HIGH ACCURACY COUNTING SCALES HELP MILTON BRADLEY WIN THE GAMEThe factory where Milton Bradley and Parkers Brothers games are manufactured produces a billion plastic parts a year. And it's important on Christmas morning that each game contains the required number of spinners, pink station wagons, rooks and pawns, or red-peaked hotels used in Monopoly.
Until recently, making sure that the exact number of pieces reached the right assembly line at the right time was one of the vexing problems facing the company's production system. "I would say more than any other single issue, this caused credibility problems for us," comments Gary P. Brennan, director of manufacturing for the Hasbro Games Group, in a recent interview with Plastics World.
The man on the firing line was Jeffrey R. Lombard, manager of injection molding at the company's largest domestic molding operation, in East Longmeadow, Mass., a suburb of Springfield. "I used to receive frequent calls from managers who didn't have enough parts to finish a production run," Lombard says. The result was a rush to mold the requisite parts.
"We had been using balance-beam scales, which were not accurate to the degree we needed, especially for small-part inventory," comments Lombard. In a former Playskool manufacturing plant, injection-molded part count in the 1980s as determined by balance beam scales was off 2-4%. For blow molded parts, the count was off 5-8%.
As parts are molded they are packaged in bags or boxes for delivery to a warehouse or right to the assembly line. The packages are weighed to determine part count. Each time an assembly line runs short, there are significant disruptions throughout the manufacturing system. "What we place into inventory may not be requested for weeks," Lombard notes. "However, when 4,000 plastic spinners are requested, there is no time for inaccuracy."
Lombard decided to upgrade to newer weighing technology, specifically electronic counting scales. The company contacted National Scale of New England, a distributor in Springfield, MA. They selected the Super Count and Quick Count scales manufactured by Setra Systems, Inc. in Boxborough, Mass. "We chose the Setra scales because of their accuracy, weighing capacity and ease of use," said Lombard. "We now have 36 of their scales in our molding operation and one scale on a cart that can be taken on to the floor for quality checks."
Molded parts at Milton Bradley are typically fed automatically via conveyors to a holding area where they can be visually inspected periodically by an operator. Then the operator pushes the parts into a bag or box where they are weighed. Many parts of the process throughout the plant are automated. For example, at one station parts are automatically bagged, weighed and then blown into a box with a puff of air.
The part count accuracy with the electronic scales is ± 1%, even for thousands of parts weighing as little as a gram a piece. Lombard says there has been a dramatic reduction in downline part outages. In addition, the inventory system typically adds a 1% variance to even further minimize disruptions. If there are a few parts left at the end of the game assembly? "We give them to the customer," Brennan adds.
Separately, the Setra scales are used to weigh parts in a statistical process control procedure. If the part weight is ± 1% of target weight, it is acceptable. Underweight parts may be faulty and unusable. Overweight parts are chewing up too much plastic.
In one example of the SPC process, five sample shots are automatically collected every half hour from an Engel press equipped with closed-loop process control. Data is electronically entered into a personal computer near the press and plotted showing the weight range compared to upper and lower limits. The monitor is easily visible to an operator nearby. If the line goes beyond the control points, a setup person is summoned to the workcell.
Concludes Lombard, "We need to produce a quality part efficiently and at the lowest cost. To achieve this, it is necessary that we utilize the finest equipment available. The Setra scales are helping to keep us ahead of the game."
As seen in part fromModern Materials Handling, September 1997.
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