Anyone with a 3D printer will eventually end up with an ugly, sagging mess – after a 3D print failed and gravity did its work on an overhang.
Overhangs, or prints without anything directly underneath them, are common in many shapes – ranging from minis for RPGs to sloping bowls, vases, or bridges. You’re going to come across those angles at some point; so how do you print them?
The easiest answer to printing overhangs is to keep them at 45 degrees or less. However, you can also use supports and several other tricks to ensure that your overhangs are supported and don’t sag or distort before they cool.
What Are Overhangs In 3D Printing?
Overhangs are any 3D printed material that doesn’t have 3D printed material directly underneath it. These overhangs naturally occur in most objects other than squares or straight shapes.
For example, the letter Y has two 45-degree angles and the letter “H” has a 90-degree angle. You’ll get angles in rounded shapes, sloping shapes, miniatures with small swords, and in anything you’re printing that doesn’t happen to be a column.
Overhangs often sag and deform for two reasons:
- The higher the angle, the less contact each line makes with the last line, because the printer is printing at an angle. This means the wall is weaker.
- The higher the angle, the greater the force of gravity on the material before it cools.
Some very common examples include windows; the arch is known as a bridge, because it’s material that bridges between two areas without overhang. You’ll have to use supports for those.
Other types of overhang are less straightforward. For example, if you’re printing at a 55-degree angle, you might be able to get away with other techniques that don’t involve supports.
4 Techniques For Printing Overhangs
If you’re 3D printing overhangs, you’ll have three basic options to do so. The first is the most common for anyone who wants to 3D print without supports.
However, the option you choose should depend on what you’re printing and what you want it to look like.
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1. Print at 45 Degrees or Less
If you’re printing at a 45-degree angle or less, you shouldn’t need supports.
However, if you’re printing very hot and very fast, you may still get some sagging, even with 45-degree angles. This means you should always check settings if you still have issues with sagging.
In addition, some people actually go out of their way to ensure that they aren’t printing anything at a steeper angle.
For example, a chamfer is a tool or technique that replaces steep angles with angles that are less than 45 degrees. That could save you a lot of hassle. Or, it could ruin your model and ruin its structural integrity.
Chamfering is a great option if steep angles aren’t absolutely essential to the look and feel or structural integrity of what you’re working with.
So, they can be worth checking and playing around with. For example, Cura has a chamfer setting built in.
2. Use Supports
Supports are the tried and true way to print overhangs and bridges. There’s nothing wrong with them.
They can be a hassle to remove. However, they will enable you to print beautiful structures with overhangs of more than 45 degrees.
Most slicers also offer the option to simply add supports. This means you don’t have to design the supports yourself.
Instead, you tick a box in your slicer, choose the support style, and go from there. In most slicers, the default setting is “line”, but you can select zig-zag, tree, or a number of other shapes.
In addition, if there are specific places you don’t want supports, you can always remove the supports from that area before printing.
You can also try reducing the number of supports as much as possible and test to see what you can get away with to minimize cleanup and support removal.
That’s especially true if you’re afraid the supports will mar the model, or you don’t know how to clean up the surface enough to hide the contact points.
If you have trouble removing supports, you can try using different support structures. For example, tree supports are extremely popular because they are easy to remove.
On the other hand, dissolvable supports allow you to print blocks of support material first and then print the object with the supports already in place.
This requires more time to print and a filament change halfway through but can reduce the time you spend removing those supports.
3. Design Supports Into the Model
Many people who dislike the look of supports try to design supports into their models.
This means that, where possible, you support bridges and overhangs with elements of design. That can mean adding decorative supports at less than a 45-degree angle. For example, using grass under a dog to support the dog.
It might also mean changing the design, reducing the slope, or otherwise taking steps to reduce the amount of support that you need.
Of course, this doesn’t work if you’re not comfortable with designing CAD files yourself.
If you’re just getting started, doing so can have a steep learning curve, and you may prefer another approach. In addition, this approach can be significantly limiting.
4. Print Overhangs on Their Sides
This isn’t always possible. However, it may be possible to simply tip your model over and print it on the side or upside down.
For example, if you’re printing a literal bridge with no ground, printing upside down solves a lot of your issues.
Often, this doesn’t work, simply because you’ll want detail on the sides that you can’t print without overhangs or you can’t print as a base.
Tips To Improve Overhangs
In many cases, you can print better overhangs or cleaner overhangs with or without supports by adjusting your printer or your slicer settings. In some, you’ll never be able to get away without supports.
However, there’s nothing wrong with supports, especially if you use PVA or design supports with thin bases, so they come off easily.
The following tips will help you improve your overhangs, so you need less support and they look more natural.
