How does the surface energy of the substrate affect the adhesion of the first layer?

The surface energy of the substrate (build plate) strongly influences the adhesion of the first layer. Surface energy is a measure of the excess energy present at the surface of a material compared to its bulk. A higher surface energy substrate promotes better wetting of the molten filament, allowing it to spread out and form a larger contact area. This increased contact area leads to stronger adhesion due to increased intermolecular forces between the filament and the substrate. Materials with low surface energy, such as untreated plastics, are often difficult to print on directly because the molten filament tends to bead up instead of spreading out. Surface treatments, such as applying adhesive coatings or using textured build surfaces, can increase the substrate's surface energy, improving first-layer adhesion. Similarly, cleaning the substrate with isopropyl alcohol removes contaminants that can lower its surface energy, further enhancing adhesion. Effective first-layer adhesion is critical for the overall success of a 3D print, and manipulating the substrate's surface energy is a key strategy for achieving it.