Mastering Bed Adhesion: Edges vs. Rafts in 3D Printing (and Why They Matter)
In the complex dance of 3D printing, ensuring that the first layer adheres perfectly to the build platform is like laying a solid foundation for a skyscraper. Get it wrong, and your entire print—hours or even days of work—risks becoming a spaghetti-like monument to frustration. In the fight against warping and separation, two important tools stand out: edge and raft. While the fundamental purpose of both is to improve adhesion, they work differently and perform well in different situations. Understanding these differences is more than just amateur knowledge; It is essential for achieving reliable, high-quality printing, especially in demanding professional applications.
The key role of bed adhesion
Before we get into the details, let’s review Why Adhesion is important. Thermoplastics cool quickly after extrusion. This cooling causes shrinkage. Uneven shrinkage, especially in the critical first layer, exerts an upward force (warping) that can peel corners of the bed or cause the entire part to separate. Ambient airflow, slightly imperfect bed flatness, challenging geometries (such as tall thin towers, high aspect ratios, or sharp corners), or materials that easily deform (such as ABS or nylon) can all exacerbate this problem. Poor adhesion will inevitably lead to printing failure. Enter adhesion aids: skirts (primarily cleaning nozzles), edges, and rafts.
What is a hat brim?
Think of the brim as a wide, flat hat worn by the printed subject, extending outward from its base perimeter. It only prints on the first layer.
- Purpose: to significant Increase surface area and contact points Located between the print part and the build plate, prevents corners from lifting (warping) and improves overall bed adhesion, especially for smaller parts with tight footprints.
- How it works: The slicer software generates a single layer of thick outline (usually 5-20 line thicknesses depending on settings) around the base of the model. This profile is tightly integrated with the edges of the build plate and the first layer of the print, creating a strong anchoring effect that counteracts warping forces.
- When to use a hat brim:
- Small parts with minimal contact area on the bed (e.g. miniature figures, narrow stands).
- Models with sharp corners are easier to lift.
- Print with materials known to deform (ABS, nylon).
- Where the quality of the underlying surface is critical (Edges leave minimal marks compared to rafts).
- Used to prevent general warping of parts with good surface area.
- Advantages of using brim:
- Minimal material waste: Much less filament is used than a raft.
- Faster print times: It only increases the time required to print thin edges, which is usually negligible.
- Easier to remove: Once printed, it usually peels off easily and cleanly.
- Maintain bottom surface quality: The underside of the print is largely untouched, requiring only minor cleanup.
- Disadvantages of using brim:
- Limited effect: May not be adequate for severe warping situations or very tall, narrow prints prone to breaking higher up.
- Scar removal: There may be small raised lines or rough edges left around the perimeter of the base layer that need light sanding or trimming.
- Limited stability: Doesn’t help with bed leveling compensation; the print surface still has to be perfectly level.
What is a raft?
The raft is more like a detachable sacrificial launch pad. It consists of multiple layers of printed material Down actual object.
- Purpose: provide a Large, stable sacrificial surface Adhered to the build plate, i.e. the actual part is printed on the build plate. The raft compensates for minor bed imperfections and provides unparalleled adhesion guarantee against severe warping.
- How it works: Slicers create a flat mesh (usually 2-5+ layers thick) that extends far beyond the coverage of the object. Then start printing on top of this raft. The raft adheres firmly to the bed, while the interface layer between the raft and the print is designed to separate more easily (usually with an air gap or using a sparse setting). The printer effectively bonds the first layer of the part to the platform rather than directly to the build plate.
- When to use a raft:
- Extremely distorted scenes