Improve the Slope
Reducing the slope of your angles can have a significant impact on the appearance of the model.
However, the more gradually you build up to a height, the more contact each layer makes with the one under it.
Improving the cooling is the most recommended tip to improve overhangs. The faster your filament cools, the less time it has to droop.
Here, the most used technique is to upgrade the cooling fans in your printer. Better fans mean more moving air and more cooling.
In extreme cases, you may also want to use quick stops, like the G04 command to pause the printer for a few seconds to allow the layers underneath to harden further.
However, you shouldn’t do this too much, as printing on a layer that’s too cold could cause issues with peeling.
Print at Lower Temperatures
The lower the print temperature, the faster your overhangs will cool and the less time they’ll have to droop.
Here, you can try reducing the printer to the minimum temperature recommendations for the material you’re using. That normally works out to:
|Minimum Temperature (Celsius)
At the same time, it’s important to check the minimum recommendations for the specific material you have. For example, metal and wood fill normally require lower temperatures.
In addition, printing at lower temperatures can cause other problems. For example, it may increase the risks of curling and peeling. It might also increase stringing, which you can solve by printing more slowly.
Reduce Layer Thickness
Reducing layer thickness reduces the impact of gravity per layer. It also reduces the time to cool that layer. Therefore, you’ll have fewer issues with sagging.
In addition, future layers will not weigh as less, giving the bottom layer the most possible time to harden enough to support the layer before the new one is added.
That can backfire because thinner layers are more prone to peeling, so you won’t want to reduce layer height to the minimum.
Instead, you’ll have to find a happy medium – usually by using thicker outer walls with thinner inner walls to get the best of both worlds.
- Thicker extrusion width is more rigid but harder to cool.
- Increase shell paths to increase the rigidity of thin layers.
Thinner layers reduce the angle at which your extruder prints. Thinner layers mean it takes more steps to create the same angle height, so each layer will be more gently sloped.
However, it will greatly increase print time.
Print More Slowly
Printing more slowly means you’ll give each layer more time to cool. You can do this by decreasing the manual printing speed in the slicer.
Some also prefer to simply print more models at once, meaning the extruder takes more time to get back to the original model.
In addition, you don’t want to slow print speed too much, as the extruder lingering in place too long can cause artifacts in your model – where the hot end starts to re-melt the existing layers.
Eventually, you want a happy middle ground.
Optimize Print Order
It’s highly possible that you can manually review how your printer is printing the walls and supports and adjust that to provide optimal support for your model.
For example, if you’re adding heavier weight onto an overhang, you could tell the printer to print other parts first.
Or, you could optimize the wall printing order to optimize structural support and strength, and hardening time for the walls that are sagging. This might not solve your issues, but it can reduce them.
If you want to ensure that your 3D print settings are good to go, you can use a 3D print overhang test file to check. For example, STLFinder offers a large number of them for free.
How To Fix Overhang Issues
In most cases, 3D print overhang issues include curling, drooping, and stringing.
Each problem has a different cause, although there can be overlaps.
If your 3d print overhangs are curling, it usually means there’s not enough contact with the layer below or the layers aren’t sticking.
In this case, you can:
- Reduce the angle of the overhang to improve filament contact.
- Reduce the layer height to reduce the angle the extruder is working at.
- Increase the heat of the extruder to improve filament adhesion. In this case, you’ll also want to increase fan speed and possibly add more cooling time for the next layer as well.
Curling can result from a number of issues with your 3D printer settings.
However, if it’s only happening with overhangs, the issue is likely that the angle reduces contact between the layers, causing them to curl up.
Drooping is the single most common issue with 3D printing overhangs.
However, you can take several steps to reduce it, including increasing cooling, increasing cooling time, decreasing layer height, and adding supports.
Stringing is a very common issue when printing overhangs.
Here, the solution is normally to reduce the speed of the print head. You might also benefit from lowering the print temperature, which will help with drooping as well.
If you still have questions about 3D printing overhangs, this FAQ may help.
How much overhang can a 3D printer do?
With the right settings, a 3D printer can do any amount of overhang that fits into the bed. However, that may require significant supports, depending on the size and shape of the model.
Without supports, you normally can’t go over 45-degree angles, although you might be able to with very careful settings.
What is the 45-degree rule in 3D printing?
If you print at 45 degrees or less, you shouldn’t need supports to print overhangs.
Otherwise, you likely need supports.
3D printing overhangs can be nerve-wracking and difficult. For many 3D printing enthusiasts, it requires learning technique, figuring out which settings affect overhangs, and finding a happy medium of reducing speed and temperature to improve cooling. Of course, you’ll never be able to do away with supports. However, you can often create beautiful overhangs with minimal supports if you get your slicer settings right.