Page 101 - Design for Six Sigma a Roadmap for Product Development

76 Chapter Three

In many companies, it is prohibited to interrupt a production worker
at work. However, for design engineers, their working times are mostly
treated as soft and disposable, because some people believe that they
always can find time later to make it up; this is obviously wrong.
Mascitelli (2004) recommended that an uninterrupted time slot for
each working day, 3 hours or more, be allocated to each design engineer
in order to greatly improve productivity.

Smooth product development job flow Again from a human factor per-
spective, a steady work pace will be much more preferred to a chaotic,
roller-coaster-like uneven workload. Also, queuing theory can provide
valuable insights into what kind of job flow pattern will make the
product development process faster and more effective. Queuing theory
is the mathematical study of waiting lines of queuing systems. A queu-
ing system is a system in which a server or servers are processing
arriving jobs. The queuing theory permits the derivation and calcula-
tion of several queuing performance measures including the average
waiting time in the queue or the system, the average number of jobs
waiting in line, and so on.
The product development process involves many projects. Each team
or engineer will work on several projects during the whole product
development process; so some projects have to wait in the queue until
the current project is finished so the team or engineer is free to work
on them. In this case, how we sequence the jobs, how we assign the
workload, and timing will make a big difference in overall product
development progress. The queuing theory can provide great help for
us in how to reduce the waiting time and how to improve the through-
put (number of projects finished per unit time).
There are several important results in queuing theory that are rele-
vant to the product development process.
1. Inefficient Batch Queue. Batch queue means the jobs are coming to
queue in big groups, or batches. For example, if a plane load of inter-
national travelers arrives in an airport customs and immigration
inspection stop, the long queue will form immediately, and it takes
a while for everyone to get cleared. If most people get out of work at
about the same time, then the traffic jam will form immediately
and it takes very long for everyone to get home. If the same num-
ber of people get out of work at very different times, then the traf-
fic time for each one will be much shorter. The implication for the
product development practice is that if we give the product devel-
opment team or engineer big chunks of work, instead of pieces one
by one, our throughput will be low.