A method of forming an image and a crease on media by an image forming system includes forming a crease formation pattern on an impression media received by an impression member. The method also includes forming the image on an image forming blanket of an intermediate transfer member by a print unit. The method also includes pressing the media against the impression member by the image forming blanket to transfer the image onto the media and to establish contact with the crease formation pattern to form the corresponding crease on the media.

A sheet processing apparatus includes: a second conveying roller pair that receives and conveys a sheet conveyed by a first conveying roller pair; a first folding roller pair that forms a first fold on the sheet; and a first rotation unit capable of rotating the second conveying roller pair and the first folding roller pair. One roller of the second conveying roller pair and one roller of the first folding roller pair are a common roller shared therebetween. The second conveying roller pair causes the sheet to be deflected and guided to the first folding roller pair, and the first folding roller pair forms the first fold on the deflected sheet by rotating the first rotation unit in a certain direction in a state in which the sheet is held by the first conveying roller pair and the second conveying roller pair.

A postprocessing device includes a pair of folding rollers, a folding blade, a transport device, a roller driver, a blade driver, and a drive controller. The drive controller selectively performs one of a first rotation control, including controlling the roller driver to keep rotation speed of the pair of folding rollers constant, while the folding blade is moving away from a nip region, and a second rotation control, including controlling the roller driver to stop the rotation or slow down the rotation speed of the pair of folding rollers, while a tip portion of the folding blade is being withdrawn from a folded portion of a sheaf of sheets folded, and to restore the rotation speed of the pair of folding rollers to original rotation speed, after the tip portion of the folding blade has been removed from the folded portion of the sheaf of sheets folded.

A postprocessing device performs postprocessing on sheets received from an image forming apparatus. The postprocessing device includes a pair of folding rollers, a folding blade, a transport device, a drive portion, and a drive controller. The drive controller controls the drive portion to match moving speed of a tip portion of the folding blade with moving speed of a circumferential surface of the folding rollers, at a time point that the sheaf of the sheets makes contact with the circumferential surface of the folding rollers, when the image forming apparatus forms the image by ink jet printing, and to match the moving speed of the tip portion of the folding blade with the moving speed of the circumferential surface of the folding rollers, at a time point that the sheaf of the sheets reaches the nip region between the folding rollers.

An image forming system includes an image forming apparatus including a fixing unit, a folding processing portion, and a pressure-bonding portion. A first recording material having a first basis weight is fixed at a first temperature by the fixing unit and then is pressure-bonded by the pressure-bonding portion after a lapse of a first period. A second recording material having a second basis weight is fixed at a second temperature by the fixing unit and then is pressure-bonded by the pressure-bonding portion after a lapse of a second period. The second basis weight is larger than the first basis weight. The second temperature is higher than the first temperature. The second period is longer than the first period.

A sheet characteristic detection system that detects a sheet characteristic, includes: a sheet characteristic detection device that includes a plurality of media sensors corresponding to a plurality of different sheet characteristics; and a hardware processor that is capable of changing a type of the sheet characteristic to be detected by the plurality of media sensors.

A calculation system includes an obtaining unit and a calculation unit. The obtaining unit obtains information of a sheet. The calculation unit calculates an amount of change in length of the sheet in a conveyance direction of the sheet heated by a heating device to fix a toner image to the sheet based on the information of the sheet obtained by the obtaining unit and an elapsed time from a time when the sheet passes through the heating device.

A post-processing device includes: a loading section that has a loading surface directed obliquely upward and in which a recording medium is loaded on the loading surface in a state where one end of the recording medium is directed downward; a supporting section that supports the one end of the recording medium loaded on the loading surface; a transporting section that is provided at a position facing an upper portion of the loading surface and that transports the recording medium downward toward the loading surface; and a pushing section that pushes a non-facing surface of the recording medium, which is opposite to a facing surface facing toward the loading surface, toward the loading surface to move the recording medium toward the loading surface, in a contact state where a part of the recording medium transported by the transporting section on a side of the one end comes into contact with the loading surface and a part of the recording medium on a side of an upper end is separated from the loading surface and comes into contact with the transporting section.

A post-processing device includes: a loading section on which a bundle of recording media subjected to folding processing is loaded; a pushing section that moves in a thickness direction of the bundle of recording media, comes into contact with a surface, and pushes the bundle of recording media to form a folded portion; and a rotating section that starts an operation from a stopped state after the pushing section moves to a predetermined position, and sandwiches and rotates the folded portion of the bundle of recording media pushed by the pushing section to form a fold in the bundle of recording media.

A post-processing device includes: a loading section that has a loading surface directed obliquely upward and in which a recording medium is loaded on the loading surface in a state where one end of the recording medium is directed downward; a supporting section that supports the one end of the recording medium loaded on the loading surface; and a correcting section that has a facing surface facing toward the loading surface and that corrects deflection of the recording medium by coming into contact with the recording medium in a posture in which a lower end portion of the facing surface approaches closer to the loading surface than an upper end portion from a side of the recording medium, which is loaded on the loading surface, opposite to the loading surface and by thereafter coming into contact with the recording medium while moving such that the upper end portion approaches the loading surface in a state where the lower end portion is in contact with the recording medium.