What Are Lattice Structures and Why Do They Matter?
Lattice structures are engineered open-cell architectures that replace solid material with a network of struts, beams, or surfaces. They are one of the most powerful design capabilities unlocked by additive manufacturing — impossible to produce with any subtractive or forming process, but printable routinely in DMLS, SLS, and FDM. The result is parts that are lighter than solid equivalents by 30–70% while maintaining specific stiffness, energy absorption, or thermal performance that solid infill cannot match.
Two broad families exist: strut-based lattices (a network of beams) and TPMS (Triply Periodic Minimal Surface) lattices (smooth continuous surfaces with zero mean curvature). Each has distinct mechanical, thermal, and printability characteristics.
Strut-Based Lattices
Strut lattices connect nodes with cylindrical or rectangular beams. Common unit cell types:
- BCC (Body-Centred Cubic): Diagonal struts connecting cube face centres to the body centre. Good compressive strength, moderate stiffness. Common in aerospace brackets.
- FCC (Face-Centred Cubic): Struts along cube face diagonals. High shear stiffness, good for vibration damping.
- Octet Truss: Combines BCC and FCC. Highest stiffness-to-density ratio of any strut lattice — approaches the Hashin-Shtrikman theoretical upper bound. Used in aerospace structural panels.
- Diamond (Kelvin): Similar to octet but with better energy absorption. Used in impact-protection applications.
Minimum printable strut diameter by process:
| Process | Minimum Strut Diameter | Recommended Minimum |
|---|---|---|
| DMLS (metal) | 0.3 mm | 0.5 mm |
| SLS (PA12) | 0.5 mm | 0.8 mm |
| MJF (PA12) | 0.5 mm | 0.7 mm |
| FDM | 1.5 mm | 2.0 mm |
| SLA/DLP | 0.3 mm | 0.5 mm |
TPMS Lattices: The Engineering Case for Smooth Surfaces
Triply Periodic Minimal Surfaces are mathematically defined surfaces that repeat periodically in three directions and have zero mean curvature at every point. This last property — zero mean curvature — means stress is distributed uniformly with no stress concentrations. TPMS outperform strut lattices in fatigue life, fluid flow applications, and printability.
Key TPMS types used in additive manufacturing:
- Gyroid (Schwartz G): No flat sections, fully interconnected open-pore channels. The most common TPMS in additive manufacturing. Used in heat exchangers, medical implants (osseointegration), and filters. Exceptional powder removal in SLS/DMLS.
- Schwartz P (Primitive): Larger, flatter pores than Gyroid. Higher permeability for fluid flow applications. Used in bone scaffolds and gas separation membranes.
- Schwartz D (Diamond): Highest surface area of the common TPMS types. Used in heat transfer applications where maximum surface area improves thermal exchange.
- IWP (I-WP): Two interconnected networks — useful for functionally graded structures where two different fluids must flow without mixing.
TPMS vs Strut Lattice: Which to Choose?
| Property | Strut Lattice | TPMS Lattice |
|---|---|---|
| Mechanical efficiency | Octet truss is best | Gyroid/D are comparable at high density |
| Fatigue resistance | Moderate — strut junctions are stress risers | High — no stress concentrations |
| Powder removal (SLS/DMLS) | Difficult — powder traps in nodes | Excellent — continuous open channels |
| Print quality | Drooping on thin struts | Self-supporting smooth surfaces |
| Fluid flow | Poor — irregular channels | Excellent — designed for flow |
| Design complexity | Low — easy to parametrise | High — requires nTopology or specialist software |
| FDM printability | Good (struts ≥ 2 mm) | Poor on standard FDM |
Software for Lattice Design
- nTopology: Industry standard for TPMS, field-driven lattice grading, and beam lattices. Interfaces with FEA tools (Ansys, Abaqus) for load-driven optimisation.
- Autodesk Fusion 360 (with Generative Design): Cloud-based generative design that can produce lattice-like outputs. Less precise TPMS control than nTopology.
- Altair Inspire: FEA-driven lattice placement with manufacturing constraints awareness.
- Siemens NX (Convergent Modelling): TPMS and conformal lattice generation for aerospace-grade workflows.
- Rhino + Grasshopper: Flexible parametric approach for custom TPMS geometries — steep learning curve but maximum design freedom.
- Meshmixer (free): Basic lattice infill for non-structural lightweighting on FDM parts.
Design Rules for Printable Lattices
- Graded lattices: Transition from dense lattice at load points to coarser lattice in low-stress regions — reduces weight by an additional 10–15% vs uniform density lattice
- Skin thickness: Always add a solid skin (0.8–1.5 mm) around lattice cores — prevents surface roughness from exposing internal struts and reduces fatigue crack initiation
- Powder escape holes (DMLS/SLS): For TPMS, the gyroid geometry self-drains. For closed-cell strut lattices, add 2–3 mm drain holes at the lowest point
- Support strategy for metal lattices: In DMLS, lattice struts act as their own supports if angled > 45° from horizontal. Gyroid and Schwartz P do not require internal supports.
- Cell size vs process capability: Unit cell should be at least 5× the minimum printable strut diameter for consistent reproduction
Applications at Layer X
Layer X regularly produces DMLS and SLS lattice structures for aerospace brackets, medical bone scaffolds, custom heat exchangers, and lightweighted motorsport components. Our DMLS machines can resolve 0.3 mm strut diameters in Ti-6Al-4V and AlSi10Mg, and our SLS line produces gyroid PA12 cores for composite lay-up tooling. See our full process capability or upload a lattice file for an instant quote.