Capacity Determination
The following exercise was developed on the basis of a communication from Barry Firth, CPIM, Melbourne, to whom we extend many thanks.
A plant runs $10 * 8$ hour shifts per normal week. A work center in the plant has 5 identical machines, each requiring one operator to run it. This is a machine-paced work center (a machine capacity). Operators get a total of 1 hour for breaks, and they usually take their breaks at the same time. Each machine requires one episode of planned maintenance per week of 3 hours, scheduled by the planner. During the last 6 weeks, the performance data in Figure 13.7.1.1 were recorded:
$$
\begin{array}{|l|c|c|c|c|c|c|}
\hline \text { Week No. } & 1 & 2 & 3 & 4 & 5 & 6 \\
\hline \begin{array}{l}
\text { Number of working } \\
\text { days }
\end{array} & 5 & 4 & 5 & 5 & 5 & 5 \\
\hline \begin{array}{l}
\text { Actual machine } \\
\text { hours (setup+run) }
\end{array} & 260 & 200 & 280 & 320 & 260 & 280 \\
\begin{array}{l}
\text { Maintenance time } \\
\text { in machine hours }
\end{array} & 15 & 12 & 18 & 15 & 15 & 15 \\
\hline \begin{array}{l}
\text { Standard machine } \\
\text { hours produced }
\end{array} & 220 & 160 & 240 & 280 & 220 & 220 \\
\hline
\end{array}
$$
Questions:
a. What is the theoretical capacity in machine hours per normal week (5 days)?
b. Taking into account scheduled nonproduction events, what is the availability (as a percentage) of machine time per normal week, without considering operator constraints?
c. What is the availability (as a percentage) of machine time per normal shift, taking into account the normal working conditions for operators?
d. If the tactical utilization is targeted to be $90 \%$, what value should be used for the utilization factor of machine time for capacity rating purposes?
e. What is the demonstrated capacity per normal week of this work center? (Adjust the data for week 2 to correct for the short week.)
f. What was the actual utilization (as a percentage) through the 6 weeks in review?
g. What was the actual work center efficiency through the 6 weeks in review?
h. If planned efficiency is targeted to be $85 \%$, and taking into account your answer to question (d), what was the rated capacity per normal week?
i. Compare your answers to questions (a), (e), and (h). What should we do now?