This article was written by Chloe Vollaro, 3D Printing Applications Engineer at Protolabs
Key Takeaways
- What are lattice structures? They are unique to 3D printing and help make parts lighter, stronger, and more heat-efficient.
- What are the challenges of lattice structures? They require access holes or supports to remove raw material or prevent sagging. They also need careful design to avoid islands or overhangs.
- What are the best technologies for lattice structures? SLA and DMLS have the most design freedom, but may need supports or drain holes. SLS and MJF have no supports, but need more access points.
- How to design lattice structures? Consider bridge distances, angles, edges, and endings of the lattice. Use a calibration object to test the settings before printing.
Lattice structures, or mesh structures, are unique to 3D printing. These lattices are a versatile tool for engineers that help make parts lighter and stronger.
They can also help reduce part volume, leading to fewer surface defects and preventing excessive stress buildup — while saving on build time and cost. The additional surface area of lattice structures can also be used in heat transfer applications.
Read on to learn how to use lattice structures in your 3D printed parts without making a mesh of things!
Lattice Structures for Different 3D Printing Technologies
With most 3D printing services, the parts are built surrounded by raw material, whether it is resin or powder. Consequently, lattice structures can’t be completely enclosed. The parts will need access holes so that the raw material can be fully removed.
In Fused Deposition Modeling (FDM), which is a type of 3D printing using filaments, the parts are built with air inside them. This means that the internal lattice of the part is enclosed by the outer walls.
Utilizing lattice structures while using more advanced resin- and powder-based 3D printing technologies is still a reality. You just need to consider the following factors:
Technologies with Support Structures
Stereolithography (SLA) and Carbon DLS are resin-based technologies that require supports when printing.
For these technologies, having a few drain holes is key for rinsing the uncured resin out of the part prior to the UV post-cure. If any uncured resin remains, it will solidify during the post-cure process.
If the lattice needs to be completely enclosed, drain holes can be added for the build and part cleaning, and then plugged before shipping.
Direct metal laser sintering (DMLS) is a powder-based technology for metal 3D printers that also requires support structures.
Unlike powder-based plastics, the metal powder is not caked onto the parts. The powder flows freely, like sand, making cleaning out of internal cavities much easier.
Industrial 3D printers like Protolabs often have a powder removal machine that shakes and vibrates parts to get powder out of complex internal channels. However, any remaining powder inside the part will solidify during the stress relief cycle. If a channel or cavity needs to be clear, ensure there are plenty of places for powder to drain.
Support-Free Technologies
Selective laser sintering (SLS) and Multi Jet Fusion (MJF) use powder-based plastic materials.
Both technologies rely on partially sintered or partially fused powder to support the parts during the build, removing the need for additional support structures. This means that the powder surrounding the parts is caked on like dried mud.
Compressed air is often used to remove the powder after the build, but a direct line of sight to the powder is required to clear it out effectively. While the air will eddy around the inside of the cavity, only the powder directly in front of the air nozzle will be removed.
Because of this, lattice structures for SLS and MJF should be designed with plenty of access points for clearing powder.
Below are examples of parts with increasing access to clean out the partially sintered/fused powder.
The first example, below, allows very little powder to be removed. Powder will be cleared in the area around the opening, but the far corners of the part will be filled with powder.
This example is better; there is significantly more access to blow out the powder. However, some powder may remain in the very back of the part in areas that are the hardest to reach.
This last example below is ideal. There is plenty of access to remove powder, and powder removal can be approached from both sides.
How to Design Your Lattice
Below are guidelines on how to design lattice structures that won’t trap raw material or require inaccessible supports.
The two main obstacles for a self-supporting lattice are bridge distances and angle from the build plate.
SLS and MJF have the most design freedom regarding support structure. The ideal lattice for these technologies is relatively open, so there is plenty of access to blow out un-sintered/un-fused powder.
Since SLA can span much larger distances without requiring supports, most lattice designs will be self-supporting. If the lattice needs to be entirely enclosed, drain holes are added to the part for the build and then plugged with the same material after removing the uncured resin from the inside.
DMLS is the most challenging technology for which to design lattice structures, as it can only span about 0.079 inches (2mm) before requiring supports. Bridge distances and self-supporting angles play a much bigger role in avoiding supports inside a lattice.
Guidelines for Self-Supporting Features
| Max Bridge | Min Angle (Degrees) | Recommended Lattice Member Thickness | |
|---|---|---|---|
| SLA | 0.300” (7.62mm) | 45° | 0.030 in. (0.76mm) |
| DMLS | 0.080” (2.03mm) | 45° | 0.050 in. (1.27mm) |
| SLS and MJF | n/a | n/a | 0.125 in. (3.16mm) |
Examples of Lattice 3D Designs
The following six examples feature different types of lattices. Each of these would be self-supporting in SLA due to short bridge distances.
However, only some of these examples would be self-supporting in DMLS. Read on to see which lattices need supports in DMLS and why.
Orange features indicate areas that require a support structure. It is important to note that while it is possible to remove support structures on the outer edges of a lattice, supports in the center of the lattice cannot be removed.
The highlighted areas need supports because the bridge distance exceeds 0.080 inches (2.03mm).
The highlighted areas need supports because the bridge distance exceeds 0.080 in. (2.03mm).
The highlighted areas below need supports because they grow in as overhangs at an angle less than 45 degrees to the build plate.
These are considered overhangs, not bridges, because each side connects back to the part at a different Z-height. The other parts do not require supports because they grow in at a high angle.
This lattice below is self-supporting because all features grow in at an angle ≥45 degrees.
The highlighted areas below need supports because the bridge distance exceeds 0.080 inches (2.03mm).
This lattice below is self-supporting because all features grow in at an angle ≥45 degrees.
Ensuring Your Lattice Edges Are Strong
The edges of the lattice also need consideration because they ensure part integrity. Even a self-supporting lattice may require some support structures where it meets a solid section of the part.
One way to avoid support structures is to make the area between the top of the lattice and the wall of the part solid. Alternatively, if some support structures are acceptable, the part can be built as is.
The lattice pictured to the left is self-supporting. However, when the roof of the part comes in, the bridge distance is too long, and these areas will require supports. The lattice on the right has the top area filled in, and doesn’t require supports.
If the lattice structure doesn’t end in a wall, as in the example above, the lattice should end as neatly as possible.
In the example below, the left side of the lattice ends in such a way that some features will need supports. The image on the left shows a cross-section representing what this part will look like as it grows in.
Notice there are four islands, in orange, that grow in floating, as opposed to growing off an existing feature. Any features that grow in like this will require supports.
The orange boxes in the picture on the right show where supports will be on this part if built as is. While these supports will be accessible, there is a risk that the fine lattice features could bend or break as part of the support removal process.
Ideally, the lattice would end in a way that avoids these islands, as with the right edge of the image below.
