US Patent 11491807 Printing apparatus

A printing apparatus includes a rotary shaft configured to rotate while holding a roll body of a printing medium, a first motor configured to rotate the rotary shaft, a roller pair configured to transport the printing medium downstream by rotating in a state of pinching the printing medium, a second motor configured to rotate the roller pair, a first sensor configured to detect a tip end or a feature of the printing medium, a second sensor configured to detect the tip end or feature of the printing medium, and an outer diameter calculating unit configured to calculate an outer diameter of the roll body based on detection by the first sensor and detection by the second sensor, wherein the outer diameter calculating unit calculates an outer diameter of the roll body before the tip end of the printing medium is pinched by the roller pair.