Saddle trees have been built the same way for centuries: a rigid frame of wood, laminated plywood, or metal that dictates how a saddle sits on a horse's back and, crucially, how little it moves. Ergon Equine has partnered with igus UK to challenge that assumption with an unusual application of additive manufacturing: six 3D-printed ball-joint housings, sintered from a wear-resistant tribo-polymer and paired with stainless steel ball studs, built into a saddle tree that's designed to flex rather than resist.
The tree in question is BioTree, described on Ergon's own product page as a "patented biomimetic system" that attaches to the underside of the company's existing NewTree range. Ergon calls it an "equine-centric alternative to traditional tree design," and the pitch is straightforward even if the engineering isn't: a horse's back moves in three dimensions as it walks, trots, and canters, but a conventional tree — wood reinforced with metal — does not. BioTree is built specifically to move with it.
Six Joints, Three Axes
The mechanism behind that flex is where the 3D printing comes in. According to the reporting from voxelmatters, BioTree incorporates six ball-joint mechanisms, each pairing a stainless steel ball stud with a 3D-printed housing. The housings are laser-sintered — SLS, in other words — from igus's iglidur i230, a tribo-polymer the company markets for exactly this kind of application: parts that need to slide or pivot against a mating surface repeatedly without lubrication, without excessive wear, and without breaking down under load.
igus picked i230 for three properties in particular: wear resistance, flexural strength, and electrostatic dissipation. That combination matters because a ball joint in a saddle tree isn't a static bracket — it's a load-bearing pivot that has to tolerate thousands of small articulations every time the saddle is ridden, transmitting a rider's weight through a joint that's simultaneously being asked to move. A brittle or high-friction material would either seize up or wear itself into slop within a season. The stainless ball studs supply the hard, low-wear bearing surface; the printed polymer housing supplies the geometry, the compliance, and — per igus's stated reasoning for choosing i230 — the ability to shed static charge rather than accumulate it.
Six joints working in concert, rather than a single hinge, is what allows the tree to articulate across three axes instead of just one. A single pivot point would let a tree rock front-to-back or side-to-side, but not both, and it wouldn't accommodate the twisting motion that happens along a horse's spine during more demanding gaits. Distributing the movement across six ball joints spreads that three-axis articulation across the structure rather than concentrating it at one stress point.
Why Print the Joint, Not Machine It
Ball-and-socket joints are old technology — automotive suspension and human hip replacements have used variations on the theme for decades. What's notable here isn't the joint concept but the manufacturing route: rather than machining or injection-molding the housings, Ergon and igus went to laser sintering.
SLS is a natural fit for a part like this for a few reasons that go beyond "it's 3D printed so it's news." A ball-joint housing is a complex, undercut-heavy geometry — a socket has to wrap around a ball stud on more than one side to retain it, which is awkward to injection-mold without multi-part tooling and awkward to machine without multiple setups. SLS builds the part in loose powder with no support structure needed for internal cavities, so the socket geometry comes out of the printer already assembled around its constraints. It also means Ergon can iterate the housing geometry — wall thickness, socket clearance, fillet radii around the load path — without cutting new tooling between revisions, which matters for a product the company itself describes as still in late-stage development rather than shipping. BioTree is being built and tested, not yet a finished commercial item, and SLS is the kind of process that supports that iteration cycle: change the CAD, print six new housings, fit them, ride-test them, repeat.
igus's iglidur line exists specifically to serve that use case — engineering plastics developed and characterized for tribological performance (wear, friction, load) that can be either machined from stock or, as here, laser-sintered directly into finished geometry. The company has spent years building a niche around "print it and it already behaves like a bearing," and a load-bearing equine joint is a reasonably on-brand example of that pitch being put into a real product rather than a demo part.
What It Means for Makers
The headline application — a horse saddle — is niche enough that most desktop-printer owners will never build one. But the underlying pattern is worth filing away, because it shows up constantly in mechanical design problems far more common than equine tack: any time a project needs a low-friction, self-lubricating pivot or slide interface that has to survive repeated cyclic load, a tribo-polymer housing paired with a hard metal counter-surface is a well-trodden solution, and it's one increasingly reachable through SLS service bureaus rather than requiring in-house injection molding.
For makers designing their own articulating mechanisms — robotics linkages, prosthetics, adjustable furniture hardware, camera gimbals — the Ergon/igus approach is a useful template: don't try to print the whole assembly in one low-friction material, and don't rely on FDM parts sliding directly against each other, which tends to gall and wear unpredictably. Instead, pair a hard, cheap, off-the-shelf metal wear surface (a stainless ball stud, a shaft, a pin) with a printed housing in a material actually engineered for sliding contact. It's also a reminder that "which process" questions in additive manufacturing increasingly come down to geometry rather than material alone — SLS earns its keep here specifically because the undercut socket shape would be a headache in almost any other process.
Bottom Line
BioTree is still in late-stage development, and Ergon hasn't published fatigue data, load ratings, or a production timeline for the printed housings. What's confirmed is the architecture: six SLS-printed iglidur i230 housings, six stainless ball studs, three axes of movement, engineered to let a saddle tree flex with a moving horse's back instead of fighting it. It's a small, specific application, but it's a clean illustration of laser sintering being chosen on its own engineering merits — geometry and material behavior — rather than as a marketing flourish.
