3D Printing Brim: When Should You Use It

Warping is a 3D printing issue that causes the first layers of the print to shrink due to the pull of layers further up. This is something that happens as the print advances. When warping becomes apparent, you may have already invested a lot of time and material on the print.

Warping can happen with many filament materials, although some are more prone to warping than others. ABS, for example, is notorious. Low-quality filaments are also more likely to warp. In addition to materials, the actual design of the model can lead to this issue. Large flat-bottomed models, for instance, might warp during printing.

Using a brim helps with warping because it acts like a net that forces the bottom of the print to stay attached to the bed. Similar to the way the upper parts of the print may try to pull the base up, the brim will pull it down, keeping it in place.

When you want to use a brim to prevent warping, the line count defining the brim’s width will depend on the surface area of your base layer. The bigger it is, the more lines the brim should have so it has enough strength to pull on the part.

Risky Geometries

Imagine printing a standing horse. Each hoof and leg prints separately, then attaches to the body as the print progresses. These small individual parts can come loose due to the slight pull of the filament with each layer added. It’s not uncommon for the print to start without problem, and a few layers up, one of the hooves detaches from the bed. The print is then ruined.

Similarly, parts with prominent curves in the first layer or even sharp corners can have trouble adhering to the table. This can be solved with brims, which help contain the geometry in place. If you’re going to print a sphere or similar geometries where there’s a very small surface touching the build plate, a brim can prevent detaching from the build plate.

Small Support Structures

If a print needs supports but doesn’t have enough space to place them because, for example, the detail they’re supporting is too small, the printer can have trouble placing such a small geometry, and the supports may not adhere correctly. Therefore, brims can help contain the geometry of the support the same way as they would with the main print. This is because plastic attaches better to itself than to any other materials, which is the reason why everything usually goes smoothly after the first layer.

A brim basically takes the brunt of the first layer adhesion effort. That way, the actual part to be printed can simply attach to the brim itself.

When Not to Use a Brim

If you’re considering a brim to check that the print bed is correctly leveled, that the filament is being extruded, or other print settings but don’t need actual first-layer adhesion aid, you’d be better off using a skirt. It uses less material and doesn’t touch the model.

Using brims is a good way to check the calibration and first-layer adhesion before starting the actual print. However, a brim can mess with the dimensional accuracy of parts, as it may be attached too firmly, requiring cutting and possibly sanding.

Brims can negatively affect parts that have a snap-fit functionality or those that need to be assembled into other parts. Such parts require high dimensional accuracy, but brims can actually change the final geometry of your model. You may not need to avoid it completely, but it’s important to consider the optimal bed orientation to preserve the print’s functionality.

In contrast, if you’re going to print a figurine, where dimensional accuracy isn’t as important, you can use a brim to help the first layer without it affecting the final result at all.

Pros & Cons

All of the above said, let’s take a look at the pros and cons.

Pros

• Brims prevent warping issues.
• They improve bed adhesion, leading to higher chances of a successful print.
• They use less material compared to a raft and are easier to remove.
• Brims don’t alter the surface finish of the first layer. When you use a raft, the first layer isn’t as smooth as one that attaches to the print bed directly because a spacing must be left between the raft and the model to make it easier to detach. With a brim, this isn’t an issue because it only goes around the model.

Cons

• Depending on how close together the lines in your first layer are, sanding or cutting may be necessary.
• If you have a requirement on dimensional accuracy but need to cut or sand the brims, this can negatively affect the accuracy.
• Brims produce a small amount of waste material.
• It’s possible to break delicate geometries when removing the brim, so a careful hand when doing so is recommended.

1. Open the “Print settings” panel, then click open the “Build Plate Adhesion” section.
2. Select “Brim” in the “Build Plate Adhesion Type” dropdown menu.
3. In the “Brim Line Count” field, you can define the width of your brim by line count.

These are the only two settings under the “Basic” settings configuration, but if you check “All” in the drop-down menu next to the “Search Settings” field, there are a few more settings for you to play with.

A couple of the settings include “Brim Distance”, which is an offset to the brim, and “Brim Replaces Support”, which replaces supports for a brim in low sections that need support. When “Brim only on the outside” isn’t activated, if the model is a standing cylinder, for example, it will also create a brim on the inside.

Simplify3D

1. Click “Edit Process Setting” on the bottom left of the interface, and the “FFF Settings” window will open.
2. Click the “Show Advanced” button on the bottom left.
3. Click the “Additions” tab, then check the “Use Skirt/Brim” box.
4. Set the “Skirt Offset from Part” to 0,00 so that it acts as a brim. If the offset was 2 mm, for example, it would be a skirt.

In Simplify3D, you don’t have a separate option for the addition of a skirt or brim; only a raft is considered a different element. The fact that it’s set up this way has an additional advantage. If you print with a brim and notice that it’s too firmly attached to the model, which would necessitate cutting or sanding, you can set the offset to 0.1 mm or 0.2 mm instead of 0. This would solve all those accuracy and post-processing cons mentioned earlier.

The purpose of this tiny offset isn’t to print the brim detached from your part, in which case it wouldn’t count as a brim. The purpose is rather to take into account your printer’s dimensional accuracy to ensure the brim isn’t over-attached.

PrusaSlicer

1. Make sure to select “Expert” mode on the top right of the interface.
2. After opening the model in PrusaSlicer, right-click on the model and scroll to the bottom.
3. Hover on “Add settings”, then select “Skirt and brim”.
4. A window will open, and you have to check which brim settings you want to configure. The settings will be added to the panel on the right side of the interface under “Object Settings to modify”.
5. Configure the settings according to your preferences.

In PrusaSlicer, you have three setting options. “Brim type” allows you to choose between outside only, inner only, or both. Additionally, you’ll also find “Brim separation gap” and “Brim width”, which are similar to those explained in previous sections.