Abstract: For making cigarettes of different filter specifications,AF12 plug assembler has to be modified.In order to realize the conversion from 6-fold to 4-fold plugs,the principle of plug flow,the structure and transmission parameters of the plug assembler were analyzed.The assembler was modified as follows:1) changing the cutting drum and grading drum into a two-piece structure and adjusting or replacing filter rod guide;2) replacing change gear Z_g2=48 to raise the rotation speed of cutting drum;3) for maintaining speed ratio unchanged,increasing the groove number of grading drum to 21;4) changing the clutch into one with 9 teeth to ensure the synchronization between grading drum and aligning drum;5) using one plug knife;6) adjusting hopper and guides according to plug length.