Raft vs Brim vs Skirt

Rafts

3D Printed Raft for a regular model
A raft is the most conservative choice (Source: Abhimanyu Chavan via All3DP)

A 3D printing raft forms the first layer of a horizontal mesh of filament deposited directly on the build platform. Upon this first layer, the print is deposited.

In the above image, the raft appears in blue.

Featured image of 3D Printing Raft: When You Should Use It?





When to Use Rafts

Raft provided for a rocket model with small legs
Rafts provided support for this rocket's small legs (Source: Abhimanyu Chavan via All3DP)

There are multiple reasons for adding a raft:

  1. Warping: Activating a raft while working with ABS filament helps to prevent the print from warping.
  2. Greater bed adhesion: Rafts can help to achieve better bed adhesion and act as a precaution against print failure.
  3. Small surface touching bed in proportion to the model: Suppose a print has tiny legs at the bottom, upon which a heavy structure is built (like the rocket pictured above). In such cases, it’s recommended to add a raft to stabilize the model and prevent a print failure.




Raft Slicer Settings

Raft provided for a rocket model with a separation distance of 0.1mm
It's important to keep the Separation Distance small (Source: Abhimanyu Chavan via All3DP)

Of the three, rafts have the most slicer settings to adjust.

  • Separation Distance is the height of the space between the raft and the first layer of the print. A tighter separation distance will make it hard to separate the raft and the model. In the above image, we can see the distance between the raft (blue colored patch) and the first layer of the model. A distance of 0.1 mm is ideal.
    • Note: A 1 mm separation should never be used and is shown in the above image for demonstration purposes only.
  • Raft Bottom Layer is the very first layer deposited on the build platform. Therefore it’s recommended that it be kept thick and printed at a slow speed. This will help to have greater bed adhesion. Ideally, a raft bottom of two layers is good for adhesion.
  • Raft Top Layer will mate with the first layer of the print. Since this layer will determine the surface finish of the bottom layer of the print, it’s recommended that you use at least two to three layers to achieve a smooth surface.
  • Raft Offset determines the distance the raft will extend outside the edges of the print. A good idea is to keep this slightly outside the print but not too extended. (This option isn’t present in all slicers.)




Pros & Cons of Using Rafts

Removing a model from a raft
Removing a model from a raft can be helped by a spatula tool (Source: ZYYX Labs)

Like every technique, using rafts has a few pros and cons. Let’s take a closer look:

Pros

  • Fewer warping issues with stubborn materials like ABS
  • Improved bed adhesion leading to higher chances of a successful print
  • Consistent print output
  • Stronger first layer

Cons

  • Rough finish on the bottom layer of the model
  • Difficult to separate from model, especially with a denser raft
  • Extra waste material
  • Possibility of breaking the part while removing the raft, especially with tiny model components

Note: Always take precautions while removing the raft as it can cause injuries.





Brims

Image showing the Brim (blue colored lines on the edges of the bottom layer)
The brim is the blue colored lines on the edges of the bottom layer (Source: Abhimanyu Chavan via All3DP)

A brim is a type of 3D printing raft that’s only attached to the outer edges of the print,  not beneath it like a true raft. It can also be thought of as a type of skirt that touches the edges of the print.

Featured image of 3D Printing Brim – When Should You Use It





When to Use Brims

A brim can help against warping
A brim can help against warping (Source: All3DP)

There are multiple reasons for adding a brim:

  1. Warping: A brim can help prevent warping and is therefore recommended to be used while printing with materials like ABS filament.
  2. Greater bed adhesion: Similar to 3D printing rafts, brims help to improve bed adhesion.
  3. Easier removal: As a safety measure or because you have trouble getting a print off the build plate, brims can help.
  4. Support for supports: Sometimes supports are really tiny and they often break off while printing. Brims can combat this by making removal easier and improve the finished appearance of a print.



Brim Slicer Settings

Image showing the Brim Width of 10 mm and Brim Line Count as 25
Finding a sweet spot of Brim Line Count between strength and ease of print removal (Source: Abhimanyu Chavan via All3DP)

Generally, there are two important settings for brims that can be adjusted for best results.

  • Brim Width is self-explanatory. This will depend on the model you’re working with.
  • Line Count is the number of contour lines in the brim. The more lines, the better the strength will be, up to a certain distance. On the other hand, with more lines, it can become harder to remove the brim from the print. Ideally, a Line Count of three to five is good for adhesion and for holding the sides of the print from warping.


Pros & Cons of Using Brims

Image of: Pros & Cons of Using Brims
Think of a brim as the melted butter surround a stick of it (Source: 3D Printer Bee)

Like every technique, brim also has a few pros and some cons. Let’s take a closer look:

Pros

  • Prevents warping issues of materials like ABS
  • Improved bed adhesion leading to higher chances of a successful print
  • Easier to remove compared to a raft
  • Smooth bottom layer surface finish (because the brim only touches the outside of the print)
  • Less material used compared to a raft

Cons

  • Still is extra wasted material
  • Contact points have to be sanded for a good surface finish
  • Possibility of breaking the part while removing the brim, especially with tiny model components



Skirts

Image showing the Skirt (blue colored lines on the edges of the bottom layer)
The skirt is the blue colored lines on the edges around the bottom layer (Source: Abhimanyu Chavan via All3DP)

A skirt is an outline surrounding the part to be printed. The skirt doesn’t touch the part like rafts or brims but is controlled in more or less a similar way. It’s useful in helping to prime the extruder, encouraging a smooth flow of material before starting a print.

Though it doesn’t support the print in any way, as with a raft or a brim, it’s very useful to understand the flow of material, bed leveling, layer adhesion, and other layer properties set in the slicer.



When to Use Skirts

Even a small skirt can help ensure an excellent print
Even a small skirt can help ensure an excellent print (Source: conny_g via Ultimaker Community)

Irrespective of the print and material, it’s advisable to use a skirt with any print. It serves some useful functions of priming the extruder and detecting any printing issues before the actual print starts and saves time, effort, and money. Adding a skirt is also uses a very minimal amount of filament.

Skirt Slicer Settings

Image showing the Skirt Line Count as 6 and Skirt Distance as 4 mm
If your model is small, you'll want to increase your Skirt Line Count (Source: Abhimanyu Chavan via All3DP)

Like brims, there are two important settings to control a skirt.

  • Skirt Line Count defines the number of lines printed in the outline. Generally, even a single skirt line is sufficient, but if the print area is small, then appropriate priming may not occur. In such a case, three lines are ideal to ensure proper priming.
  • Skirt Distance defines how far the skirt is from the print.

Pros & Cons of Using Skirts

A skirt compared to a brim
A skirt compared to a brim (Source: Fab Academy)

Like every technique, brim also has a few pros and cons. Let’s take a closer look:

Pros

  • Primes the extruder
  • Detects issues while printing
  • Uses less material than rafts or brims
  • Simple check before the actual printing starts, which can save time, effort, and money
  • Helps in defining the print area

Cons

  • Makes use of a small amount of additional material apart from the print, which is waste material

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