A liquid packaging machine produces liquid packaging bags from roll film by cooperatively controlling the vertical seal roller, horizontal seal roller, and cut roller. These rollers are driven separately by servomotors as a multi-axis servo mechanism. Positioning control on the moving film is essential to make bags of accurate size. To achieve accurate positioning without lowering productivity, we propose two control methods. One is a two-step velocity control of the horizontal seal roller. This method enables continuous and high speed production of bags of arbitrary size. The second is phase control, which determines the accuracy of the cutting position on the film according to the sealing position. Phase control changes the rotary phase difference of the horizontal seal roller and the cut roller by adjusting the high feeding velocity of the cut roller, or by adjusting the low feeding velocity of the cut roller. The control system developed was applied to a DANGANV liquid packaging machine.

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