Machine Vision Inspection of Heat Seals at Full Line Speeds, 1998 Polymers, Laminations & Coatings Conference Proceedings

Heat seals applied at full line speeds are in common usage in many applications. Several factors influence the integrity of the finished heat seal. These include tool alignment and tray, tub, or cup alignment within the tool; sealing web placement; tool contact time, temperature, and pressure; and the presence/absence of tramp material between the sealed surfaces. Tramp material between the surfaces to be sealed can account for a high percentage of defective seals. In this instance, machine vision inspection of the area to be sealed prior to seal application may be all that is necessary to produce acceptable process yields. If more rigorous inspection is required, it is often possible to inspect the seal at full line speed after application. This inspection can detect channel leaks, insufficient seal width, improperly sealed areas, or holes in the sealing web. The application of machine vision to the inspection of heat seals generally involves a study to ensure complete understanding of the particular process, followed by in-plant demonstration, then full implementation. Where tramp material on the area to be sealed is the primary cause of poor heat seals, the work can generally proceed directly to on-line implementation.