Separating Compression and Tension Inside a Lattice

Most structural problems come down to two forces: compression, which squeezes, and tension, which pulls. A material that handles one well may handle the other poorly, and most real parts experience both. The advanced move in lattice design is to stop treating a structure as one undifferentiated lump and instead route each force to the members best suited to carry it.

Compression and tension, briefly

Compression is a pushing force that tries to shorten or crush a member; tension is a pulling force that tries to stretch it. The distinction matters because materials and shapes respond very differently to each. Concrete is strong in compression but weak in tension, which is why it is reinforced with steel. Slender members buckle under compression long before they would snap under tension. Knowing which force is acting where is the first step to designing for it.

How force flows through a lattice

In a lattice, an applied load does not stay put. It travels through the network of struts and surfaces, splitting at each node and following the stiffest available path to the supports. Along the way, some members end up pushed (in compression) and others pulled (in tension). Mapping these load paths, often with finite element analysis, reveals which parts of the lattice are doing which job. Once you can see the flow, you can design around it.

Telling compression and tension zones apart

In a loaded structure, compression and tension regions are usually predictable. The top of a simply supported beam compresses while the bottom stretches; the inside of a bend compresses while the outside pulls. Simulation makes this explicit, colour-coding members by the force they carry. Identifying these zones tells you where to add stiff, buckle-resistant members and where to allow slender, flexible ones, rather than over-building the entire part to survive its worst-loaded region.

Designing to isolate each force

Once the zones are known, several strategies separate the forces. Compression members can be made thicker, shorter, or curved to resist buckling. Tension members can be slender, since pulling does not cause buckling, which saves weight. Density can be graded so compression-heavy regions are denser and tension regions lighter. Cell orientation can be aligned so struts run along the dominant force direction. The aim is a structure that is exactly as stiff or as flexible as each region needs, and no more.

The truncated icosahedron as nature's template

Nature solved this problem long ago. The truncated icosahedron, the same shape as a buckyball or a soccer ball, distributes load so that its pentagons and hexagons share force evenly across a closed cage. It is a naturally balanced arrangement of compression and tension, which is exactly why it recurs from molecules to domes. C6XTY builds on this geometry deliberately, using the icosahedral arrangement as a starting point for lattices that separate and manage forces by design rather than by accident.

A practical example: zoned cushioning

Consider a printed cushioning part such as a footwear midsole. Under a footstep, some regions need to compress and absorb energy while others need to stay supportive and spring back. By grading the lattice, denser and stiffer where support is needed, lighter and more compliant where cushioning is needed, a single printed piece delivers both behaviours. The adidas 4DFWD midsole is a well-known example, using thousands of tuned struts so density controls support and cushioning across one monolithic lattice. The same logic applies to helmets, seating, prosthetics, and vibration mounts.

Where expert geometry pays off

Isolating compression and tension across a complex part is where lattice design moves from textbook to craft. It takes experience to choose where to stiffen, where to lighten, and how to keep the whole structure manufacturable. This is the heart of what C6XTY's founder, Sam Lanahan, consults on: isolating compression and tension to whatever scale the application requires, drawing on decades of work with the icosahedral geometry he learned in part from Buckminster Fuller. For teams pushing a lattice to do several jobs at once, that focused expertise can shorten the path to a design that actually performs.

Key takeaways

• Compression squeezes and tension pulls; most parts experience both, and materials respond differently to each.
• Loads flow through a lattice along predictable paths, putting some members in compression and others in tension.
• You can isolate each force by sizing, orienting, and grading members so each region is exactly as stiff or flexible as needed.
• The truncated icosahedron is a naturally balanced template, and isolating forces well is C6XTY's core expertise.

Related reading

• How Geometric Lattices Outperform Solid Material on Strength-to-Weight
• How to Design Lattice Structures for 3D Printing
• What Are Bucky Balls, and Why Is Their Shape So Strong?

Frequently asked questions

What is the difference between compression and tension?

Compression is a pushing force that tries to shorten or crush a member, while tension is a pulling force that tries to stretch it. Many materials handle one far better than the other.

Can a single lattice handle both compression and tension?

Yes. By designing different members to carry each force, one lattice can be stiff where it resists crushing and flexible where it stretches, all within the same part.

How do you find compression and tension zones in a structure?

Finite element analysis maps how load flows through the structure and colour-codes members by the force they carry, making compression and tension regions clear before you finalise the design.

Why does isolating these forces save weight?

Tension members can be slender because pulling does not cause buckling, while only compression members need to be thick or braced. Designing each for its actual job avoids over-building the whole part.

How does C6XTY approach compression and tension?

C6XTY uses the icosahedral geometry of the truncated icosahedron to balance and separate forces by design, and its founder Sam Lanahan consults on isolating compression and tension at whatever scale a project needs.