There are two main model types. First, the **traditional model** uses distributions to represent most timings in the model. The conventional model can increase or decrease volumes with simple changes. If built correctly, the models are accurate and efficient. The disadvantage is traditional models take longer to create

The second model type uses actual historical data to drive the model (**Real Data Model**). Model changes show the efficiency gains or losses, given the number of arrivals and defined flow. The advantages include reducing the modeling time (usually by 80%), quickly changing the arrival date range, and easy validation – known inputs provide known outcomes. The disadvantages of “real data modeling” include difficulty changing the amplitude of arrivals; it is challenging to change routing.

# Method for Building a Traditional Model

There are many ways of building a traditional model, but reduce backtracking and rework by using the build order shown below:

**Flow the process**

Before spending time on the model’s behavior, ensure the flow is correct. To model the existing process accurately, walk the process with the process expert, taking notes as you go. You will uncover many critical elements by being in the work area. Pick up copies of forms or documents used in the process. Make notes as you go noting the process, timing, and resources used. Finally, go back to your computer and draw the flow diagram without entering any times, capacities, or resources.

**Animate the model**

Create a simple animation of the flow to verify the flow integrity. Next, create a periodic arrival that will separate the entities by enough time to allow only one entity in the process. With default times, this is usually 30 to 60 minutes between arrivals. Finally, change the time on routes to represent the approximate route length (i.e., a one-inch route would have a one-minute move time while a ten-inch route would have 10-minutes.)

Watch the model run and check the model against your notes. Make notes on the model of those things that you don’t understand, then return to the process expert and review the animated model.

**Simplify and correct**

Undoubtedly you will discover changes, addition, or simplifications to the model. Correct the model and perform a second review with the process expert. You will likely also obtain additional information about how the process runs during this phase. Finally, rename and save this model to **preserve** the **Live Animation** for future use. By taking the previous steps, you will save hours of work. Always get the flow correct before adding other aspects of the model. The Creqation of a flow-only model may seem like additional work, but you will save time creating the model in this fashion.

**Timing and capacities**

Enter the timing and appropriate capacities, input and output queues, and model logic. Save and run the model often to check for model errors. Save often.

**Arrivals**

Enter arrivals to represent the actual arrival patterns.