An example image forming apparatus includes a simplex path for conveying printing medium passing through a fixing unit provided in a main body to a discharge port of the main body, a duplex path for turning over printing medium and conveying the printing medium to the simplex path, and a discharge unit for selectively conveying a first printing medium and a second printing medium in different directions, wherein the first printing medium includes an image formed on one surface passing through the simplex path, and the second printing medium includes an image formed on two surfaces and passing through the simplex path after passing through the duplex path.

A printing system for cut sheets includes a controller configured to control the printing of image data on a plurality of sheets and scheduling the plurality of sheets in a printing order, a paper path comprising a duplex printing loop and a rotational functional component arranged in the duplex printing loop for guiding and processing a printed sheet for two passes along or on a surface of the rotational functional component, a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data, in two passes, one side per pass. The controller is configured to schedule one-sided printed sheets for a first pass guided along or on the surface of the rotational functional component and two-sided printed sheets for a second pass guided along or on the surface of the rotational functional component by using the duplex printing loop and to determine a distance between subsequent sheets guided along or on the surface of the rotational functional component such that a location on the surface of the rotational functional component is covered by printed sides of two-sided sheets at most a maximum number of times before the location on the surface of the rotational functional component is covered by an unprinted side of a sheet. The maximum number is determined by a degree of pollution caused by the marking material printed on two-sided printed sheets when taking a second pass along or on the surface of the rotational functional component.

A printing system for cut sheets includes a controller configured to control the printing of image data on a plurality of sheets and scheduling the plurality of sheets in a printing order, a paper path comprising a duplex printing loop and a rotational functional component arranged in the duplex printing loop for guiding and processing a printed sheet for two passes along or on a surface of the rotational functional component, a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data, in two passes, one side per pass. The controller is configured to schedule one-sided printed sheets for a first pass guided along or on the surface of the rotational functional component and two-sided printed sheets for a second pass guided along or on the surface of the rotational functional component by using the duplex printing loop and to determine a distance between subsequent sheets guided along or on the surface of the rotational functional component such that a location on the surface of the rotational functional component is covered by printed sides of two-sided sheets at most a maximum number of times before the location on the surface of the rotational functional component is covered by an unprinted side of a sheet. The maximum number is determined by a degree of pollution caused by the marking material printed on two-sided printed sheets when taking a second pass along or on the surface of the rotational functional component.

A printing system for cut sheets includes a controller configured to control the printing of image data on a plurality of sheets and scheduling the plurality of sheets in a printing order, a paper path comprising a duplex printing loop and a rotational functional component arranged in the duplex printing loop for guiding and processing a printed sheet for two passes along or on a surface of the rotational functional component, a print engine arranged in the duplex printing loop and configured to dispose marking material on the sheets according to the image data, in two passes, one side per pass. The controller is configured to schedule one-sided printed sheets for a first pass guided along or on the surface of the rotational functional component and two-sided printed sheets for a second pass guided along or on the surface of the rotational functional component by using the duplex printing loop and to determine a distance between subsequent sheets guided along or on the surface of the rotational functional component such that a location on the surface of the rotational functional component is covered by printed sides of two-sided sheets at most a maximum number of times before the location on the surface of the rotational functional component is covered by an unprinted side of a sheet. The maximum number is determined by a degree of pollution caused by the marking material printed on two-sided printed sheets when taking a second pass along or on the surface of the rotational functional component.