Building a Rough Master Production Schedule in a Supply Chain

From an aggregate plan, a planner must disaggregate the available information and build a rough master production schedule (MPS) that identifies the batches produced in each period at the level of each product family. We return to the Red Tomato example to illustrate a simple approach to disaggregate an aggregate plan. Although this approach is not necessarily optimal, it is simple to implement and allows for a feasibility check. More sophisticated methods (e.g., see Bitran and Hax, 1981) are available if a planner wants to search for better solutions. These methods, how­ever, are difficult to implement and may not be able to reflect all the complex realities. For this reason, we propose this simple approach.

Consider the aggregate plan in Table 8-4. The plan calls for a workforce of 64 and a pro­duction of 2,560 aggregate units in Period 1. We know that the production constraint is feasible at the aggregate level, but we will need to check feasibility at the disaggregate level. The first step is to divide the production quantity of 2,560 across the six families. We do so in the ratio of expected sales (using percentage share from Table 8-1), as shown in Table 8-9 (see worksheet Chapter8-Table8-9). Thus, the plan is to produce 256 units of Family A in Period 1 because it represents 10 percent of sales. The next step is to identify the number of planned batches for each family. To get the feasibility of the plan, we divide the planned production quantity by the aver­age batch size and then round the answer down. For Family A, the planned number of setups (batches) is thus 256/50 = 5.12 rounded down, which equals 5. As a result, the average batch size of Family A produced in this period will be larger than 50 (about 51). We similarly obtain the planned number of setups (batches) for each of the other families in Period 1, as shown in Table 8-9. To check the feasibility of the planned schedule, we calculate the setup time and the produc­tion time for the planned number of batches and units of each product family. From Table 8-9, the total planned production and setup time is 10,231.4 hours (209 for setup + 10,022.4 for pro­duction). Given the 64 people planned, the available production time in the period is 64 X 160 = 10,240 hours. The planned schedule thus seems feasible.

Source: Chopra Sunil, Meindl Peter (2014), Supply Chain Management: Strategy, Planning, and Operation, Pearson; 6th edition.