Which property is essential for a material used in 3D printing to ensure durability over time?

Fatigue strength is the property crucial for materials used in 3D printing to ensure durability over time. This characteristic refers to a material's ability to withstand repeated loading and unloading cycles without experiencing failure. In many applications, components are subjected to dynamic stresses that can lead to fatigue, so having high fatigue strength helps prevent cracks and fractures that can develop over extended use.

While ductility is important for allowing materials to deform without breaking, it doesn't directly correlate with long-term durability under cyclic stress. The melting point is relevant for the processing of materials during 3D printing, ensuring that the material can be extruded or sintered effectively, but it does not influence the material's performance under operational conditions. Electrical insulation might be significant for specific applications, but it doesn't relate to the mechanical durability of a printed part. Therefore, fatigue strength stands out as the most relevant property for ensuring the longevity and reliability of 3D-printed components.