What is the primary purpose of thermal fusion in FDM layers?

The primary purpose of thermal fusion in Fused Deposition Modeling (FDM) layers is to bond the layers together for structural integrity. In the FDM process, the thermoplastic filament is heated to a molten state as it is extruded through the nozzle. When the molten material is deposited onto a previous layer, it does not just sit on top; instead, it undergoes thermal fusion where it partially melts the already extruded material. This allows the new material to merge and adhere strongly to the previous layer as it cools and solidifies.

This bonding is crucial for creating a cohesive and durable finished product since it enhances the strength of the object, ensuring that it can withstand stress and strain during use. A part with inadequate bonding between layers may exhibit weakness, leading to delamination or failure under load. Therefore, effective thermal fusion is essential for achieving the desired mechanical properties in an FDM print.

Other factors, such as flexibility during deposition, overall weight reduction, or surface finish, may play a role in the overall print quality but are secondary to the critical need for strong layer adhesion which results from thermal fusion.