Although most people consider the first layer the start of a print, it isn’t always the first thing to be printed on the build plate. 3D printing raft and brim (an adhesion assistant) can be 3D printed before the first layer of your 3D model to make it stick well.
These adhesion aids are designed to accomplish two primary goals. Before beginning your print, lay out some filament to ensure your printer’s extrusion is functioning correctly. The second goal is typically to aid the first layer in maintaining its connection to the build plate throughout the print.
This article will discuss 3D printing raft vs brim adhesion aids because they are all unique in structure and usefulness. We’ll go over each kind of assistant in detail, including what it is, when to use it, some benefits and drawbacks, appropriate slicer settings, and more.
We’ll also examine the main settings for rafts and brims in the most recent stable versions of Ultimaker Cura and PrusaSlicer. Due to their popularity as 3D slicer programs, we chose them.
3D Printing Raft
Rafts in 3D printing are crucial to improve bed adhesion and prevent warping. Rafts are typically used when working with ABS filament because it is more likely to warp or develop an elephant’s foot. In contrast to resin printing, only FDM 3D printing uses rafts.
What Is 3D Printing Raft?
Our first type of adhesion aid is a raft, and it is the most intensive in terms of adhesion aid, material use, and print time. A 3D printed base is added underneath your actual print when you activate a raft. This base is several layers tall and slightly larger than the first layer of your print’s maximum area.
Because plastic sticks to plastic the best, using a raft gives any model excellent first-layer adhesion. Additionally, with this adhesion type, there will always be more surface area touching the build plate because a raft has a larger area than your printed model.
Additionally, since your print doesn’t actually contact the print surface, any build plate irregularities (such as dents) will probably only affect the raft. Further, adhesion-related problems like warping will primarily impact the raft structure and less affect your printed model. Which you’ll discard anyhow, improving the quality of your model.
Of course, a raft uses much more filament and extends print time than a skirt or brim because it functions as a small print inside a larger print job. However, it might be worthwhile for some 3D prints about which we’ll speak next.
When to Use 3D Printing Raft?
When do you use a raft, then? Rafts are excellent for any rectangular or similarly shaped models with sharp corners because they are handy for securing the corners of a model down. It’s best to use this feature on models where bed adhesion has been a problem because it offers more bed adhesion than brim adhesion assistants.
Of course, models with a small surface area touching the print surface benefit significantly from using rafts. The first layer of your print will adhere to the plastic raft rather than the build plate, resulting in a stronger bond. Additionally, a raft will increase the surface area connecting the build plate.
However, you should only consider using a raft if you aren’t concerned with material usage or print time, as rafts significantly increase both. A brim might be a better option if you still need some bed adhesion assistance and want to reduce print time and material consumption. In addition to using a lot of materials, rafts also produce a lot of waste. And although rafts outperform the competition in bed adhesion, they frequently result in unattractive bottoms.
It’s also important to note that rafts are the typical adhesion method for ABS printers. That’s because rafts are typically successful at resolving the bed adhesion issues that this material presents.
Advantages of 3D Printing Raft
- Provides the best bed adhesion for prints and lowers the risk of warping compared to the brim.
- Verifies that the print bed is level, the extruder is operating correctly, and the nozzle is clear.
Disadvantages of 3D Printing Raft
- Compared to other adhesion aids, most material consumption, and waste.
- the longest additional print time compared to other adhesion aids
- Print removal from the raft structure is complicated. This may lead to inaccurate bottoms.
3D Printing Raft Settings in Cura and PrusaSlicer
Let’s move on to the settings we can use now that we know the potential benefits of including a raft. Keeping track of your results is useful when making adjustments. Setting adjustments should be made incrementally, whether values increase or decrease. This will make it easier for you to gradually assess the progress (or regression), enabling you to adjust your ideal settings quickly.
Your 3D printer, the filament you’re using, the room’s ambient temperature, and even the build platform will affect how these settings are configured. As a result, one setting might not be appropriate for all purposes. Before you find the perfect setting, you’ll probably go through some trial and error. With that, let’s look more closely!
The setting of 3D printing Raft is located in different sections in Cura and PrusaSlicer. Cura sees raft as a build plate adhesion type. In contrast, PrusaSlicer puts it under the Supports material section and doesn’t allow us to tweak this setting like Cura. We will explain some main raft features below.
