What might be a result of not properly laying down the first layer during FDM printing?

Not properly laying down the first layer during Fused Deposition Modelling (FDM) printing can lead to failed prints primarily due to poor adhesion. The first layer is critical in establishing a strong foundation for the rest of the print. If this initial layer is not properly adhered to the build surface, several issues may arise, such as warping, lifting, or even total displacement of the print as it progresses.

The first layer typically requires careful calibration regarding height, temperature, and speed to ensure it bonds effectively. If it's too high above the build plate, the filament may not stick. Conversely, if the nozzle is too low, it may squish the filament excessively, leading to blockage or uneven application. Consequently, a failed print, characterized by layers that are inconsistent or not sticking together, is a common result when the first layer is mismanaged.

The other options—successful prints, detailed replicas, and increased print speed—are not outcomes associated with a poor first layer. In fact, these are typically compromised when the initial adhesion is lacking.