Sheet processing device, image forming apparatus, and image forming system

An image forming apparatus comprising:

• an image forming section to form an image on a sheet;
• an upstream device including multiple rollers to:
• convey the sheet, on which the image is formed by the image forming section, in a conveyance direction;
• and
• perform a sheet processing;
• a downstream device downstream from the upstream device in the conveyance direction, the downstream device including a sheet sensor to detect the sheet;
• and
• circuitry configured to control a timing to rotate the multiple rollers to perform the sheet processing in response to a detection of the sheet by the sheet sensor,
• wherein the downstream device includes a first housing, and
• wherein the upstream device includes a second housing.

A sheet processing device comprising:

• an upstream device including multiple rollers to:
• convey a sheet in a conveyance direction;
• and
• perform a sheet processing;
• a downstream device downstream from the upstream device in the conveyance direction, the downstream device including a sheet sensor to detect the sheet;
• and
• circuitry configured to control a timing to rotate the multiple rollers of the upstream device to perform the sheet processing in response to a detection of the sheet by the sheet sensor,
• wherein the upstream device is removably attached to the sheet processing device.