Page 207 - ExtendSim User Guide
P. 207

Processing 181
Setting the processing time
which block will get the item. For instance, a Queue that holds items for three Activity blocks would look like the model below.
Simple Connections model
☞ If two machines are free when an item comes out of the queue, the machine that was first con- nected will get the item. With simple parallel connections, even just disconnecting and then reconnecting a connection could change the order of activities getting items.
Unless it is completely unimportant in the model, you should always explicitly state the order- ing for parallel activities using the Select Item In and Select Item Out blocks. See “Items going to several paths” on page 161 for examples of how to control the flow of items to parallel pro- cesses.
Setting the processing time
Activities involve a processing time or delay that is the amount of time it takes to perform a task. Processing time can be static or can vary dynamically depending on model conditions. It can be random, scheduled based on the time of day, customized depending on the item that is being processed, or any combination of these.
You model the processing or delay time explicitly using the Activity or Workstation blocks or implicitly by specifying the length and speed in the Transport or Convey Item blocks. The Activity block is most frequently used to represent a process or operation, and is illustrated in most of the examples for this module
☞ The models discussed in this section can be found in the Examples\Discrete Event\Process- ing\Time folder.
Processing time for an Activity
In the Process tab of the Activity block you can select that the delay is:
• Aconstant.ThisuseswhichevernumberisenteredintheDelay(D)field.Seealsothedis- cussion of “Fixed processing time” on page 182.
• FromtheDconnector.TheprocessingtimeisthevalueattheDinput,overridingany value initially entered in the Delay (D) field. For example, see “Fixed processing time” on page 182 and “Scheduled processing time” on page 182.
• Anitem’sattributevalue.Withthisoption,youcanselectanattributetocontrolthepro- cessing time. This is illustrated in “Custom processing time” on page 184.
Discrete Event

   205   206   207   208   209