Most 3D models are drawn realistically, where 1” in the model = 1” in the “real world.” These models must be scaled to fit into a 3D printer. When a model is scaled uniformly to a size that will fit into a 3D printer, everything becomes much smaller. The level of detail that 3D printers can produce is limited in size. It is safe to assume that anything smaller than .01” will not resolve well on most 3D printers. Therefore, certain details of a 3D model may be too small to be seen in the 3D printed version. Others will be too small to survive the printing process. These details must be adjusted or removed.
A window mullion, for instance, drawn at 1” thick, will be too small to be printed at a typical model scale such as 1” = 16'. The 1” mullion at 16th scale is roughly .005” thick; too small for the 3D printer. This mullion needs to be enlarged to 3”- 4” in the “real world” model in order to make it large enough at model scale to be visible in the 3D print.
A column supporting a deck, as another example, will need to be much larger than .01 to support itself and survive the 3D printing process. Freestanding objects like columns generally need to be in the .05” - .1” range to print successfully. A 16th scale model's .1” column is actually 20” thick in the “real world” scale 3D model.
Print tolerances for 3D printers vary between manufacturers and 3D printing technologies. It is important to find out what the tolerances are for the type of 3D printer you are planning to use in order to properly adjust the thicknesses of the 3D model.