Your Guide to Cura Tree Supports

Why do you need support structures?

3D printing is unique among manufacturing processes for its ability to produce incredibly complex shapes. Some 3D printing processes, like Fused Deposition Modeling (FDM), however, need a bit of help sometimes to achieve these intricate geometries. Some support, if you will. 

3D printers struggle to print certain features, like overhangs and bridges, because the filament is not adequately reinforced and will succumb to gravity if they are printed in mid-air. That’s where support structures come in. Supports are automatically generated in slicer software programs such as Ultimaker Cura and enable 3D printers to produce parts with overhangs and bridges. 

Overhangs are shapes on a 3D model that jut out at angles of over 45°. Bridges, for their part, are horizontal structures that typically connect two vertical structures. Supports are required to print both these elements so that the filament layers are supported as they are extruded.

There are two main types of support structure: normal supports—also known as linear supports—and tree supports. Regular supports are vertical structures that grow straight up to support overhangs and bridges. This type of support structure reinforces the entire overhang area and typically consists of a solid shell and infill.

Tree supports, the subject of this article, are more organic in shape, growing like tree branches around the 3D model to support overhangs and bridges. One of the defining characteristics of tree supports is that they are printed wider at the base of the model and gradually taper off, providing adequate support while minimizing contact points with the 3D printed part. Tree supports are also hollow, consisting primarily of a shell, which is easy to remove post-printing. 

Recommended reading: Cura Support Settings Explained

Unlike linear supports, tree supports wrap around the 3D model, providing support directly where needed.

How Cura Tree Supports Work

In the FDM 3D printing process, a print head extrudes melted thermoplastic filament onto a build platform. As the material is deposited, it begins to solidify. This is repeated layer by layer until an object is built up. In general, supports are needed when the layers of the print do not have enough support from the layers underneath them. 

Cura tree supports differ from regular supports in that they can be printed at different angles, rather than straight up. This enables them to adapt to the printed model’s geometry easily. In other words, they are printed around the model. Cura tree supports ultimately provide direct reinforcement to overhangs using the tips of their branches. This unique approach not only provides adequate support, it also results in fewer contact points between the support structure and the printed model. In the end, this makes the tree supports easier to remove.  

In Cura slicer software, tree supports can be activated under “Support” settings. There are also several parameters related to tree supports that you can adjust. Below are some of the key Cura tree support settings you should know about:

• Support placement: With this setting, makers can choose between two options: “touching build plate” and “everywhere”. Touching build plate will generate supports only using the build platform as a base. Everywhere, on the other hand, will generate supports from both the build plate and the 3D model, if needed.

• Support overhang angle: Setting your support overhang angle will determine at what degree overhangs will require a support structure. All FDM 3D printers can print overhangs of up to 45° without supports, and many can handle angles of up to 50-55°.

• Support branch angle: This setting is unique to tree supports. The support branch angle controls the maximum angle that tree supports will be printed at. A higher value for the support branch angle will result in more freedom for branches to be printed around the model (this means fewer contact points). That said, increasing the support branch angle too much can lead to less supportive branches. A lower support branch angle will result in more vertical branches that are more stable.

• Support branch distance: This parameter determines how far the top of the support branches will be to the edge of the overhang. A lower value for branch distance will result in more contact points, which will provide greater reinforcement and increase the quality of the overhang. However, a smaller branch distance can also make the tree support branches harder to remove.

• Support branch diameter: This setting controls the minimum width of the branch. In other words, how small the branch diameter will be at its thinnest point. A smaller branch diameter will reduce the amount of material usage, but a wider branch diameter will provide greater stability.

• Collision resolution: This slicer setting for tree supports ensures that the supports don’t intersect with the 3D model when they are generated. 0.2 mm is the default collision resolution setting in Cura. Increasing the value can lead to faster printing times, but lower quality tree supports.

