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Extrusion.

Extrusion

Automatic dies for blown film, quick-tool-change systems and robot product-handling devices for profiles, and a new die-centering system for pipe were some of the more notable entires in extrusion equipment. Also reported below are an improved feedblock for flat-die extrusion, a novel in-barrel melt-viscosity sensor, a twin-screw blown film coex system, lots of new controls, and sophisticated new bag machines, among other developments.

BLOWN FILM LINES

In blown film, the novelties were in automatic dies, twin-screw coextrusion of "window" film, and a tiny twin-die system for 3-in. layflats. There was also news in increasing sophistication in controls, winders, and bubble cooling.

As reported last month (p. 13), a particularly interesting development in blown film technology was the appearance of the second commercial automatic die, a mechanically operated version from Reifenhauser, in contrast to the thermally controlled Optfil P automatic die first introduced in 1988 by Windmoeller & Hoelscher. During the exhibition, Reifenhauser claimed to have minimized the gauge variation on a three-layer, 60-mm-thick film from [+ or -]6-8% at start-up each day, to a max. of [+ or -]2% using the Reicoflex Piezo-Translator automatic die-bolt adjustment system, with profiles routinely in the [+ or -]1.5% range.

Meanwhile, W & H unveiled its Optifil Plus control system, designed to provide "modular" automation of blown film lines in three levels. The first, operation data recording, enables several extrusion systems to be connected to a host computer, which surveys production, faults, downtime, and causes of malfunction. A "partial automation" feature allows the basic system to be tailored by adding supplementary modules such as thickness gauging, width control, or profile control. The highest level is a fully automated process-control package that can store and retrieve data on several hundred products and supply printouts to document factors affecting quality. The system can be expanded to control a whole extrusion plant by connecting the film lines to the host computer via a local area network.

A new BF12 Baroflex coextrusion line from Barmag can produce blown film with five or seven layers, using EVOH or nylon as barrier layers. The die rotator, which can mount either five- or seven-layer dies. A crane runs on rails into the die area to exchange the die. Downstream equipment is the same as that used with Barmag's standard five-layer film.

In addition, the company showed a new blown film die with what was described as an "optimized" melt-distribution system that separates the melt flow into two independent flow paths and spreads it evenly over the entire die circumference. The distributor plug dispenses the melt in opposite directions, which results in a two-layer film, both layers consisting of the same resin.

In downstream equipment, Barmag introduced new winders, consisting of two main components: the contact roll unit and the winder itself. The contact roll unit has a large, grooved contact roll that is driven by a d-c motor, and incorporates the entire mechanism for automatic roll exchange, a stretcher roller, and a measuring roll to monitor winding tension. The winder consists of a carriage that can be moved horizontally on special rails. Pneumatic cylinders move the carriage, apply pressure to the contact roll and maintain a constant gap between the package and the contact roll.

Kuhne GmbH (represented by O/K International) demonstrated its K 70 Turbo Cool Line for HDPE with a 63-in.-wide take-off, secondary nip, and automatic winder capable of 492 ft/min. An important feature of the system is an internal bubble stabilizer mounted on the IBC exhaust pipe, whose height can be adjusted externally during production. A perforated iris diaphragm, also height-adjustable, is positioned at the stabilizer to ensure that the film neck lies evenly on the stabilizer cone.

Also displayed was Kuhne's new fully automatic contact winder, FOW 1/H 16 CC. It can be used for contact winding with controlled contact pressure, contact winding with center assist, and center winding at a constant gap. It can produce 47-in.-diam. rolls for contact winding and 39-in. rolls for center winding.

Two new blown film lines were on hand at the Alpine exhibit. A new computer-controlled, three-layer coex line combined 50-mm, 90-mm, and 65-mm extruders, an oscillating take-off with turning-bar system, and automatic tandem winder (WDP 20) with take-off speeds of up to 492 ft/min. Also shown for the first time was the HS 75 R blown film line. It has a rotating extruder said to be capable of high outputs in monolayer extrusion--e.g., 772 lb/hr of LLDPE. The system includes a new internal/external cooling combination ICS/PEAC, and new ECS I process-control system for throughput measurement and take-off speed control.

Betol Machinery combined twin-screw extruders with specialized blown film equipment to produce coextruded PE "window" film through a BTS4 die. The extruders use fully intermeshing trapezoidal screw geometry, said to provide consistent outputs of melt at the die, enabling blown and cast films to be produced without the aid of a gear pump. The ability to coextrude a colored film with a clear window eliminates a secondary printing operation.

Macro Engineering introduced an interesting twin-die mini extrusion line feeding a twin-lane bag machine. The line was capable of producing 60 lb/hr of 3-in.-layflat LDPE at speeds of 150 ft/min. One reason for the comparatively high output rate is the machine's dual-lip air ring, which the company claims is a unique component for a die that small. Macro has reportedly sold such a line to the Evenflo Corp., which is using it to produce baby-bottle liners.

