Optimal Modularity in Manufacturing Operations: Lessons from the Bill of Operations

Lean manufacturing principles have revolutionized the manufacturing industry, emphasizing efficiency, waste reduction, and customer-focused production. To achieve these goals, it’s essential for manufacturing managers and supervisors to build a robust operations management system. In this article, we explore the concept of a “Bill of Operations” and its parallels with the familiar “Bill of Materials.”

Bill of Operations vs. Bill of Materials

Just as a Bill of Materials (BOM) outlines the components and quantities needed to create a final product, the Bill of Operations defines the necessary labor operations required during the manufacturing process. While a BOM ensures that the right materials are used, the Bill of Operations addresses “how” a product comes together, covering the labor side of manufacturing.

Like modular sub-assemblies in a BOM that can be used in various products, the Bill of Operations can also employ modular elements called “Operations.” These Operations, when designed properly, offer reusability, refinement, and optimization of labor processes.

Designing the Bill of Operations

To design an effective Bill of Operations, you must start by understanding the Takt Time, which is the time between products completing the production process to meet customer demand. This Takt Time is crucial in dividing the manufacturing process into medium-sized labor elements – the Operations.

The rule of thumb here is to target an Operation time of about 1/5th of the Takt Time at the highest production rate planned. This provides flexibility to adapt to changes in Takt Time and maintain a balanced production line.

Defining Operations entails breaking down the entire production process into manageable, Operations. These Operations should ideally be executed by a single operator, in a single cell, and with a specific set of tools or machines. Following these guidelines is essential for achieving modularity in your manufacturing processes.

Determining the Number of Operators and Cells

The number of Operators needed is based on the Takt Time. For example, if your Takt Time is 2.5 hours, you’ll require a different number of Operators than if it’s 1 hour. These figures provide initial estimates to help design your production line, which you can refine later.

The number of Cells, often equal to the number of Operators, is influenced by factors such as available floorspace and the ability to minimize work in process and throughput lead time. For some industries, a simple one-Cell-per-Operator approach may not be the best; you might need to consider multiple Operators performing different Operations simultaneously on the same product.

Why Don’t ERP Systems Support the Bill of Operations Model?

Many ERP systems are not inherently designed to support Lean Manufacturing. They often rely on batch scheduling and lack the flexibility required for Lean principles. Lean Manufacturing focuses on agility, responsiveness, and minimizing waste, which traditional ERP systems may not fully accommodate. As a result, many organizations opt for specialized Lean Manufacturing scheduling software.


The Bill of Operations is a fundamental concept in Lean Manufacturing, offering the modularity and flexibility required to streamline assembly and manufacturing operations. By implementing the principles discussed in this article, you can transform your manufacturing processes and achieve greater efficiency.

Next Steps

Manufacturing is evolving, and digital solutions are becoming increasingly vital for efficient production. If you’re looking for ways to define and manage your manufacturing operations more effectively, we invite you to contact us or visit our website at optegritysolutions.com. We’re here to support your journey towards achieving optimal modularity and efficiency in manufacturing operations.

Feel free to reach out to me, Josh, at josh@optegritysolutions.com, if you have any questions or need further guidance on your manufacturing journey.

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