When the corners of a 3D printed model lift off the build plate, it warps into a messy tangle of plastic. This is usually due to poor bed adhesion. You can use tools like the Raft and the Brim to help. Is a raft better than a brim? Should I always use one of them? They are different tools for different jobs. This blog post details the differences between 3D printing raft vs brim, their use cases, and introduces a third tool: the Skirt. Let's dive in.
Table of Contents
I. What Is a Raft in 3D Printing?
II. What Is a Brim in 3D Printing?
III. Quick Overview: 3D Printing Brim vs Raft Comparison
IV. 3D Printing Raft vs Brim: What Are the Differences?
V. Brim vs Raft 3D Printing: How and When to Use Them?
VI. And What About a Skirt?
I. What Is a Raft in 3D Printing?
A raft is a thick, grid-like platform that your printer first places on the printing platform. Your actual model will then be printed on this raft.
Imagine you're building a house on soft, uneven sand; you'd first lay a wide, solid wooden platform to distribute the weight and maintain stability. The raft acts similarly.
It creates a brand-new, high-grip surface for your model, allowing it to adhere firmly, thus avoiding problems such as small contact points on the model itself or a less-than-sticky build plate. Check out the blog to learn more: What is a Raft in 3D Printing.
II. What Is a Brim in 3D Printing?
A brim is a flat, single-layer extension that outlines the base of the model, similar to the brim of a hat. It's fused to the model's edges.
To use a house analogy, if the foundation is already on solid ground but might shift at the edges, you'd pour a wide, thin walkway around the foundation to stabilize it. The brim serves a similar purpose.
It increases the surface area of the first layer, so the plastic grips better and prevents corners from lifting.
III. Quick Overview: 3D Printing Brim vs Raft Comparison
Let's quickly compare 3D print raft vs brim using a table.
|
Feature |
Raft (The Platform) |
Brim (The Anchor) |
|
Primary Purpose |
Creates a new foundation. Provides a high-adhesion surface for the model to print on top of. |
Reinforces existing edges. Increases the model’s own bottom layer adhesion to prevent warping. |
|
Structural Relationship |
Model is printed on top of it. Connected via a separable gap layer. |
Fused to the model’s outer edges. It is an extension of the model itself. |
|
Best Use Case |
Tiny bottom contact points (miniature feet), complex bottom surfaces, poor build plate adhesion, tricky filaments like ABS. |
Large, flat prints prone to corner lift, tall and skinny prints, general-purpose adhesion insurance. |
|
Post-Processing |
Must be peeled away, leaving a textured (often grid-like) bottom surface on the model. |
Must be trimmed/cut off, potentially leaving a slight line on the very edge of the model’s bottom. |
|
Print Cost (Time/Filament) |
High. Uses significant extra material and adds considerable print time. |
Low. Uses a minimal amount of extra material and adds little time. |
A raft is a detachable base printed beneath the model, replacing the build plate for better adhesion. However, it consumes more material and takes longer.
In contrast, a brim is a thin border attached to the model's edge, enhancing adhesion without replacing the plate. It's faster and uses less material.
IV. 3D Printing Raft vs Brim: What Are the Differences?
Let's break down the differences between a raft and a brim in 3D printing, so you can choose the right one for your print job.
1. Primary Purpose
Their basic jobs are different.
A raft is used when your print cannot adhere at all. It creates a brand new, grippy surface for the model to sit on, fixing bad plate adhesion or an awkward bottom shape.
A brim provides extra grip. It stops the edges of a print that should stick from curling up due to stress. It makes existing adhesion stronger; it doesn't create a new foundation.
2. Structural Relationship
This affects how you remove them.
The model prints on top of the raft, with a small gap in between. They are separate, so you peel the raft off like a sticker from its backing.
The brim is printed as part of the model's first layer and is fused directly to the model's outer edge. You must cut or snap it off, like trimming excess plastic from a molded part.
3. Ideal Use Cases
Think of a raft as your heavy-duty fix. Use it when:
- The model has tiny contact points with the bed (like animal feet).
- You're using tricky filaments like ABS that warp easily.
- Your build plate surface is damaged or has poor adhesion.
It's the go-to option when normal printing conditions are likely to fail.
Think of a brim as your everyday insurance. Use it when:
- Printing large, flat objects (like boxes).
- Printing tall, thin models that might wobble.
- You've had slight warping before or just want extra security.
It's a smart, low-cost habit that prevents most common warping. It's a wise and low-cost habit that prevents most common failures without significant downside.
4. Post-Processing
A raft changes the model's bottom finish. You'll get a textured, often grid-like surface instead of a smooth one. This is fine for hidden or functional parts, but not for visible surfaces.
A brim keeps the model's bottom surface smooth. You only need to clean up the very outer edge where it was attached, which is usually easy to sand or trim.
5. Print Cost
Using a raft is expensive. It uses a lot of extra material and adds significant time to your print, like paying a high premium for guaranteed success.
Using a brim, on the other hand, is much cheaper. It uses minimal extra material and adds very little time. For a small cost, you can significantly improve printing reliability. Read the blog How Long Does 3D Printing Take.
V. Brim vs Raft 3D Printing: How and When to Use Them?
Should you use a raft when 3D printing? The answer is: rarely. Consider a raft only as a last resort for severe adhesion problems that a brim and a well-calibrated printer cannot solve. Overusing rafts wastes time, filament, and ruins your model's bottom surface quality.
To achieve excellent bed adhesion, you should follow these steps:
1. Ensure your build plate is impeccably clean (use isopropyl alcohol) and perfectly leveled. A flawless first layer solves the majority of adhesion issues. Check out our blog post on How to Clean 3D Printer Bed.
2. For common warping or to boost grip, the brim is your first choice. In your slicer's adhesion settings, select "Brim". A width of 5-8mm is a good start. Slice and preview to see the anchor-like outline around your model.
3. Switch to a "Raft" only if your model has a tiny contact area (like miniature feet) or you're using a notoriously warp-prone filament (like ABS). You can adjust settings like the "Raft Extra Margin" for a larger, more stable foundation.
4. Post-processing with care:
- For a Brim: Once the print cools, use a deburring tool, craft knife, or your fingers to gently snap or cut the thin brim away from the model.
- For a Raft: Flex the build plate or use a spatula to lift the entire “model+raft” assembly off. Then, patiently work a tool into the gap between them to pry the raft off. It may require some effort but should separate cleanly.
VI. And What About a Skirt?
Do not confuse a Skirt with a Brim. A skirt is a few lines printed around but not touching the model. It does not aid adhesion. Think of it as a "warm-up lap" for your printer: it primes the nozzle and lets you make a final visual check of the nozzle height and bed level.
So, to keep these three in mind: Skirt = Warm-up. Brim = Anchor. Raft = New Foundation.
| Type | Core Purpose | Contacts Model? |
| Skirt | Purges nozzle & verifies leveling. | No |
| Brim | Prevents warping by anchoring edges. | Yes, fused to edge. |
| Raft | Creates a new, high-adhesion print surface. | Model prints on top of it. |
VII. Conclusion
So, Is a brim the same as a raft? Of course not. Now you understand their different functions. The key to perfect adhesion is a high-quality first layer. Skirts should be used as best practice for every print. Use brims extensively as the first line of defense against warping. Furthermore, reserve rafts for special and tricky situations.
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