Direct Injection and Dual Density: Revolution in Running Shoe Sole Production Made in Germany
It doesn't matter whether a runner is running a marathon, a half-marathon or a 10K: The goal is always to waste as little energy and power as possible with every step. The running shoe industry has been supporting this goal for several years by optimizing the mid-soles of running shoes by using highly reactive Energy-Return-Foam technology.
Today, the so-called "supercritical" foams offer the highest energy return characteristics. However, all too often they also have a major disadvantage: when they are engineered on an EVA basis, the material tends to fatigue over time. With every load, the foam is compressed more. And that triggers a vicious cycle: when a runner e.g. overpronates due to their body or foot structure, they put more stress on the sole at a certain point and the foam fatigues faster at that point. This in turn will then promote the weak point in the runner's body structure and may lead to negative movement patterns.
For this reason, we looked for alternatives to EVA-based foams for our nmblFoam® and chose PU. This continuously dense foam is characterized by a deep and, above all, permanently consistent energy return. In addition, our PU-based nmblFoam® technology has a compression set 10x higher than conventional EVA foams, i.e. a significantly better ability to return to its original shape. This is not only beneficial for the runner, but also for the environment, as running shoes with PU soles can be worn significantly longer. And because our PU soles are hydrolysis-free, no runner has to worry about the sole simply disintegrating at some point. This is especially beneficial in hotter or more humid climates.
Good for runners and for the environment
When it comes to manufacturing the soles, we rely on a revolutionary new process: Joe Nimble is the only manufacturer in the running shoe sector to have brought the so-called direct injection process to production maturity for its current top model Ultreya®. This means that the soles are no longer glued, as is common in the industry, but are directly injected into a mold.
This has advantages for runners and for the environment. This type of production saves water and energy, as the sole no longer has to be heated or melted. At the same time, we can abstain from using glues, which can have a negative impact on cushioning in the shoe by providing an additional intermediate layer or stiffening joined materials. The connection between the sole and the upper is also improved because the midsole bonds firmly to the upper during production.
An absolute novelty in the industry is also to combine Direct Injection with Dual Density. This allows us to inject the sole automatically in two densities. The frame of the sole ensures a stable landing and the inside provides soft cushioning. This manufacturing process is so far unique in the market, but offers runners greater stability than classic midsole foams, in which the running sensation can often feel spongy.
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The highly automated manufacturing process also allows Joe Nimble to profitably move production of the Ultreya® back to Europe and Germany. This makes us less dependent on supply chains. And it brings us closer to the goal we aim for with every new development step: to produce our shoes in a CO2-neutral way for the foreseeable future.