How to Use Rafts, Brims, and Skirts in 3D Printing

In the world of 3D printing, creating a successful print often depends on more than just the filament and printer settings. Proper bed adhesion is a critical factor, and features like rafts, brims, and skirts play a pivotal role. These foundational tools can make or break your print—literally. In this tutorial, we’ll dive deep into each of these techniques, explain when to use them, and provide technical guidance to optimize your 3D printing projects.

What Are Rafts, Brims, and Skirts?

Before we delve into their specific applications, let’s define each term:

Rafts

A raft is a horizontal grid of extruded filament layers placed underneath the entire model. It serves as a base on which your print is built.

Brims

A brim is a series of extruded lines that extend outward from the base of your print, like the brim of a hat. Unlike a raft, it does not sit beneath the model but only touches the perimeter.

Skirts

A skirt is a loop of extruded filament that surrounds the print but does not touch it. It acts as a primer for your extruder to ensure a consistent flow of filament.

Understanding Their Functions

Each of these tools serves a distinct purpose in the 3D printing process. Let’s explore how they work:

1. Rafts

When to Use:

● Poor Bed Adhesion: Rafts are ideal for materials prone to warping, like ABS, where direct adhesion to the print bed may fail.

● Uneven Bed Surfaces: If your print bed isn’t perfectly level, a raft creates a flat, uniform base for the model.

● Small Contact Area: For models with a small footprint or intricate designs, rafts improve stability.

Technical Considerations:

● Height and Layers: Set the raft’s base layer height slightly thicker than your model’s initial layer to enhance adhesion.

● Separation Distance: Ensure the raft detaches cleanly by adjusting the separation distance in your slicer settings.

2. Brims

When to Use:

● Warping Issues: Brims are particularly effective for stabilizing models with a small base by increasing the contact area with the bed.

● Preventing Edge Lift: They help keep the edges of prints flat and adhered, especially with materials like PLA or PETG.

Technical Considerations:

● Number of Lines: Adjust the number of brim lines to ensure sufficient stability without excessive material waste.

● Width: A wider brim provides better adhesion but requires more cleanup after printing. 

Function on the Print Bed

Brims

Brims serve as an extension of the model’s base, creating additional contact points with the print bed. This prevents edges from lifting and ensures that small or delicate parts remain securely adhered throughout the printing process. They are particularly useful for minimizing warping and stabilizing parts with minimal surface area.

Rafts

Rafts act as a foundational platform for the model, compensating for uneven or imperfect print beds. By providing a consistent, level surface, rafts enhance overall print stability and reduce the risk of warping. They are especially useful for challenging materials or large prints.

Mouse Ears a Simple Adhesion Technique

Mouse ears are small, flat discs added to the corners or edges of a 3D print model to increase bed adhesion. Like brims, mouse ears help stabilize parts of the model that are prone to lifting during the printing process.

When to Use Mouse Ears

● Warp-Prone Areas: For models with sharp corners or narrow features that tend to lift.

● Support for Small Details: To provide additional adhesion without covering the entire model base like a brim.

How Mouse Ears Compare to Brims

● Targeted Adhesion: While brims cover the entire perimeter, mouse ears focus on specific areas, reducing material use.

● Ease of Removal: Mouse ears are typically easier to remove since they are limited to specific spots rather than surrounding the entire print.

Difficulty of Removal

The ease of removal for rafts, brims, and skirts varies significantly, and knowing how to handle each type can save time and frustration.

Rafts

● Challenges: Rafts can adhere strongly to the model, especially if the separation distance is too small. Removing them can sometimes damage the model if done carelessly.

● Tips: Use a scraper or a spatula to gently pry off the raft. If the raft is particularly stubborn, consider increasing the separation distance in your slicer settings for future prints.

Brims

● Challenges: Brims are generally easier to remove than rafts but can leave behind minor material residues on the edges of the model.

● Tips: Carefully peel off the brim by hand. If necessary, use a hobby knife to trim away excess material for a clean finish.

Skirts

● Challenges: Skirts are the easiest to remove since they don’t touch the model. However, they can occasionally stick to the print bed.

● Tips: Simply lift the skirt off the bed once the print is complete. Ensure the bed is clean to prevent sticking in future prints.

Skirt Height and Number of Outside Lines

Skirt Height

The height of a skirt is typically set to match the first layer height of your model. This allows you to:

● Diagnose Bed Leveling: A consistent skirt height indicates that your bed is properly leveled.

● Prime for Multi-Layer Prints: For taller prints, you may increase the skirt height to ensure filament flow remains consistent.

Number of Outside Lines

The number of skirt lines determines how many loops of filament are printed around the model. Adjusting this setting can help:

● Improve Extruder Priming: More lines ensure the nozzle is fully primed before the actual print begins.

● Diagnose Material Flow: Observe multiple skirt lines to detect issues with extrusion or filament feed.

Setting the right skirt height and number of lines helps achieve a clean start for your prints and reduces potential issues later in the process.

Removing Brims, Skirts, and Rafts Stuck on the Print Bed

Occasionally, brims, skirts, or rafts may stick stubbornly to the print bed, making removal challenging. Here are some tips to safely and effectively handle this issue:

1. Use a Scraper or Spatula: A flat, wide tool such as a scraper can be slid under the stuck material to gently lift it off the bed. Ensure the tool has a smooth edge to avoid damaging the print bed.

2. Apply Heat: Reheat the print bed slightly to loosen the material. Materials like PLA can become more pliable with a bit of warmth, making removal easier.

3. Soak the Bed: For non-electronic beds, apply a small amount of warm water or isopropyl alcohol to dissolve any adhesives or loosen the filament.

4. Use a Plastic Tool: Avoid using sharp metal tools that might scratch or gouge the print bed. Opt for a plastic scraper or similar tool.

5. Prevent Sticking in the Future: Ensure the bed surface is clean and properly treated with adhesives (if needed) to strike the right balance between adhesion and removability.

Using a Brim Cutter

A brim cutter is a specialized tool designed to cleanly remove brims and other excess material from 3D prints. Here’s how to use one effectively:

1. Select the Right Cutter: Choose a cutter with a sharp blade and a comfortable grip for precision.

2. Secure the Model: Hold the model securely to avoid accidental slips that could damage the print or cause injury.

3. Trim the Brim: Position the cutter at the edge of the brim and gently slice away the excess material. Work slowly to ensure a smooth finish.

4. Smooth the Edges: After trimming, use fine-grit sandpaper or a file to smooth any rough spots left by the cutter.

Safety Tips

● Always cut away from your body and hands to prevent injuries.

● Wear safety gloves if possible to protect your fingers during trimming.

● Keep the cutter’s blade sharp and properly maintained to reduce the risk of slips or uneven cuts.

Using a brim cutter not only speeds up post-processing but also ensures professional-quality results for your prints.

Comparing Rafts, Brims, and Skirts

Here’s a side-by-side comparison to help you decide which technique suits your needs: