Image forming apparatus and method to determine cutting state of sheet medium

A method implementable on a controller of an image forming apparatus configured to cut a sheet medium by moving at least one blade of a cutter, the method comprising:

• receiving, from a signal output device, a signal indicating a variation over time in a value correlated with a moving load for the at least one blade in cutting the sheet medium;
• and
• based on the signal output from the signal output device during the cutting of the sheet medium, determining which state the sheet medium is in among a plurality of states including:
• a first state where the sheet medium is cut normally, the first state being identified in association with a first pattern of variation over time of the signal output from the signal output device;
• a second state where there is an abnormality occurring in cutting the sheet medium, the second state being identified in association with a second pattern of variation over time of the signal output from the signal output device;
• and
• a third state where there is an abnormality, different from the second state, occurring in cutting the sheet medium, the third state being identified in association with a third pattern of variation over time of the signal output from the signal output device, the first pattern, the second pattern and the third pattern being different from each other and classified by comparisons using two different signal level thresholds,
• wherein the image forming apparatus comprises:
• a conveyor configured to convey the sheet medium in a conveyance direction;
• a print engine configured to form an image on the sheet medium conveyed by the conveyor;
• the cutter comprising:
• a first blade configured to come into contact with a first surface of the sheet medium conveyed by the conveyor;
• a second blade configured to come into contact with a second surface opposite to the first surface, of the sheet medium;
• and
• a moving device configured to move the at least one blade, selected from the first blade and the second blade, along an intersecting direction with the conveyance direction, the cutter being configured to cut the sheet medium along the intersecting direction by the first blade and the second blade collaborating with each other;
• the signal output device;
• and
• the controller.