FEA: Markforged Simplifies Structural Simulations of Printed Parts

Eiger software enables you to simulate multiple materials or printed parts without complex pre- and post-processing.

Most simulation engineers are used to working with isotropic materials. We know the exact makeup of the material all the way through a component. Simulation of anisotropic materials isn’t impossible, but much of it is done in the realm of scientific research. Using a material like wood in simulation is also possible, but engineers might have to simplify its properties to a more simplified orthotropic framework.

Simulation results from Eiger showing a factor of safety and deflection.(Image: Markforged.)

Simulation results from Eiger showing a factor of safety and deflection.(Image: Markforged.)

The current prevailing method of simulating anisotropic materials is for the simulation engineer to tell the program during pre-processing which phases of the part act like one material and which act like another one. This is time consuming and involves more than a little guesswork, or at least guided assumptions. 3D-printed parts pose another set of complications for simulation engineers. The fastest and simplest way to run a simulation for an additive manufactured part is to say that it’s one material and one density all the way through, but this doesn’t hold a high degree of fidelity to the actual physical components and systems.

To address these challenges, the engineers at Markforged recently announced new functions added to its Eiger software—simulation capabilities. These new functions are built to give engineers the ability to better simulate the geometrical complexities that come from a 3D-printed part. It can also help engineers deal with anisotropic issues like internal continuous fiber reinforcement. Bringing new functions into the software side of 3D printing might be long overdue, and this has the potential to bring great changes for simulation engineers.

The Good and Bad of Simulating 3D-Printed Parts

Rick Dalgarno, senior product marketing manager at Markforged, talked with engineering.com about the simulation functions in their Eiger software platform and how the 3D printing company is using simulation to improve engineering workflows. He says that simulation of additive parts starts with the same issues as any manufactured component. Environmental conditions, load cases, contacts and interfaces all factor into how the parts will be used in the field and affect the simulation. Printed parts present an extra challenge because of anisotropic material properties and geometry.

3D printing is also unpredictable on a simulation level. Engineers can work inside the printer settings to control percent infill, number of walls on the cross section, layer height and temperature. But how do these options translate to the simulation world when assessing the final product? Fused filament fabrication extrudes filaments along pathways; when lines meet, voids can form at the junction. Those voids can create orthotropic behavior even when a printer is only using one material. Meanwhile, recreating the infill patterns to represent the true 3D-printed component would add multiple levels of geometry and bog down processors.

Using the continuous fiber filament that is found in many of Markforged’s products comes with its own set of design trade-offs. Engineers use continuous fiber filament for specific design reasons, such as adding stiffness or strength to a part. However, a printed component with continuous fiber becomes even less homogeneous and less predictable. Simulating this material means that the solver needs to know what parts of the geometry are polymer and which are fiber. The act of placing fibers in the material matrix makes the full component highly orthotropic, and now the orientation of the fibers must be defined to get the best possible results with the highest degree of fidelity.

How Does Markforged Run Simulations Easier?

Using the simulation functions of the Eiger software, traditional bottlenecks in simulation workflows for 3D-printed and continuous fiber components are now automated. Meshing, material region assignments, and orientation definitions are all handled within the software. A user who wants the software to do the heavy lifting can set up the loads and hit solve to get results. The current goal for the Eiger simulation software is to simplify work, traditionally done by a finite element analysis (FEA) analyst, to get faster results with a high degree of fidelity.

The software shows the user a Factor of Safety to understand how strong the part is, uses deflection values to estimate part stiffness and shows what the load is when the part begins to yield. Working in the linear elastic region and zoning in on the predictable regions of stress makes the data sets much smaller and more manageable. Current studies show the user maximums for different factors as well as the deform part shape, but the next generations of the software could include contour plots and show where high and low deflections and stresses are found. 

Dalgarno noted that this is a full-fledged FEA solver, with many of the pre- and post-processing steps automated for the user who might not be comfortable wading into the deep simulation waters. The simulation functions in Eiger were available to customers in April, and the technology comes from Teton Simulation Software, which was acquired by Markforged in 2022.

The idea was to start very simple, creating a highly accessible tool that would have immediate value for the customer base. This is because the user base for 3D printing is diverse. Some users have no previous simulation or FEA experience and may struggle to bring the conditions from the shop floor into the simulation realm. Meanwhile, FEA engineers and designers will see a new simulation tool and wonder how soon it will be before it can do thermal studies, compressible flow dynamics and impact testing.

Time for the Software to Catch Up to the Hardware

Experience with 3D printing has wildly changed over the last two decades. The first additive manufacturing part I held in my hands was a stereolithography fuel component back in the early 1990s. It felt like magic—to think that the fabrication of a plastic prototype component that would typically require a mold and 6 weeks could be built overnight with no mold. Today 3D-printed parts seem to be everywhere.

There’s also been a shift to thinking of 3D printing as a toy as opposed to a tool for prototyping. Plastic dinosaurs or cosplay helmets might be infinitely cooler than a set of parts you’ve printed to check fit and function. But this is not as useful on an engineering level.

Printing hardware has also grown in stature year after year to let engineers and hobbyists print bigger parts with more detail and definition. New materials come online along with different nozzle types and larger gantries to print things as big as houses or as small as a few microns.

While additive manufacturing hardware has shifted and evolved, software hasn’t really seen similar improvements. Slicers evolved from G-code generation to proprietary code to open source. And that code changed to accommodate the hardware changes and smaller movements. Different infill sizes and configurations came along and innovative ways to build supports were born, but that all felt very physical. The software changes were happening to make the physical 3D printing easier rather than make the printed part in the virtual world before it’s printed.

The big players in simulation have 3D printing simulation tools, but most are akin to digital manufacturing and used for workflow communication and increasing throughput instead of structural analysis or computational fluid dynamics. Dalgarno says that perhaps this is the era when additive manufacturing software really ramps up, bringing new capabilities that are wildly different from what we can do today.