Plastics Technology

DEC 2018

Plastics Technology - Dedicated to improving Plastics Processing.

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Closed-Loop Bottle Control Saves Truckloads of PET for Blow Molder For Mexican beverage producer GEPP, automatic control of the stretch-blow molding machine based on in-line bottle wall-thickness measurement has saved literally tons of PET resin every day. Line 1 at GEPP's Hermosillo plant has trimmed the weight of its 2L low-carbonation PET bottle from 52 to 46 g. Given operating speeds of 24,000 bottles/ hr, the 6-g (11.5%) reduction is saving the company approximately 7 tons of resin in each 48-hr production run. This impressive saving has been accomplished despite challeng- ing environmental conditions at the plant, where temperature swings by 40° F or more throughout the day. As noted by Jesús López, GEPP corporate technical manager, "You don't want to put the same amount of heat on a 90° preform as a 70° preform." Successful lightweighting demands strict adherence to the material-distribution recipe for the bottle. That is a lot harder to do when working with less material, says López. GEPP's success is attributed to the Process Pilot system from Agr International. Located in the blow molder takeout area, the Pilot's sensors measure the thickness of each bottle at 12.5-mm intervals along the sidewall. Agr's control algorithms instantaneously analyze the measurements and compare them with the recipe. If necessary, the Pilot adjusts the appro- priate machine function—for example, tweaking the preblow setting or lamp temperature. In addition to savings from lower material consumption, the Agr system has enabled GEPP, the exclusive bottler of PepsiCo beverages in Mexico, to speed changeovers among six different bottles blown on Line 1 in sizes from 600 ml to 3L. It used to take an average of 1.5 hr to replace the molds on the 16-station blow molder and then another 30 min for process verification and quality checks. Now, with Process Pilot, the machine produces good bottles on startup, with no need for sampling and tweaking, making each changeover 25% faster and saving 6000 bottles of startup scrap. Likewise, when jams occur, "Pilot brings the process back to baseline two to three times faster," López says. What's more, improved bottle consistency with Process Pilot produces fewer disruptions in downstream labeling, capping and shrink-wrapping. López hopes to install Process Pilot on Hermosillo's second blowing line and to establish the plant as the model and training site for all GEPP's 25 PET bottle operations. Autonomous Optimization Proves Its Worth in LSR Molding A tricky LSR injection molding demonstration at the Fakuma 2018 show in Germany in October was made possible by a new type of simulation technology that automatically performs multiple iterations to home in on a desired outcome. Introduced at the previous year's Fakuma by Sigma Enginering, Sigmasoft Autonomous Optimization is similar to an automated design of experiments (DOE), except that it seeks an optimized result based on the programmer's instructions (see June feature for details). At Fakuma 2018, Momentive Performance Materials operated a molding cell producing an LSR pot holder with a challenging honey- comb design. Its largest dimension is 210 mm and overall thickness varies from about 3 to 7.5 mm. But the honeycomb walls are only 1 mm thick, and the 83-g shot has a max. flow length of 135 mm from two gates. According to Momentive, this project would have been "very difficult to realize without simulation." This type of product had never been injection molded before—only compression molded. "We didn't know what exact injection pressure or clamp force would be required," says Momentive's Oliver Franssen, senior global marketing leader for transportation. It was essential to determine in the short- est possible time whether the part could be molded on a machine small enough to fit in the company's booth. "Also, we wanted to avoid two costly mistakes—air entrapment and excessive tempera- ture difference across the cavity." Sigma ran a total of 60 different simulations, involving three different filling times and 20 different gate positions, over about two days using Sigmasoft Autonomous Optimization. The software evaluated all the results to identify the best solution. The software determined optimal placement of two gates and, in a second optimization, the position, length, and temperature of electric heaters in the mold. The result was a 55-sec cycle time with no flash, no short shot or air entrapment, and reduction of temperature differences in the cavity from 40° C initially to no more than 10°. Based on the results of the virtual analysis, the mold was built by Emde MouldTec in Germany. The extremely compact tool needed no cold-runner block for sprueless molding; instead, Emde's cold-runner head was attached directly to the 90-ton SmartPower injection machine from Wittmann Battenfeld. Larger Freeformer from Arburg Can Print Three Materials Last month, Arburg introduced a larger model of its 3D printer, the Freeformer 300-3X. It has a part-carrier surface area of 300 cm2, almost 50% larger than on the model 200-3X. It can build 50% wider parts measuring up to 234 × 134 × 200 mm. "3X" stands for three moving axes (x, y, z) of the part carrier. Like the previous models, this Freeformer uses standard molding or extrusion pellets as raw materials. What's new is the ability to build parts from three components, such as a hard-soft combination plus a support structure. Also new is a two- part build-chamber door, which enables the feed hoppers to be refilled while the printer is operating by opening only the top half of the door. Software upgrades over the past year include a more user-friendly operator interface, updated slicing soft- ware, "smart" automatic generation of supports adapted to the individual part, pressure regulation to improve adhe- sion of the first layer to the base plate, and new or revised material profiles. 12 DECEMBER 2018 Plastics Technology PTonline.com T E C H N O L O G Y A N D I N D U S T R Y N E W S St ar t ing Up

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