What Are Rafts in 3D Printing? How & When to Use Them

Are you struggling with distorted prints or poor adhesion on the first layer? These common 3D printing issues often lead to failed prints. One potential solution is using a raft, a temporary base layer that increases stability and bed adhesion. This guide will explain what a raft is, when and how to use it, and offer troubleshooting tips to help you achieve consistent, high-quality prints.

What Is a Raft in 3D Printing?

In the context of 3D printing, a raft is a temporary, sacrificial layer of extruded plastic printed directly onto the build plate before the main object begins. It serves as a stable foundation that improves first-layer adhesion and helps prevent warping or print failure, especially when using challenging materials like ABS. Think of it as an extra support structure that ensures your model sticks properly to the print bed, even if you’re working with a less-than-perfect surface.

How a Raft Is Made?

When preparing your file for 3D printing, slicer software allows you to enable a raft. The software then automatically generates the raft structure, printing it before your main model begins. A typical raft consists of three main parts:

• Base layers: These are thick, sturdy layers that stick to the build plate, providing a solid foundation.
• Middle interface layers: Slightly thinner than the base layers, these serve as a buffer between the raft and the object.
• Separation layers: These layers make it easier to remove the printed object from the raft after printing is completed, ensuring no damage to your model.

This layered structure ensures strong adhesion to the build plate while also enabling easy removal of the raft without damaging your 3D printed model.

Types of Rafts in 3D Printing

Different types of rafts are available depending on your specific needs. Here are the common types:

• Full Raft: A multi-layer raft that offers maximum stability and bed adhesion, making it ideal for ensuring a solid foundation, particularly when printing with warping-prone materials.
• Thin Raft: Fewer layers, faster printing, easier removal, but offers less support than a full raft.
• Custom/Advanced Raft: User-defined settings in slicers such as Cura or PrusaSlicer (including air gap, offset, etc.) to tailor the raft’s properties to your needs.
  Zig-Zag Raft: This type uses minimal filament and creates a zig-zag pattern. It’s great for quick-release prints but might not offer as much adhesion support as other types.

Each raft type strikes a different balance between material usage, ease of removal, and bed adhesion, with the full raft being the most reliable for stability.

Raft vs. Brim: Which Should You Use?

If you’re trying to avoid warping, both rafts and brims are useful. However, rafts are more effective in protecting your printing surface from filament contractions and potential damage due to poor calibration, thanks to the cushion-like layer it forms between the surface and the object. In contrast, a brim only increases the surface contact area and helps prevent warping. But, when removing the brim, you might leave some filament on the first layer, which could affect the surface quality.

Why Use a Raft in 3D Printing?

A raft in 3D printing isn’t just a useless extra layer, it provides significant benefits, particularly when dealing with common printing problems:

• Stronger Bed Adhesion: Rafts improve adhesion to the print bed, especially for materials like ABS or when using a build plate that doesn’t offer optimal grip.
  
• Reduced Warping and Curling: By providing a cushion between the hot bed and the print, rafts help ensure that layers cool evenly, reducing the risk of warping, especially with materials prone to contraction.
• Better Support for Small or Delicate Parts: For models with a small footprint or intricate details, a raft creates a sturdy foundation, reducing the likelihood of the print wobbling or detaching midway.
• Helps with Uneven Beds: If your print bed is slightly damaged or uneven, a raft can compensate for these imperfections, providing a smoother surface for printing.
• Smoother Bottom Surface: The raft absorbs imperfections from the build plate, ensuring that the bottom of your print is smooth and free from defects like elephant’s foot or rough edges.

When to Use a Raft in 3D Printing

Rafts aren’t needed for every print, but they can be extremely helpful in the following scenarios:

• For Difficult Materials: Rafts are beneficial for printing with materials like ABS, ASA, and Nylon, which are prone to warping due to thermal stress.
• For Challenging Geometries: Rafts provide stability for prints with:
  • Small footprints that might peel off.
  • Slender edges or tall, narrow sections requiring additional support.
  • Large bases susceptible to thermal distortion.
  • Intricate designs that require a reliable first layer.
    
• For Uneven or Imperfect Beds: If your print bed is slightly warped or damaged, a raft can create a flat and even surface for the print to adhere to.
• When Other Adhesion Methods Fail: If methods like glue, tape, or brims don’t resolve adhesion issues, a raft can offer the extra support needed.
• For a Cleaner First Layer: Rafts help absorb imperfections, giving your printed object a cleaner and more polished first layer, which is essential when print aesthetics matter.

When to Skip a Raft

Rafts aren’t always necessary, and in some cases, they can even be counterproductive:

• For Easy-to-Print Materials: Materials like PLA or PETG, particularly when using a clean, leveled bed, usually stick well without a raft.
• To Reduce Print Time & Waste: Rafts require additional layers and filament, so if print speed and material efficiency are concerns, it’s best to skip the raft.
• When Surface Finish Matters: Rafts can leave marks on the bottom of your model after removal. If you need a flawless bottom surface and other adhesion methods are working fine, avoid using a raft.
• When a Brim is Enough: For larger, flatter models, a brim can offer sufficient adhesion with less material and faster cleanup.
• If the Base Is Already Large and Stable: Models with a wide, flat base typically don’t need a raft, as they’re less likely to suffer from adhesion or warping problems.

How to Add Rafts in Your Slicer?

Most slicers let you add rafts to your prints. Here’s how to do it using Creality Print as an example:

1. Open your slicer software and load the print file.
2. Navigate to the Support tab and click Enable Support.
3. Locate the Raft option and adjust the settings for raft layers and separation distance (Z distance).

Common Problems with Rafts & Fixes

While rafts can solve many common 3D printing issues, they come with their own set of potential problems. Here’s how to address some common raft issues:

• Raft Sticks Too Well to the Print: This occurs when the air gap is too small or there is over-extrusion. To fix this, increase the separation distance (try ~0.4mm), calibrate your flow rate, or adjust your bed temperature (especially for PLA).
• Print Won’t Stick to Raft: This could happen due to a large air gap, high print speed, or not enough top raft layers. To resolve this, lower the separation distance (~0.1mm), slow down the print speed for the first layer, or add extra top layers to the raft.
  Raft Lifting from the Bed: If your raft is lifting, check the bed level and re-level if necessary. Also, adjust the bed temperature (e.g., PLA at 50-60°C, ABS at 90-100°C) and clean the bed before starting the print.

Best Practices for Printing with Rafts

Here are a few tips to help you get the most out of using rafts:

• Adjust the raft separation distance to make removal easier.
• Ensure the first layer of the raft is well-calibrated and adheres firmly to the build plate.
• Use proper temperature settings for your filament to prevent warping, even with a raft.
• Experiment with raft thickness and density to find the best balance between stability and material usage.