Downtimes Tab

Downtimes are used to model interruptions in the processing of entities at activities. Downtimes may represent scheduled interruptions such as shifts, breaks, or scheduled maintenance. Or, they may represent unscheduled, random interruptions such as equipment failures. Usage based downtimes can only be defined for single capacity activities. The amount of time the activity is down and the timing for going down are defined in this tab.

Basis Three types of downtimes are available:

Scheduled: A scheduled downtime is one that is planned for, and thus taken into account in the output statistics as such. The time spent in a scheduled downtime will be deducted from the total scheduled hours reported in the output statistics and, therefore, will not be considered in computing utilization, percent down, and so on.

Unscheduled: Unscheduled downtimes are not planned for and will appear as such in the output statistics.

Usage: Usage downtimes are used to model downtimes that occur after being in use for a certain amount of time, such as if a machine fails due to wear after so many hours of operation. Usage downtimes are different from scheduled and unscheduled downtimes because usage downtimes are based on operation time, which does not include blocked time. Scheduled and unscheduled downtimes are based on total elapsed simulation time (operation time, blocked time, idle time).

Frequency The clock time (usage time for usage downtimes) between the start of successive downtime occurrences. This option may be an expression. This field is evaluated as the simulation progresses, so the time between downtimes can vary.
(First Time) The time of the first downtime occurrence. If this field is left blank, the first clock downtime will occur according to the frequency field.
Interruptive If this box is checked, any processing at the activity will be immediately put on hold for the duration of the downtime. If left unchecked, the downtime will begin as soon as any in-progress processing at the activity is completed.
Time The duration of the downtime.
Resource Optionally, select a resource required by the activity for the downtime.
Priority If you have chosen a resource to use for the downtime, you may optionally choose a priority for the resource. When the downtime occurs at the activity, the activity will attempt to get the resource using this priority. If the priority is set to Interrupt, the resource will be preempted from the work it is performing to perform the setup at this activity.
Disable Check this box to disable the downtime during simulation. This is useful for ignoring the downtime without deleting it from the list.