Sheet-based additive manufacturing methods

A method of fabricating a part, the method comprising steps of:

• forming a stack from at least two sheets of fusible material, the at least two sheets comprising a bottom sheet that comprises a bottom-sheet top surface, a bottom-sheet bottom surface, and a bottom-sheet thickness, separating the bottom-sheet top surface and the bottom-sheet bottom surface, and a top sheet that comprises a top-sheet top surface, a top-sheet bottom surface, and a top-sheet thickness, separating the top-sheet top surface and the top-sheet bottom surface, wherein the bottom sheet and the top sheet are stacked such that the top-sheet bottom surface and the bottom-sheet top surface form an interface between the top sheet and the bottom sheet;
• directing a laser beam through the top-sheet top surface and through the top-sheet thickness such that the laser beam passes through the top-sheet top surface and through the top-sheet thickness without transferring energy to any portion of the top sheet so that no portion of the top sheet is melted;
• and
• transferring the energy from the laser beam, directed through the top-sheet top surface and the top-sheet thickness, to multiple spaced-apart regions of the interface between the top sheet and the bottom sheet such that only a portion of the top-sheet thickness, abutting the multiple spaced-apart regions of the interface between the top sheet and the bottom sheet, and only a portion of the bottom-sheet thickness, abutting the multiple spaced-apart regions of the interface between the top sheet and the bottom sheet, are melted;
• wherein melted portions of the top sheet of the stack and the bottom sheet of the stack define a fused portion of the of the stack and the fused portion of the stack defines at least a portion of the part.