CAST FILM AND SHEET

A high-barrier PET sheet coex line from Welex featured a number of new developments. Two 3-1/2-in. extruders and two 2/2-1/2-in. extruders were tied together by a new DB (double-barrier) feedblock that was capable of producing sheet with up to 11 layers, including two barrier and four adhesive layers. A new sheet take-off design has primary and secondary cooling rolls. The primary three-roll stack has 450-mm diam., hard-surfaced rolls to quench the sheet rapidly from both sides, as well as to permit close approach of the die to the roll nip to avoid sheet droop. Residual heat is removed by two 600-mm, thin-wall cooling rolls. Individual drives are provided for each roll section, and on the last primary roll to reduce sheet stresses. The entire system was controlled by a new Ultima II console, with color graphics and trend-monitoring capability. A touch-screen interface eliminates the need to type on a keyboard.

Incidentally, Welex's Frank Nissel sees an upsurge of interest in amorphous PET sheet extrusion and thermoforming as an alternative to PP and PVC.

Barmag also demonstrated its expanded capabilities in multilayer cast film at its R&D facility in Remsheid-Lennep, W. Germany. Depending on the raw material and film-thickness range, either chill-roll units with various string-up systems, or finish-roll units may be used. Up to five extruders can be integrated into lines for extruding PP, nylon, PET, and HIPS. Gear pumps guarantee uniform melt discharge. The feedblock is said to permit quick alteration of desired layer positions.

A new, multifunctional Dynatronic winder was demonstrated on W & H's Filmex cast film line. The winder, which has a max. roll diam. of 31-1/2 in., provides automatic roll changing and allows for core preparation and finished roll removal in multiple slitting.

BIAXIALLY ORIENTED FILM

Higher line speeds and increased winding diameters are two trends in BOPP film production. Bruckner, for example, reports max. line speeds of 984 ft/min for 13-ft-wide BOPP film, and winding diameters of 47 in. on 26-ft-wide film.

Cellier displayed a new clip system for BOPP film that it claims has been tested at 1968 ft/min. The clip reportedly uses only a fraction of the lubricant used by other chain systems on the market, protecting the product from contamination.

Also introduced by Cellier was a new heating roll with a permanently sealed circulation chamber. Liquid inside the chember is heated to a vapor either electrically or by gas. The vapor reportedly circulates inside the sealed double jacket at higher speeds than in circulating-fluid systems. Other advantages are said to be even temperature distribution and clean operation.

PROFILES, PIPE AND TUBING

As we reported last month (p. 13), one of the most novel extrusion exhibits at the show was a PVC window profile line from Krauss-Maffei, which utilized quick tool changing and robotics, two technologies that may be making a crossover from molding to extrusion. Accompanying photos show some of the essential features of the quick-change system. Other new features of the line included ionized air jets to blow off the sawdust and eliminate "static cling." A differential gearbox on the puller reportedly ensures the same pulling force on both belts, which are guided at both ends to prevent misalignment. Also, KM has added new features to its MC3 controller, including built-in gravimetric feeding control (adapted to Inoex hardware).

An automatic pipe-die centering device was also new from Krauss-Maffei (see photo). Pipe wall-thickness distribution is measured by up to eight ultrasonic sensors fitted around the circumference of the pipe inside the vacuum tank immediately after the sizing unit. This position is said to enable the sensor heads to react quickly to differences in wall thickness, so that deviations can be corrected almost immediately. Also, they're cooled by the circulating water, so no temperature variations can distort the readings. Because the sensors are stationary and take readings simultaneously, measurements are not complicated by possible machine-direction thickness variations.

The actual adjustment is made by a rotating mechanical socket wrench, driven by a computer that memorizes the last position of each diebolt, so that the wrench socket can slip onto the bolt easily.

Another new development in profile extrusion is a 65-mm twin-screw extruder with planetary gearing from Battenfeld Extrusionstechnik (rep. by Purnell International). It is said to reach a wide range of speeds in just one reduction stage and to operate at a high torque ratio, giving higher throughput.

The entire profile system is controlled by a newly-developed BEC 2000 control. A configurable alarm system warns of setpoint deviation and malfunction. The control's modular architecture permits full open- or closed-loop control, various means of communication, and coordination of extruder control and subordinate systems.

A method of dual extrusion of PVC window profiles on a standard extrusion line was shown by Actual Plastics Technology Corp. The system requires changes in the die and calibration only; extruder and downstream equipment remain unchanged. The central part of the system is Dual Extrusion Synchronization, by which the wall thickness of both profile strands can be optimized as both profiles are pulled off with the same force and speed. A control value--either a critical measurement right after the die or a relevant wall thickness measured after the first calibrator--is stored as a reference in the microprocessor.

Corma, Inc. introduced the model 820 HSL vacuum corrugator, which eliminates the need for vacuum bars. Output is 1750 lb/hr. One advantage of the machine is that it can form a wider range of plastics than usual, according to Corma's president, Gerd Lupke. The company has sold one unit to a customer in Holland for 36-in. corrugated pipe, and a machine to form 60-in. pipe will come on the market in about a year.

Betol demonstrated a new version of its bubble-tube extrusion line that uses a new microprocessor to provide an improved degree of selection and control of bubble dimensions, wall thickness, and spacing. The production of controlled bubbles provides a medical tube with a built-in funnel connector, avoiding the need for injection-molded connectors on straight tubes.

