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Extrusion & compounding.

Our pre-NPE look at extrusion may have turned up most of the major equipment developments, but suppliers still had some surprises up their sleeves when the show opened its doors. Several machine builders made new pushes into the controls realm by coming out with their own supervisory control and data-acquisition (SCADA) systems. Also, a number of brand-new or greatly revamped gauging systems appeared for the first time.

Compounding, too, had its share of control advances. And the show saw the U.S. debut of a novel two-roll continuous mixer. We also have some more details on a uniquely instrumented line for evaluating twin-screw mixing elements.


Thanks in part to the easy availability of "application enabling" software, several machinery suppliers came out with new PC-based supervisory control systems--ones capable of monitoring several lines at once. Many of the systems are based on third-party software that gives the machinery makers a quick-and-easy route to building customized control applications and graphical user interfaces.

For blown film, Alpine American of Natick, Mass., introduced the Advanced Extrusion Supervisor (AES) IV. It ran at the show as part of the company's three-layer coex blown film line with auto profile control. According to sales manager Dave Nunes, the AES provides "total control" of process parameters as well as SPC trending and recipe storage. Soon after the show, Alpine planned to integrate its DOS-based auto-gauging or Profile Optimization System into the Windows-based AES IV.

In addition to its Unistack adjustable sheet take-off and universal-jointed die (see PT, May '94, p. 54), Welex Inc. of Blue Bell, Pa., had its new Ultima III system on hand; it's the company's first SCADA system. PC- and touchscreen-based, Ultima III controls drives, temperatures, downstream equipment, and upstream feeders and blenders. It has a graphical display of all process parameters, alarms, and recipe functions. "Anything you can do on the instrument panel, you can do on Ultima III," says process control manager Randy Sloyer. The system costs about $100/loop. Another new product is intended for Welex customers that haven't jumped into SPC/SQC yet. Ultima SPC consists of a plug-in card to collect data and SPC software running under Windows on an IBM-compatible PC. Price is about $2500.

Other companies showing control solutions included two makers of sheet lines. Mega Machinery of Fontana, Calif., had its new touchscreen controller on its three-layer sheet line (PT, May '94, p. 53). And HPM Corp. of Mount Gilead, Ohio, has used Wonderware to create a supervisory control system for its TMP tubing extrusion line, which featured downstream equipment from ESI of Stowe, Ohio.


For quality-conscious film and sheet producers, the many gauging suppliers at the show provided more details about systems featuring beefed-up computer capabilities and even a few brand-new sensors.

NDC Systems of Monrovia, Calif., showed the new noncontact laser-caliper gauge we reported in May. At the show, v.p. Yudie Fishman explained that the new gauge addresses earlier problems with laser triangulation gauges, including their sensitivity to vibration, calender-roll runout, and temperature changes--all of which dynamically change the distance between gauge and product. To combat these obstacles, the new NDC gauge relies on a new stabilized scanning frame and new electromagnetic sensor with an on-board transputer to correct for the dynamic distance changes. The new laser gauge comes in one- and two-sided versions for products up to 1.5 in. thick.

Also new from NDC is an improved beta-gauge system that uses a higher-efficiency detection system rather than a stronger nuclear source to improve accuracy. According to Fishman, the system uses a nuclear source that is only 17-20% of the strength of conventional gauges. Still, Fishman reports, the new system has detected 1/32-in. streaks while scanning at 12 in./sec.

Contour View from Eurotherm Gauging Systems in Billerica, Mass., is the company's latest operator-interface development. Now part of the company's Extrusion Cell CIM system, this new X-Windows graphics tool provides the line operator with real-time and historical 3-D representations of the film or sheet product. In the past, operators could only view summaries of current status and historical trends.

Navigating around the new display with touchscreen arrows, users can monitor trends associated with any lane on the web. When used with an auto-die system, the system provides die-bolt heater graphing for each control zone; this last feature springs from the company's year-old Melt Flow Model, a die-bolt mapping tool. As another aid to operators, Eurotherm has also added context-sensitive "Help" features.

Ohmart Corp., Cincinnati, introduced an eddy-current, noncontact caliper sensor for sheet and foam products over 5 mils thick. The new gauge reportedly controls accuracy-threatening variations in air pressure around the sensing head.

And LFE Industrial Systems, Clinton, Mass., introduced Windows-based software for its gauging and control systems.


Ohmart Corp. also has expanded its Concept One system from gauging alone to a total extrusion control that includes all extruder and downstream parameters. Built on a Pentium-chip PC running OS/2, the Web Process System can move gauging and other process information into Excel or other spreadsheet software for viewing in a variety of graphic or spreadsheet formats. System cost is said to be well under $100,000 for total control.

