The Cereal Plant That Runs Its Model Before Every Shift
A Make-Store-Pack Plant Checks the Plan Before the Floor Does

A major cereal maker runs a make-store-pack plant around the clock. Simulation Dynamics builds a model of the plant, and the planners put it to daily work: before each shift, they run the model to see what could go wrong during that shift, so they can change the plan before the trouble reaches the floor. The model treats cereal as flow, not as individual items. That is what makes it fast enough to run every shift.

The business

A major cereal maker · a make-store-pack cereal plant

The question

What is likely to go wrong on the next shift, and what should the plan do about it?

The model

Three to four making lines, about four large storage bins plus small portable totes, and six to seven packing lines

How it is used

Run by the planners before every shift

Source

SDI project records · SDI’s Winter Simulation Conference paper

What the plant is up against

The plant is a make-store-pack plant. Three to four making lines produce the cereal. Between making and packing sit about four large storage bins and a fleet of small portable totes. Six to seven packing lines fill the boxes.

Making and packing run to different clocks. Making thinks in pounds per hour and long runs. Packing thinks in cartons per minute, package sizes and changeovers. The bins and totes absorb the difference, as long as the right cereal is in the right place when a packing line needs it. When it isn’t, a packing line sits idle while storage is full of product nobody is packing yet, or making has to slow down because there’s nowhere to put what it’s making.

Whether that happens on a given shift depends on the schedule, the state the last shift left the plant in, and which lines are running which sizes. All three change from shift to shift.

Why it needs a flow model

Many simulation tools move product through a model one item at a time. Cereal isn’t items. Counting every piece, or even every box, makes a model far too slow for a plant that runs around the clock. SDI models the cereal as flow instead: rates through the machines and levels in the bins, with an event only when a rate changes.

How the plant uses it

This is an operating model, not a one-time study. Before each shift, the planners run the model on the shift ahead and look for trouble coming: a packing line about to run out of cereal, storage about to fill, a changeover landing at the wrong moment. If the model shows a problem, there is time to change the plan before the shift starts, instead of finding out on the floor.

A model is only useful that way if it runs fast and speaks the plant’s language. Rates, bin levels and schedules are what planners already talk in, and a flow model answers in the same terms.

What changes

• A plan checked before every shift. SDI’s project history lists this plant among its successes: the plant puts the model to work instead of shelving it after a study.
• Trouble caught in the model first. A starving packing line, a full bin or a badly timed changeover shows up while the plan can still change.
• Parts other plants can use. The building blocks made for this model are shared with the company’s other plants. SDI standardizes them as its Plant Builder library.

Try the same kind of plant

The Sandbox has a demo vegetable plant with the same make-store-pack shape, built the Plant Builder way: two making lines, eight surge bins and five packing lines, with campaigns, changeovers and bins that can only feed lines packing the same product. Is the problem the plant, or how it’s scheduled? →

Where this work comes from

Built by Simulation Dynamics, the team behind ReliaSim · evidence: SDI project records; R. A. Phelps, D. J. Parsons and A. J. Siprelle, “Non-Item Based Discrete-Event Simulation Tools,” Winter Simulation Conference.