Post-processing apparatus that performs post-processing on sheets discharged from image forming apparatus

An image forming system comprising:

• an image forming apparatus that forms images on sheets;
• and
• a post-processing apparatus that applies post-processing to the sheets output from the image forming apparatus,
• wherein the post-processing apparatus comprises:
• a first conveyance path along which a sheet is conveyed;
• a buffer unit that receives the sheet conveyed from the first conveyance path and temporarily holds a predetermined number of sheets so as to be overlaid on one another;
• a second conveyance path along which the predetermined number of sheets from the buffer unit are conveyed when the temporary holding by the buffer unit is terminated;
• a stacking unit that stacks the predetermined number of sheets conveyed toward a first direction from the second conveyance path;
• a moving unit that comes into contact with the uppermost sheet among the predetermined number of sheets stacked on the stacking unit and moves the uppermost sheet further toward the first direction;
• a regulating unit that is provided downstream of the moving unit in the first direction and that comes into contact with an end portion of the stack of sheets on the stacking unit to regulate the position of the stack of sheets, the end portion of the stack of sheets being an end portion on the downstream side in the first direction;
• and
• a control unit that controls the predetermined number of sheets, the predetermined number of sheets being the number of sheets that are to be temporarily accumulated in the buffer unit and conveyed to the stacking unit together,
• wherein the control unit determines the predetermined number of sheets based on one or more physical parameters that affect a frictional force generated on the surface of the sheet.