Engineering Execution System vs MES

Manufacturing Execution Systems (MES) govern the execution of production activities on the shop floor.

They coordinate machines, operators, work orders, and production sequences to ensure that manufacturing proceeds according to plan and within defined constraints.

From a production perspective, MES provides operational control.
From an engineering execution perspective, however, MES operates after a critical transition has already taken place.

What MES systems model

MES systems are designed to answer questions such as:

What is currently being produced?
Which operations are executed on which machines?
What is the production status of a work order?
Are quality, timing, and resource constraints being met?

To do so, MES focuses on:

production orders and routings,
machine and operator states,
real-time execution feedback,
and production performance indicators.

This makes MES essential for production execution, but not for understanding how engineering work becomes executable.

MES systems assume that engineering execution has already reached a sufficient level of readiness.
They do not govern how this readiness is achieved.

What MES does not represent

MES does not model the execution of engineering work itself.

Specifically, MES does not make explicit:

how engineering work converges toward manufacturing readiness,
how unresolved dependencies delay the transition to production,
how partial or unstable definition affects executability,
or how engineering workload accumulation shapes downstream production risk.

MES observes execution after the handover from engineering to production, not the execution dynamics that precede it.

Engineering Execution as a distinct system layer

Engineering Execution refers to the execution of engineering work that leads to production readiness.

This execution layer:

precedes manufacturing execution,
unfolds under evolving product definition,
and determines whether production execution can start without disruption.

It is structurally different from MES logic and cannot be derived from shop-floor execution data.

MES executes production.
Engineering Execution determines whether production execution can begin without instability.

Relation to Product Flow

Product Flow is an Engineering Execution System (EES) that makes this pre-production execution layer explicit.

From the perspective of Product Flow:

MES remains responsible for controlling manufacturing execution,
while engineering execution is analysed as a separate system domain leading up to production readiness.

Product Flow does not replace MES.
It complements MES by exposing readiness gaps, unresolved dependencies, and structural execution risk before manufacturing execution begins.

Why the distinction matters

When engineering execution is assumed to be complete at the point of handover:

instability enters production unnoticed,
execution risk shifts downstream,
and disruptions appear as production problems rather than engineering ones.

Separating Engineering Execution from MES logic allows readiness to be assessed before production execution is initiated.

This comparison reflects the analytical perspective underlying Product Flow.
It does not evaluate MES tools, vendors, or shop-floor implementations.