What does MRP do, and what does APS do?
Material Requirements Planning
Determines what raw materials and components are needed, when, and in what quantities. A logistics question: what needs to be procured and produced.
Production Planning
Determines in what order and at what time operations should be carried out on machines, labor, and tooling. A scheduling question: how to produce efficiently.
The two systems work in sequence: MRP determines what needs to be produced, APS specifies when, on which machine, and in what order.
Material planning: POEM MRP · Production planning: POEM APS
When is MRP enough on its own?
For less complex facilities, the MRP module is often sufficient:
- The product structure is simple and stable
- Production lead times are predictable and change little
- Capacity is generally not constrained and machine downtime is rare
- The order book is consistent with no urgent interleaved orders
- Sequencing optimisation offers no meaningful savings
When do you need APS alongside MRP?
APS becomes necessary when managing capacity constraints exceeds what a person can reasonably oversee:
- Production runs across multiple machines and parallel processes simultaneously
- Capacity utilisation regularly reaches or exceeds 80–90%
- Deadlines follow each other closely and delays have direct business consequences
- The order book changes dynamically with frequent urgent orders coming in
- Changeover times are sequence-dependent and optimising them yields meaningful savings
- Coordination is required across multiple sites or production units
The tell-tale sign: when MRP is no longer enough
When the production manager spends an increasing share of their day manually reconciling Excel spreadsheets with ERP data…
When maintenance reports routinely rewrite the next day's plan…
When a single urgent order takes hours to reschedule around — these are all signs that the business has outgrown the planning framework MRP provides.
Our POEM APS system works precisely at this layer: it takes the production tasks coming from MRP and, taking all capacity constraints into account, generates an optimal and executable production sequence — then replans within minutes whenever circumstances change.
Summary
MRP and APS are not competitors. MRP is the tool for material requirements planning; APS is the tool for production planning. In any serious manufacturing company, the two work side by side, integrated with each other.
The question is always: is MRP still sufficient on its own, or does the complexity of your production already demand APS as well? How many manual interventions does the plan require each week? What proportion of committed deadlines are actually met? How much time is spent on rescheduling?
Would you like to assess whether your company needs APS alongside MRP?
Get in touch and our expert will help you find the right solution.
Want to explore this topic in more depth? Join our free webinar! We'll be discussing live when it makes sense to add APS to your MRP setup — and what that looks like in practice.