Raft layers constitute a thin, sacrificial base of filament that a 3D printer lays down first on the print plate to ensure optimal adhesion for the subsequent design layers of your actual print. These layers are temporary and are not part of the final printed object.
Understanding Raft Layers in 3D Printing
In the context of Fused Deposition Modeling (FDM) 3D printing, a "raft" is a specific type of support structure designed primarily to improve the first-layer adhesion of a print to the build platform. As defined, a raft is "the thin layer of filament that the printer puts down first for the best adhesion to the print plate." (10-Apr-2023)
Think of raft layers as a foundation that ensures your main structure (your design layers) has a stable and consistent surface to build upon, preventing common issues like warping or detachment during the printing process.
Key Characteristics of Raft Layers:
- First to Print: Raft layers are the very first material extruded by the printer for a job.
- Adhesion Enhancer: Their primary purpose is to maximize grip to the print surface.
- Sacrificial Layer: Rafts are "not part of your print." (10-Apr-2023) They are intended to be removed and discarded after printing.
- Interface for Design Layers: "Design layers go on top of this" (10-Apr-2023), meaning the actual model is printed directly on the raft, not the build plate.
- Improves Stability: By providing a larger contact area, rafts help stabilize prints, especially those with small footprints or challenging geometries.
Raft Layers vs. Design Layers
It's crucial to distinguish between the raft and the actual part you want to print.
| Feature | Raft Layers | Design Layers |
|---|---|---|
| Purpose | Print adhesion and stability; sacrificial | Form the final 3D printed object |
| Contact with Plate | Direct contact with the print plate | Printed on top of raft (or directly on plate) |
| Part of Final Print | No, "is not part of your print." (10-Apr-2023) | Yes, constitutes the actual object |
| Removal | Intended to be removed and discarded after printing | Remains as the finished product |
| Surface Quality | Typically rough, not aesthetically critical | Aim for smooth, high-quality surfaces |
When to Utilize Raft Layers
While not always necessary, rafts are particularly beneficial in certain 3D printing scenarios:
- Poor Bed Adhesion: For materials notorious for warping or poor adhesion (e.g., ABS, Nylon), a raft can provide a more reliable base.
- Small Footprint: Objects with very small contact areas with the build plate can be unstable. A raft increases this area, improving stability.
- Uneven Print Beds: If your print bed isn't perfectly level, a raft can help compensate by creating a consistently flat surface for the print.
- Delicate First Layers: For prints with intricate or thin features on the very first layer, a raft can protect these details by providing a solid foundation.
- Reducing Elephant's Foot: While not its primary purpose, a raft can sometimes help mitigate "elephant's foot" (where the first few layers expand outwards) as the actual print starts above the raft.
Practical Considerations for Using Rafts
Using rafts can add a few extra steps to your printing workflow:
- Increased Print Time: Printing extra layers for the raft naturally adds to the overall print duration.
- Material Consumption: A small amount of additional filament is used for the raft.
- Post-Processing: After printing, the raft must be carefully removed from the base of your object. This typically involves snapping or peeling it off, which can sometimes leave minor marks on the first layer of your print that might require sanding or trimming.
- Slicer Settings: Most 3D printing slicer software (like PrusaSlicer, Cura, Simplify3D) offers options to enable and customize raft settings, including layer height, air gap between raft and print, and raft density.
In summary, raft layers are a fundamental tool in 3D printing for ensuring successful first-layer adhesion and overall print stability, serving as a disposable foundation for your creations.