Raft Print Speed (Cura)
As its name suggests, this setting governs how quickly your printer prints the raft structure. In Cura, several sub-settings, including Raft Top Print Speed, Raft Bottom Print Speed, and others, regulate the print speed for various raft features. For a firmly adhered raft, we recommend keeping the print speed for the raft much slower than your typical print speed (like first layer speed). Cura’s default print speed of 25 mm/s works great for this.
Raft Extra Margin (Cura) – Raft expansion (PrusaSlicer)
The Raft Extra Margin specifies how far the raft extends past the first layer region along the X-Y plane. In this regard, Cura’s default value for this setting is 15 mm. However, if you want to save some filament or if the print is nearly as wide as the print area, you can lower it. For instance, your raft will be 35 x 35 mm if you print a 20 x 20 x 20 mm cube and use a 15 mm Raft Extra Margin.
Raft Air Gap (Cura) – Raft contact Z distance (PrusaSlicer)
The Raft Extra Margin specifies how far the raft extends past the first layer region along the X-Y plane. In this regard, Cura’s default value for this setting is 15 mm. However, if you want to save some filament or if the print is nearly as wide as the print area, you can lower it. For instance, your raft will be 35 x 35 mm if you print a 20 x 20 x 20 mm cube and use a 15 mm Raft Extra Margin.
Raft Top Layers (Cura) – Raft layers (PrusaSlicer)
The Raft Top Layers setting regulates the height of the raft structure. This setting’s default value of two is adequate, but depending on how your prints turn out and how much filament is used, you might want to increase or decrease it. A 3D print with too few top layers might not adhere well because the raft’s top won’t be as smooth as one with too many top layers, which uses more filament.
3D Printing Brim
The brim is our second type of adhesion aid. Brims are in the middle of the three adhesion assistants with more bed adhesion than skirts but less than rafts in Cura. We’ll discuss the benefits and drawbacks of brims and the ideal settings in Cura.
What Is 3D Printing Brim?
Brims and skirts share a lot in common. Both are multi-line structures that surround the first layer of a printed model and are always only one layer tall. However, unlike skirts, a brim is never separated from the first layer by any space. It is always attached directly to it. A brim increases the surface area in contact with the print bed to keep a print adhered.
Brims enable you to verify that your printer is appropriately extruding filament and that the bed is level where your print will be placed.
Although the number of nozzle passes (lines) can be changed, a typical raft’s brim is typically narrower. This indicates that most brims require fewer materials than rafts and take less time to print.
It’s crucial to remember that brims must be taken off after a print is finished because they attach to a model. While you can simply pull on the brim to tear it off, this typically leaves some behind, so you might need to use a small blade to cut it off the top layer of your print.
Even after doing this, the brim will still have changed the dimensional accuracy of your printed model. So it’s worthwhile to experiment with various tools, such as the frequently used wire cutters. Sanding could be beneficial as well.
When to Use 3D Printing Brim?
A brim is often considered the best option because it provides bed adhesion while keeping material consumption and print time reasonably low. Therefore, we advise using a brim for large flat-bottomed models with corners or other models prone to bed adhesion problems such as warping. For these kinds of prints, a brim will help keep them adhered to the bed while minimizing filament usage and waste compared to a raft.
However, suppose the accuracy of the printed model is crucial. In that case, you might want to avoid using brims because they directly impact the dimensional accuracy of the area of the first layer of your print. Usually, this is the case with functional prints that are intended to be put together using additional components.
Also, if you want a smoother texture on the bottom of your print instead of a rougher one like you might get when using a raft, you might want to use a brim. Additionally, suppose your model has a brim. In that case, the bottom layer will match the texture of your build plate, resulting in a very smooth bottom if you’re printing on a glass bed.
Advantages of 3D Printing Brim
- Moderate material use and waste production
- Slightly longer print time (less than a raft)
- Enables excellent bed adhesion for the initial layer of prints
- Shows that the print bed is level, the extruder is operating correctly, and the nozzle is clear.
Disadvantages of 3D Printing Brim
- Sanding or cutting might be required.
- Brims generate a relatively minimal amount of waste.
- It is advised to remove the brim carefully because it is possible to break delicate geometries.
3D Printing Brim Settings in Cura and PrusaSlicer
Setting up a brim can vary slightly depending on your slicer software. You’ll observe variations in how various slicers approach them. Brim settings, for instance, are one of the “Build Plate Adhesion” settings in Cura. It has its own settings category, “Skirt and Brim”, in PrusaSlicer and is grouped with skirts.
