Both the inflow and the outflow are influenced by different
kinds of disturbances, which can be derived from the impact
network as well. The inflow will be interrupted randomly by
all kinds of trouble, which occur in the upstream process step.
Temporarily, the work in process will absorb the interruption.
With longer interruptions of the inflow, the minimum work in
process will be reached, which also leads to a drop of the
outflow. All kinds of disturbances do also occur in the
considered process step itself, which results in a drop of the
outflow. Just as described before, the work in process is able
to absorb this interruption before it reaches the maximum
work in process and also causes a drop of the inflow. The
occurring disturbances were derived from maintenance
literature [26]. Fig. 7 shows the trend of the stock of produced
parts exemplarily for one working day with three shifts. The
curve shows several break downs. At the end of the last shift,
customer needs are fulfilled and no more parts are produced