The Pros of Cura Tree Supports

Cura tree supports have several benefits, which have made them increasingly popular within the maker community. Let’s take a look at some of the main benefits tree supports offer.

Less Material & Printing Time

Open source Cura software developers first came up with tree supports as a way to reduce the amount of material waste generated by supports. They were successful in this effort: tree supports use significantly less material than standard supports because they are almost entirely hollow and because they taper in width. This helps to reduce material waste and material costs. As an added bonus of using less material, tree supports are also faster to print than conventional support structures. Cura software will tell you how much material supports will use and how long a print will take, so you can directly compare standard and tree supports for a given print job.

Smoother Surface Finish

Another reason to use tree supports is that they can improve the surface finish quality of 3D prints compared to traditional supports. This benefit is owed to the simple fact that tree supports are designed to minimize contact points with the 3D model. In some cases, the only touch points between the tree supports and the 3D printed object will be the tips of the branches that support the overhangs. Tree supports therefore require minimal post-processing and shouldn’t affect the quality of intricate or finely detailed 3D prints.

Easy Support Removal

Easy support removal is another consequence of having minimal contact points between the tree supports and the 3D printed model. Normal supports can sometimes bond to the 3D printed model making removal challenging, even requiring tools like pliers to take them off. Tree supports on the other hand consist of a shell around the print with minimal contact points. In most cases, this means they can be peeled off the final print by hand without significant risk of damage.

Recommended reading: Improving your 3D printing success rate with Ultimaker Cura

Tree supports are generally easier to remove than linear supports because they have fewer contact points. Image Credits: Ultimaker

The Cons of Cura Tree Supports

Now that we’ve seen the benefits of using tree supports, let’s take a look at the potential downsides.

Longer slicing times

The main disadvantage of using tree supports is that the support structures require more processing power than traditional linear supports. Because tree supports have a more complex geometry than linear supports, they take longer to generate in slicing software. This can minimize the benefit of faster support printing times (though rarely negate it).

Less suitable for soluble PVA supports

Due to their complexity in shape and geometry, tree supports can also present a challenge if you are using a soluble support material such as PVA. PVA is a harder material to print compared to PLA or ABS and some 3D printers can therefore struggle to achieve the finer shapes that characterize the tops of tree supports. Cura therefore recommends using its tree support function primarily for non-soluble support materials.

When to use Cura Tree supports?

While the disadvantages of Cura tree supports are minimal compared to the advantages, there is still a time and a place to use them. In some cases, standard 3D printing supports may be more beneficial. In others, tree supports are the clear way to go. There are three main scenarios where tree supports make the most sense.

First, if you are printing an object where the visual quality is of the utmost importance, tree supports are highly beneficial. Because tree supports are designed to have fewer connection points to the 3D printed part, removal is easy and results in fewer marks or imperfections on the part’s surface. 

Second, if you are trying to consume less filament, tree supports will generally use less material because they are hollow shells. If you need greater stability, you can also choose to print tree supports with a low infill density. Using less material for supports will help you minimize material waste and cut back on material costs in the long run.

Third, tree supports are highly beneficial if you are printing a component that requires tight tolerances. Because regular supports sometimes need to be cut off, makers need to sand down the support remnants from the part surface. Sanding and other post-processing steps can influence the part’s dimensional accuracy. Tree supports on the other hand require minimal post-processing (often no post-processing) and can be removed without affecting the part’s tolerances. 

Recommended reading: How to Remove Supports from 3D Prints

Conclusion/Key Takeaways

Whether you are a beginner or experienced maker, it is important to know what features are at your disposal when it comes to 3D printing. Still a relatively new option in Cura slicer, tree supports provide many advantages that makers may not yet be familiar with. With the knowledge in this article, however, you should be prepared to make the most out of automated tree supports and their print settings.

References

Ultimaker, 2022. "Tree supports: What are they and how do they work?" [Internet]

https://ultimaker.com/learn/how-to-use-tree-supports [Accessed June 2, 2022]