Understanding Materials Requirement Planning (MRP) Inputs

Materials Requirement Planning (MRP) is a production planning and inventory control system used to manage manufacturing processes. Most MRP systems are software-based. An MRP system calculates how much material is needed and when, based on production schedules. To do this accurately, it requires several key pieces of information as input. Let's look at the essential inputs for an MRP system.

Master Production Schedule (MPS) Input

The Master Production Schedule (MPS) is a crucial input to the MRP system. It details the production plan for finished goods. Specifically, the MPS tells the MRP system:

• What products are to be manufactured.
• How many units of each product are needed.
• When these products need to be ready.

Think of the MPS as the "demand" or the "what to build" part of the MRP equation. Without knowing what you need to produce and by when, the MRP system cannot calculate the required components and raw materials.

Bill of Materials (BOM) Input

The Bill of Materials (BOM) is another fundamental input for the MRP system. The BOM is essentially a recipe or a list of all the components, subassemblies, parts, and raw materials required to build one unit of a finished product. It also shows the hierarchical structure of the product, indicating which components go into which subassemblies.

• The BOM specifies exactly "how" the product is put together and the quantity of each part needed.
• It details the relationships between parent items (assemblies) and child items (components).

The MRP system uses the MPS (what to build) and the BOM (how to build it) to determine the gross requirements for each component and raw material.

Inventory Status File Input

The Inventory Status File is the third critical input to the MRP system. This file provides up-to-date information about the current stock levels of all items, including finished goods, subassemblies, components, and raw materials.

Key information contained in the Inventory Status File includes:

• Current on-hand quantity for each item.
• Quantities of items already on order (scheduled receipts).
• Lead times for ordering or manufacturing items.
• Safety stock levels.
• Allocation of inventory to specific orders.

The MRP system uses the Inventory Status File to adjust the gross requirements (calculated from MPS and BOM) by subtracting the inventory that is already available or expected. This calculation results in the net requirements – the actual quantities that need to be ordered or produced.

Combining the Inputs in MRP

The Materials Requirement Planning (MRP) system takes these three inputs – the Master Production Schedule (MPS), the Bill of Materials (BOM), and the Inventory Status File – and performs calculations to generate planned orders.

Here's a simplified view of the MRP process inputs:

All three inputs are essential. Without the MPS, MRP wouldn't know what demand to plan for. Without the BOM, it wouldn't know which components are needed to meet that demand. Without the Inventory Status File, it wouldn't know if the required components are already available or on the way, leading to potentially incorrect ordering or production decisions.

Therefore, the input component(s) to the Materials Requirement Planning (MRP) system are the Bill of Materials, the Master Production Schedule, and the Inventory Status File. This means "All of the options" is the correct description of the inputs.

Revision Table: Key MRP Concepts

Additional Information: Beyond Basic MRP Inputs

While MPS, BOM, and Inventory Status File are the core inputs for basic MRP, more advanced systems or related planning processes might also consider:

• Routing and Capacity Data: For MRP II (Manufacturing Resource Planning), which goes beyond just materials to include other resources like labor and machinery, information on production routing (the steps involved) and work center capacities is needed.
• Sales Orders/Demand Forecasts: The MPS itself is often derived from sales orders, demand forecasts, and production strategies. These underlying demand signals could be considered upstream inputs.
• Supplier Data: Information about supplier lead times, minimum order quantities, and costs can also be relevant for procurement decisions informed by MRP outputs.

Understanding these primary inputs is fundamental to grasping how MRP functions to determine material needs and schedule production and purchasing activities effectively.