MEDIA RESOURCE Using the Actable App, scan this page to watch a video on ME Elecmetal’s expan- sion. For instructions on how to use the app, go to page 51. To watch online, go to
www.metalcastingtv.com.
as possible. Te back charge can wait because that will only extend the melt down time for the heat. Two furnaces were more resilient
to delay propagation. During process- ing of the current heat, the next heat would still be melting down, so the delay would not immediately result in lost production time. For the first month of produc-
tion with three furnaces, processing times averaged 85 minutes due to improper prioritization of resources. ME Elecmetal wrote a new critical path for processing heats that defined all the actions affecting the current heat that should take precedence over the other furnaces. Processing is always the prioritized event with three furnaces. Once staff became experienced with the critical path and realized melt down events were no longer the rate limiting step and did not need to be priori- tized, processing times dropped to the 65-minute average goal.
Opportunities for Improvement With Three Furnaces
Due to the additional wait time
included in the three-furnace pro- cess cycle, slag accumulation became
Figure 3. The scrap bay open bin layout is depicted.
more severe than with two furnaces. Te additional slag accumulation led to an approximate 30% increase in the frequency of furnace repair events to maintain adequate furnace conditions while also causing more refractory damage during each heat. Furnace repair events also increased in frequency because working all three furnaces together became more cost effective than service a single fur- nace. Refractory patch use increased approximately 17% on a net good ton basis. Energy usage increased 4% due to the melt operators needing to run the furnace longer to compensate for cooling during the wait time. Te most obvious way to improve the melt process would be to optimize processing times to 60-minute averages, which would decrease the wait periods. Eliminating the wait periods would correct for some of the issues discussed above and increase production rates.
Other departments in the facil-
ity would need to be enhanced to account for the additional production levels. Under specific conditions of high mold count per heat or difficult molds, the melt shop may be on hold for molding to produce the correct molds needed to pour the next heat. Any optimization to molding will benefit melt. Additionally, space on the pouring floor is a limited resource and may require additional wait time for the floor to be partially cleared to allow upcoming molds to advance onto the floor. Tis time is not always available when heats are continually arriving from melt. A disadvantage of vacuum molding is the molds need to be hooked up to the vacuum system until the metal has solidified to ensure proper mold/casting dimensions are maintained. In turn, this results in a much more complicated pouring infrastructure than what is encoun- tered in a typical sand casting facility. A larger floor would allow more heats to be available for pouring and give molding a larger head start. Plant- wide optimization would be needed to fully utilize the production capacity of the melt shop.
Molding and pouring at ME Elecmetal are over 30-year-old pro- cesses and have undergone countless improvements; most of the quick fixes to improve process performance already have been implemented. Add- ing additional capacity would require capital additions to the process.
Figure 4. The ladle stand is shown with a tilted ladle.
Tis article originally was presented at the 2014 Steel Founders Society of America Technical & Operations Conference.
August 2015 MODERN CASTING | 25
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