Exercise: Create a Simulation Model

Open Process Simulator. Start with a blank Microsoft Visio® worksheet, the Process Simulator Ribbon Menu at the top, and the Autodesk Factory Design Utilities Asset Browser on the left.

Drag an entity (part) onto the canvas from the Asset Browser menu on the left and assign any applicable properties in the Properties window on the right.

Drill down or search the Asset Browser to find the right assets (Model Locations/Activities) to place on the layout – in this case, two CNC lathes.

Continue to add equipment as needed. For this example, one milling machine and an inspection station were added.

The activities also have properties, primarily process time, which is defined by a probabilistic distribution that is determined based on plugging in historical processing times for each machine into the Stat-Fit program, which comes with Process Simulator.

After adding all the locations/activities (assets), define the work units (entities) routing for the material workflow by using the Visio connector tool to drag lines from the work unit to appropriate locations. The arrows from the entity to the first pieces of equipment are called arrivals. Arrivals have properties, namely arrival patterns, which are defined in the Properties window to the right of the drawing. Right-click on the connector to access properties.

Finish defining the part routing and then define any Route properties that may be needed (Processing Requirements). In this case, a rework loop is added for 10% of the work coming off the end of the line, so in the route properties window, 10% is added to indicate the 10% of the parts follow this rework route from the visual inspection machine back to the milling machine.

Next, resources will be added. Resources are not a mandatory element of a Process Simulator model, but in this case, since a worker and a forklift are a part of the example, they were added as resources.

In order for the man resource to be utilized to inspect, he is assigned as the resource for the visual inspection station with a triangular distribution T(3,5,10) minutes to ensure his inspection time has some realistic process time variation.

Similarly, the forklift resource is assigned as the resource for the route, which delivers parts from the vertical milling machine to the inspection station.

Finally, another optional element, a path network, will be added for the forklift. It is named ForkliftPath. A path network defines all the travel or movement options for a resource. The inspector doesn’t require a path network because there is no need to model his movement, only his utilization while inspecting.

After creating the ForkliftPath path network, it is assigned to the forklift resource.

Notice the running clock time in the upper right and which scenario is being run in the upper left. Each scenario ran for 40 hours. Also, notice that the inspector turns green when he is being utilized.

When the simulation is done running, view results in Output Viewer. A standard out-of-the-box dashboard of reports displays automatically. You can also create additional dashboards and reports by adding more tabs and using the report types from the charts menu. Based on what we see in this dashboard, we want to test a couple more scenarios with different rework rates to see the effect on throughput.

Add two more scenarios to compare to baseline, a second scenario with a 5% fail rate and a third with a 15% failure/rework rate. Simulate scenarios again.

View the results of the two additional scenarios compared to the baseline scenario with a 10% rework rate. It’s overly simplistic, but not surprisingly, the scenario with the lowest rework rate had the highest throughput, and the one with the highest fail rate had the lowest throughput.

Once the model has been optimized in Process Simulator, it can now be opened in AutoCAD or Inventor, and physical factory design can begin.

ProModel Design Methodology