We have used an optical fiber sensor for in-situ monitoring of product shrinkage during injection molding. The sensor, consisting of a bundle of optical fibers with a sapphire window at its end, is positioned in the ejector pin channel of the mold so that the sapphire window sits flush with the inside cavity wall. When the molded product shrinks, it separates from the wall and sapphire window, and establishes the geometry of a Fabry-Perot interferometer. During the molding of polystyrene, polypropylene and polyethylene, we observed optical interference fringes, and by counting fringes, a measurement of shrinkage was made.
Proceedings Title: Proceedings of the Society of Plastics Engineers Annual Technical Meeting
Conference Dates: May 1, 1999
Conference Location: New York, NY
Conference Title: Society of Plastics Engineers. Technical Meeting
Pub Type: Conferences
injection molding, interferometer, optical fiber sensor, polyethylene, polypropylene, polystyrene, process monitoring, shrinkage