Why MES fails for bespoke engineering

Manufacturing Execution Systems (MES) are widely adopted to control and monitor production activities. They provide visibility into operations, resources and shopfloor events once manufacturing execution begins.

In bespoke engineering environments, however, execution problems often emerge long before production reaches a stable state. These problems are frequently attributed to incomplete planning, insufficient discipline or late changes.

The recurring failure of MES in such contexts is not a matter of configuration or adoption. It is the result of a structural mismatch between what MES is designed to execute and what bespoke engineering projects require to be executed.

The MES execution assumption

MES operates on the assumption that manufacturing execution follows a sufficiently defined product and process structure. Bills of materials, routings and work instructions are expected to exist at a level that allows production events to be tracked and controlled.

This assumption holds in serial or repetitive production environments, where engineering has largely stabilised before execution begins. In bespoke engineering, it does not.

Execution before definition stabilises

Bespoke engineering projects are characterised by overlapping phases. Engineering, procurement, manufacturing and assembly proceed in parallel, often under commercial and scheduling commitments made before definition is complete.

Execution therefore begins while essential interfaces, dependencies and assemblies are still evolving. Manufacturing is not delayed until engineering concludes; it is initiated under partial and provisional definition.

MES is not designed for this condition. It presumes that execution follows definition, not that execution and definition co-evolve.

Visibility without executability

MES provides visibility into what is happening on the shopfloor. It reports operations performed, resources consumed and deviations from planned processes.

What it does not represent is executability. MES does not evaluate whether assemblies are structurally ready to be executed, whether dependencies are resolved or whether interfaces are mature enough to support downstream work.

As a result, execution may appear under control while assemblies remain non-executable in practice. Problems surface only when physical integration or rework makes structural gaps unavoidable.

Why configuration does not solve the problem

Attempts to adapt MES to bespoke engineering often focus on increased flexibility. More variants are introduced, routings are loosened and exception handling is expanded.

These adaptations address symptoms, not structure. They do not change the underlying assumption that execution is driven by predefined production logic.

In bespoke engineering, execution is driven by the evolving readiness of assemblies, not by the progression of operations. MES has no structural reference for this dimension of execution.

The execution domain MES does not cover

The failure of MES in bespoke engineering is therefore not a failure of technology. It is the consequence of applying a system optimised for manufacturing execution to a domain where engineering execution remains active and decisive.

This domain exists before and alongside manufacturing. It governs whether work can proceed coherently under changing definition and unresolved dependencies.

Recognising this distinction is a prerequisite for understanding why execution breaks down in bespoke engineering long before production metrics signal a problem.