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182 Processing
Setting the processing time
• Specified by a distribution. This choice provides a random processing time, based on the distribution and its arguments selected in the dialog. An example of this is shown in “Ran- dom processing time” on page 183.
• Fromalookuptable.Thischoiceallowsyoutouseanattributevaluetospecifytheparam- eters of a random distribution. With this option, two popup menus and a table appear. The first popup is for choosing a distribution; the second is for selecting an attribute. The table is where the processing time for each type of item is characterized. with each row containing a different set of arguments for the selected distribution. As each item enters the block, its attribute value identifies which row in the table the item is associated with, and thus what its processing time is based on. This option is illustrated in the “Simulate Multitasking Activity model” on page 199.
Processing time for other activity blocks
The Workstation block works much like a Queue combined with an Activity block. It has most of the same options (shown above) for setting the processing time as the Activity. (Because of its internal queue, the Workstation does not have a D input connector.) The Convey Item and Transport blocks calculate an implicit processing time based on the settings for speed and length entered in their dialogs. They are discussed in “Transportation and material handling” on page 200.
Fixed processing time
Set the delay in the Activity dialog if the delay doesn’t change and you know how long it is. For example, if Machine A always takes 5 minutes to process parts, enter the value 5 as the processing time in the Activity’s dialog. This is most common in the early stages of model building when you use constant parameters to get repeatable results.
Another method for having a fixed or constant processing time is to connect to the D input of the Activity block. For instance, you can connect from a Constant block (Value library) or a Slider control, as shown at right. If you use the Slider, you can manipulate it with each simulation run, or within a simulation run, to see the effect of various processing times.
Connecting to the Activity’s D connector overrides any manual entry in the Delay (D) field.
Slider control used to
set Activity’s processing Scheduled processing time time
If a process takes a specific amount of time under most conditions, but
takes another amount of time if the conditions are different, you can schedule the processing time. This is common when simulating worker performance, where output could be a factor of time.
Discrete Event

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