Rafts, Skirts and Brims!
This tutorial will help you understand the differences between rafts, skirts and brims. All three techniques provide a starting point for your model, but they have different uses and advantages.
A Raft is a horizontal latticework of filament that is located underneath your part. Rafts are primarily used with ABS to help with bed adhesion. Rafts are also used to help stabilize models with small footprints, or to create a strong foundation on which to build the upper layers of your part. If your only concern is bed adhesion, you may want to skip to the brim section, as this can typically accomplish the same goal as a raft and is much faster to print.
- Import the STL model file
- Add a Process
- Double-click on the Process to open the FFF Settings window (or click Edit Process Settings)
- Click Show Advanced (if it is not already visible)
- Click on the Additions tab
- Place a check mark beside Include Raft
- Raft Layers gives you control over the height of your raft. For this part, we used 3 layers.
- Raft Offset determines how far the raft will extend beyond the part. Our 3.00mm setting means that the raft will be 3.00mm larger than the outline of the part.
- Separation determines the distance between the raft and the part. The distance will impact the removal of your raft, and can be fine-tuned according to your model and your filament. Typical distances range from .14mm – .2mm.
- Raft Infill controls the density of the interior of your raft. The infill percentage of a raft should be high enough to ensure that the first layer of your model is flat, but not so high that the raft becomes solid and bonds to your model. We used 80% infill for the test part.
Adjust any of these settings and then click OK to save your Process Settings. Click Prepare to Print! to move into the Preview. If everything looks satisfactory, you are ready to print from an SD card or over a USB cable.
When your print is completed, remove your part from the print bed as a single piece and begin to peel the raft away from your part. Usually this can be done by hand, but in some cases you may need a scraper or thin spatula to pry the raft from the model. This is a good time to assess your raft separation distance and note any changes you would like to try on your next print.
A skirt is an outline that surrounds your part but does not touch the part. The skirt is extruded on the print bed before starting to print your model. Skirts serve a useful purpose because they help prime your extruder and establish a smooth flow of filament. Observing your skirt also allows you to detect any printing or leveling errors before you start printing your actual model. A Skirt is typically offset 3-4mm from the part. It may have 1-2 layers and 1-2 outlines. Note: If you have enabled Supports under your model, the outline of your skirt may be extended to surround the supports.
There are other potential uses for a Skirt. For ABS parts, a tall skirt can be constructed, as high as your model if desired, to thermally insulate the main model from any drafts. A tall skirt can be used with a dual extruder to “catch” oozing from the secondary nozzle before it moves to the main model.
Unlike a skirt, a Brim has a 0.00mm offset from your model. A Brim is attached to your part and extends outward, similar to the brim of a hat. Brims typically have several outlines and may be 1-2 layers tall. Brims are often used to stabilize small parts or “islands” (isolated sections of a model, such as 4 legs of a table) because brims help these delicate areas stay connected to the print bed.
In this example, we will add a Brim to a Thingiverse file. For our test, we scaled this model to 50%.
Import the STL file and add a Process. Double-click on the Process to open the FFF Settings window. Click Show Advanced, then click the Additions tab and place a checkmark beside Include Skirt/Brim to add a Brim. For the test, we used a 0.00mm offset, 1 layer, and 10 outlines (5-10 outlines are typically used to gain a larger surface area).
After you are finished with the Preview, print from your SD card or print over USB. After the model is finished, take your model off of the bed as one piece and remove the brim with your fingernail or a scraper/spatula.
Congratulations on learning more techniques to help you improve your 3D printing options and success!