3D Printed Digital Foam Hockey Helmet Goes On Sale

Digital foam is a lattice. Instead of a block of expanded polymer with random cell size, the liner is a modeled structure of struts, nodes and open cells. The designer chooses cell size, strut diameter and wall thickness, so stiffness can change from one region of the helmet to the next without changing the material.

The print process builds that lattice layer by layer. For helmet liners the common route is powder bed fusion with a thermoplastic elastomer, or material extrusion with a flexible filament. Powder bed gives finer struts and cleaner nodes; extrusion is cheaper but struggles below about 1 mm strut diameter, where the nozzle path starts to break up.

What makes it digital is not the machine. It is the fact that the energy absorption curve is designed rather than measured after the fact. Change the cell size in the temple region and you change the deceleration profile there, and you can do it without a new mold.

A word on language. Suppliers use digital foam, lattice, and printed foam interchangeably. Ask for the cell size, strut diameter, relative density and base material before you compare two quotes. Those four numbers decide the part.

Printing pays off when the geometry is doing work that a uniform foam block cannot do. A helmet shell is a good example: the occipital region, the crown and the jaw need different stiffness, and a single molded foam density forces a compromise across all three.

Same logic applies to other protective and cushioning parts. Chin bars, shin guard padding, seat inserts, prosthetic sockets and robot end-effector pads all have load paths that vary across the surface. If your part has one uniform load, digital foam is an expensive answer to a simple question.

There is also a fit argument. Printed lattices can carry variable thickness and variable cell size inside one continuous part, so the liner follows the head form or the mating surface instead of being glued in pieces. Fewer bonded joints usually means fewer failure points and less assembly labor.

The trade-off is cost per part and build time. Powder bed machines are slow, and a full helmet liner can take many hours per unit. That is fine for custom or small-batch work. It stops being fine when you need thousands of identical liners per month.

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  Good fitVarying load zones, custom fit, low to medium volume, complex curvature
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  Poor fitUniform load, high volume, flat or simple geometry, tight unit cost
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  WatchMinimum strut diameter and unsupported overhangs drive the print cost

The base polymer does most of the work. Thermoplastic polyurethane and similar elastomers give good rebound and fatigue life, which matters because a liner is compressed thousands of times. Photopolymers print finer but tend to be brittle under repeated impact, so we rarely recommend them for anything that takes a real hit.

Relative density is the single most useful design number. It is the volume fraction of solid material in the lattice. A 20 percent lattice is soft and light; a 40 percent lattice is stiff and heavy. Energy absorption per unit mass peaks somewhere in the middle, and that peak moves with the strain rate.

Strut diameter sets the print floor. Below roughly 0.8 mm, most powder bed systems lose node integrity and the lattice becomes unpredictable in testing. Cell size sets the other end: cells larger than about 20 mm behave like a spring rather than a foam and can buckle locally.

For the hard parts, we machine the same design in metal or rigid plastic. A 5-axis cut of a lattice mold insert, or a machined aluminum test fixture that holds a printed liner at the correct angle, is often what turns a prototype into a repeatable test.

A printed lattice is usually the front end of a program, not the end. Once the geometry is validated, teams often want the same cell pattern reproduced faster and cheaper. That is where a machined mold insert enters the picture.

We cut mold cores and cavities from aluminum or tool steel on 3-axis and 5-axis centers, holding ±0.005 mm where the lattice ribs meet the parting line. The cavity geometry comes straight from the validated lattice model, so the molded part keeps the same regional stiffness. Roughness matters too: Ra 0.8–1.6 μm on the cavity face gives a clean release without polishing away the rib detail.

Molding is not always the right answer. If the part is still changing every few weeks, keep printing it. Injection tooling only earns its cost when the design is frozen and the annual volume is real. Below a few thousand units a year, printed or vacuum cast parts usually stay cheaper.

For low-volume bridge production we also run vacuum casting and urethane casting from a machined master. A 5-axis machined master pattern, finished and sealed, can produce a few dozen castings in a soft tool, which covers field trials before steel is cut.

One practical note on the supply chain. A program like this touches printing, machining, finishing and inspection. Keeping them in one shop shortens the loop when the lattice needs a tweak after impact testing.

Lattice parts fail in ways that look different from molded foam. Instead of a crack, you get collapsed cells in one band, or detached nodes where the print did not fuse. Visual inspection alone will miss both, so plan on dimensional and mechanical checks.

Start with dimensional. Measure strut diameter at several locations with a vision system, and check overall liner thickness at the load zones. Compare cell size in the model to the cell size on the part; a 10 percent drift changes stiffness more than most people expect.

Then run drop or impact tests on the actual assembly, not on a coupon. Coupons tell you about the material. The assembly tells you about the load path, and the load path is the reason you chose a lattice in the first place.

Keep the process data with the parts. Layer height, laser power, build orientation and post-processing all shift the result. If a build is later reproduced with different parameters, the impact curve will move, and you want a record of what changed.