The Nordson EDI head system allows Evertis de México to maintain tight tolerances and avoid instability.
Nordson Corporation’s co-extrusion head system has enabled an extrusion processor specializing in semi-rigid PET-based packaging sheets to comfortably maintain layer uniformity within tolerances while avoiding defects in the products it produces. They usually appear in asymmetric layer structures.
Evertis de México SA de CV, a manufacturer of thermoformable panels for food packaging (such as poultry, cheese and processed beef) and other non-food applications, recently installed a Nordson EDI coextrusion head system to produce a wide range of structures. These include standard, medium barrier and high barrier multilayer films with thicknesses from 180 to 1016 µm (0.180 to 1.016 mm). Barrier layer structures are often asymmetric, in the sense that the thickness of the material or layers above the core layer is different from that below. The precise flow control of Nordson’s EDI system made it possible to maintain close layer tolerances in these structures while simultaneously preventing “waviness”, “zig-zag” and other defects caused by instabilities at the interface between layers.
“At Evertis, we strive to improve our production methods and consistently deliver high quality products,” said Aprigio Pinto, Director of Production at Evertis de México. “We work with leading equipment suppliers that we can count on for excellent customer service and support. This philosophy is essential for Evertis de México, given our constant growth in the markets in which we operate.”
“Thanks to the immediate responses of Nordson’s technical support team, Evertis de México is guaranteed high-quality equipment and services at a competitive price in the market,” said Jacques Tillet, director of maintenance at Evertis de México. “At Evertis, we produce semi-rigid barrier PET film for food and non-food applications, and it is crucial that we maintain the uniformity of the layers within tolerances all the time. The Nordson EDI head system allows us to control the interface of the layers and therefore avoid product defects such as curling. By implementing this system, we are confident that our customers will always receive high quality products.”
Solving the challenges posed by asymmetric multi-layered structures
“As critical layer interfaces move into regions of higher shear flow paths, coextrusion instabilities are more common in structures that are asymmetric,” said Nordson EDI Chief Technology Officer Sam G. Iuliano. “Our main system produces aerodynamic currents and refines them at the confluence. Additionally, the ease with which adjustments can be made allows the system to be very versatile in terms of layer configuration and product width.”
The main components of the Nordson EDI head system used by Evertis de México are as follows:
? Ultraflex™ head with Multiflow™ II-G manifold and internal width adjuster. Nordson designed a manifold or flow channel within the collector to reduce shear stress levels at the layer interfaces, improving layer uniformity. At the same time, the manifold sections at each end of the header are dimensioned to accommodate internal width adjusters to change the width of the product.
? Ultraflow™ VS Adjustable Power Block. The feed block combines the streams of molten material from the separate extruders into a multi-layer “sandwich”, which is then distributed by the extrusion head to the target product width. The Ultraflow VS feed block includes adjustable “mix planes” located where the melt streams join the central flow channel. These features enable balancing of combined flow rates, and when operating in “free-floating” mode, automatically compensate for changes in layer thickness ratios that accompany changes in product structure. Adjustments can be made without removing the power supply block from production, increasing uptime and versatility of the final product. Another adjustment that can be made online is the use of a selection wheel that allows changing the sequence of layers in the structure.