Why Execution Always Varies from the Plan (and What That Really Means for Manufacturing Systems)

Execution always varies from the plan. We know this, we plan for it, and we bake inefficiencies into the planning process to deal with that variability, extended order lead times, safety stock, lower planned machine utilization, overtime, expedited freight, and premium freight. We do this because the cost of misalignment is high. Yet even with those safeguards in place, we still pay penalties depending on contract terms, or we miss better outcomes because we couldn’t optimize purchasing, operations, or logistics.

That’s the reality for most manufacturers today.

The reason this continues to be the norm is because most systems weren’t designed to handle variance in real time. They were not built to adjust when execution inevitably moves away from the plan. As a result, we resort to rigid planning, apply buffers, and absorb unnecessary costs.

The ability to bridge the gap between planning and execution, by reconfiguring workflows and applications, is no longer just an organizational aspiration. It is now a requirement, and composability is the concept behind this. It’s not about making existing systems incrementally better; it’s about shifting the way we look at architecture entirely. Systems should be built from building blocks that can be configured, reconfigured, and ultimately extended as business needs evolve.

What Composable Systems do differently

Composable systems aren’t just more flexible. They’re more aligned with how real manufacturing happens. Planning, scheduling, order management, sequencing, dispatching, and execution functions are interconnected and constantly changing. The ability to quickly configure and re-configure how those systems interact, how data flows between them, and how decisions get made is foundational.

Legacy Manufacturing Execution Systems (MES) and Advanced Planning and Scheduling (APS) systems were never built, never designed, for this level of adaptability. Most APS tools are stateless; they plan as if the shop floor operates in a vacuum. Most MES tools are disconnected from enterprise planning systems, and they execute blindly. Bridging these two systems through composability is the key to getting a single version of the truth across operations and enabling workflows that are actually grounded in the real-time state of the factory.

It’s not replacement, it’s reinvention

This isn’t just about replacing one system with another. It’s about adopting a more modular approach to building a Smart Factory solution that tackles both your current issues and your long-term operational goals. Whether that involves integrating with your legacy solutions, replacing outdated or homegrown systems, or designing new workflows across business functions, the platform should support it. Quickly. Iteratively. And with minimal technical obstacles.

Execution will always vary from the plan. But the way we respond to that variance is where real value is created, or lost.

If you want to go deeper into how composability works in practice, especially in APS/MES environments, this is where the conversation gets interesting.