Resource planning in production — capacity, finite scheduling, lean

Resource planning is the practical art of allocating people, machines, tools, materials and time across competing production demands. In the standard MRP-II view it lives inside the production-planning module of the ERP; in lean production it lives on the shop-floor Kanban board; in complex make-to-order operations it relies on APS optimisation. All three views are valid, and most DACH Mid-Market manufacturers run a combination — ERP for the master plan, lean for the day-to-day execution, APS where bottlenecks demand it. This page explains capacity planning under finite and infinite assumptions, the role of lean methods alongside ERP, and the practical integration patterns that work in mid-market manufacturing.

Capacity planning: finite vs infinite

The MRP-II logic in most ERPs runs by default with infinite-capacity assumptions: schedule each production order against its required lead time and assume the work centres can absorb it. Infinite-capacity scheduling is computationally cheap and produces a clean master plan — but it lies when the work centres are loaded close to capacity. Finite-capacity scheduling respects the real availability of each work centre, shifts overloaded orders forward or back, and produces a plan that is achievable rather than aspirational. Modern ERPs (SAP S/4HANA, Microsoft Dynamics 365 F&O, abas, proAlpha, oxaion) support both modes, often with a coarse finite plan in the ERP and detailed finite sequencing in an APS overlay. Choosing the right mode is a question of how loaded your bottlenecks are: under ~70% loading, infinite is acceptable; above ~85%, finite becomes essential.

Resource types and their interchangeability

Resource planning has to differentiate between resource types. Machines are typically single-purpose with deterministic capacity (one CNC mill, one shift, eight hours minus set-up time). People are multi-skilled with qualification-based capacity (an operator certified on three machines is fungible across them). Tools (moulds, dies, fixtures) are often the hidden bottleneck because one tool can only be in one machine at a time. Materials are constrained by lot sizes, shelf life and supplier lead times. A good production-resource-planning module models all four types and lets the planner see, for any given production order, which resource type is the binding constraint. ERPs vary a lot here: proAlpha and abas handle multi-resource constraints natively; some lighter products treat the work centre as a single dimension and require an APS overlay for realistic planning.

Lean and Kanban alongside ERP

Lean methods (Kanban, pull production, just-in-time, takt-time pacing) operate on a different time horizon than ERP planning. ERP sets the master plan for the next 4–12 weeks; Kanban handles the execution detail at hourly resolution. The two have to coexist without contradiction. A mature DACH manufacturer typically uses ERP / APS for the production schedule and material flow into the shop floor, then drops to Kanban (physical card or digital eKanban) for the last 24–72 hours of execution. The ERP must support the Kanban supermarket logic: replenishment triggered by consumption, fixed lot sizes, fixed safety stock, no MRP push for the Kanban-controlled SKUs. Microsoft Dynamics 365 F&O, SAP S/4HANA, abas and proAlpha support this natively; lighter products may need third-party eKanban add-ons (e.g. Staufen, SCC).

APS for fine-planning depth

Advanced Planning and Scheduling (APS) sits between ERP and shop floor when fine-grained planning depth matters. The APS optimises the sequence of orders against finite-capacity constraints, sequence-dependent set-up times, tool availability, raw-material lots and customer due dates. DACH-relevant APS products include Asprova (Japanese vendor with strong DACH presence), Siemens Opcenter APS (formerly Preactor), ORTEC Production Planner, Felios (German specialist) and INFORM's OPTI suite. Implementation effort and licence cost are substantial — typically 80–400 kEUR for a mid-market deployment — so the throughput uplift needs to justify the investment. The integration to the ERP runs over a documented APS interface (usually OData or REST), with the ERP keeping master data, BOM and routing as the source of truth.

Selection criteria for production resource planning

• Finite-capacity scheduling at work-centre level
• Multi-resource constraints (machine, operator, tool, material)
• Qualification-based operator planning
• Sequence-dependent set-up-time handling
• Tool / fixture availability tracking
• Kanban / eKanban support with replenishment triggers
• Visual planning board with drag-and-drop rescheduling
• What-if scenarios with sandbox plan
• APS interface (OData / REST) for fine-planning extension
• OEE feedback from MES for plan-vs-actual analysis

When APS becomes essential

Practical rule of thumb: APS pays back when (a) one or more bottlenecks are loaded above 85% of capacity, (b) set-up times exceed 15% of total operation time, (c) sequencing decisions visibly affect throughput, or (d) due-date reliability is a competitive differentiator and the ERP's native planning cannot deliver it. Below those thresholds, the right answer is usually to tighten the ERP master data, train the planning team, and harvest the easy wins before adding APS complexity. The premature APS purchase is one of the more common Mid-Market-manufacturing IT mistakes — expensive and often disappointing because the data foundation isn't ready.

Related Topics

• Production planning overview
• Production planning and ERP
• PPS system comparison
• Top ERP for machinery