MRP - Material Requirements Planning in Logistics

MRP: The foundation of modern logistics and materials management

Material requirements planning, internationally known as Material Requirements Planning (MRP), is a central procedure for planning and controlling production processes. Originally developed in the 1960s, the concept has evolved from a pure computational process to a fundamental building block of modern ERP (Enterprise Resource Planning) systems. It answers the three crucial questions of production: What is needed? How much is needed? And when is it needed? For warehouse and contract logistics, a deep understanding of the MRP principle is essential, as it directly influences the processes, space utilization and efficiency in the logistics property.

What exactly is MRP and how does it work at its core?

Basically, MRP is a computerized inventory management and planning system. Its main goal is to ensure the availability of materials for production while keeping stock levels to a minimum. The process is based on three central sources of information:

1. Master Production Schedule (MPS): This plan specifies which final products are to be completed and in what quantities and when. It is the direct specification from sales and demand planning.
2. Bill of Materials (BOM): The bill of materials is the "recipe" for a product. It lists in detail all raw materials, assemblies and individual components required for the production of an end product.
3. Inventory Records File (IRF): This file contains precise information about all available materials, including stock levels, goods already ordered (open orders), lead times, lot sizes, and supplier data.

From these three sources, the MRP system calculates the net requirement for each individual component. It determines the gross demand from the production program, compares it with the available stock and open orders, and plans the orders, taking into account replenishment times, in such a way that all materials are available exactly when they are needed in production.

What role does MRP play in warehouse logistics?

For warehouse logistics, the result of an MRP run is of crucial importance. It dictates the rhythm and structure of operational processes.

• Goods receipt: MRP systems generate order proposals that lead to specific orders. Warehouse logistics must prepare for the delivery of these orders. The system specifies which items arrive in what quantity on which date. This enables precise personnel and resource planning at the goods receipt gate and for the storage processes. A well-functioning MRP system prevents unforeseen deliveries that can lead to chaos and overload.
• Storage space allocation and utilization: Since MRP aims at "just-in-time" provision, materials are ideally not stored for a long time. This has a direct influence on the requirements for the logistics property. Instead of huge block warehouses for raw materials, more dynamic systems such as pallet racks, flow racks or even cross-docking areas are often needed to ensure fast material handling. The key figure inventory turnover frequency is directly positively influenced by an efficient MRP.
• Picking and provisioning: The output of the MRP system is the basis for production supply. The warehouse must pick the calculated net requirements on time and feed them to production. This can be in the form of pre-assembled assembly kits or the direct provision of pallets on the production line. Errors or delays in the warehouse have a direct impact on compliance with the production schedule.

Question for practice: How does inaccurate inventory management in the warehouse affect the MRP system?

Answer: Inaccurate inventory data is pure poison for any MRP system. If the warehouse reports a higher stock than physically available ("phantom inventory"), the system incorrectly assumes sufficient availability and does not trigger an order. The result is a sudden shortage of materials, which leads to expensive production shutdowns. If the reported stock is lower than the real one, the system orders material unnecessarily, resulting in unnecessary storage costs and capital commitment. Permanent inventory or cycle-counting procedures are therefore essential for MRP-controlled companies.

MRP and the requirements for modern logistics real estate

The principles of the MRP also shape the physical infrastructure, i.e. the hall itself. A logistics property that works for an MRP-controlled company must be more than just four walls and a roof.

• Flexibility of space: The required storage space for raw materials and finished goods fluctuates depending on the production program. A modern hall should allow for areas that can be flexibly divided in order to be able to set up buffer warehouses or staging zones as required.
• Proximity to production: The connection to the production site is crucial. Ideally, the warehouse is directly connected to the production hall to minimize transport routes. For external logistics service providers, geographical proximity and excellent transport connections are a decisive location factor.
• Technical equipment: The implementation of warehouse management systems (WMS) that communicate seamlessly with the higher-level ERP/MRP system is a must. Automated conveyor technology, connection to automated guided vehicles (AGVs) and a robust WLAN infrastructure for mobile data collection (MDE) are often standard today.

What is the difference between MRP I, MRP II and ERP?

The development of the systems shows a constant expansion of the planning focus:

• MRP I (Material Requirements Planning): This is the original concept that focuses purely on material requirements planning and inventory management.
• MRP II (Manufacturing Resource Planning): In the 1980s, MRP I was expanded to take into account other production resources such as machine capacities (Capacity Requirements Planning - CRP) and personnel in addition to the material. MRP II integrates materials planning into a broader business context, including financial and business planning.
• ERP (Enterprise Resource Planning): ERP systems are the next evolutionary stage. They integrate all of a company's business processes—from finance, human resources, sales, and marketing to the entire supply chain—into a single, centralized database. Today, MRP II is a core module of most ERP systems (e.g. in SAP S/4HANA, Oracle NetSuite or Microsoft Dynamics 365).

The role of the contract logistics provider in the MRP environment

For a contract logistics service provider that takes over the warehouse and production supply for a manufacturer, understanding the customer's MRP system is existential. The service provider becomes an integral part of the customer's supply chain.

• Data exchange: A seamless IT connection via EDI (Electronic Data Interchange) or API interfaces is essential. The logistics provider receives the demand and staging lists directly from the customer's MRP system and reports back inventory changes, incoming and outgoing goods in real time.
• Service Level Agreements (SLAs): The performance of the logistics provider is measured against hard key figures derived directly from the MRP requirements: delivery reliability, inventory accuracy, picking quality and response times.
• Value-added services: Often, the contract logistics provider not only takes care of the storage, but also upstream assembly activities, quality controls or the assembly of production kits – all timed by the specifications of the MRP.

Question for practice: What is the advantage of outsourcing production logistics to a specialized service provider in an MRP environment?

Answer: The main advantage lies in the focus on core competencies. The manufacturer can concentrate on production, while the logistics expert can make full use of its efficiency in warehousing, picking and transport. A professional contract logistics provider can often ensure higher inventory accuracy and delivery reliability through specialized processes and economies of scale, which increases the stability of the entire MRP process. It also provides flexibility in the face of fluctuating demand, which is often difficult for a manufacturing company with its own logistics to map.