Aggregate Production Planning and Master Scheduling Techniques
Aggregate Production Planning Techniques
There are many models to perform aggregate planning, differentiating three groups:
- Intuitive or Trial and Error Models: To get the plan as a reference, one or several plans are developed from the results or past experiences. From them, different improvements are experimented with to try to reduce costs. The trial and error method uses graphs to display the various planning strategies.
- Analytical Models: These are based on mathematical models of two types:
- Mathematical Programming Based: The best known are Holt, Modigliani, Ruth, and Simona. We also have models based on linear programming and transportation, including Bowman. Finally, we have models based on goal programming, such as Goodman.
- Heuristics: The best known, the management coefficients model, makes a series of data points for labor, production, and decisions that were successful in the past. Using regression techniques, it reduces those equations that best fit the historical data. As for parametric programming, the goal is to find a routine that determines decision rules for labor and production. One model used in practice is PSH (Production Switching Heuristics).
- Simulation Models: The most used models are:
- Model Search Rule: This takes as its starting point an aggregate plan characterized by certain values that meet the needs of production and calculates the total costs involved.
- Programming Model Simulation: Similar to the above, but is used only for specific cases of seasonal demand.
The Master Production Schedule
The master production plan specifies the amounts and dates of production in relation to specific products, quantities and dates in relation to the components purchased or processed, the sequence of work or individual orders, and finally the short-term assignment of resources or individual operations.
To build the master plan, the first step is to decompose the aggregate quantities into units of final product, reflecting what time and what activities are needed to develop them.
Once you’ve built all this, you will get a proposed master plan that will be valid if the load generated is compatible with the available capacity. In case you have capacity, the proposed master plan becomes final. If not, take additional transient steps to increase capacity or change the master production plan proposal.
This master plan will be a viable starting point for planning materials.
The process used for the breakdown consists of 5 phases:
- Decomposition of product families plan added.
- Accrual of units of products in time intervals.
- Sizing batch ordering and setting of dates for achieving them.
- Setting the initial master production schedule based on demand.
- Determining the availability to engage with customers.
To check whether the proposed master production schedule is reliable from the point of view of capacity, we have two techniques:
- The capability list: Calculate the loads that will cause the master production.
- The resource profiles: Similar to above, but the loads are distributed among the periods covered by the time the final product and supply components.