Image forming apparatus and control method for printing without a margin

An image forming apparatus that forms an image on both surfaces of a printing material without a margin by forming an image of a size that is larger than the printing material, the image forming apparatus comprising:

• an image forming unit adapted to form an image to be larger than a printing material so as to form the image on the printing material without a margin;
• an image bearing member adapted to bear the image formed by said image forming unit;
• a transferring unit adapted to transfer the image formed on said image bearing member onto the printing material;
• a fixing unit adapted to fix the image transferred by said transferring unit to the printing material;
• a double-sided conveying unit adapted to turn over the printing material output from said fixing unit and return the printing material to said transferring unit;
• a printing material type determination unit to determine a type of printing material by (i) a user designation or (ii) a sensor for detecting the type of printing material;
• a first detection unit adapted to detect a first size of the printing material in a convey direction before transferring the image onto a first page of the printing material;
• a second detection unit adapted to detect a second size of the printing material in a direction that is orthogonal to the convey direction before transferring the image onto the first page of the printing material;
• and
• a setting unit adapted to set a size of the image,
• wherein (i) in a case where the first size of the printing material is unknown, said setting unit sets a size of a first image corresponding to a first page of the printing material in the convey direction to a size corresponding to a predetermined maximum size of the printing material, and (ii) in a case where the second size of the printing material is unknown, said setting unit sets the size of the first image corresponding to the first page of the printing material in the direction that is orthogonal to the convey direction to the size corresponding to the predetermined maximum size of the printing material, and
• wherein said setting unit sets a size of a second image corresponding to a second page of the printing material to a small size that is smaller than the size of the first image, the size of the second image being set based on the first size detected by said first detection unit, the second size detected by said second detection unit, an adjustment amount for a change of a size of the printing material due to fixing of the first image to the first page of the printing material, and a correction of the adjustment amount due to the type of the printing material determined by said printing material type determination unit.