Raft and Edge: 3D Printing Bed Adhesion

Mastering the Build Plate: Raft and Brim – Your Guide to Conquering 3D Print Bed Adhesion

Bed adhesion: It is the cornerstone of successful 3D printing. When the first layer drops, it’s an exciting moment that perfectly sets the stage for the entire manufacturing process. However, warping, curling and catastrophic detachment plague even experienced builders and professionals. Making sure the plastic is securely fastened is critical, especially if thermal stress occurs during the printing process.

Most slicing software provides tools to solve these problems, raft and hat brim are the two most common adhesion aids. While they share a common goal of preventing prints from lifting off the bed, they work differently and excel in different scenarios. Smart choices can significantly impact print success, surface finish, material usage and post-processing efforts.

Understanding the basic principles of adhesion is key. When the thermoplastic filament exits the heated nozzle and strikes the cooler’s printing plate, it undergoes rapid cooling and solidification. This creates molecular bonds and Mechanical grip on the build surface. However, differential cooling is the enemy. The hotter layers above shrink as they cool, pulling on the cooler, adherent lower layers. This creates internal stresses that manifest as warping (edges lifting from the plate), often resulting in failed prints or dimensional inaccuracies.

This is where adhesion aids come in.

Deconstructing a raft

Imagine printing your actual parts on the basis of sacrifice. This is essentially a raft.

• structure: A raft consists of the following parts multi-layer A thick, flat grid platform is formed beneath the model.

  • Base layer: The lowest layer (usually 1-3 layers) is dense and strong to maximize contact with the build plate.
  • Interface layer: The top layer of the raft is printed slightly differently (usually with increased clearance or decreased density/flow) to create Controlled separation layer. This is crucial!

• Function: The raft solves several aspects of the adhesion problem:

  1. Expand surface area: It greatly increases the surface area that adheres directly to the bed, creating a strong anchoring force.
  2. Thermal buffer: It acts as a thermal insulator between the thermal print plate/cooling surroundings and the critical first layer of the actual part, thereby reducing thermal shock gradients.
  3. Leveling compensation: Small flaws in bed leveling are masked because rafts create newwhich is theoretically a flat surface on which your model will be printed.
  4. Stress redistribution: Warpage stresses within the part are transferred downward into the thicker, more stable raft structure, rather than purely pulling the corners of the model away from the bed.

• Best use cases:

  • For printing highly deformable material (ABS, Nylon, PC). The thermal buffer of a life raft is invaluable here.
  • Models are minimal bed contact (tiny feet, pointed base, complex bottom features) naturally have weak adhesion.
  • slightly Curved or uneven print platform (Although a fixed plate is always better).
  • A slight sacrifice in bottom surface quality is acceptable.

• trade off:

  • A lot of material wasted: Rafts require a lot of filament.
  • Increase printing time: Printing additional layers adds considerable time.
  • Post-processing: Removing a raft can be tedious and risks damaging fragile features on the raft bottom your model. Achieving clean separation relies heavily on adjusting the interfacial layer gap.
  • Potential surface defects: The top surface of the raft (now the bottom of the model) usually has a noticeable texture.

deconstructing the edge

Treat the edge as a flat horizontal extension around the edge according to Your model is glued directly to the plate and the print itself.

• structure: brim made of single layer (sometimes 2-3 for increased strength) extends outward from the outermost geometry of the bottom layer of the model. It is similar to the brim of a hat.
• Function: The brim focuses on peripheral reinforcement:

  1. Increase peripheral adhesion: It creates a wide skirt of material around the base of the model, significantly increasing the overall edge area that blends with the board. it’s like "extra hands" Press the perimeter edges to counteract the upward curling force.
  2. Anchor point: Particularly effective in fixing troublesome corners and thin protrusions that are easy to lift first.
  3. Minimal material impact: Focus the material exactly where it is needed (peripheral edges).

• Best use cases:

  • Materials and Moderate tendency to warp (PETG, ASA, sometimes PLA in ventilated environments).
  • Models tend to appear corner lift Although bed adhesion was good elsewhere.
  • Printed with Thin or long walls/profiles At the base.
  • Condition Bottom quality is crucial (The edges do not touch the bottom surface of the model).
  • Combined with other bonding strategies such as adhesives/textures.

• trade off:

  • Limited effect: Less effective for extreme warping machines (like pure nylon or large ABS parts) or models with really tiny footprints.
  • Surrounding highlights: If you have poor center adhesion, you won’t be able to fix the issue underneath the core body of your print.
  • Edge cleaning: Removal requires care along the perimeter edge, although is usually much easier than raft removal. Small marks or lines where edges join may require light sanding.
  • Circumference size: The printing footprint on the print platform can be significantly increased.

Raft vs. Brim: Head-to-Head Comparison Chart

Making the right choice: factors to consider

1. Material: ABS? Strongly considering raft. People’s Liberation Army? Unless there is a problem with the part geometry, edges are usually sufficient. Polyethylene glycol? Edges are often needed to combat slight stickiness-induced curling.
2. Model geometry and dimensions:

   • footprint: Small contact area -> tilt towards the raft. Large flat bottom -> skirt or hat brim is enough.
   • Corner/Side: Lots of sharp corners -> edges are targeted. Tall/thin structures -> benefit from a brim or raft.
   • Bottom details: Need a perfect underside? Bream is the clear winner.

3. Build board conditions and environment:

   • Well-ventilated room or poorly sealed? Amplify warping -> upgrade to raft if edge fails.
   • The bed is uneven? Raft can help temporarily compensate (and fix the bed permanently!).

4. **Priorities