APS vs ERP: why your ERP is no longer enough to plan your production

During a recent Ortems go-live at a manufacturing client, a machine broke down on the plant's main bottleneck. First week in production, and already the worst-case scenario.

The operations director told us that, under their usual way of working, a breakdown of that magnitude tied up his five planners for a full day before they regained control of the plan.

This time: 15 minutes.

No one had worked harder than usual. No one had gotten smarter overnight. The only thing that had changed was the tool.

What your ERP does well — and what it will never do

An ERP is a transactional system. It records what happens in the business: orders, inventory, hours, invoices. And it does that very well.

Planning is something else. When a machine goes down on a Tuesday morning with 47 active orders, the ERP won't tell you in what order to restart production, which orders to prioritize, or which customers to call first. All the information is there, somewhere in the system. The answer is not.

So the answer comes from the planners. From their experience, their Excel files, their late evenings.

Your ERP's planning module: a false solution

Most ERPs include an MRP module, and that's often where operations directors believe they've settled the question. MRP calculates what to produce and when. The problem is that it does so at infinite capacity: it assumes your resources are unlimited, that line A is never saturated, that no machine ever breaks down.

It gets worse. MRP treats each constraint separately. Production sequences, setup times, operator skills, material availability, customer priorities: in real life, all of this plays out at once. In MRP, never.

And when the unexpected happens, there's no automatic plan B. The plan has to be rebuilt by hand, from scratch, while production waits.

That's exactly why our client's five planners lost a day with every breakdown.

What an APS actually changes

An APS like DELMIA Ortems starts from the opposite problem: it first models the full set of real constraints — machines, skills, materials, priorities — then calculates a plan that respects all of them at once.

When the unexpected happens, the system recalculates. Not in a day. In a few minutes.

That's what happened during this go-live. The breakdown was entered into the system, the optimization rerun, and the new plan accounted for the unavailable bottleneck. The planners spent those 15 minutes validating the result rather than rebuilding it.

APS and ERP: complementary tools

The APS does not replace the ERP. The ERP remains the source of truth: inventory, orders, bills of materials, lead times. The APS connects to it, produces a feasible plan, then sends the result back to the ERP for execution. Each tool does what it does best.

The real question to ask

Our client didn't have a bad team. Five competent planners, a good ERP, processes in place. And despite all that, a machine breakdown paralyzed planning for an entire day.

It wasn't a competence problem. It was a tooling problem.

If your planners still spend their days rebuilding plans by hand, the question deserves to be asked: what are we asking them to work with?