Also new for the Concept One system is SQL compatibility so that recipes and roll reports can be more easily archived in commercial database-management products.


Measurex Corp., Cupertino, Calif., has integrated all its gauging and web-inspection products into a single package based on an "open" Local Area Network (LAN) architecture called MXOpen LAN (PT, May '94, p. 53). Marketing manager Pat O'Neill explains that previously discrete systems--such as the video-based web-inspection system--now reside on a single network and can be viewed from a new X-Windows operator interface. This integration lets processors view data from the web-inspection, thickness-gauging, and other quality systems all though a common touchscreen interface on a variety of workstations.

In a related move, the company rolled out two new workstations. The Application Station supports various data-collection, process-monitoring, and configuration tasks, while the Process Manager is a real-time process-control computer.

Another brand-new piece of the MXOpen package is an extrusion temperature-control processor (TCP)--an earlier temperature controller had been discontinued due to an incompatibility with MXOpen architecture. TCP, which can be configured for analog or digital signals, can handle up to eight control loops. TCP setup can be accomplished from Build View, an MXOpen configuration tool.

Extrusion-specific, pre-programmed sequences, or "function blocks," also come with TCP. These include one called Weekend Temperatures, which places all temperature loops in standby mode, and one called Ramp and Soak, which ramps up and holds temperatures at one or more setpoints during automatic startups.

Measurex also announced a new cooperative relationship with Allen-Bradley Co., Highland Heights, Ohio, which has implemented a software driver that makes its PLCs compatible with Measurex's Open Data Exchange for MXOpen LANs. According to Measurex's O'Neill, the agreement provides a communication protocol between the two companies' products lines, paving the way for complete interoperability.


Davis-Standard Egan, Somerville, N.J., showed a new line of "MAC" (Metric Air-Cooled) extruders. In these machines, the extruder plenum is integral to the machine base, which helps carry heated air away from the extrusion area more quickly. The MAC also uses a common blower to draw ambient air into the extruder and then to carry away the heated air.

Addex Inc. of Boston showed off a new extruder with a finless "Tornado" air-cooling system. NPE marks the first time the company has shown its own extruders--it used to buy them from Davis-Standard. Addex has built about seven machines over the last two years, but this one is the first with the Tornado system, in which air travels through a double-wall stainless-steel chamber insulated with fiberglass. Cooling air enters from the top and hot air is blown out the back of the machine. A honeycomb hole arrangement lets air flow from the double-wall chamber onto the barrel.

HPM had its new 6-in. TMP (Torque Master Prodex) extruder on hand. This pre-engineered, modular machine is air-cooled and costs 10-15% less than the company's more customized molds.


Moving a few notches down in size, Randcastle Extrusion Systems, Inc. of Cedar Grove, N.J., has come out with a patent-pending surge suppressor for its side-discharge extruders, which have diameter of 1-in. and smaller. Derived from Randcastle's established viscous-seal technology, the new suppressor region starts where the main part of the screw ends, extending well beyond the extruder's side-discharge port. Flights on the suppressor have a geometry similar to the screw's metering section--but in a reverse pitch.

According to company president Keith Luker, the suppressor works by absorbing excess polymer flow during pressure peaks and, through the action of the reverse flights, returning that polymer when the pressure ebbs. High-pressure periods fill a greater length of the suppressor than periods of low pressure. Luker says the device reduces surging by roughly 20% but, with further development, should be able to achieve a 40% reduction.

Though primarily associated with laboratory machines, Randcastle side-discharge extruders also see use as screw pumps on larger lines from a variety of extrusion OEMs. At NPE, for instance, a twin-screw medical tubing line from American Leistritz used a Randcastle screw pump as a pressure builder for the compounding machine. Among the seven extrusion lines it showed, Randcastle introduced its first bench-top fiber line.


Filmaster of Fairfield, N.J., showed a new "crate system," a compact blown-film line that can be packed into a single shipping container. Unlike past crate lines, the new system now can include in-line bagmaking--though the bag machine goes in its own box.


HPM showed off HGL-2, an adjustable roll stack that underwent a makeover for NPE. Roll diameter has been increased from 18 to 24 in. for higher production rates. And a new split bearing lets users change rolls without disassembling the stack.


Also new from Davis-Standard Egan was the new CODA sheet die, an internally deckled model for cast film. The deckle has been customized for higher-viscosity film resins and features a "positive seal"--one that is not dependent on melt pressure.

In addition to introducing a new technology for extruding lip adjustment range and an updated automated die (see PT, May '94, p. 52) EDI of Chippewa Falls, Wis., reported working on its first internally deckled die for cast film; it should be ready by year's end.


