The Data Centric Architecture of a Factory Digital Twin
Figure
2-2 : An RTN for a multiple step manufacturing process .
The RTN represents a network of nodes alternating between materials and tasks and connects the process ingredients to final products . The RTN is connected to the physical processing equipment and other limited resources such as labor . Each task may be run on one or more pieces of equipment and / or occupy renewable resources , and each material may be stored in one or more pieces of equipment . Thus , we can associate a list of equipment and / or renewable resources with each node in the RTN . Renewable resources in the RTN are those that are occupied during some specified time periods in the execution of a task and then are available for other uses when the task does not need them . Labor is an example of a renewable resource , or different pools of specialized labor .
Specifying a task , a piece of equipment , a start time and a batch size ( or extent for rate processes ) fully determines an instance of a process task . Each process task instance corresponds to an activity that must be performed and is represented as a box on the Gantt Chart . Materials created by one task at a certain time and consumed by another task later must be stored somewhere during the intervening time .
One of the many features that set advanced FDT technology apart from older technologies is the explicit tracking of material storage . A realistic schedule specifies exactly how much of each material is available and in which vessel it is stored at every point on the timeline or at least guarantees that the implied storage is feasible in practice . The presence of a non-zero amount of material in a storage vessel over a time interval is indicated by storage activity on the Gantt Chart ( see Figure 5-1 ). This feature is of less importance in a plant that makes automobile engines because cylinder heads can be stacked on the factory floor if need be – as such storage is less of
102 February 2025