I have been working with many companies of late, helping them improve their operations by employing "lean manufacturing" principles. In working with these companies, I have found simple simulation exercises to be most valuable in illustrating concepts and conveying an understanding of how those concepts can work in any organization.
The key to an effective lean simulation is simplicity. The simulation should allow participants to construct something using different manufacturing scheduling techniques. The "something" should not be complicated. In fact, we have used paper cutouts to illustrate key points.
To start the lean simulation, plan to build the designated product in a batch-scheduling mode. This means that each component of the product should be processed in a predetermined quantity through each stage of production. For example, your simulation may consist of two parts that are assembled together. The first part can be a paper square with a hole punched in the center. The manufacturing processes for this part are shear (use scissors to rough cut the squares from a sheet of paper), finish cut, (use scissors to cut final shape) and punch (use a single hole punch to place a hole in the center of the square). The second part can be a triangle with a bend in the center. The manufacturing processes for this part are shear (again use scissors to rough cut the triangles from a sheet of paper), finish cut (use scissors to cut final shape) and bend (use a ruler to crease the triangle, then bend it). The two parts are assembled with two staples.
Start by producing batch sizes of five of each component. This means the square and triangle must undergo their respective shear operations in batches of five, and the entire batch must be completed before the components can move to the next operation. Once both parts complete their respective manufacturing cycles, they can be sent to assembly.
For the first simulation round, load each step of the manufacturing process with five parts so the participants have something to work on. Place a mark on one of the triangles and one of the squares that are to be cut from the paper sheet. Use these marks to track progress of each component through the manufacturing process. Produce parts for 10 minutes, and at the end of the simulation, record the following data: work in process (WIP is the number of components completed but not assembled and the number of assemblies in process but not completed), cycle time (time to get one piece of the square and the triangle completed and assembled) and productivity (time per piece—in this case, take the total number of pieces produced divided by the 10-minute timeframe). The results of this first simulation will typically be poor. There will be much WIP inventory, few assemblies will be completed, some people will be waiting for work as others work at a feverish clip, and the cycle time will be long (it is likely that neither of the marked parts will make it through the entire process in the 10 minutes allowed). There will also be a sense of confusion—not atypical of a normal manufacturing day.
In the second simulation round, reduce the batch size to one, but maintain the batch scheduling concept that calls for making parts as soon as you have material to work on. Run the simulation for the same period of time and record the same information. In this case, the WIP inventory should be a little better; there may be more assemblies completed, but the cycle time will still be long. The productivity number will be about the same or perhaps a little better.
Finally, the third simulation should be run, not in batch mode, but in pull mode. Place one square at each workstation and two at the assembly station. In this round, parts should only be made when the square in the subsequent operation is empty. To start the simulation, there should be one part placed in each square so everyone has something to work on. The "pull scheduling rule" of only making a part when it is needed by the next operation must be strictly followed. The results of this final round will demonstrate the advantages of a lean process employing a pull scheduling system. There will be little WIP inventory, more assemblies will be completed, and the cycle time will be reduced.
I have found these simulation exercises to be a fun and effective way to learn about the advantages of lean manufacturing. Try a simple simulation exercise in your operation. You may be surprised at the results and be motivated to streamline your manufacturing processes with the aid of lean concepts.