Raft vs Brim vs Skirt
Rafts
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.
When to Use Rafts
There are multiple reasons for adding a raft:
- Warping: Activating a raft while working with ABS filament helps to prevent the print from warping.
- Greater bed adhesion: Rafts can help to achieve better bed adhesion and act as a precaution against print failure.
- 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
Of the three, rafts have the most slicer settings to adjust.
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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
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
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.
When to Use Brims
There are multiple reasons for adding a brim:
- Warping: A brim can help prevent warping and is therefore recommended to be used while printing with materials like ABS filament.
- Greater bed adhesion: Similar to 3D printing rafts, brims help to improve bed adhesion.
- Easier removal: As a safety measure or because you have trouble getting a print off the build plate, brims can help.
- 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
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
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
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
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
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
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