What do honeycombs, spider webs, tree trunks, coral, and even your own skeleton have in common? They’re all examples of naturally occurring lattice structures.
These powerful structures are most often made up of a regular, repeating pattern of interlocking “unit cells,” from simple boxes to complex, continuously curved surfaces. Other lattices involve more organic, irregular structures. In both cases, lattice structures provide unique capabilities due to their distinct combinations of strength, flexibility and surface area.
Importantly, lattice structures were impossible to manufacture on a small scale until the introduction of 3D printing, also known as additive manufacturing (AM). Because AM techniques build up structures layer by layer — as opposed to removing or “subtracting” material from a solid block — they can reproduce intricate lattice structures with a wide range of materials from plastic to metal to resin.
Lattices are now a hallmark of 3D printing, and additive manufacturing solutions come with tools that enabled designers and engineers to use them in vast range of product types.
But lattices are much more than an unusual design element. As we will see, they are revolutionizing product performance across many industries from aerospace to athletic shoes.
Lattice structures have unique properties that are extremely attractive to product designers and engineers as they deliver surprising strength and rigidity while using less material than conventionally manufactured parts. While this may seem like a simple concept, it results in a wide range of advantages:
Lattices use less material than solid structures. Basically, these structures do not add material anywhere it is not critical for maintaining strength and stiffness. The economic impact of this can be significant, allowing manufacturers to produce the same number of products with a lower investment in materials and typically a shorter print time. Lighter products also help considerably with fuel efficiency. Lattices save money on the back end because 3D printing wastes less material than, for example, machining a solid billet of titanium.
The unique construction of lattices gives them a total surface area that is orders of magnitude greater than that of the same size solid part. This is particularly helpful in applications that use surface area to achieve an efficient fluid, thermal or chemical interaction, such as heat exchangers.
To increase the strength-to-weight ratio of a part, designers will typically remove material from non-critical areas. Lattice structures offer a powerful way to optimize this process. Due to their geometric design, lattices can help achieve significant strength and rigidity while minimizing the amount of material involved. The result is of course a much better strength-to-weight ratios than with conventionally made parts.
Perhaps the most important advantage 3D-printed lattices deliver is the ability for designers to escape the rules and constraints of traditional manufacturing. Governed by a new set of rules and possibilities, lattices allow designers to pursue innovative, complex, and organic designs that perform as well or better than their more conventional counterparts.
There are dozens and dozens of subtypes of lattices, but these structures tend to fall into one of three categories. These categories are established by the geometric shape of the lattice’s unit cell.
Planar lattices are the simplest type of lattice. It takes a 2D (or planar) arrangement of unit cells, most commonly a honeycomb, and swipes it in three dimensions. Other examples of planar lattices include voronoi (mix of polygons) and kagome (triangles).
This type of lattice, like in crystals, can be built from 3D cells that tessellate volume. Examples of such cells are icosahedral (irregular), tetrahedral (four triangular faces), rhombicus (four-sided), dodecahedron, truncated octahedron or their combinations. 3D Voronoi is another popular way to generate such structures.
Strut lattices (also called beam lattices) are constructed with a series of interconnected rods (or beams) in various configurations. The struts may be joined at the vertex, edge, or face, as well as at multiple points. Combining these connections using 3D uniform patterns or via stochastic algorithms gives rise to a variety of lattices.
Triply periodic minimal surfaces (TPMS) rely on complex equations (such as sin(x)cos(y) + sin(y)cos(z) + sin(z)cos(x) = 0) that can’t be generated with conventional CAD tools. One of the most well-known is the gyroid, which occurs naturally in butterfly wings and has special thermomechanical properties.
A traditional FCOC heat exchanger was redesigned in 3DXpert with gyroids replacing the original tubes.
Lattice structures create a wide range of interesting and powerful design opportunities, helping to solve some of the most persistent challenges in manufacturing. Popular applications of lattice structures include:
Because lattices use less material, they weigh less. This is lattice structures can be used for “lightweighting,” a design process that aims to achieve a specific performance specification with the lightest possible structure.
Often this process is aided with Design for Additive Manufacturing (DfAM) tools that allow designers to create shapes and geometries that were not possible using conventional CAD software.
Lightweighted parts have big implications on fuel efficiency in automotive and aerospace manufacturing, where every ounce saved delivers a substantial reduction in fuel costs.
A heat exchanger is a device that facilitates the process of heat exchange between two fluids that are at different temperatures. You can find them in many engineering applications, such as refrigeration, heating and air conditioning systems, power plants, chemical processing systems, food processing systems, automobile radiators, and waste heat recovery units.
Lattices are unlocking new opportunities for heat exchanger optimization because they have a very high surface-to-volume ratio that enables extremely efficient heat transfer.
Recently the University of Dayton Research Institute worked with Oqton to redesign a fuel-cooled oil cooler (FCOC) by replacing the original tubes with a gyroid structure. The gyroid was used to enhance heat transfer, automatically seal opposite fluid domains, optimize the flow path, all while allowing different sizing of fluid domains to accommodate the varying viscosities of fuel and oil.
