Here’s the process that we follow for designing a Mixed Model Line, summarized into 13 distinct steps. The topics discussed in this post can be studied in more detail from several books available in the market. The source book we used was The Complete Guide to Mixed Model Line Design.

Leonardo Group Americas has proposed a complete methodology that we communicate in the form of a series of flow charts or Roadmaps. Our MMLD Roadmap is a series of multilevel charts that guides the Line Designer through all the steps to completely plan, design, deploy, and monitor a Mixed Model Line.

In this post we will focus primarily on the Roadmap steps associated with the data and calculations necessary to design the Value Stream’s physical layout. This is how we do it!

1. Identify Target Area: Unless you are dealing with a very small Value Stream, it would be only the rare occasion when you get to redesign an entire factory all at once. The norm tends to be that you will start by redesigning a section of the factory and continue to redesign a subsequent area after the preceding project has reached some degree of maturity. So, think about starting modestly, learn the MMLD tools and practices and take your time. No points are awarded for rushing.
2. List Products: A list of products that flow through the manufacturing area needs to be extracted from the manufacturing system to be included in the line design calculation model. With this step, think about starting to build a spreadsheet where the rows are the products you plan to build in your Mixed Model Line.
3. Assign Volumes: The product list must include the desired production volumes for a pre-determined planning horizon. These volumes will allow the line design model to calculate Takt, the maximum processing rate, by process. Here you will be making an assumption of Mix and Volume. Start by getting 18-24 months of sales history per product and 12-18 months of forecast to begin the analysis. Just be aware: After all the analysis, the determination of the MMLD Designed Volume will be a decision.
4. Identify Processes: Within the MMLD methodology, a process is defined as sequential work steps carried out by a person, a machine, or a combination of both at constant volume. A process has a distinct starting point, a distinct end point and sequential work steps between those two. Assemble a list of processes. A good place for this may be a separate worksheet in the Excel workbook you started in the previous step.
5. Create Process Flow Diagrams (PFD): These are diagrams that display the relationship of manufacturing processes required to make a product. Go to the manufacturing floor and spend time recognizing the processes you listed before. Every product must have a PFD, but many products can have the same PFD. Draw them on paper one at a time.
6. Build Process Flow Matrix: Create a table called the Process Flow Matrix. Use the original spreadsheet where all the products were the rows, and now take the processes from the PFDs and name a column after each process. Then, one PFD at a time, place an X at the intersection of every product process relationship displayed on that PFD. This will aid the design team in the identification of product families and in the adjustment of the line design model for scrap, rework, and optional factors.
7. Document Standard Work Definitions: The next step in the methodology is to document the work by product/process relationship. Take a look at the Process Flow Matrix, and everywhere you see an X, that is one Standard Work Definition you have to write. By doing so, we will obtain critical data to populate the line design model, and use the information to develop standards for shop floor training.
8. Perform Resource Calculations: With all the data necessary under control, you will input all the data into the line design calculation model and will calculate the required number of resources per process (the number of people and machines). This resource calculation tool is usually developed from the Process Flow Matrix, and an example can be seen in The Complete Guide to Mixed Model Line Design.
9. Do Workstation Definition: Once you know the number of resources required, you will allocate the work breakdown into workstations by process. This task will include the detailed definition per workstation of all the required steps of work, quality control checks, TQM control points, tooling, materials, and consumables.
10. Balance Workstations: Since perfect balance is rarely possible, you will apply a series of techniques to all workstations, to make sure that they can operate within target times. The balancing tools are applied in a prescribed sequence based on simplicity of the tool as well as cost of application.
11. Create Physical Layout: Once you have all the elements described above you will develop a conceptual layout of the target area, this first layout normally ignores all constraints and focuses on product, material, and people flow. Once the conceptual layout is completed, the next step is to adapt the conceptual layout to the realities of the available facilities by developing a layout that accounts for all the factory constraints.
12. Formalize Deployment Plan: A detailed plan of the steps necessary to bring live the new line will have be created by your team and submitted to management for approval. This plan must include all the steps necessary to go from the current state to the freshly designed line.
13. Celebrate Line Live: This is the day when you turn the switch to “on” and start building multiple products in a flow on the same Mixed Model Line. During this activity, you will need to train and monitor the operators on the improved processes, tools, and workflow. The line supervisors will also need training and support on how to “read” the visual signals of the line, as well as on process balancing techniques to ensure a smooth flow.

As you can tell, MMLD is about learning the tools and practices and using them. It is definitely not about guessing or trial and error. Using the tools is the best way to become an expert on this skill that is in high demand. But we do understand that for some of us, designing a Mixed Model Line is a one-in-a-lifetime opportunity. So, if opportunity knock on your cubicle door, do not let it get away!