I continue here my discussion on “resiliency” and how it relates to green and sustainable manufacturing. Recall that I started with a standard dictionary definition of resiliency as the capability of a body under strain to recover its original size and shape after some external disturbance or deformation. It also listed the ability to recover from or “adjust to misfortune or change.”
Engineers think of the first definition in terms of a “rubber band” which can be stretched and then, when released, returns to its original shape. This is certainly a recovery from change as well. I also believe this includes “inoculation” to disruption and risk – the rubber band is designed to recover.
In my last article we ventured into the muddy waters of “equilibrium state” of a manufacturing process or system. The idea was that resilience refers to the ability of an engineering system to return to equilibrium. But, I don’t want to confuse equilibrium in the sense of mechanical equilibrium we learned in our early physics course. There we said that equilibrium was the state in which the sum of the forces, and torque, on each particle or element of the system is zero or thermal equilibrium wherein there is no exchange of energy between an object and the surrounds – meaning everything is at the same temperature.
I inferred that, here, equilibrium was essentially a stable operable state that the system returns to following a disruption that would tend to move the system into another state of operation – presumably less stable, or less profitable, or less environmentally benign.
So, what are the various dimensions (or axes) of resiliency?
We can think about measures of responsiveness, recovery and regeneration for starters. Returning to the information from NIST on resilience (specifically National Institute of Standards and Technology, 2008, “Strategic Plan for the National Earthquake Hazards Reduction Program: Fiscal Years 2009-2013”) one might argue that resilience entails three interrelated dimensions: reduced failure probabilities; reduced negative consequences when failure does occur; and reduced time required to recover.
So, how do these relate to green or sustainable manufacturing? To what extent can elements of manufacturing, as practiced, be implemented to reduce the likelihood of failure, minimize negative consequences when some disruption or failure occurs and, finally, minimize the time to recover (that is, get back to “equilibrium”)?