Rethinking Cushioning and Impact Protection: The Lattice Advantage

Creating lattice structures with traditional manufacturing techniques such as injection moulding is almost impossible without the intervention of additive manufacturing. Where it is feasible, the costs are likely to be high. It makes, sense, therefore, to skip the moulding process and produce parts directly through additive manufacturing.

Rethink foam!

“Lattice structures are porous structure composed of repeating cellular unit, which widely developed and used in aerospace, automobile, biomedicine and other fields because of their low density, high specific strength, high specific stiffness, good energy absorption ability, excellent thermal and acoustic insulation…” Ruochen Ding et al 2020 IOP Conf. Ser.: Mater. Sci. Eng. 727 012001

Lattice structures have such excellent energy absorption capacity per unit mass. It’s hardly surprising then, that, in recent decades, lattice use has become a hotspot for research for its energy absorption properties. And, it’s even less surprising that we are starting to see 3D printed elastomeric lattice structures replace traditional foams in everyday use, from footwear to seating to sports protection.

Closed-cell foams of varying density is tried and tested in the sports arena with regards to impact absorption. It’s found on everything from protection padding to trainer midsoles. The cellular nature of foam produces a long stress plateau in the loading response, allowing them to absorb large quantities of energy at low peak stress. The disadvantages of foam are that the resultant product can be excessively bulky, it is a poor thermoregulator, and fatigue fractures can occur after excessive impact. Maximising impact absorption therefore requires multiple functional performance zones, and this usually comes from the costly assembly of multiple foam parts.

So, what is the additive manufacturing advantage? Well, currently, the lattice structures that offer the solutions to thermoregulation, bulk and those fatigue issues can only really be produced through 3D printing. Furthermore, dependent upon lattice configuration and the materials used, the energy/impact absorbing properties can be increased or decreased as desired without necessarily having to add to the bulk; and depending upon the size of the printer used, those different configurations can be included on one part, thus reducing the cost and time of assembling a protection pad or cushion.

Design Engine

Carbon, pioneers of the revolutionary additive manufacturing process, Digital Light Synthesis, have spent the last few years perfecting the Carbon Design Engine, a lattice creation tool that can digitally generate and manufacture finely tuned elastomeric lattices, driven by clinical and, with true customisation in mind, individual data.

Imagine that! A road bicycle seat custom crafted to give you comfort and protection according to your own body’s topography. Or, a circuit racing seat moulded around your own morphology, ensuring ultimate protection around your most vulnerable, exposed areas that doesn’t compromise your car’s weight limits. Indeed, by adjusting lattice configuration and depth on custom midsoles, Carbon and Adidas’ launch of the Futurecraft 4D and AlphaEdge 4D training shoes have raised the bar for athletic performance.

For those interested in exploring lattices using the range of elastomeric polyurethanes offered by Carbon, Paragon Rapid Technologies offers: FPU 50 – an impact, abrasion and fatigue resistant semi-rigid material; EPU 40, a highly elastic, energy absorbing Shore A 70 elastomeric polyurethane; EPU 43, a soft, energy damping elastomer with Shore A 76; EPU 45, an energy damping, strain-rate sensitive elastomer; and SIL 30, a Shore-A 35 biocompatible, tear-resistant silicone urethane.

Picture courtesy Carbon: Examples of different lattice cell types, cell sizes, and strut diameters to create varied impact performances

As a Paragon customer, you will have access to the Carbon Design Engine. The Carbon Design Engine takes the guess work out of designing lattices for varying impact protection levels. The extensive Carbon Lattice library is leveraged according to your mechanical responses and materials requirements. Our additive manufacturing team will collaborate with you and Carbon to identify appropriate materials; as well as load-compression options for your particular application. Remember, with the additive manufacturing process, one part can contain several different lattice configurations. The result will be outstanding performance, comfort where required, and, of course, the requisite thermal and mechanical attributes.

Applications and Examples

SIL 30 is biocompatible, tear resistant and very soft, making it ideal for audio devices.

The obvious applications for impact absorbing and cushioning lattice structures are in the automotive and aerospace sectors, such as the creation of custom car seats or lightweight, breathable pilot and passenger seats; in the sporting goods sector, for the creation of helmet liners, body protection pads for impact sports, custom bicycle seats for elite athletes, and training shoe midsoles; in the medical and healthcare sector for items such as orthopaedic pads and prosthetic components; and in the consumer goods sector, including industrial protection gloves, head sets and lightweight padding on wearables such as backpacks and baby carriers.

A custom car seat

Additively manufactured lattice components are an ideal solution for the manufacture of automotive upholstery that is customised to the user’s needs. Porsche’s recent launch of it’s 3D printed bodyform bucket seat, ‘A seat as individual as its driver’ utilises 3D printed elastomeric lattices in its ‘comfort layer’ and in padding areas such as thigh and shoulder rests. Although not designed by scanning an individual driver to create the ultimate, individual comfort and impact balance, the behaviour of the lattice layer means that the bucket seat conforms to the individual’s body profile. Because of the nature of the elastomeric material, material fatigue and permanent impressions are a thing of the past.

Sporting goods

Design freedoms offered by additive manufacturing means that periodic structures can be tuned on a cell by cell, part by part basis, enabling protection to be engineered towards specific energy requirements. Until now, protective pads such as mountain biking knee pads, cricket pads and equestrian body protectors have been bulky and hot for the wearer. Helmets have been uniformly padded and require replacement immediately the shell has cracked or the foam started to deconstruct.

The US football helmet

Image courtesy Carbon: A generic helmet liner constructed in EPU 45, with multiple lattice configurations

In the last four years, Carbon and US sports equipment manufacturer Riddell have spun on-field impact protection on its head. The Diamond helmet platform features a digitally manufactured liner using the Carbon DLS process that has been contoured precisely to the head of the athlete. Using Riddell’s head scanning process, combined with data derived from over five million types of impact, every liner created is tuned to ensure energy from linear and rotational impacts are dissipated appropriately, minimising damage to the wearer. Each liner’s lattice configuration varies according to likely impact. Furthermore, the open cell structure means less sweat accumulation – far more comfortable than traditional foam.

Industrial Wearables

Construction and rig workers, indeed all workers at high-risk sites, need tough, durable hand protection. The lattice provides designers with an opportunity to engineer lightweight gloves with specific impact protection zones without adding significantly to the bulk of the gloves or compromising movement.

Image courtesy Carbon: EPU 43 Safety Glove Render

In conclusion

The shortcomings of foam are becoming a thing of the past. Lattice designs using engineering and production grade elastomers means lighter weights and less bulk, enhanced performance, enhanced safety, and importantly for the wearer or user, a greater level of comfort. While Carbon’s Design Engine is not the only lattice creation tool available, it is tried and tested, comes with a range of specially formulated materials and is easily accessible to Paragon customers. To learn more, contact us at Paragon on sales@paragon-rt.com.