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QRM Blog: Understanding the Queuing Guy’s Definition of Utilization

by Charlene Yauch, Associate Director, QRM Center        


Professor Charlene Yauch  It is a long-standing tradition in manufacturing to try to get machines and people to work 100% of the available production time. If you don't, you are not getting the maximum benefit from those resources, right? To fully appreciate why 100% utilization is not a reasonable goal, we first need to understand how the Queuing Guy defines utilization. Who is the Queuing Guy? He's Rajan Suri, the founding director of the Center for Quick Response Manufacturing. His application of system dynamics to manufacturing comes from extensive study of queuing, a branch of operations research that emphasizes how systems behave when there are people or things waiting in line. Others who study queuing also have really good knowledge and intuition about how manufacturing systems behave. So, let's compare how the Queuing Guy defines utilization to what most practitioners believe. 

 In my interactions with manufacturing companies, it appears that the most common way to define utilization is to compare the time spent producing to the time available for production. So, a machine that is available for an 8-hour work shift would be utilized 75% of the time if it was producing parts for 6 of those 8 hours. This common way of looking at utilization causes some problems related to decision making. If a machine is 75% utilized using this definition, a manufacturing manager may think that there is 25% spare capacity. He or she may decide to load more work onto the machine. The problem is that the 25% of time spent not making parts may be used for other things such as machine setup or troubleshooting. If the machine is "busy" being set up for the next job, then it is not available to produce parts. Similarly, if the machine breaks down, then it cannot produce parts until it gets repaired. Because of that, we need to instead use a definition of utilization that is consistent with queuing theory; it is the percentage of time that the machine is not idle. If any other activity is going on, the machine is considered utilized. 

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QRM Center Plans for Growth Under New Leadership of Dr. Leyuan Shi and Dr. Charlene Yauch

Dr. Leyuan Shi, an international expert takes over as Director

Dr. Leyuan Shi, a professor in the Department of Industrial and Systems Engineering at University of Wisconsin-Madison, has taken over as the new Director of the Center for Quick Response Manufacturing.  


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Dowding Industries Featured in October Issue of “The Fabricator”

The implementation of both shop floor and office cells at QRM Center member company Dowding Industries is featured in the October issue of “The Fabricator” magazine.  Located in Eaton Rapids, MI, Dowding Industries recently embarked on an aggressive QRM journey, but their commitment has already achieved remarkable results.


Rajan Suri's latest book, "The Practitioner's Guide to POLCA," selected as ISE magazine's "Book of the Month" for June 2018

The June 2018 issue of ISE magazine selected Rajan Suri's new book, The Practitioner's Guild to POLCA as it's "Book of the Month." ISE is the monthly magazine of the Institute of Industrial and Systems Engineers, the premier international society for industrial engineering.


Suri's New POLCA Book Receives Glowing Review on Popular European Blog

Rajan Suri's new book, "The Practitioner's Guide to POLCA"  has received a very thorough and overall very complimentary review from a well-known blogger in Europe. Dr. Jaap van Ede's blog, "business-improvement.eu," focuses on business improvement methodologies and is widely read (typically thousands of hits daily). To link to the full review, please click Read More, below.

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