Checkweighers keep DVDs under wraps

Checkweighing is a rising star at WEA Manufacturing, a Commerce, CA, division of AOL/Time Warner, Inc. No longer in a bind over assembly of famous TimeWarner movies on DVD, WEA uses a flexible weigh table from Loma Systems that accommodates a wide range of both rigid and flexible packages up to 13 lb. This allows WEA to consistently package all of the DVD components, ensuring that each pack includes everything it's supposed to. For WEA, dynamic checkweighing has been key to streamlining package assembly while eliminating any missing components from the pack, a potential headache for DVD movie purchasers.

WEA manufactures the DVDs and assembles the multiple packages, which can include various components, using both manual and automatic processes. WEA must ensure that all components are included in each and every pack prior to sealing. In addition to the disk itself, the DVD components include an outer plastic jewel case, a paperboard insert printed with literature about the movie and the movie title copy, or liner notes, as well as graphics, coupons, cross promotions, security devices or other inserts, all shrink-wrapped in clear film.

To improve the packaging integrity of a range of DVD titles, WEA initially ordered a pair of Loma Systems' AS PWT (Powered Weigh Table) checkweighers, installing one in April. The second system will go onstream this summer. WEA tells PD that it has since placed orders for additional systems, to help meet increasing productivity demands.

For a brief time, the company had been manually spot-checking the packages, a more time-consuming process that it says yielded less-than-accurate results. Packs would have to be manually pulled off-line to be spot-checked.

With so many package configurations and variables, WEA needed a more efficient, easy-to-operate system that could inspect the multiple package types, each with different components, explains process and automation engineer Julio Bautista. "We didn't have a way to verify that all of the package components for each individual package were included, so it wasn't long after we began manufacturing DVDs that we turned to checkweighers. Otherwise, we'd waste a lot of shrink wrap and labels if we had to inspect a package."

The checkweighers are designed to provide 100-percent inspection, and to count the number of packs weighed, total the number of overweights and underweights, and provide weights associated with the counts, allowing the company to gain a higher degree of packaging assembly accuracy without destroying the shrink wrap or causing assembly-line downtime.

Automatic and manual assembly
Since the company uses a variety of assembly methods to pack the disks, the benefits of automatic checkweighing are important, Bautista says. The DVD packs can weigh anywhere from 190 to 200 g, depending on the components included inside the case. "Some booklet inserts weigh more than others," he adds. "We know that checkweighing can save us plenty in material costs and missing components. We haven't done a study to get the overall savings figures, but there are far fewer problems."

The California facility serves the Western half of AOL/Time Warner's U.S. market base and assembles the majority of DVD components into unit packs automatically. Currently, this is performed on three assembly lines, Bautista says. More lines will be installed to cope with growing volumes and demand.

The manual packaging area assembles both DVD sets and individual DVDs with custom components. Assembly can also be performed in a hybrid setup using some automatic equipment and some manual functions, followed by manual case packing and palletizing. Bautista says he's looking to automate further if volumes continue to increase.

The three automatic lines feature pick-and-place systems from Italy that pick jewel cases and insert the disks, booklets and other components into the cases.

Checkweighing follows, after which security labels, peel-off tabs and pressure-sensitive labels are applied to the packs on machines from CTM or Labelette. Then, the cased DVDs are shrink-wrapped on Doboy equipment.

"We have about ten pieces of equipment integrated into each assembly line," Bautista tells PD. "There are also employees feeding the jewel cases with the disks. In any one of those operations, it's theoretically possible there might be a misfeed."

Police unit
WEA carefully analyzed the operation to determine which checkweighing model to use. "The AS PWT Powered Weigh Table was designed for applications requiring a high degree of accuracy," says Loma's Gary Wilson. "In food production and in the packaging industry in general today, people don't want to take the time and personnel to statically weigh things, preferring to weigh products in motion, travelling on a conveyor belt, which is what WEA wanted. If you're producing foods that require less giveaway and need sophisticated feedback information, statistical giveaway data and other features, you're going to need another type of system. But WEA's system basically acts as a policeman weigher that has the simplicity of calibration and setup, and makes sure all product components are where they should be and that the DVD device has been assembled properly. There's no weight legislation issue at WEA. It doesn't need to declare weight on its packaging, like food companies do."

The AS PWT dynamic checkweigher has a loadcell weight capacity for products weighing up to 6.5 lb and weighs items in milliseconds, which is especially suitable for the DVD packs, Bautista says. The packaging operation typically packs the DVDs during two 12-hr shifts a day. Accepting products up to 16 in. wide and 24.5 in. long, the weigher features an ergonomically positioned user interface that includes a 100-product memory that allows WEA to input data for various products. The weigher also features a self-prompted setup menu for easy operation, and one-time dynamic calibration for product setup.

In order for the checkweigher to properly do its job, it must first be calibrated with the finished package, which includes weighing the DVD disk itself, the outer case and the additional inner-pack components. A rejection air blast bumps any unacceptable package off-line.

Built to NEMA 12 4X IP55 and IP66 standards with a 304 stainless-steel bead finish, the checkweigher is especially suitable for this nonfood application, WEA says. Its powered weigh platform handles most package shapes and uses advanced weight-sampling techniques for high accuracy and repeatability. A low center of gravity yields high accuracies, while heavy-duty AC motors on the infeed and outfeed conveyors come standard.

Certain package components–the outer case and paperboard graphic insert that wraps around the case–are likely to vary in weight. The checkweigher affords weight-tolerance sensitivities within ?0.5 g, but can be adjusted to compensate for weight deviations and maintains production statistics to monitor and improve packing efficiencies.

WEA compensates for various package weights by first weighing the DVD packs on a static scale for a point of reference and then by dynamically (in-line, in-motion) calibrating the AS PWT systems with the particular package. This gives the checkweigher a reference point in which to set up a target weight, a minimum weight of the lightest components, and an overweight measurement of heavy components.

AS PWT's multiple-product weight memory saves the calibrations, which can be reset periodically as a precaution, but once they're set for each individual package, they're stored in memory. "Weight value is entered into the checkweigher and then we calibrate it," Bautista explains. "Then we decide on the plus/minus tolerances. How sensitive we want the system to be depends on the weight experiences we've had. We usually calibrate between plus or minus one and two grams."

Extra measure of confidence
With the checkweighing systems in place, WEA is even better equipped to further Time Warner's commitment to offer the best movie products possible, a happy ending for any movie.

More information is available:

Checkweighers: Loma Systems, 630/588-0900. Circle No. 225.

Label applicators: CTM Integration, Inc., 330/332-1800. Circle No. 226.

Label applicators: Labelette Co., 760/734-417. Circle No. 227.

Shrink wrappers: SIG Doboy, Inc., 715/246-6511. Circle No. 228.