High-barrier plastic cups cost less, look good

5 Min Read
High-barrier plastic cups cost less, look good

Paper Machinery Corp. (www.papermc.com) has been making paper-cup forming machines for more than 50 years. This year it has introduced the first machine in the industry that can make two-piece convoluted containers from plastic, in this case, from extruded polypropylene sheet. PMC is demonstrating a model 1002P (P is for plastic) machine making 12-oz plastic containers at this year?s PACK EXPO and gave PD an exclusive behind-the scenes look at the machine as it was being fine-tuned for the show.

"This machine opens a whole new area of technology," says market development manager Mike Hansen. "We spent considerable effort addressing the barrier capabilities of paper, but convolute forming of paper has inherent characteristics that will prevent high barrier levels from being achieved. Foil, even when combined with other laminates or extrusions, fails to achieve product protection for key markets, and it?s costly. With our plastic containers, we achieve polymer flow essentially by welding the seal areas to form a high-barrier container. And, compared to injection-molded or thermoformed containers, ours have superior graphics at less cost. Why? Because the material is preprinted prior to forming."

The PP used for the sides and bottoms of the containers have additives to aid in rigidity and to assist the bottom-forming process. The material is made by Spartech Plastics (www.spartech.com) and is printed on a specially adapted flexo press by Interpress Technologies (www.iptec.com).

The Model 1002P is an intermittent-motion rotary machine that produces 225 containers/min. The bottom material is delivered to the machine as a continuous web, while the sidewall blanks are fed to the machine by a special pick-and-place mechanism. The machine performs a series of steps to cut the bottoms from the web and assemble the bottoms and sides into the finished containers. Following are the steps to make a cup:

  • The web of bottom material enters the machine over a series of rollers, including two rollers with sensors and metering motors to maintain control. The unwind stand is equipped with a splicer that allows for roll changes on-the-fly to maximize output. A splice-detection sensor automatically skips splices in the bottom roll to improve tooling life and machine uptime. The web then enters a cutout station, where the bottoms are cut out of the web and placed on a mandrel by a cam-actuated rod that simultaneously punches and draws the material to form a bottom skirt. The bottom is held in place on one of seven mandrels by vacuum.

  • The machine indexes. The material is treated with hot air to prepare the bottom to be sealed to the sidewall blank.

  • The machine indexes. Vacuum cups swing in, pick a sidewall blank out of the magazine and place it flat on a horizontal shuttle table. The table pushes the blank forward into the grippers on the transfer turret, which rotates the blank underneath the sidewall heaters.

  • The machine indexes and rotates the sidewall beneath the mandrel holding the bottom skirt. Folding wings fold the sidewall around the mandrel and bring the preheated bottom disc and preheated sidewall blank together to produce a container shell, while a seam clamp descends and seals the side seam. At this point, both the bottom and the side are together, but are not yet sealed together.

  • The machine indexes, and a nozzle heats the inside of the container and the bottom skirt in preparation for forming a 3-ply recessed bottom with both primary and secondary seals.

  • The machine indexes. As it turns, the bottom skirt is pushed outward to its final position.

  • The container is pushed into the bottom in-curl station, which starts to form the bottom. In this procedure, a station travels in and folds the bottom of the side in and around the edge of the bottom panel.

  • The machine indexes into the bottom-finishing station. A spinning wheel moves in and finishes sealing the bottom to the sidewall by applying pressure.

  • The container is blown off of the mandrel and into a pocket on the rimming turret. The container then goes through three consecutive rimming stations, where the container is pushed into dies to completely form the rim. The rim can be formed as standard, elongated or flat, depending upon the needs of the package.

  • The machine indexes to the discharge station, where a blast of air blows the container out of the pocket and through a tube to an accumulation area outside of the machine.

The PMC 1002P is controlled by an Allen-Bradley programmable logic controller and a Panel View 600 operator panel from Rockwell Automation (www.rockwell.com). In addition to providing control, the screen provides the operator with troubleshooting information, including the location and cause of any material jams in the machine and a preventative maintenance schedule. A servo drive feeds the bottom web into the machine, while the container-manufacturing operations inside the machine are cam-driven.

The 1002P is unique in its adaptation to form containers from plastic sheet, says Hansen. "The basic 1002 model is also unique and has revolutionary means of forming paperboard cups and containers," he adds. "It runs paperboard at 300 containers per minute, which is twenty-five percent faster than the 1001 model it replaced. This evolution of speed in a synchronized indexing machine is truly remarkable."

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