METHOD AND APPARATUS FOR REGISTRATION OF A SEAL

摘要

A plastic bag making machine including a cylindrical drum with a variable diameter is disclosed. A plurality of seal bars, substantially parallel to the drum's rotational axis, define the circumference: of the drum. Bags are made from a film that includes registration marks detected by a detector disposed near the film's path. A detector detects the revolution of the drum and an encoder provides signals indicative of the position of the film. A controller determines the distance between the registration marks using the output of an encoder as a position signal and adjusts the diameter of the drum in response to the determined distance. The controller also determines the position of the seal bars relative to the registration marks and adjusts the diameter of the drum in response to the relative position.