Question

how a 3d printer works

Answer 1

The 3D printing process turns a whole object into thousands of tiny little slices, then makes it from the bottom-up, slice by slice. Those tiny layers stick together to form a solid object. Each layer can be very complex, meaning 3D printers can create moving parts like hinges and wheels as part of the same object.

Answer 2

3d printer generally melts plastic or any other sutiable material which solidifies quickly.
thus various layers of motlen material are overlapped to form a rigid object.