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 The manufacture of blown plastic film is affected by many variables. Blown films are produced by extruding molten plastic resin through a small annular die, where it emerges as a film. It is then blown upwards with a flow of refrigerated air that cools the plastic and forms a large diameter tube. A surrounding tower captures the bubble before it collapses, and routes the blown film down to a rolling mechanism. Monitoring temperature alone throughout the process can be challenging enough, especially when manufacturing multi-layer film. Additionally, when many employees have access to the temperature controllers without the ability to accurately quantify the results of changes, establishing a consistent processing window while minimizing scrap and downtime can be a daunting challenge to even the most experienced manufacturer.
Controlling the process
Always on the lookout for technology improvements, Pliant, which produces film and flexible packaging products for personal care, medical, food, industrial and agricultural markets, explored a new system for their South Deerfield, MA, facility. Pliant operates blown mono and coex film lines at this plant, producing films for a variety of applications. Two of their three-layer lines, which had five heat/cool zones per extruder barrel and over 30 temperature control zones overall, were being controlled by an antiquated analog unit (described by plant personnel as a “black box with flashing lights”) that gave no insight into the process. With no way to monitor the controller’s performance on the multi-layer blown film line, and with downtime a fairly frequent occurrence, Pliant decided it was time to upgrade their controller technology.
 Pliant called in a local distributor, FM Keefe Company, Inc., Springfield, MA, to develop a solution. This control systems integrator had serviced this facility for several years as an engineering resource and systems integrator, giving them extensive technical understanding of Pliant’s processes. George Holman of FM Keefe met with the machine operators and supervisors to find out what they wanted in a control system. After understanding their needs, Holman’s team selected the PPC-2000 from Watlow, St. Louis, MO.
The PPC-2000 controller provides flexibility with easy-to-setup multi-loop process control and programmable logic control in one complete package. The PPC-2000 is a powerful and cost-effective approach for extrusion applications where other controls can be awkward, time-consuming to use, and do not adequately control the process. It offers a very user-friendly alternative to strategies employing PLCs with discrete controls.
Window into the process
 The company’s old controller, with its lines of scrollable text, made it extremely difficult for operators to distinguish data from among the three extruders. Because multiple operators had access to the controller on the shop floor, it was difficult to keep control over changes made to the processing parameters, or even to identify what changes had been made.
Pliant is now able to speed time to market with their customized PPC-2000. The controller provides vast resources for trouble-shooting resulting in greater productivity levels and reduced process downtime.
The new control system uses a 19-in. color touch screen with Watlow’s ANAWIN HMI software. ANAWIN software has data logging, graphing capability, auto-tuning, recipe management and built-in alarm handling features, which add to the versatility of the process controller. The use of this simple, menu-driven, full featured and customizable software in the PPC-2000 eases channel parameter setup and monitoring. The package allows all the control loops to be viewed and edited from tables. Because no programming was necessary, productivity was immediate.
 One of Pliant’s favorite features of the new controller‘s display is its color-coded graphics which clearly show operating data associated with each extruder and each die. Operators can see real-time parameters on each, as can supervisors from a remote computer located in an office overlooking the shop floor. By using pictures and quick reference features, the controller reduced Pliant’s engineering efforts through easy-to-setup PID control parameters with “fill-in-the-blank” and pull-down menus.
Pliant was able to size the controller to fit their application, and precisely control up to 48 temperature zones and process loops with a single unit. Because the PPC-2000 is modularized, it can grow with Pliant’s system, to allow various analog and digital I/O modules plus control loops to be centralized into one compact unit and programmed as an integrated system. The controller features several digital & analog I/O modules allowing users such as Pliant to select from a wider variety of field I/O devices to match specific application needs. Touch screen displays and LCD interfaces were also implemented for easy viewing and editing of parameters.
Broad benefits
By implementing this programmable process controller, Pliant was able to save time and money, benefitting employees from the shop floor to upper management.
 “The PPC-2000 offered tangible benefits to all areas of our company,” said BJ Goclowski, optimization manager of Pliant Corporation. “Machine operators were very pleased to be able to give direct input into how to customize the control system. Because the Watlow system was so easy to use and understand, they felt it made their jobs easier. Everyone in the company liked the intuitive screens with color pictograms of the die, extruder, barrel and all control zones.”
“The data provided by the PPC-2000 is invaluable to the managers and supervisors responsible for troubleshooting and optimizing the process,” continued Goclowski. “Remote screens enable us to monitor the line, collect and view historical data to identify trends, and make adjustments. This was not available in our previous system. Remote access also provides a good place to conduct recipe management and configuration upgrades.”