Two members of the next generation of screen changers were previewed at the show. Extek Inc., Danvers, Mass., plans to commercialize its first continuous model at the beginning of next year (PT, April '94, p. 13). And John Brown's Beringer Div., Marblehead, Mass., revealed further details about its prototype Ultra Lock slide-plate model (PT, May '94, p. 59). Among its many new features is a patent-pending improvement in the company's high-temperature-polymer seal. According to marketing manager Don Macnamara, this new Hydra-Seal technology captures the bulk of the polymer ring in steel to keep it from migrating into the melt stream--because of shrinkage, head pressure spikes, or damage from screw flights. The steel leaves a small bit of polymer ring exposed so that the ring can still translate melt pressure into an axial loading of seal onto slide plate.

Another feature of the new design is a spin-on threaded ring connector to lock the screen changer to the extruder. In this arrangement, turns of an adapter ring bring extruder and screen changer together on opposite threads--as opposed to the usual body that screws directly into the extruder. Macnamara says this provision eliminates the possibility of a stuck screen changer. Standard Ultra Locks are intended to operate at pressures up to 10,000 psi and at temperatures up to 600 F. Sizes are from 2.5 to 8 in. with a production rate range of 250 to 4500 lb/hr.


A novel continuous mixer developed by Germany's Condux GmbH appeared at the show. It's marketed here by Charles Ross & Son Co. of Hauppauge, N.Y. Building on the two-roll-mill concept, the Ross-Condux Shear Roll Extruder processes medium-to high-viscosity materials between two open counterrotating rolls. The rolls have spiral grooves that act like screw flights to transport the material from the feed to the discharge end. Three times longer than conventional roll mills, the Ross Condux units have a 7.5:1 L/D. As in a standard batch roll mill, each roll runs at a different speed and temperature, causing the material to form only around the front roll. An adjustable roll gap--from 0.5 to 5 mm--controls shear rate.

Gravimetric or volumetric feeding options are available, and the machine can separately dose fillers, fibers, and additives. Materials leaves the machine in either continuous strips or, with the help of various granulation options, as pellets. Throughputs are in the 3-30 liters/hr range for the smallest unit with 121-mm roll diam., up to 300-1500 liters/hr for the largest unit with 600-mm rolls. Max. temperatures are up to 450 F.


Another of the more novel compounding exhibits at the show was the Twin-Screw Mixing Element Evaluator (TSMEE) from Werner & Pfleiderer Corp. of Ramsey, N.J., and the Polymer Processing Institute (PPI) in Hoboken, N.J. This system pairs a split-barreled ZSK corotating extruder with instruments for continuously gathering rheological and morphological data, which together provide clues to optimal screw design. According to PPI senior research engineer Mohamed Esseghir, the system's Helical Screw Rheometer (HSR) employs "invert-cut" screws to pump the polymer while avoiding the transient pressure effects created by flight passage. Pressure, speed, and temperature data collected as the melt flows through the HSR are converted to viscosity/shear-rate information by the system's on-board computer.

The optical system supplied with the TSMEE monitors melt morphology continuously. It includes a melt-flow cell with a matched optical microscope and video camera, plus image-analysis software. W&P supplies the system, but the one at PPI is also available on a contract basis for $1500/day.


On the compounding side, Berstorff Corp.'s ECS Div., Charlotte, N.C., which focuses on controls, showed a supervisory system capable of bringing audio and visual signals from the shop floor to the q-c lab--or front office. According to ECS v.p. Nelson Hopcus, the SCADA video display had been available as a separate system, but now it's integrated into the process-control environment. Images now pop up as a window on the same computer monitor that looks at process parameters and SPC trends.

Farrel Co. of Ansonia, Conn., showed new Wonderware-based control packages for its whole line of compounding equipment--everything from its new twin-screw extruders to continuous and Banbury-type mixers.

American Leistritz Extruder Corp., Somerville, N.J., showed its new EMCS control package as part of a direct extrusion line that handles compounding and medical-tubing production on a single line (PT, May '94, p. 82).


Gneuss Inc. of Charlotte, N.C., introduced a redesigned version of its diverter valve for extrusion startup. Intended mostly for compounding/pelletizing lines, it resembles a slide-plate screen changer, but it diverts the melt through a valve until the line is producing on-spec product. This keeps needless contamination out of the pelletizing system. The new inexpensive model replaces an earlier version that cost up to 30% more.
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Author:Ogando, Joseph
Publication:Plastics Technology
Date:Aug 1, 1994
Previous Article:Injection molding.
Next Article:Blow molding.

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