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178 Processing
Commonly used blocks
This chapter will discuss different ways to use activity-type blocks and how to control process- ing time and the availability of items and resources. It will cover:
• Processing in series and in parallel
• Settingtheprocessingtime
• Bringinganactivityon-line
• Interrupting processes: preemption and shutdowns • Multitasking
• Kanbansystems
• Material handling and transportation blocks
☞ The models discussed in this chapter can be found in the folder Examples\ Discrete Event\Pro- cessing. That folder also contains some subfolders, as indicated in the relevant sections of this chapter.
Commonly used blocks
The following blocks will be the main focus of this chapter. The block’s library and category appear in parentheses after the block name.
Activity (Item > Activities)
Processes one or more items simultaneously; outputs each item as soon as it is finished. Can also be used for multitasking.
Convey Item (Item > Activities)
Moves items on a conveyor from one block to another. Has dialog settings to define
whether the conveyor is accumulating or not, what the length of the item is, and how far and how fast the item moves.
Create (Item > Routing)
Creates items or values randomly or by scheduled. Can be used to control shutdowns for the Activity block.
Shutdown (Item > Resources)
Used to control shutdowns for an Activity (Item library) or Valve (Rate library). Useful
for setting random or constant time-between-failures (TBF) and/or time-to-repair (TTR).
Transport (Item > Activities)
Moves items from one block to another. Has dialog settings for defining how fast and how far the item moves.
Workstation (Item > Activities)
Acts as a FIFO queue combined with an Activity block, holding and processing items.
Takes in one or more items at a time, holds them in FIFO order, processes them simulta- neously, then outputs each item as soon as it is finished.
Systems and processes
Systems encompass one or more processes, which are a series of activities that achieve an out- come based on the inputs. Some examples of processes, the events that might drive them, and the items that flow through or are consumed by the process are:
Discrete Event

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