NEW FEEDBLOCK

ER-WE-PA, introduced its Lambda feedblock for flat-die extrusion, said to avoid problems of encapsulation and instability when coextruding polymers of different viscosity. ER-WE-PA's Dragan Djordjevic describes it as the "shortest feedblock on the market," since avoiding long channels after combining the polymer layers is, in his view, a key to preventing instability. Rather, it's best, he says, to "spread and squeese" the layers to final width and thickness immediately after the layer configuration is assembled. Thus, the short-land feedblock is actually built into the coathanger die. Trials are said to have shown improved results with polymers such as nylon, PET and polycarbonate in distribution and encapsulation control. The feedblock has a slot for external adjustment of the skin layer, and quick-change modules permit adjustment of the layer structure.

CONTROLS AND SENSORS

Krauss-Maffei demonstrated its COSMOS (Central Online Supervising Machinery Operating System) that permits interlinking of mixed machinery pools. The central computer is an IBM-compatible PC that can link up to 64 data-acquisition stations and to a host computer. Machines equipped with MC2 or MC3 control systems can be connected directly to the central computer, allowing access to all machine data and functions, including setpoints, actual values, alarms, and step displays.

ER-WE-PA showed off its EXACT process control, a modular system that provides centralized control of temperature, automatic dies, and other functions, and provides alarm indication, production data storage, and data logging. Modularity means that it can be configured at any level and later be extended to a comprehensive control system, and is based on IBM-compatible OS/2 operating software.

A gravimetric control, the Dosex 90, which measures the consumption of primary and secondary components was introduced by Inoex. Each dosing station is designed as a modular system and can weigh up to six components per extruder. One reported advantage of the gravimetric system, which was incorporated into Reifenhauser's closed-loop process control for blown film, is that it can compensate for bulk-density changes in resin or colorant. The result is not only good batch control but better layer-thickness control in coextrusion, according to Reifenhauser-Van Dorn's manager of blown film systems, Hector Marchand.

A spectra Beam FSIR (Full Spectrum Infrared) sensor from Aeonic Systems is said to be able to measure substrates difficult or impossible to gauge using previous techniques. The unit is claimed to monitor across the near-IR spectrum, and optics allow access to a broader range of the spectrum (1.3 to 3.4 microns). This is said to provide information to perform a variety of measurements at once.

New extrusion controls and sensors were also shown by Gneuss Kunststofftechnik, firm known primarily for screen changers (see below). The company is testing a prototype system to control extruder drive and barrel temperatures, gear pump, and screen changer.

A novel development from the company is a viscosity sensor (VM2) that uses two separate pressure-measuring diaphragms--one at the end of the sensor, pointing radially toward the center of the melt stream (as in standard sensors), and a second one on the side of the sensor tip pointing upstream along the melt-flow axis, sensing the motion of the material. Unlike standard sensors, this method distinguishes increases in melt pressure resulting from screen blockage, for example, from true viscosity changes.

Also on hand was a microprocessor-based melt-pressure amplifier (DMV 1000) that is said to be compatible with many different transducer systems.

FILTRATION SYSTEMS

A fully automatic, self-purging model was one of several new versions of its continuous, rotary-filler screen changer introduced by Gneuss (see illustration and PT, Sept. '89, p. 51). The self-purging feature--especially useful for recycling or scrap-reprocessing operations--allows each screen pack to be used repeatedly. Purging is accomplished by diverting a small amount of melt through a portion of the screen in a direction oppsoite to the main melt flow, purging the screen of dirt particles. The firm plans to estabilish a demonstration lab and spare-parts operation in New Jersey this year.

A continuous-flow filtration (CFS) system was introduced by Beringer Co. Its dual-flow, single-slide-plate design is said to provide uninterrupted polymer filtration during screen changes without breaker-plate handling or cleaning, and without polymer degradation. A microprocessor control handles positioning and prefilling operations.

BAG-MAKING EQUIPMENT

Servo drives and electronic controls appear to be the state of the art in bag machines. A new generation of Polytronic PE bag makers with servo drives and electronic controls was presented by Windmoeller & Hoelscher. Size changeovers are accomplished by entering new settings in a Procontrol electronic controller. Seven servo drives in the machine's intermittent-feed section eliminate the need for clutch-and-brake units, gear trains, and belt transmission. The servo motors make it possible for welding time to be freely selected and adjusted independent of feed. Web tensions can be matched to suit the properties of the film. The unit's modular construction reportedly provides easy access to machine areas. A T-shirt version of the machine is said to be one year away.

Also featuring servo drives and microprocessor control was a new bottomweld bag making machine (SA 91 E-11) from Alpine Elba, capable of individual bag folding and stacking. The new SA 90 E-11 servo-driven T-shirt bag machine was also shown (PT, July '89, p. 73).
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Article Details
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Title Annotation:K'89 Report
Author:De Gaspari, John
Publication:Plastics Technology
Date:Jan 1, 1990
Words:2781
Previous Article:Injection molding.
Next Article:Compounding.
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