Rockwell Automation Arena Packaging Users Guide - Manual (Page 78)

A RENA P ACKAGING T EMPLATE U SER ’ S G UIDE
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Essentially, any module that can reference a variable or expression can potentially refer-
ence variables for logical purposes. For a detailed discussion of the modules in the Arena
template, refer to the Arena User’s Guide or online help.
References in Arena Packaging template modules
Arena Packaging template variables can also be referenced in certain dialog box prompts
of Packaging modules. The two most common areas where the variables are referenced
are:
„
Control conditions for machines, conveyors, and palletizers.
„
Additional conditions for Conveyor sensors.
The variables can also be referenced in any other dialog prompt that accepts an expression.
Note: Take advantage of Arena’s Expression Builder. When referencing Arena Packaging
variables in a module or animation object, note that the names and syntax of the variables may
be accessed easily using Arena’s Expression Builder. To load the Expression Builder, first select
the expression field you want to edit. Then right-click the mouse and select “Build Expression…”
from the right-click menu.
Updating variables
During a model run, Arena Packaging template variables are not updated continuously. By
default, they are updated only when current values are required by the Arena Packaging
engine for statistical or logical purposes.
This minimization of updates is the most efficient approach in terms of model run speed.
However, you may consider it insufficient for animation. In particular, variable values for
conveyor accumulation levels and equipment throughputs might appear “choppy” and
thus hard to visualize.
Also, when incorporating discrete logic into your model, an entity may require the current
values of variables at a specific time for logical purposes (e.g., branching, assignments,
etc.). In these cases, the last values updated by the internal engine could be too outdated.
The next two sections describe features in the Arena Packaging template that address
these issues.
Updating variables for animation
Arena Packaging allows you to force regular updates of the Packaging variables (and thus
system status) just for animation purposes. You do this by specifying the Max Time Btw.
Updates within the Simulate module. These updates are performed in addition to the
necessary updates required by the Packaging template’s algorithms.