The Marvel City Mini Mill’s efficient heat treat furnace has helped the facility pro- duce more pipe than the engineers initially thought it could.


dustry standard of 20-ft. lengths, rather than being limited to the 18-ft. pieces the company previously made, an 11% improvement in efficiency. The sum of the efforts has been a facility that has ex- ceeded the expectations of its designers. “We wanted the transition from our Burlington plant to the Mini Mill be seamless for our customers,” Torok said. “It wasn’t seamless. The quality and consistency of the product made in the Mini Mill is greater.”


Lean Steps In


Geoff Maffett, director of operational excellence for Mueller Water Products, said that while it may seem counter- intuitive, lean processes are as viable in jobbing environments as they are in high production facilities. So when the Marvel City Mini Mill


was charged with the task of adding products to its daily runs to meet market needs, a team of lean specialists was brought in to allow the plant to con- tinue to produce pipe at levels above the company’s original expectations. The Marvel City Mini Mill makes pipe in four diameters—6-in., 8 in., 10


20


in. and 12 in.. Each requires different casting machine settings. To produce more part numbers, those settings must be changed more frequently. Changing among the two smaller diameters or the two larger diameters is what the operators call a minor change, which requires only mold swapping. Going to one of the smaller diameters to one of the larger diameters is a major change. Here, in addition to changing the mold out, several other parts have to be changed. This process can be lengthy. In fact, when the mill first started operating, it took nearly 10 hours to perform a major changeover. Enter the lean team. “The first thing you do in any [quick changeover project] is separate the internal and external events,” Maffett


said. “The team identifies those activi- ties (called ‘internal’ events) that can only be done with the machine down. Every remaining activity is an ‘external’ event and must be done while the machine is running, such as staging things line-side so that as soon as the machine goes down, you are ready to fix it.” (Maffett suggests imagining a racing pit crew. An internal event would be changing the tires on the car. The external events involve having the new tires and equipment needed to install them in place prior to pulling the car into the pit.) To lean the process of changing


between pipe sizes, Maffett and the lean team videotaped everything in the process, separated the internal and external events and determined where


MODERN CASTING / July 2010


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