The longitudinal, or back, seam is the main vertical seal that runs along the back of a bag made on a Vertical Form Fill Seal (VFFS) machine. This seam holds the package together and affects its strength, appearance, and leak resistance. Factors such as overlap width, sealing temperature, and dwell time determine how well the seam performs under load. Unified Flex VFFS systems use precise temperature and pressure control to ensure durable, consistent back seals that maintain bag integrity throughout filling, transport, and storage.
