A sea change is happening in the design of production lines, based on Lean principles. What used to be considered “best practice” regarding mixed-model line design is evolving in a new direction. This short article lists the ways in which this change is happening.
What is a “State-of-the-Art” Lean assembly line? Following is a general description of its main characteristics, that could be implemented in virtually any production environment:
1. Optimized material delivery. Often a material delivery method is developed to make it easier for the material handler, or to reduce material handling costs. The impact on the operators themselves is a secondary consideration, and it is not unusual to see additional material selection effort transferred to the people actually doing the value-adding work. Our approach in a new design is to address both concerns, but to make it very easy for the operators to get access to and select the parts they need, without excessive walking and handling. A key tool in this strategy is the use of AGV (Automated Guided Vehicle) carts, to routinize material delivery and automate the delivery process.
2. Quality at the Source. This is not a new idea, but in an optimized line design the units are not released to the next workstation until critical quality steps and checks have been completed. These steps could be as simple as an operator confirmation, or as complex as an automated torque gun setting. Once both the work and the quality checks have been completed, the unit is released and moved automatically to the next station.
3. Moving to the work. In today’s highly-configured, mixed-model production lines, “flexing” to where the work needs to be done is necessary and not an option. Conveyors, large material storage racks, and fork-truck delivery aisles are all barriers to operator movement. Ideally the production floor is open, and all conveyors and large racks are replaced with flexible and asynchronous AGV workstations and material delivery carts. This will depend, of course, on the size of the product and the type of work being done.
4. Live work instructions. The display of unit-specific work instructions will be triggered by the arrival of a specific unit at a workstation. Given the high number of options and configurations typical on today’s production lines, this function is critical to ensure quality and to eliminate the “tribal knowledge” that may currently be necessary.
5. Follow a proven line design methodology. Concepts like takt time, line balancing, and standard work are often misapplied when applied to a mixed-model production environment. The same concern applies to material delivery strategies. These subjects are a core competency of the Leonardo Group.
This all sound like a lot of work, and it is. Consider, however, the alternative. If the new approach can be scaled easily over time, if productivity and inventory turns take a jump up, and if quality work is essentially guaranteed, then this approach could be the least expensive option.