3D Printing Overhangs: What They Are & How to Improve Them

3D printing overhang is a unique structure, and it's challenging to achieve perfect print results with them. It's possible to avoid overhangs when designing a 3D model, but this will limit creativity. Thus, it's difficult to eliminate them in 3D printing. Although adding supports can create perfect overhangs, they might decrease the surface accuracy of the printed object and lead to increased printing time and material costs. There are many printing techniques to improve overhangs, as well as various methods to avoid overhangs. It's essential to choose the right solution that suits your needs to enhance the quality of your prints.

Printing with reliable 3D printers and adjusting print settings in slicer software can significantly improve poor overhangs, while modifying your 3D model design, adjusting the print orientation, and generating supports can help you avoid overhangs. Let's explore what 3D print overhangs are and how to improve them.

What Are Overhangs in 3D Printing?

3D print overhang test

(3D printer overhang test)

When printing overhangs on an FDM 3D printer, the part is built layer by layer, extending outward from the bottom, eventually forming a slope angle, and there is no support at the bottom. Therefore, creating models with overhangs is more challenging compared to those without any protruding parts. Failed overhangs display drooping and curling layers, and even worse, they collapse. Due to gravity and insufficient cooling, the material will not fully solidify resulting in deformation and sagging downwards.

The 45-degree rule can answer the question of how much overhang a 3D print can have without support. Overhang angles greater than 45 degrees require support structures for achieving high-quality prints, whereas angles less than or equal to 45 degrees can be printed directly, maintaining clean overhang quality.

Fortunately, there are many printing techniques available to successfully print overhangs beyond 45 degrees.

What Is the Difference Between Bridge and Overhang?

Bridges and overhangs in 3D printing are quite similar, but the noticeable difference is that a bridge has layers at a 90-degree angle supported at both ends, while an overhang looks like a slope with a single end. Their similarities include no support at the bottom and being challenging to print. A bridge typically follows a 10mm rule, indicating that a bridge length of 10mm is ideal, while a 45-degree rule for an overhang can get good results.

Here's a more intuitive example to help you understand their differences: the letter 'H' is like a bridge, often forming a 90-degree angle, whereas the letters 'T' and 'Y' have arms extending outward at different angles, resembling an overhang.

How to Get Better 3D Print Overhangs

1. Reduce Printing Speed and Flow Rate

Slow down to overhang 3D printer
(Left: Before speed adjustment; Right: After speed adjustment)

When printing 3D print overhangs, reducing the print head speed allows the filament sufficient time to cool down and harden, thus, improving print quality. If, after decreasing the speed, you notice signs of over-extrusion such as excessive material on the overhang surfaces, you can fine-tune the flow rate within the slicer settings to reduce the amount of material pushed out by the extruder.

2. Lower Print Temperature and Enhance Cooling

3D printer strong cooling fan

(Anycubic Kobra 2 Pro fast printer with upgraded cooling )

You can try lowering the nozzle temperature, which, similar to reducing speed, helps the melted filament solidify quickly. Try making slight adjustments to it. If you're using popular PLA filaments, it's advisable to check the 'Best Temperature for PLA' article to find the optimal temperature.

Insufficient cooling can lead to various issues, such as 3D pillowing on the top layer and poor overhangs. A strong cooling system helps plastic solidify rapidly, reducing problems like overhang drooping and curling. Therefore, check your printer fan and ensure it operates at 100% when printing overhangs.

3. Print with High-Quality and Dry Filaments

High-quality filaments to improve overhangs

Always use filaments from trusted and reputable brands, as they typically offer quality-assured products that result in high-quality overhangs. Some low-quality filaments may contain impurities during production and might suffer moisture damage due to poor packaging. Anycubic is a trusted manufacturer of 3D printers globally, offering basic PLA, tough PLA Plus, textured Silk PLA, and Matte PLA. Additionally, they also provide High-speed PLA for printing, ASA Filament for high-temperature resistance, and PETG for high toughness.

Properly storing and keeping your filament dry ensures that your overhanging layers remain intact and smooth. Store them in a dry environment, such as a sealed container, along with desiccants. What's more, an oven, a food dehydrator, or a filament dryer box are effective tools for drying filament that has unfortunately absorbed moisture.

How to Avoid 3D Print Overhangs

Orient 3D model to reduce overhangs

1. Edit Your STL File

If your part doesn't have strict dimensional requirements, you can modify the model in CAD software. Adding chamfers helps reduce slopes greater than 45°, making them into slopes less than 45°. Additionally, design steep slopes as 90-degree bridges, as they are easier to print.

Another simpler way to avoid overhangs is by using programs like Cura or Meshmixer, to split your 3D model. Then, after printing, you can use glue to assemble your split 3D parts.

2. Orient Your 3D Model

Changing the orientation of your model can minimize supports and reduce overhangs and bridges. You don't always have to use vertical printing. Try other orientations, such as rotating 90° for laying flat, or rotating 180° for flipping upside down.

3. Add Support Structures to Your Model

Using supports is one of the most effective methods to create perfect printing overhangs. Adding supports beneath these overhanging sections can be generated automatically by the slicing software's algorithm or added manually by yourself. After printing, supports must be manually removed. If noticeable support marks appear on the surface, they can be smoothed out by sanding.

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