This page contains a tutorial demonstrating how to build a production system model for an assembly process. This tutorial assumes that the reader has reviewed Map a Production System and Model a Production System. If not, please refer to those sections of the Help Menu before continuing.
Airplane Assembly Company
The Airplane Assembly Company fabricates and assembles roughly 250 airplanes for several major airlines each year. For the upcoming new year, they have secured orders totaling 500 additional planes. Because of the increase in demand, the company is forced to expand into a new, larger assembly facility. In the startup of the new facility, the company experienced 8 weeks of missed production targets.
The Airplane Assembly Company has outlined the following goals and provided the following details to improve performance going forward.
Objectives
- Catch up on late production
- Meet all production targets going forward
- 60-day lead time for airplanes
Constraints
Keep additional spending below the budgeted amount of $200,000.
Build the Model
Begin at the Process Library menu and create a production process called “Airplane Assembly”.
Next, open the production process and draw a single production routing with the following characteristics. Add all relevant data depicted below. All input fields not mentioned in this section’s tables should be kept as their default values.
| Shape | Shape Name | Sequence | Process Center | Average Nominal Process Rate per Machine (Units/Hour) | SCV of Process Times for a Transfer Batch |
|---|---|---|---|---|---|
| Stock | Raw Materials | ||||
| Operation | Install Fuselage | 100 | WS-1 | 0.3125 | 1 |
| Operation | Install Wings | 200 | WS-2 | 0.0714 | 1 |
| Operation | Install Seats | 300 | WS-3 | 0.0667 | 1 |
| Operation | Install Engine | 400 | WS-4 | 0.05 | 1 |
| Operation | QC | 500 | QC | 0.1042 | 1 |
| Stock | Airplanes |
| Process Center Name | Work Schedule | Batching Type | Number Available |
|---|---|---|---|
| WS-1 | 2x7x12 | Sequential | 1 |
| WS-2 | 2x7x12 | Sequential | 1 |
| WS-3 | 2x7x12 | Sequential | 1 |
| WS-4 | 2x7x12 | Sequential | 1 |
| WS-5 | 2x7x12 | Sequential | 1 |
Work Groups
Use the default work group for this example. Work groups can be added to allow for different shifts depending on the employees who interact with different elements of the system. Refer to Work Groups for a complete description of work groups and their data elements.
Units
Next, open the Unit of Measure menu and create a unit of measure named “Airplane” for the airplanes that will flow through the production system. The Default Unit of Measure can be renamed, or the user can create a new one. A unit of measure is required to account for various WIP types that flow throughout a production system. Refer to Unit of Measure for a complete description of UOMs and their data elements.
Product Flows
Next, open the Product Flows menu. By default, every new model will come with a product flow named “Default Product Flow”. Any routing generated will automatically be assigned to this product flow. First, open the default product flow and rename it to “Airplane Assembly”. Adjust the other fields, including plotting parameters, so that the screen looks like the following image. Close the menu. Refer to Product Flows for a complete description of Product Flows and their data elements.
Routings
Next, open Routings. A routing named “Route 1” will be visible. Open the Route 1 edit menu and rename the routing to “Assembly”. Refer to Routings for a complete description of Routings and their data elements.
Items
Recall that the Airplane Assembly Company needs to produce 500 planes in the next 50 weeks. This creates an average demand of 10 planes per week. Within the plant, aircraft are transferred in batches of 2 due to storage limitations. The total cost of producing a plane is $25 million. There are currently no aircraft on hand to fulfill demand as they are a “Made to Order” item.
Now, open the Items list. Open the “Default Item” and rename its Description and ID to “Airplane”.
Select the unit of measure created above. Next, change Transfer Batch, Total Unit Cost, On Hand Qty, Average Number of Orders, Variance of Orders and Current Reorder Quantity to match the following table. Keep all other values as they are.
| Parameter | Value |
|---|---|
| Description | Airplane |
| ID | Airplane |
| Unit of Measure | Airplanes |
| Transfer Batch (Units) | 2 |
| Total Unit Cost ($) | 25,000,000 |
| On Hand (Units) | 0 |
| Average Number of Orders (Per Period) | 10 |
| Variance of Orders (Per Period) | 10 |
| Current Reorder Quantity | 6 |
The item table input menu should look like the following when finished. Refer to Items for a complete description of Items and their data elements.
Item Routings
Next, open the Item Routings list. Item routings tell the model which routing to send each item. Create a new Item Routing and name it “Airplane Assembly”. Select the Routings drop-down menu and select the appropriate routing. In this model, there is only one routing. In others, ensure the correct routing is selected for each item. Now, select the item drop-down menu and select the Airplane item. For this model, keep Fraction of Releases at its default value, 100%. The screen should match the following image. Refer to Item Routings for a complete description of Item Routings and their data elements.
The model is now complete and ready to be analyzed. The following article provides guidance on how to interpret the results of the model.