Lattice Search

24 min

Find unit cells to meet the performance and aesthetic criteria for your designs in Design Engine's metamaterials library.

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Filters

Lattice Search Demo

Foam to Lattice Workflow

Launch Lattice Search from the quick-access button on the upper right of the design user interface.

You can also launch Lattice Search from inside the Strut Lattice tool, under Lattice Type. This will enable you to apply unit cell from your search directly to an input mesh, as shown in the demo video below.

Filters

Thousands of lattices are available in the metamaterials library and Design Engine provides filter options to narrow your results by performance and by lattice parameters.

Performance Filters

Two filters are available to search by stiffness within the unit cell's stress-strain curve: modulus and stress at 25% strain. You can also search by volume fraction to estimate the weight of the lattice.

Simulated Testing

In order to have performance data for thousands of lattices, the library utilizes simulated testing.

Simulations have been developed and validated from physical experiments on a wide cross section of EPU 40 printed lattice pucks.

Results yield a stress/strain curve and volume fraction for each lattice. For more details, read Building Carbon's Metamaterials Library.

Because data is based on simulations, final part performance may vary.

Our simulated mechanical response data reasonably matched experimental data on the small set of lattices we tested in a physical setting. However, these tests were performed with ideal, simple parts in a controlled environment. We do not expect the precise numbers shown to accurately describe performance of parts that are more complex or used in less ideal settings. The data like the stress-strain curves shown in Design Engine are best used as a comparative tool in evaluating a lattice’s performance relative to other lattices. Actual lattice behavior depends on specific use and is subject to variation inherent in manufacturing processes and different environments in which products are used. Users should validate lattice behavior in settings specific to their needs.

For more information on stress-strain graphs, reference Stress-Strain Curves.

For more information on volume fraction per lattice type, reference Mass Comparison

Shore hardness is measured with a durometer, which uses a small pin as the testing plunger, and provides a unitless measure of hardness via a dial or digital readout. The pin plunger is very small, ranging in diameter between 1.1 - 1.4 mm. As illustrated below, a lattice can miss the measurement entirely as the pin falls in the negative space between struts. Even if the durometer pin hits a strut to get a reading, the pin is too small to get an accurate sense of how the lattice is performing, which relies on how the struts work together as a unit. Testing lattice compression requires a platen or plunger that spans across one unit cell at a minimum, ideally multiple unit cells.

The pin applies a load to a depth of 0-2.5 mm, which most closely aligns with the modulus measurement used in Design Engine. If you are trying to match a material where you only have shore hardness data to pull from, you can approximate the roughly similar modulus metric via a conversion formula provided below.

Convert Shore Hardness to Modulus.xlsx

Note this conversion is approximate and should be considered a rough correlation only. The formula uses A.N Gent's equation for ASTM D2240 Type A durometer hardness.

Qualitative Comparisons

You may not have a quantitative performance metric in mind, and that's okay. Many designers approach lattices with other known materials in mind or just want to know what ballpark their application falls in to get started with lattice design. Below are some examples of common materials to give you a rough range of stress at 25% strain to help you gauge the stiffness of your lattice design in a qualitative comparison.

	Extra Soft	Soft	Medium	Firm	Stiff
Stress at 25% Strain (kPa)	0 - 20	20 - 80	80 - 200	200 - 1000	1000+
Reference Materials	Marshmallows Melamine Sponge	Gummy Bears Yoga Mat	Flip-flops Foam Roller	Eraser Cork	Tires Lumber
Reference Foams	Memory Latex Packing High Density Polyurethane	Rebond Neoprene EVA Foam similar to Poron XRD	VN600 Foam similar to D3O Aero	EPS VN740 Foam similar to D3O Decell VN1000
DLS Production	Material-dependent	Good	Good	Good	Often too dense
Applications	Comfort	Comfort	Supportive	Protective	Rigid

If you have a particular foam in mind that you are trying to replicate, see the Foam to Lattice Workflow example below.

Note that combining lattices with skins or using thicker boundary struts than the body of the lattice, can make the structure feel slightly stiffer in performance.

Lattice Parameter Filters

Standard lattice parameters can also be used to filter down results.

Cell Size

Narrow the cell sizes that appear in search results based on your part geometry and manufacturability.

Strut Diameter

Narrow the strut diameters that appear in search results based on your material.

Lattice Type

Lattice Search catalogs lattice types for both tetrahedron mesh and hexahedron mesh scaffold types.

Scaffold Type

Toggle between tet and hex scaffold type to search per mesh preference.

Hybrids are only available for tet mesh types.

The primary lattice types available will vary to match the selected scaffold type.

Tet Lattice Types

There are more options than just the five primary tet lattice types available in the Strut Lattice operation.

Two additional tet lattice types appear in the library: Kelvin (Tet) and Star (Tet)

Hybridized lattice types are also available in many combinations

Hybrid Lattice Types

The example here is 1/3 Star and 2/3 Voronoi. The unit cells of each type merge together to create a unique unit cell in the noted proportions.

Hybrid lattices are named by their components, using the first three letters of each lattice type, followed by their proportions as a percentage.

In this example: StaVor_3366

Hex Lattice Types

To create a lattice using a Hex Mesh, you must generate the Hex Mesh via the Hex Mesh operation before you can select and apply unit cell parameters via the Strut Lattice operation.

