Index tab forming system

An index tab forming system configured to sequentially form index tabs to a plurality of sheets, the index tab forming system comprising:

• a rotary die cutter including a die cut roller in which a sheet-like blade die used for index tab forming is mounted and a receiving roller arranged parallel to the die cut roller with a predetermined spacing to the die cut roller;
• a rotational position detector configured to detect a rotational position of the die cut roller;
• a memory configured to store a position of a front end of a top index tab of the index tabs, a shift distance between the index tabs, the total number of index tabs, and a position of a front end of an index tab portion of the blade die;
• a sheet stacker configured to stack a sheet stack;
• a sheet feeder configured to feed the sheet one by one from the sheet stack;
• a conveyance unit configured to convey the sheet received from the sheet feeder to the rotary die cutter, the conveyance unit including:
• a conveyor extending between the sheet feeder and the rotary die cutter and configured to convey the sheet;
• a sheet detection sensor arranged in downstream of the conveyor and configured to detect a position of the sheet;
• and
• a conveyance roller pair arranged parallel to the die cut roller and configured to convey the sheet;
• and
• a controller configured to:
• count the number of times that the conveyance unit conveys the sheet to the rotary die cutter;
• calculate a rotational speed of the conveyance roller pair based on the rotational position of the die cut roller, a detection signal generated when the sheet detection sensor detects a sheet position, the number of times that the conveyance unit conveys the sheet to the rotary die cutter, and a shift distance between the index tabs, the conveyance roller pair being configured to cause a front end of an index tab portion of the blade die and a front end of each of the index tabs formed on the sheet to match at the lowermost point of the die cut roller;
• and
• control a rotational speed of the conveyance roller pair based on the calculated rotational speed,
• wherein the blade die has a circumferential length that is longer than a length of the sheet so that the index tab is formed at any position of the sheet in a conveyance direction.