Core
The inner side of a part. The core is an area inside the part where the amount of binder applied is reduced (usually in order to save on binder) to a preset percentage of the maximum binder deposition (e.g. 25 or 50%).
Its size is defined by the part size and the (defined) Shell thickness. The core is therefore (usually) created automatically by defining the shell thickness.
A part may also have no core. This may be the case for small parts whereby the combined shell thicknesses are larger than the part cross sections, or it may be a deliberate choice not to create a core inside a shell (e.g. when the part is rather large and feared to break in the green state).
Sometimes, a grid is designed inside the core, in order to (further) increase strength of the green part.
Defining Shell, Grid and Core is done through the Shell-Grid-Core feature, explained in detail in chapter 6. Features and Functionality