The master production plan translates the product group targets in the sales and operations plan into periodic production quantities for each product . It is the input for material requirements planning, and all sub-plans are derived from this plan.
Scope
Selection of the master plan scope: Managing only critical products in the master plan, not all products. Criteria for criticality may include revenue share, long lead times, bottleneck resource utilization, or strategic importance.
Seasonal planning: Determining production quantities in weekly or monthly segments.
Rough capacity control: Calculating the load the plan places on critical resources and detecting overruns early.
Frozen period management: Establishing a structure where the short-term plan is unchangeable, the medium-term plan is subject to limited modification, and the long-term plan is flexible. A constantly changing plan is not a plan at all.
Available quantity calculation: This shows how much of the planned production is already tied to orders and how much is open to new orders.
Inventory projection: Seeing how inventory levels will trend over time once the plan is implemented.
Plan revision and impact analysis: To assess the impact of a change on sub-plans and delivery commitments.
Why is a frozen period necessary?
Constant changes to the production plan have three consequences on the field: the number of installations increases, material preparation is wasted, and it's impossible to know when any job will be completed. Moreover, most of the changes stem from non-urgent demands.
The frozen period introduces a cost and an approval mechanism for these changes. Changes are not prohibited; however, it makes visible who is making changes, for what reason, and at what cost . This transparency alone significantly reduces the number of changes.