Gridded hex mesh with equal-sided cuboids

Lattice Search assumes a gridded Hex Mesh with equal XYZ hexahedron dimensions.

This equal-sided cuboid is the cell size of the strut lattice unit cell shown in the meta-materials library (MML).

When reviewing lattice performance in the MML, reference the closest approximate cell size to your hex mesh.

Note that when using the apply unit cell option when launching Lattice Search directly from the Strut Lattice operation, the cell size will not be applied, as the cell size of your Hex Mesh will be used. Only the lattice type and strut diameter will carry through.

Your actual hex lattice performance may vary depending on the type of hex mesh you use and the size and proportions of the hexahedrons in your hex mesh.

Note that there is a Star lattice type available for both tet and hex scaffold types.

Material

Elastomers

The metamaterials library currently catalogs lattices in Carbon's elastomeric materials:

Carbon Elastomers Energy Return and Stiffness

Energy Return to Damping EPU Pro 50 | EPU Pro 90 | EPU 41 | EPU 46 | SIL 30 | EPU 40 | EPU 43 | EPU 45 Soft to Stiff SIL 30 | EPU Pro 50 | EPU 41 | EPU 40 | EPU 43 | EPU 46 (tunable stiffness) | EPU 45 | EPU Pro 90

For more guidance and manufacturability information, reference the Lattice Parameters lesson.

Lattice Search Demo

https://player.vimeo.com/video/723872614

Note that using Lattice Search for a zone will only apply the lattice type to the zone, rather than all unit cell parameters.

When performance data is not available within the metamaterials library, a button to request performance data is available within the Strut Lattice tool.

Foam to Lattice Workflow

One of the key challenges that designers face when designing with a lattice is not having a clear path to mimic the mechanical performance and aesthetics desired. Searching a vast library can be a daunting task if you don't have specific performance criteria in mind.

A common path in lattice design is to have foam characteristics in mind as a benchmark for finding lattices that perform in a similar capacity.

Compare to Foams in Library

Carbon tested a cross section of common foams to capture data in the same format as the library's lattice simulation data, to provide a reference point for finding unit cells. For more details on Carbon’s testing and data modeling, reference this white paper.

Filter by Foam

In the materials filter, click on foam to see all foams available in the metamaterials library.

Generic Foam Details

Several of the foams we tested are from broad generic categories. To provide more context, below are the retailer specifications for these foams.

Generic Foam	Common Application	Retailer Specs
Closed Cell Foam (EVA)	Exercise Mats	EVA Foam "Firm" Density: 2.0 pcf (0.032 g/cc)
High Density Foam	Furniture Cushions	EverFlex V54 54 ILD (240 N) Density: 2.9 pcf (0.046 g/cc)
Latex Foam	Mattresses and Cushions	N28 28 ILD (125 N) Density: 6 pcf (0.096 g/cc)
Memory Foam	Mattresses and Cushions	13 ILD (58 N) Density: 2.5 pcf (0.040 g/cc)
Neoprene Foam	Gaskets	3 psi to compress 25% (20.7 kPa*) Density: 10.0 pcf (0.160 g/cc)
Packing Foam	Packing/Shipping	Y37ch Foam 35 ILD (156 N) Density: 1.2 pcf (0.019 g/cc)
Rebond Foam	Carpet Padding	90 ILD (400 N) Density: 8.0 pcf (0.128 g/cc)

* Results of Carbon testing did not match retailer specs. Testing conditions may vary results.

Foam to Lattice Search

Filter Foam Performance

Select foam to match

Check the box to compare

Filter modulus range close to foam

Choose a range +/- a couple hundred because the linear elastic range is generally a small part of the data set.

Filter stress at 25% strain range close to foam

Choose a tight range for best results

Filter Lattice Parameters

Select materials for application

Energy return in example

Select cell size range to suit geometry

Select strut diameter range to suit resin and cell size range

Select volume fraction range to suit weight goals

Optionally filter to preferred lattice types

Compare Results

Select up to 5 options to compare foam

Highlight foam for clarity

Hover cursor over strain at 50%

Match the closest compression metrics

Closest lattice

Apply unit cell to generate strut lattice

Check Unit Cell Manufacturability

In this example, Voronoi with a 10mm cell size and 0.8mm strut diameter closely matches our high density foam.

Check that the unit cell conforms well to your design space

Verify manufacturability for the unit cell

In this case, the parameters are well within the range of Voronoi's manufacturability in Carbon's DLS production

For manufacturability information for tet lattices, reference Unit Cell Manufacturability.

Compare to Other Foams

Align Data If you have your own foam testing data, you may need to align your data to match the format in Design Engine before comparing data.

Stress - Strain

Data may be in Force (N) - Displacement (mm) units rather than Stress(kPa) - Strain (%). The same curve may appear slightly different when plotted in different units, which can throw off your search results.

Stress

Divide force by the surface area of the testing apparatus on the sample.

If testing was performed by a plunger, use the plunger surface area. If a platen was used that covers the full sample, use the surface area of the sample.

Strain

Convert the displacement dimension to a percentage of the sample thickness.

Plot Curve and Compare to Lattices

Plot stress-strain curve

Plot data points at 2, 4, 6... 60% strain to match Design Engine graphs

Use the cycle 2 curve if you have multiple cycles

Perform a lattice search per the foam to lattice workflow above