4 rows — independent axial spacing for moment resistance
Bearing element Standard 1.75mm nylon filament, ±0.02–0.05mm diameter tolerance. Continuous closed torus per row.
Intermediate race geometry Hexagonal or octagonal profile — load-adaptive contact flats. Self-compensating under increasing radial load.
Outer race material Gray PLA — rolling contact surface. Octagonal interior bore for filament torus interface.
Assembly method Topology lock — filament tori in sealed channels. No adhesive, no fasteners. Permanent assembly.
Scale range ⌀16mm height 5mm (minimum demonstrated) to caster wheel scale. Identical construction at all sizes.
External hardware None. 1.75mm nylon filament is the only purchased input.
Generation status First prototype. Geometry verified. Parametric CAD available for shaft diameter and housing size adaptation.

Print your own.
Scale to your load.

Design files for the Evolutiv Hex Race Caster are available through shop.evolutiv.ai. Parametric source with configurable shaft bore, housing diameter, row count, and race polygon geometry available as part of the Evolutiv Bearing Library.

→ Get Design Files Read EFC disclosure