You can have a brim either only on the outside or both on the outside and inside with Cura. But PrusaSlicer gives you options to choose between “outer brim only”, “inner brim only” and “outer and inner brim”. You can add an offset to the brim in each of the three possibilities. You can avoid having to sand your print afterward if you input values of 0.1 or 0.2 mm.
Regardless of the variations, anyone with some experience can quickly grasp the gist of any new piece of software. In the following sections, we’ll go into more detail about setting up a brim in Cura and PrusaSlicer.
Brim Width (Cura & PrusaSlicer)
This setting controls how wide (in millimeters) the brim is. Adjusting the brim width directly affects the Brim Line Count, another slicer setting that measures the width in nozzle passes. The larger the brim width, the more adhesion your brim will provide, but the more filament it will take and the longer your print will be. A brim width of 8 mm works quite well for most 3D prints. If you still have adhesion issues or larger models with corners, consider increasing it. These objects are most likely to experience warping.
Brim Line Count (Cura)
This setting is another way of changing the brim width in the Cura slicer. It has an effect on Brim Width and vice versa. Suppose you have a 0.4 nozzle, and you set the Brim Width to 8mm, and Brim Line Count will be 20mm, and If you set the Brim Line Count after setting the Brim Width to 25. Cura will deactivate the Brim Width settings and change it to 10mm.
Brim Distance (Cura) – Brim separation gap (PrusaSlicer)
This controls how far the innermost line of the brim is from the outermost wall of the first layer of the print. The default value is 0, and we recommend keeping this setting because it ensures that the brim attaches to the first layer of the 3D print.
Brim Minimum Length (Cura):
The “Brim minimum length” is the smallest distance of a brim that can be recognized by your slicer and printed. If your slicer calculates that a brim around your sliced model will be under this value, it won’t be included in the actual print. Leaving it at 250 mm should work just fine.
Brim Only on Outside (Cura) – Brim type (PrusaSlicer):
This activatable feature controls whether brim structures can be printed around the internal features of a model. Turning this setting off will ensure that a brim structure is only printed around the exterior perimeter of a model. So, if you have a model like a hollow and your model’s bed plate touching surface is too small. Then you will need this option activated.
Also, PrusaSlicer allows you to use the inner brim only option. So you can use brim advantages without affecting the outside surface of your 3D object.
Bonus Bed Adhesion Techniques
After discussing rafts and brims, you might find knowing a few additional bed adhesion tips and tricks helpful. If you’re looking for a way to keep the first layer of your prints firmly attached to the print bed. Other strategies for keeping your 3D prints grounded are listed below:
- Use glue or another adhesive: Our first piece of advice is to apply glue or an additional adhesive, like Magigoo, to your build plate. The filament flowing out of your printer’s nozzle will stick to the bed more readily thanks to these sticky materials, producing a better first layer.
- Increase bed temperature: Another element that affects how well the first layer adheres to the print surface is bed temperature. Increasing it is a great way to make your first layer adhere better, but be careful not to raise it too much. The Source of your bed adhesion issue may not be where you think it is (e.g., level bed).
- Level the bed: Before beginning a print, leveling the bed should be done. Because an uneven bed will almost certainly cause problems with the first layer and the rest of the 3D print. To ensure that the nozzle remains at a constant height above the print surface throughout, we recommend that you level your bed before every few prints. To properly lay out the filament, also be sure to set the appropriate Z-offset.
- Change the build plate: Sometimes, bed adhesion problems may persist even after trying everything. If you have an outdated or heavily-used build plate, replacing it might be the best course of action, though it shouldn’t be your first choice. Consider getting a glass or PEI-coated build plate if you plan to replace it because these offer excellent first-layer adhesion.
- Dry your filament: Last but not least, drying your filament can aid in bed adhesion, albeit in a different way than the other suggestions we’ve offered. Furthermore, drying out your filament makes it easier to adhere the 3Dprint to the surface in contrast to our other tips, which focus on getting the printer’s parts to provide bed adhesion. This can be accomplished by either using a filament dryer device or gently heating the filament.
Which type of bed adhesion are you using the most?
Let us know in the comments below or on our Facebook page to let us know your ideas, and we would appreciate seeing pictures of your works of art!
