What is MRP? MRP I & MRP II Defined

Material Requirements Planning (MRP I)

Following the strict APICS definition, MRP (more accurately MRP I, read MRP-one) is a system that helps a manufacturer plan their purchasing and production activities, and when necessary, create the required purchase orders and production orders in time to meet customer commitments.

This leads to the Great Paradox of Manufacturing:

  • An inventory control system helps you maintain an inventory of your materials.
  • An MRP system helps you maintain no inventory of your materials
    (or with MISys you can choose to maintain a minimum-level inventory to protect against unpredictable supply chain interruptions)

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Without an MRP system, manufacturers typically react by purchasing material they might need. With an MRP system, based on their manufacturers purchase material they definitely do need.

Many manufacturing systems combine the distinct functions of MPS (Master Production Schedule) and MRP into one called MRP. It is possible to create an MPS without an MRP, but not possible to create an MRP without an MPS. If you are convinced that the software you are considering performs the functions described here, then strict adherence to the terminology is not that important.

Manufacturing Resource Planning (MRP II)

As the term implies, Manufacturing Resource Planning (aka MRP II, read MRP-two), is an extension to MRP I that goes far beyond planning and acquiring the materials needed for production, but every other resource related to the successful operation of a manufacturing plant, including people and machinery.

Some impressive demonstrations can be made by manufacturing software vendors selling “fix all your problems with one click” systems. In our opinion, MRP II requires a level of sophistication and expense far beyond that of most of our prospective customers. Ford Motors and Caterpillar depend on MRP II to run their manufacturing operations. MRP II is a big job – one best reserved for the big boys.

MISys Manufacturing

MISys Manufacturing is best described as an MRP I system, although it does have a few MRP II-like features, including the powerful Capacity Manager. This tool analyzes the load every active production order is placing on available resources (work centers) and displays where and when capacity overloads are occurring.

Using the tool, you can manually reschedule the offending production orders to take better advantage of available resources.