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Weighing and Batching System Ensures Material Availability, Eliminating Downtime

June 18, 2008
The Material on Demand system from Meese Orbitron Dunne Co. enables machine operators to draw material from one hopper during production and, when it is empty, continue drawing material from the second hopper without halting production to wait for more material.

Production was humming along at the Madison, IN, plant of the plastics designer and manufacturer Meese Orbitron Dunne Co. (MOD). Bulk containers were being molded four at a time, one group after another like clockwork, until the plastic resin ran out. Even at MOD, the 17th largest rotational molder in the United States with 28 plastics molding machines in four different facilities, reaching the bottom of the resin barrel meant a precipitous and unscheduled end to production.

While idled workers awaited the forklift that brought a fresh container-load of the powdered material from storage, the machines that had already been heated to their ideal molding temperature began to cool. The lack of on-hand, ready-to-mold material not only triggered a production delay, it also forced the crew to reheat the machinery before resuming production. This process consumed both time and energy—two of the company’s most precious commodities. The fact that many other plastics processors had relied on this or similarly untenable systems for years offered little comfort to Michael Dorsey, MOD’s vice president of manufacturing and engineering.

Squeezed by sharp cost increases in plastic resin, energy, and freight, Dorsey sought to minimize these costs and their impact on margins. Identifying this oddly impractical yet entrenched material-handling and storage approach as the leading cause of unplanned downtime, Dorsey and his team of design engineers went to work on a new approach.

Material on Demand

The result of Dorsey’s efforts is the Material on Demand system. A novel approach to storing and dispensing powdered, granular, or liquid materials, this system features two durable plastic hoppers set side by side in a steel rack that is placed near the molding machine. Each hopper can hold up to 800 lb of material—the same amount of material a typical Gaylord or container-load of plastic material holds. Machine operators draw material from one hopper during production. When the hopper is empty, they can continue drawing material from the second hopper without halting production, while the forklift operator removes the empty hopper and restocks it with a fully loaded hopper.

The new system eliminates downtime and costly machine reheating. In addition, by removing material availability as a factor in determining when a production run ends, the system no longer requires operators to estimate the number of parts or products that can be manufactured per container-load of material. Under the old system, a machine capable of running four or more molds at a time occasionally would have been run with only one or two as material petered out. By ensuring that the maximum number of molds is filled throughout the production run, the Material on Demand system promotes efficient allocation of machine capacity and efficient energy consumption.

Weighing and Batching for Quality Control

A lift truck sets a hopper loaded with 900 lb of plastic material into the steel frame of the Material On Demand system.

If the old material-storage approach common to many plastics processors seems inefficient, the method by which material is loaded into the molds must seem doubly confounding. In most plants, operators lean into open Gaylords to scoop out resin and carry it to a scale for weighing. The accuracy of the shot weight depends on the operator’s patience and willingness to return excess material to the Gaylord or collect more if necessary. Scooping material from a Gaylord and dumping into a smaller container causes significant contamination and spillage, resulting in material waste and labor time to clean it up. This procedure also subjects operators to ergonomic hazards by forcing them to lean farther and farther into the Gaylord the emptier it gets. When approximately 50 lb of material remains, the Gaylord is usually tipped over to empty it, resulting in even more contamination, spillage, and waste.

A machine operator at Meese Orbitron Dunne’s
Madison, IN, plant dispenses powdered plastic resin
from the Material on Demand system.

The Material on Demand system eliminates ergonomic hazards, contamination, and spillage by employing a weighing and batching assembly under each of the two hoppers. Operators place a small container on a scale under the hopper and dispense material using a valve that MOD engineers designed specifically for powdered materials. When the exact amount of material required is dispensed, the operator shuts off the valve and the small preweighed container is removed. To reduce lifting, the scale is placed on conveyor rollers, permitting the filled container to be rolled forward during removal. By ensuring that the exact amount of material is dispensed and loaded into the mold without spillage, MOD has reduced waste and eliminated machine downtime resulting from material shortfalls. Consequently, parts quality has become even more consistent and reject rates have fallen, eliminating the costly reruns that used to result from contamination or underfilling of the mold.

National Rollout

When it was tested at a single rotational molding machine, the Material on Demand system streamlined and accelerated production to such an extent that the company quickly manufactured and installed more than 50 such systems in its four facilities nationwide. Some of the machines are equipped with up to six hoppers to accommodate multiple color requirements. “The old approaches had become accepted in the industry because they evolved when the cost of material and energy were far less significant in terms of overall costs,” says Dorsey. “With a rising cost structure to manage, it was critical for us to address every facet of operations, including how we store and handle our material. We haven’t had a single machine idled for lack of material since we installed this system last year, and our material yield due to less waste has increased by over 5%. The ergonomic value of less fatigue and potential back injuries to our operators is an intangible benefit not yet fully realized.”

According to Dorsey, virtually any plant that dispenses measured batches of a material—whether powder, granule, or liquid—will derive similar benefits from the Material on Demand system.

For more information on the Material on Demand system, contact Meese Orbitron Dunne Co. at 800-829-4535 or visit www.shipshapecontainers.com.