Page 98 - Lean six sigma demystified

Chapter 2 Lean Demy S tifie D 77

applets that could be put together easily to make remarkably complex systems.
This is where I learned the religion of reuse.
Our software development team was tasked with delivering a new informa-
tion system on an incredibly short timetable. We looked at the functionality and
the time available, and we all agreed that we couldn’t do it unless we created
reusable modules for almost everything.
In a 6-month window we built 40,000 lines of code that were the equivalent
of 250,000 lines of custom code. We made our deadline, and the code was
much more reliable because it was used in so many places. Reuse gave us speed
and quality.
One of my heros in software development, Fred Brooks, said “The most radi-
cal solution for constructing software is not to construct it at all. The reuse of
software n times multiplies the productivity of developers by n.” Although this
thought is over 30 years old, it’s still true, but most software developers feel the
need to redevelop rather than reuse existing code; this is why so many software
projects are late and short on functionality.

Reuse at Toyota

George reports that between 60% and 80% of Toyota’s designs reuse existing
materials, components, and assemblies; this radically reduces their time to mar-
ket. That means that only 20% to 40% of the new functionality needs to be
designed and developed. Is it any wonder Toyota can bring a new car to market
in half the time of the big three?

The Law of Lead Time (Little’s Law)

Lead time = (number of things in process)/(average completion rate)

If you can double the completion rate, you can cut lead times by 50%. Reuse
can help you do this by reducing the number of custom parts required to pro-
duce a final product.

The 80-80-80 Rule

George says “With reuse, the probability of meeting specs without a significant
overrun is very high because you already know it has worked before.” If an
innovation consists of 80% reuse, then lead time can be cut by 80% at 80% average
utilization [of existing resources].