METHOD OF MAKING A BAG USING A VISION SYSTEM ARRANGEMENT

A system and method for making bags in a continuous in-line process includes a central processing unit and a camera oriented to take an image of a bag based on a triggering signal. The camera provides an image to the central processing unit. The central processing unit is programmed to process the image and calculate a timing signal based on the image. A cylindrical rotatable drum having at least one seal bar provides a triggering signal to the central processing unit, to trigger when the camera should take the image. A perforation knife is controlled by a servo drive. The perforation knife is downstream of the drum. The servo drive receives the timing signal for activating the perforation knife from the central processing unit. The CPU uses the image and based on the distance between the seal region and the perforated line, counts pixels to result in an actual pixel count. The CPU then calculates a pixel count error by subtracting the actual pixel count from a predetermined pixel count setpoint. This information is then used by the CPU to either advance or retard the perforated knife in its perforation step. This results in a bag having a shorter skirt length, which reduces waste and cost. In another embodiment, the image taken is of the seal region only, and based on the image, the CPU either advances or retards the perforation knife in the perforation step, downstream of the point in which the image was taken.