Innovative five-layer sheet extrusion system for multi-colored food packaging

20 Jul 2011

Welex Inc has developed a new custom nine-extruder, five-layer sheet extrusion system for a leading European custom sheet manufacturer for the production of multi-colored striped sheet for thermoformed yogurt cups.

Multi-colored striped yogurt containers are a big market in Europe and Welex’s innovative system broadens the capabilities for thermoformers of these form, fill, and seal containers.

“This system is truly one of our most ambitious projects and sets a new mark for the number of extruders on one die,” said Wayne Lewis, Welex president. “It is a highly sophisticated and complex line in terms of the number of extruders and components and significantly elevates the capabilities of sheet makers and packaging companies.”

The machine’s nine extruders can be configured to provide virtually unlimited multiple stripe and layer combinations, according to Welex.

The system produces sheet up to 60-in (1500 mm) wide with a thickness range of 0.020 to 0.060-in (500 to 1500 microns) at a rate of 3000 lb/hr (1500 kg/hr). The nine extruders are 2.5-in and 3.5-in 30 LD vented, air-cooled versions with two-stage screws to run high-impact PS (HIPS) in a range of colors.

The five-layer sheet construction includes a crystal PS gloss layer, a five-color (fully custom-configurable) stripe layer, a white layer, a scrap foam layer, and a white bottom layer. The scrap foam layer is produced via a proprietary gas-blown foam process.

The system can also run PP with no equipment changes.

Each mobile-mounted extruder includes a slide plate screen changer and gear pump for high-precision output. The extruders feed into a valve distribution block before the die for easy control of the individual component destinations in the multi-manifold and feed block equipped die.

Welex Sentinel color touch screen modular control interfaces are incorporated into each extruder and the sheet take-off to ensure robust and straightforward extrusion control.

Each of these reports via Ethernet/IP fieldbus protocol to the central Welex Super Sentinel supervisory workstation with its oversized widescreen formatted HMI display for process optimization. The supervisory system provides complete line status at a glance, simplifies startup, and maintains unlimited recipe storage.

WelexConnect technology is preinstalled to permit monitoring, troubleshooting, actuating, or software updating from any location.

The sheet profile is monitored by a Scantech x-ray gauging system which controls the Welex Autoflex thermal expansion bolt-actuated die. This gauging method has many advantages over more commonly used beta ray systems including the ability to measure a smaller area for more precise measurement and control.

The sheet extrusion line also features the Welex Evolution individual roll drive sheet take-off system which boasts automatic roll gap controls and a set of water flow driven secondary cooling rolls to assure uniform sheet temperature at the end of the line prior to winding onto jumbo rolls.

The novel system has already been shipped and is expected to be in production next month.

Source: Welex Inc.