1. The 2 Constants: Metrics and Bottlenecks
What is the first assembly line that most people think of? Most supply chain
professional’s answer would be Henry Ford’s Model T assembly line. Assembly and production
lines have been around for many years and there are still many that exist today that are very
similar to the Model T assembly line. There have been many efficiency improvements,
automation and technology advancements since the Model T production line but they will all
have in common two things. Those two things are metrics and bottlenecks.
Metrics exists to measure performance over a period time and guide the company on
how to optimize the supply chain. Some of the most common metrics associated with
production or assembly lines are efficiency, quality, total cost, throughput, and cycle time.
These metrics really shine a light on how operations within the line are performing but also on
where issues might be. Metrics are crucial to measure
success and to improve, yet sometimes companies don’t use
the right metrics. Bill Waddell from the Lean Management
Institute stated that, “the flaw in most performance
measurement schemes is a failure to differentiate between
metrics that measure overall process or value stream outcomes, and metrics of events and
activities at isolated points along the value stream. Management focus must be on total cost,
and metrics such as labor efficiency and machine utilization should only be data points that
shop-floor managers can use or not as they see fit to help them attain lowest total cost.” The
metrics that measure total costs are the most valuable metrics. When the entire company along
Figure 1.1

2. with the assembly line have the unified goal of lowering those total costs metrics, massive
growth in the company will follow.
Everyone knows the saying, “you are only as strong as your weakest link.” This saying
applies to many situations such as sports teams but it definitely applies to a production or
assembly line. The weakest link in an assembly line is the bottleneck within it. The bottleneck is
the slowest process within the production or
assembly line. Every production line has the goal
of making the line faster and more cost
effective. Dr. Eliyahu Goldratt’s “Theory of
Constraints” speaks of constraints and how to
approach improving a production line. It is
stated that the, “core concept of the Theory of Constraints is that every process has a single
constraint and that total process throughput can only be improved when the constraint is
improved. A very important corollary to this is that spending time optimizing non-constraints
will not provide significant benefits; only improvements to the constraint will further the goal
(achieving more profit).” Production line managers go through the cycle everyday of trying put
fires out on the production line and to try to make it run smoother and faster. If they use the 5
focusing steps the the Theory of Constraints, they have a better chance of seeing improvements
and a faster throughput time. The five steps are outlined in figure 1.2. From my own experience
on a jet production line, I used these five steps and saw great results. I realized that sometimes
eliminating a bottleneck can be as easy as cross-training employees. There will always be a
Figure 1.2

3. bottleneck in a production or assembly line, so it is always beneficial to continually implement
these steps.
Production and assembly lines have come a long way in the past 100 years. There is still
growth and improvement to be had. Two things will always exist in the lines, and those are
metrics and a bottlenecks. These two constants not only exist in manufacturing and assembly
environments but also across entire supply chains and value chains. It doesn’t always take
technology advancements to improve productions lines. What will help on a daily basis is
quality metrics and improving the bottleneck.
By: Jackson Horne
http://leaninstituut.nl/publications/1106/Manufacturing_Metrics.pdf
http://www.leanproduction.com/theory-of-constraints.html