The machine Leonardo da Vinci designed to produce a continuous supply of printed letters was a printing press.
Leonardo’s notebooks include a design for a printing press that used movable type and a mechanism intended to improve the efficiency of printing. The proposal reflects his interest in automating repetitive work through linked mechanical parts.
Printing presses already existed in Europe before Leonardo’s design. Johannes Gutenberg’s mid-fifteenth-century improvements had helped make mechanical printing with movable metal type practical. Leonardo therefore did not invent printing itself; his contribution was a proposed refinement of press machinery.
The design is also associated with efforts to keep type and paper aligned and to make repeated impressions more systematic. As with many Leonardo inventions, the surviving evidence is a drawing or design rather than proof of a completed machine that entered commercial use.