Top Advantages—FDM Sparse Fill

The FATHOM Design and Engineering Team Weigh In

When 3D printing with FDM, designers and engineers can choose between using a solid fill pattern or a sparse fill pattern. Solid fill designs result in parts more traditionally associated with 3D printing, block-like structures with consistent density throughout. But sparse fill has some significant advantages over solid fill. We sat down with FATHOM Industrial Designer Ava DeCapri and Mechanical Engineer Bethany Casarez to find out their favorite aspects of this design technique.

Top 4 Advantages of Using FDM Sparse Fill in 3D Printing

1. Reduced Weight, Part Cost, and Build Time

Ava DeCapri, FATHOM Industrial Designer—“With traditional manufacturing there is often no way to easily reduce the material used inside of a solid part which often doesn’t need to be completely solid. But by using geometry in a smart way, a sparse filled part can be just as strong as a solid part.”

Bethany Casarez, FATHOM Mechanical Engineer—“I use sparse fill to save material and reduce time. Many parts don’t require the strength of a solid plastic block. When this is the case, I always sparse fill them to save material which saves money, as well as time—I’m impatient. For many applications, weight reduction is a high priority—drones, ergonomic hand tools, prosthetics—to name a few. Sparse filling is a great and easy way to reduce the weight of a part while maintaining a lot of stiffness and strength.”

2. Easy Manipulation of Mechanical Properties through Design

Casarez—“An interesting thing that sparse filling allows you to do is control the center of mass of an object. You can control the densities of different regions of a part, and make certain regions denser than others. For ergonomic hand tools, you can control how the tool is balanced to reduce unwanted loading conditions for repetitive actions. You can also choose to make regions of a part that experience high stress conditions denser than regions with low stress.”

DeCapri—“When you start getting into more complex fills, you can start to manipulate the mechanical properties of the material. Introducing spring-like infills, for instance, can give your part some elasticity that otherwise would not be present in a solid filled part.”


3. Crazy Aesthetics, Without Any Additional CAD Work

DeCapri—“I often utilize sparse fill to add an aesthetically pleasing pattern to a part, if the sparse fill is left exposed, without having to create the geometry in a CAD program. You can load copies of the same part onto one build and select a different infill for each part, generating designs that have many different surface patterns without doing any work in CAD.”

Casarez—“By removing the top and bottom layers of a sparse filled part, you can see the crisscrossing internal structure. You can change the sparse fill parameters to create different patterns that are really visually complex.”

4. Self-Supporting Parts = Easy Post-Processing

DeCapri—“Many sparse fill patterns are self-supporting, so they don’t really produce any challenges with post processing the parts, because there isn’t any support material in the sparse filled volume that you would need to clean.”

Is there a project you’ve completed recently not under NDA that shows what can be done with sparse fill?

DeCapri—“One of our coolest examples of what you can do with infill patterns is probably the giant FATHOM logo we produced for our Oakland office. We created a custom infill that was designed to look as though it is filled with random extrusions of filament, but really is a complex pattern of overlapping angles of filament paths.”

Casarez—“Another cool project we did recently was to create molds for structural mycelium. The mycelium has to dry on the mold, so we created tiny gaps in the 3D printed part to allow air to flow through the mold and expedite the drying process. This also created a very interesting texture on the surface of the mycelium, very similar to paper pulp packaging.”

Guidelines & Considerations

Fortus machine owners can experiment with the different sparse fill settings by tweaking parameters in Insight, the Stratasys slicing software. Design series printers such as the Dimension and uPrint have the option to create a high-density or low-density sparse fill, but the software does not allow the tweaking of any tool path parameters—default settings are compulsory. Don't have a Fortus system? FATHOM customers can request FDM parts with the sparse fill option (save money and reduce part weight, provided that the part strength reduction is acceptable for the application). Learn more by talking with an account manager.

To learn more about sparse fill techniques, including finishing, drying, and other best practices for sparse filled parts, check out recent instructional papers from Stratasys—this 3D printing technique is suited for Fortus FDM Additive Manufacturing Systems:

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