Blown-film line makes debut at new extrusion lab.

Brand-new blown-film technology is on display at a 10,000-sq-ft extrusion lab just opened by Sano Inc., a Cincinnati Milacron Co., Passaic, N.J. The lab is showcasing a production-scale, three-layer film line with 50-ft tower and some special features that will be introduced publicly for the first time at NPE '91 this month in Chicago.

The new technology featured on the blown-film line--namely, in process controls, winders, and single-screw extruders--represents initial results of an on-going engineering program, code-named Wolfpack, that speeds product development, according to Michael Yahr, v.p. of sales and marketing. One hallmark of the program is "simultaneous engineering," in which various levels of product development are integrated for faster engineering releases. Lead times reportedly can be 30-50% shorter than with conventional production methods.

NEW PROCESS CONTROLS

One new introduction is Sano's first proprietary extrusion control system. The control panel, which is located on its own platform close to the line's 22-in. oscillating coextrusion die, uses hardware that was first incorporated on Cincinnati Milacron's injection molding machines, plus applications software designed for blown- and cast-film lines.

According to controls engineering manager Anthony Lawson, there are currently four levels of the software. Two of these will be demonstrated at NPE. Level 1, Sano's basic entry into the market, includes temperature, recipe management, alarming, diagnostics, temperature control, and SPC/SQC functions. Level 2 performs supervisory functions, and ties auxiliary equipment, such as gravimetric extrusion controls, blending systems, and gauge controls, into the computer system.

One feature of the process control system is extensive diagnostic capabilities through a menu-driven set of screens. An example of its accuracy is a heater diagnostics package that detects power loss to 1% of the barrel heat zone, making it possible to pinpoint where the loss in amps has occurred. Until now, sensors that measure current have detected power loss to about 25% of the heat zone, claims Lawson. This system detects impedance changes in each heater band in a heat zone, and in fact has an alarm that predicts heater burnout before it occurs.

Another claimed advantage is the added flexibility of its software-based control system as compared with standard PID controls. "Situation-based adaptive control" on the IBC (Internal Bubble Cooling) system, for example, reportedly will modify an algorithm to compensate for gradual changes in an operating situation.

The key here is that it will recognize both fast loops and slow loops and respond to each differently. If clogged blower filters are replaced, it will recognize the appropriate algorithm to optimize bubble size control. On the other hand, it is flexible enough to respond to more subtle operating conditions by learning the gradual in-plant changes in temperature and humidity. This flexibility is said to be an advantage over standard PID loops that may over-respond to longer term changes.

The next stages of control will tie downstream equipment such as nips and winders to the central computer. Integration of the entire line is expected to be accomplished by the end of this year, and the goal for plant-wide integration is set for the following 12 months. Approximate price of levels 1 and 2 of the process control system is $40,000.

VERSATILE LINE

A number of features add to the line's flexibility for running coextruded product. The line is fed by one 4 1/2-in. and two 3 1/2-in. models of the newly introduced Cincinnati Milacron single-screw extruders. Each extruder is equipped with a 30:1 L/D barrier-flight screw, through which up to 10% PIB tackifier can be injected at the end of the feed section for cling/stretch film production. Cincinnati-Milacron's full line of single-screw extruders includes 2 1/2-, 3 1/2-, 4 1/2-, and 6-in. models, and include air-cooled and water-cooled versions. Typical horsepower levels range from 75 to 400 hp. The machines will be equipped with Flenders low-noise gear-boxes.

The extruders feed a 22-in., three-layer oscillating die (although there is room to add an oscillating hauloff at the top of the tower). A circular bubble enclosure protects the bubble between the die and collapsing frame. Rollers in the collapsing frame are equipped with their own drives to minimize friction.

A "pseudo nip," located just before the upper nip at the top of the tower, narrows the space between film layers without actually pinching them closed, and minimizes the amount of air escaping when edge-fold slitting below the nip. Two corona-treating stations at the top of the tower and two below the lower nip allow either side of the web to be treated.

The lower nip assembly is equipped with a second set of nips below the primary set and slitters. This acts as a tension-isolating device that prevents a "zipper effect" as the webs are separated just prior to winding, which enables the line to handle stretch film more easily.

Takeoff is performed on two single-turret winders equipped with precise turret control and an automatic, enveloping, nonadhesive cutoff device. These two features will be incorporated into Sano's next generation of winders still under development, according to Richard Previty, product manager for cast film and winding systems.

The new winders will be designed along a modular, "building-block" approach in which various options can be added to a common, pre-drilled frame. The standardized frame will readily accept upgrades such as multiple slitting devices, dual-direction automatic transfers, drives for specific rollers, and proximity lay-on, according to Previty.

The advantages of this approach reportedly are shorter delivery times and lower cost of new equipment. Additionally, this flexibility will permit users to add modules to the equipment to rapidly meet the requirements of changing markets. Nips, hauloffs, and corona treater equipment eventually will also be designed with the same approach.

Future expansions in the new laboratory possibly will include cast film and sheet lines, according to Yahr. (CIRCLE 56)