BAG MAKING MACHINE

PROBLEM TO BE SOLVED:To improve the cut-out and cut-off precision of a plastic film by a method wherein the plastic film is cut out at a first set position by a punching machine,a notch is formed,the shape of the notch is read as image data and a slippage between a second set position and the position of a cutter is calculated to control the cutting. SOLUTION:After a plastic film 2 is intermittently fed to heat-seal it by a heat sealer 3,the film 2 is cut out at a first set position by a punching machine 5 and a notch is formed. The film 2 is cut off by a cutter 6 at a second set position for the notch. When the film 2 is cut off,the shape of the notch is read as image data by a video camera 12 installed near the cutter6,and a positional slippage between the second set position and the position of a blade of the cutter 6 at the time of stop of film feed is calculated based on the image data. The amount of elongation and contraction of the film 2 between the heat sealer 3 and the punching machine 5 is calculated based on the calculated value to correct the positional slippage.