8/17/2007 - Lose a Pound of Raw Material, or Two Hundredths of a Pound?

A foundry in the Selma, Alabama, area makes automotive parts twenty-four hours per day, seven days per week.  Each batch of molten metal has a small amount of various chemical additives to enhance the batch and make a better component for use in many types of automobiles.

One of these additives is molibium.  Molibium (commonly referred to in the foundry world as 'molly') is used to increase the part's heat stress levels.  When an engine component becomes extremely hot, its expansion, contraction, and breakdown qualities are inhibited.  This increases the life of the part.

Each batch of molten steel needs only a small amount of molibium, anywhere from one to twenty-five pounds, dependent upon the batch and its use.  Molibium is a valuable commodity.  A small amount will affect a large batch of steel. 

Molibium, as well as other additives, are kept in storage bins until they are needed for a batch.  When an operator is ready to use an additive, he pushes a "start" button to start the feeder.  The feeder sends material out to a small, steel bucket, waiting below.  The bucket is resting on an old mechanical scale.  When the scale is balanced, a photo-eye is contacted, and the feeder works.  When the target weight is reached, the scale arm moves off the photo eye, switching a relay, and stopping the feeder.

It is an old process, and fairly ingenious.  The problem is in its accuracy.  The mechanical scale often would miss its target by up to ten percent or more.  Engineers at the foundry felt that they were losing at least one dollar per batch.  Those dollars added up quickly. 

Montgomery Scales & Systems stepped in with an idea.  An electronic scale with a thirty pound capacity would easily reach two-hundredths of a pound readability.  This would save the foundry millions of dollars.

The systems group built a control panel utilizing the Mettler-Toledo IND780, an ALLEN-BRADLEY Micrologix 1100 plc, and an ALLEN-BRADLEY Panelview operator interface.

The system was then programmed to meet the foundry's various desires.  A Mettler-Toledo 8624 remote display was added for the operator at the scale.

The foundry is now adding molibium at an accuracy which they could only dream of before.  The other three main additives will be integrated soon.  The Mettler-Toledo IND780 can control up to four scales, so with the addition of three more scale bases, the entire additive area will soon be seeing unprecedented accuracy and savings. 

The foundry personnel are smiling, as are many manufacturers in the Montgomery and Central Alabama region since Montgomery Scales & Systems moved into the area and changed their weighing world. 

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