Abstract: To adapt YB618 carton overwrapper to American carton format and anticlockwise tear tape,the folding steps in YB618 overwrapper were modified after analyzing the existing folding procedures.The cam mechanisms were redesigned and side folders were modified.The movable folders were removed,two fixed folders were reserved to complete the folding of wide long flaps.Movable side folders were designed for folding the narrow side flaps,the rear flag folding action was no longer needed.The modification was tested by a Pro/E simulation model at 80 carton/min(800 packet/min),the results showed that:1) The movement of two side folders satisfied design requirements,and completed the actions for narrow and wide flaps,and applicable to YB618 carton overwrapper for American carton format.2) The curvature of center trajectories of Cam 2 and Cam 3 was continuous,which met the requirements of cam movement,and their corresponding minimum inside and outside curvature radii satisfied the structure requirements of cam rollers of 16 mm in radius.3) The average effective running efficiency of modified overwrapper reached 88.09% with average noise level of 80.6 dB,the packaging quality met the requirements of standards,and the machine ran well.