Page 433 - ExtendSim User Guide
P. 433

Delaying Flow 407
Controlling a Valve’s maximum rate
Rate library blocks and the bottom line is Item library blocks. A Decision block (Value library) transmits values from a Valve (Rate library) to a Gate (Item library).
Changeover Quantity Goal model
Since its initial goal has been set to “none”, the goal status is Off and flow through the Produc- tion Gate valve is stopped at the start of the simulation. However, when an item passes through the Get block (Item library) labeled Start Goal, a message is sent to the Production Gate valve’s G (goal) input connector. Once that happens, the valve’s goal switches from Off to On and the goal quantity is set to the value of the item’s Quantity attribute (5000 gallons).
In the bottom portion of the model, when the item leaves the Get block it moves into the Queue, where it is blocked from leaving by a Gate block. The Gate will remain closed until the Production Gate valve reaches its new goal of 5000 gallons. At that time the goal switches from On to Off, the flow stops (because that is the option set on the Control Flow tab), and the value at the GS (goal status) output is set to 3 (indicating that the goal has ended).
As a result, the Gate opens and the item moves into the Changeover Activity block where it is delayed for the amount of time required to perform a changeover. After the changeover has been completed, the item cycles back and initiates the next production cycle.
☞ By default, a Valve’s GS (goal status) output connector reports the following values: 0 when there is no goal
1 when a goal is starting
2 when a goal is in progress
3 when a goal has ended
4 when a goal is interrupted
Discrete Rate

   431   432   433   434   435