Adidas 4DFWD 3D Printed Running Shoe: How the Lattice Midsole Gets Made

The 4DFWD midsole is not a foam block. It is a lattice of bowtie-shaped cells printed from a photopolymer resin, built in one piece on a digital light synthesis printer. Each cell is designed to buckle in a single direction when loaded, so vertical force from heel strike is redirected forward instead of being absorbed and lost.

That behavior comes from cell geometry, not from material softness. Change the strut angle or the node thickness and the shoe changes character. This is why the design cycle is fast: a new cell pattern can be printed and ridden within days, while a foam midsole would need a new mold before anyone could feel it.

For an engineer, the interesting part is not the marketing. It is that the part is a single continuous structure with internal features no mold can release. Undercuts, hollow nodes, variable wall thickness along the same strut: all free in printing, all expensive or impossible in injection molding.

The trade-off is throughput and unit cost. One printer produces a limited number of midsoles per cycle, and the resin is not commodity material. Printing wins on complexity and iteration speed; it loses on volume.

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  Printed in one pieceNo bonded layers, no adhesive joints in the midsole lattice.
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  Directional bucklingCell shape converts vertical load into forward displacement.
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  Geometry-drivenStiffness comes from strut angles and node size, not just resin grade.

A printed lattice does not sit in the shoe on its own. It bonds to an outsole, meets a strobel board or lasting board, and has to hold its shape through assembly. Those surrounding parts are still made the traditional way, and that is where mold and fixture work enters the picture.

Outsole molds for a running shoe are typically aluminum or steel, cut on 3-axis and 5-axis machining centers. A tread pattern with sipes, radiused edges and varying depth across the forefoot is a classic 5-axis job: the tool has to reach into pockets and stay perpendicular to a changing surface. Where a printed midsole has a curved top surface, the mating outsole cavity usually needs that same curve machined into it, so the two parts nest without gaps.

Assembly fixtures matter more than most people expect. A lattice midsole is compliant, so it deflects under clamp pressure. If a bonding fixture pushes unevenly, the midsole cures into a twisted shape and the finished shoe rolls to one side. We machine matching fixtures from 6061 or POM so the load path is controlled and repeatable.

For low-volume or sample runs, printed fixtures and printed molds are often enough. Once a design is frozen and volumes climb, machined aluminum tooling takes over because it holds tolerance longer and survives more cycles.

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  Outsole molds5-axis cut aluminum or steel for tread depth and radiused edges.
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  Bonding fixturesMachined 6061 or POM, profiled to the midsole underside.

Additive and subtractive processes are not competitors here. They solve different problems, and picking wrong costs either money or time. The question is rarely which process is better in general, it is which one fits this geometry at this quantity.

Print when the part has internal channels, lattices, hollow nodes or organic surfaces that would need a mold with multiple sliders. Print when you expect three or more design revisions before a decision. Print when the run is small and tooling amortization would dominate the unit price. Custom 3D printing covers prototypes and bridge production without a mold commitment.

Machine when the part is prismatic enough to reach with a cutter, when the material has to be structural metal or engineering plastic, or when the surface has to be a sealing face. Tolerances of ±0.005 mm and finishes down to Ra 0.2–0.8 μm are machining territory, not printing territory.

A middle path works well for footwear and sports equipment. Print the complex core, machine the load-bearing collar, hinge pin or mounting plate, then assemble. You get the geometry you cannot mold and the strength you cannot print.

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  Choose printingLattice or internal geometry, small runs, heavy design iteration.
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  Choose machiningPrismatic load paths, metal parts, tight tolerances and sealing faces.
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  Combine bothPrinted core plus machined structural inserts, assembled after.

Printed midsoles use photopolymer resin cured layer by layer. The cured part is elastic and fatigue-resistant enough for running cycles, but it is not a structural material in the metal sense. You would not machine a load-bearing bracket from it.

Structural shoe components, molds and fixtures are a different story. Aluminum 6061-T6 is the default for molds and fixtures because it machines cleanly, conducts heat well and resists corrosion. For higher cycle counts, 7075 or pre-hardened steel holds up longer. Titanium TC4 (Ti-6Al-4V) shows up in cleat plates and prosthetics where weight and strength both matter.

On the plastic side, POM is common for fixtures and wear surfaces because it is dimensionally stable and self-lubricating. PEEK handles heat and chemical exposure where POM would creep. For cosmetic shells, ABS, PC and PMMA machine and finish well, and carbon fiber sheet is an option when stiffness per gram is the constraint.

Pick the material from the load case, not from the price list. A fixture that sees 500 cycles is a different problem from a mold that sees 100,000.

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  Photopolymer resinPrinted lattice midsoles and flexible prototype parts.
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  6061-T6 aluminumDefault for molds, fixture bodies and heat-conducting plates.
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  POM and PEEKWear surfaces, bushings and high-temperature fixtures.
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  Ti-6Al-4VCleat plates and prosthetic hardware where mass matters.

A machined mold is not finished when the last pass ends. Bead blasting or tumbling removes tool marks from non-critical surfaces. Anodizing protects aluminum molds and fixtures from wear and gives a consistent look on visible parts. Laser marking handles part numbers and cavity IDs, with a minimum character height of 1.5 mm so it stays legible after handling.

Inspection is where a lattice part and a machined part diverge. A printed lattice is checked for overall dimensions, cell integrity and bonding surfaces. A machined mold is checked for cavity depth, corner radii and sealing surfaces against the drawing.

We inspect 100% of parts before shipment, with raw material verification, in-process monitoring and a final check. Reports are available on request. For a running shoe project, that means the outsole mold, the fixture and any machined inserts all carry their own inspection record rather than a single pass/fail at the end.

If a dimension drifts mid-run, we catch it at the machine, not after assembly. Rework on a finished shoe is far more expensive than a corrected toolpath.

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  Surface treatmentAnodizing, bead blasting, tumbling, polishing, laser marking.
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  InspectionRaw material check, in-process monitoring, final inspection.
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  DocumentationInspection reports supplied on request with each order.