Apparatus for winding a strip (58) of web into a cartridge (40), the cartridge including an enclosing shell (42, 44); a spool (46) mounted for rotation within the shell, the spool being engageable externally of the cartridge (51, 53) for rotation; the spool comprising a core (54) with features (56) for attaching an end (60) of the strip to the core; an axially extended opening (50) through the shell for advancing or withdrawing the strip; and a light-shielding door (52). A tool (94) inserts the end into the cartridge and attaches it to the core. A winding motor (354) rotates the spool to draw the strip into the cartridge. During the winding, a rotatable air bar (92) adjusts the path of the strip to prevent contact with the peripheral edges or walls of the opening.