AR-F15 (serv.man2). Service manual - Sharp Copying Equipment Service Manual (repair manual). Page 117

The alignment motor (M5S) drives the alignment plates each time a sheet is output, putting

both left and right edges of the sheet in order. The alignment plate motor is a 4-phase stepping
motor. The position of the alignment plate is identified in reference to the number of motor pulses
from the alignment plate home position sensor (PI5S).

The following briefly describes what takes place when the saddle stitching mechanism oper-

ates on two sheets.

1) When the first sheet has been output, the alignment plates butt against the left and right edges

of the stack (first alignment). The alignment plates leave the home position in advance and
remain in wait at points 10 mm from the edges of the stack.

Sheets

Paper positioning 
plate

Alignment
plate

Alignment

plate

Alignment plate 
home position sensor
(PI5S)

2) The alignment plates move away from the edges of the stack over a short distance and then butt

against the edges once again (Second alignment).