Sometimes, it’s the simplest questions that are exactly the hardest ones to answer. In a post last week, I wrote about a book I read some time ago called The Goal (wikipedia entry). In it, the main character struggles to identify both the goal, increased profitability, and constraints of that goal, production bottlenecks and sales limitations, in a manufacturing plant he oversees in an effort to save it from being shut down. Based on that premise, I asked what the analogue is to engineering. What exactly is the goal for engineering? What are the constraints keeping engineering from that goal?

Now the first instinct with things like this is to start throwing out answers. However in this case, it makes sense to revisit the exercise that the main character, Alex Rogo, went through to find his answers. This specific approach is called the Evaporating Cloud method (wikipedia entry). Now, we’re not talk about about Cloud Computing (wikipedia entry). This methodology is a way to identify the goals and constraints within a system. The following is an excerpt from wikipedia that is found in the book.

Evaporating Cloud example from ‘The Goal’
Goldratt has illustrated the use of the evaporating cloud technique in a discussion of the economic production quantity model, as applied to a production line. The prerequisites are to run large batches (node D) and yet to run small batches (node Not-D). These are clearly in conflict. The requirement that D is trying to meet is to reduce setup cost (node B), whereas the Not-D prerequisite is intended to reduce carrying cost per unit (node C). Both requirements are aimed at the objective (node A): to reduce cost per unit.The assumed causal reasoning between the conflicting D nodes is something like “there is no way we can run large batches and small batches at the same time.” This conflict can be challenged by distinguishing between production batch size (between setups) and transfer batch size (between workstations), and so allowing different sized batches for different purposes.

A very useful exercise from the book that the main character used was to maximize or minimize a specific measure or constraint and see if that would obtain the overall goal. For example, what happens if you maximize the throughput of the plant? Does that mean it would be avoid being shut down? Of course not. That produced product had to be sold. After iterating he came to the final set of constraints or variables that really mattered.

Now that we have this context, what should our answers be?

What is the goal of engineering?

What are the constraints to achieving that goal?

Take care. Talk soon. And thanks for reading.