Every Failure is a Learning Opportunity
Case Study: When Design Fails Manufacturing Reality
Success is easy to celebrate; failure is often the better teacher. It exposes hidden assumptions, tests decisions, and reveals where design intent breaks down in practice.
This cautionary case study involves an OEM, its long-standing design consultancy, and a component manufacturer brought in late to rescue a ruggedised industrial controller. By then, critical design decisions had already been made.
Form Must Follow Function
Designing a new product is a complex and time-consuming process, with a multitude of decisions throughout the project. During the concept and early development stages, decisions must be taken to ensure the product performs in the real world. This Industrial controller was designed for harsh environments and required special attention to the human interface aspects of the design. The success of this project was not just about doing the job, it was about creating a product that could be manufactured to a high specification and provide a robust and reliable user experience.
When designing any product with inputs or outputs, electromechanical component choice is critical to operational performance and should be considered at the earliest stages of development. This is where the component manufacturer can add real value and ensure that the finished product meets all the specifications and simplifies manufacturing. Tolerances, assembly, operational access, mechanical stress, are just some of the issues that can impact production and the user experience.
In this case, the design consultancy made key component decisions early in the development without consulting with the component manufacturer to check for potential design limitations. As a result, issues did arise and the manufacturer was consulted during the latter stages of the design, once assembly realities had been established. At this point other decisions had been locked-in including the design of the enclosure. Workarounds were being sort to fix tolerance issues.
Design for Manufacturing
Mechanical tolerances of the internal PCB stack were the root cause of the problem. Within the enclosure several subassemblies were stacked vertically, with external interface connections on the top and bottom faces of the device. The internal tolerances of each subassembly accumulated and resulted in unacceptable tolerances at the external interfaces. The machined enclosure apertures also had horizontal manufacturing tolerances to take into consideration.
The manufacturer of the interface components was asked at the eleventh hour to provide tolerance data and run tests to determine if these could be relaxed to accommodate the realities of the design. On their own, the interface components could not operate safely within the vertical stack specifications. There was a solution that compensated for the horizontal tolerances of the enclosure but compromised the overall aesthetics of the design.
The result was a product design that was impossible to manufacture within the tolerances of the enclosure and interface components. The OEM was faced with a choice: redesign the product sub-assemblies or scrap the project altogether. They chose the latter, resulting in time and money wasted and disappointed end users who had been promised the product. The reputational and financial damage to the OEM and their design consultancy was significant, and the two parted company, ending a long-standing collaboration.
The key lessons from this story are: Engage component manufacturers early in the design phase to leverage their expertise and experience; Simplify the design where feasible and adhere to specified parameters; Comprehend the manufacturing process to prevent decisions that hinder assembly and compromise the quality of the final product. And whilst all this sounds logical, there are plenty more examples of poor design decisions that have resulted in production or field failure.
Learn more about design for manufacturing.
Duncan Nicol 2026