Lattice structures are ideal for impact absorption. By varying the density and cell type of lattices, designers can create structures that absorb energy and redirect it more effectively than traditional foam.
This ability to absorb and redistribute impact forces in multiple directions has wide-ranging applications in consumer goods that need to be strong but flexible, like running shoes and bike helmets, among many others.
Osseointegration is the process of connecting living bone tissue to the surface of an implanted device. Lattice structures are particularly well suited for medical implants that promote bone growth because they can be 3D printed as part of the implant — as opposed to a separate coating that is applied to a machined part.
Lattice structures in these implants resemble a porous grid where the pore size, strut size and porosity levels can be adjusted for a specific person’s implant. This allows more effective osseointegration, resulting in more comfort for the patient, faster cell growth and a stronger bond between the implant and the bone.
Lattice structures made from polymers behave similarly to foam in that they can deform and return to their original shape. These 3D-printed foams can be used to increase the cushioning ability of bicycle seats, helmets for football and hockey, other sports equipment, and prosthetic devices.
With 3D-printed lattices, product design and engineering teams gain a powerful way to solve a range of practical challenges. In other words, product teams can combine the ability of lattices to reduce weight, increase strength, absorb energy, and improve customization in ways that have never been done before. In addition, DfAM tools make it easier than ever to generate and apply these lattices.
Lattices are sometimes used as a design feature for eyewear. Designed and manufactured with 3DXpert.
Additively manufactured lattice structures are already making a meaningful difference in a wide range of industrial applications. Some of these include:
Lighter components that maintain necessary strength are very attractive in the automotive world. Porsche, for example, made a 3D-printed e-drive housing that contains a lattice structure inside of a solid exterior. The lattice structure reduced the weight of the housing by 40% and the weight of the e-drive by 10%.
In another example, an Italian product development firm called Puntozero designed a cold plate for a high-voltage converter using gyroids that was 25% lighter with a 300% greater surface area than the previous design.
Lattice structures have been incorporated in spinal implants for treating degenerative spine diseases. These lattice structures reduce stiffness and allow forces to be transmitted into the spine, which helps reduce bone atrophy around the implant.
Lattice structures made from titanium used in knee implants have been shown to maintain the natural mechanical loading in the tibia after knee replacement surgery, which conventional metal implants were unable to do.
As in the automotive industry, 3D-printed lattice structures allow aerospace manufacturers to dramatically reduce a part’s mass to increase fuel efficiency and reduce fuel costs. Any mass reductions to the part also allow the vehicle to increase its payload, which directly affects profitability.
Examples include landing gear parts that use 3D-printed metal to improve reliability while reducing weight and an electrical generator housing that incorporates a high-density lattice with more than 10 million elements. Other popular applications of lattices in aerospace include the heat exchangers discussed earlier and structures that absorb and redirect energy, such as a vibration-absorbing part in a rocket body.
Lattice structures are appealing in architecture due to their ability to capture a very large surface area while minimizing materials. Branch Technology, for example, has created a 3D-printed lattice using ABS plastic reinforced with carbon fiber that is used as the core of a modular wall system that is both lightweight and durable.
Lattice structures can be made with a range of materials, including metals, polymers and composites. Selecting the right material for a specific application is important because the material choice will affect the size and density of the lattice.
In general, softer and more elastomeric materials require a smaller, denser arrangement of unit cells with thicker struts and nodes to prevent sagging during the 3D printing process. Metals and more rigid materials allow you to use larger unit cells with thinner struts.
While 3D-printed lattice structures create important opportunities for product designers and engineers across multiple industries, they are not a silver bullet. Just as they deliver unique properties, they also bring unique challenges.
Complex lattices can be difficult to print because the 3D models can be too large for computers to comfortably convert into printable STL files. This can cause slowdowns and increase the risk of data loss. This is why 3DXpert software from Oqton integrates design and print preparation, eliminating the need to convert the lattice to an STL file prior to printing.
For osseointegration products, the distribution of pores is a critical success factor for bone growth and one of the most difficult design aspects to evaluate. 3DXpert includes dedicated pore distribution histograms to validate these lattices for medical products. Similarly, the software includes tools for understanding the interactions between the open side of a lattice and the human body in medical applications. These tools help prevent any sharp, protruding struts that could cause tissue damage.
3DXpert also allows designers to detect and adjust lattice struts with very low horizontal angles, which may compromise printability, as well as adjust and define dedicated slicing parameters to ensure optimal part quality and faster production.
Creating products with complex lattice structures can also seem intimidating to those who are not intimately familiar with all of the ins and outs of additive manufacturing. This is where 3DXpert’s Heat Exchanger Application can be very helpful. It includes features that are designed to streamline design of lattice structures and additive manufacturing workflows, so teams can easily create lattice structures and iterate quickly to find the best approach.
It is critical to note just how new these lattice structures are. Some of these geometries were literally impossible to manufacture as recently as five years ago. It is understandable that product designers are still exploring how best to take advantage of these structures in product designs and with new 3D printing techniques.
What is most exciting is the potential these structures have to push the envelope of product design, leading to lighter, less expensive, more efficient products that exceed expectations for performance.