Management is happy as well. Since implementing this process controller, there has been zero downtime caused by the control system and thereby a reduction in overall downtime. In the future, Pliant could also pinpoint material costs and optimize resin usage for each production run because the controller can monitor both raw material usage and percent regrind and/or additives to set the color mix using load cells. A power management feature can also reduce power costs. The auto-tune feature compensates for varying thermal lags on different extrusion machines, ensuring that Pliant’s extruders are up and running quickly. Production runs are very repeatable, owing to the unlimited recipe/job setups available in the PPC-2000. Each job is a fixed menu of zone setups, set-points and alarms.
 The overall savings to Pliant, the robustness, expandability and ease of use of the upgraded process control all combine to make Pliant’s production more efficient and cost effective. Machine operators, supervisors and management all benefit, making its introduction into the plant a welcome one. Because of this success, future plans call for retrofitting other blown film line controllers at this plant with PPC-2000 units.
For more information:
Pliant Corp,
www.rsleads.com/306df-102
FM Keefe Co. Inc,
www.rsleads.com/306df-103
Watlow, Booth 144
www.rsleads.com/306df-104
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 Co-injection Molding Catches On
According to Spirex Corp, Youngstown, OH, OEM interest in co-injection molding throughout the world has been growing. An alternative to single screw, single barrel injection molding, the company’s Twinshot co-injection, multi-material molding process enables a conventional machine with a single barrel and screw to inject two materials in a single shot, with one material totally enclosing the other. Plasticizing occurs on the single screw with a two-stage design. Starve-feeding controls the ration of materials in one or both of the screw stages. Materials can be commodity resins, engineering resins, or a combination. For instance, given a thick wall part that needs to be foamed while maintaining a smooth outer surface, one can feed the ski layer into the first hopper, the foam/resin into the second hopper. The resulting light part will have no sinks and a cosmetically finished outer surface.
 This process carries many benefits: it can encapsulate low cost material, including off-spec, regrind or recycled material with up to a 30% savings on material costs; encapsulate foamed material, thus reducing sink and warp and improving strength-to-weight ratio; produce soft touch parts in a single molding operation; encapsulate reinforced materials within a cosmetic surface; easily convert to single-material mode, by simply supplying the same material to all feeder hoppers. Other advantages of this design include simultaneous material extrusion, leading to extremely fast recovery time; independent heat control on the two melting zones; a rugged design; and easy screw and barrel installation and removal. The system can be retrofitted to most standard, cold sprue injection molding machines with at least 20:1 L/D available.
Several OEMs have incorporated this technology in their new machines. Van Dorn Demag, Strongsville, OH, has added it to their Cadence Series, large tonnage Caliber Series, and even in their Molder Action Network aftermarket and retrofit services. Spirex has installed the Twinshot system on a machine in the Network’s Process Solutions Center, and on a Van Dorn Demag machine located in the Spirex Technical Center in Youngstown, Ohio, allowing for customer demonstrations, training and trials at both locations. Scott Kroeger, marketing director for Van Dorn Demag comments: “We’re constantly seeking new technologies that will help our customers improve their products, even offer new ones, while reducing their costs and enhancing their productivity. By simplifying the multimaterial encapsulation process and cutting material costs, the Twinshot co-injection system meets our goals.”
 Negri Bossi, Mississauga, ON, will make the multimaterial molding system available on all their new injection molding presses. Larry Pascucci, general manager at Negri Bossi remarks, “Negri Bossi is always keen to provide its customers with cost-effective cutting-edge technological solutions for molding applications. The Twinshot single-screw co-injection system does just that and more. It allows the molder to simplify his co-injection equipment requirements, eliminate the need for additional space and reduce the cost of manufacturing.”
Toshiba Machine, Elk Grove Village, IL, will be making the system available on all its hydraulic and electric injection molding machines. “This additional equipment option gives Toshiba Machine one more benefit to better serve our customers,” adds Tim Glassburn, vice president of sales at Toshiba Machine.
Spirex Corp designs and manufactures complete plasticating systems that include screws, front-end components and barrels for injection molding, extrusion and blow molding. The company also remanufactures plasticating components; offers laboratory services, including rheology and melt flow analysis; lab trials; and processing support.
For more information:
Spirex Corp, Booth 1045,
www.rsleads.com/306df-156
Van Dorn Demag, Booth 2202,
www.rsleads.com/306df-157
Negri Bossi, Booth 1815,
www.rsleads.com/306df-158
Toshiba Machine Co, Booth 1676,
www.rsleads.com/306df-159
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