MPS, setup, and capacity

A master production schedule states which finished items the business intends to complete and when. It connects demand planning to the detailed component plan. A clear MPS records good units, due periods, and the policies used to manage inventory. It should not silently mix machine starts with customer-ready output. This lesson begins with perfect yield so that inventory logic is visible. Northstar has small and large bottles, separate opening inventories, and weekly demand. A lot-for-lot MPS adds only the good units needed to avoid negative ending stock. No safety stock or minimum batch is assumed unless a scenario explicitly introduces it. A level plan spreads output across periods. It can reduce sudden load changes, but it may build inventory before demand. It may also fail in an early week even if total output equals total demand. Always test the rolling balance; horizon totals alone conceal shortages that occur before later production arrives. Product mix matters because small and large bottles may consume different amounts of time. A total of fifty bottles is not a capacity measure unless their route times are identical. Multiply each item’s planned starts by its own minutes per start, then add any setup requirements using the stated batch convention. An MPS is a coordination decision. Sales needs a completion promise, purchasing needs dates for component needs, and the shop needs a workload it can execute. If one of these views changes, examine the others. The schedule can remain a useful proposal while an open constraint prevents commitment. Keep a baseline and a revised version for every major scenario. Compare inventory, weekly workload, and late units. A plan with lower total overtime may create more early stock. The right choice depends on stated priorities and constraints; report the tradeoff with numbers instead of declaring one policy universally best. A shift on a calendar is not automatically the time available for production. Breaks, planned maintenance, and other fixed duties may remove time. This exercise supplies usable shift time directly, so do not subtract breaks again. In a real plan, the source of that usable number must be documented. The core case requires twenty nine good bottles. At ninety seven percent expected yield, Northstar plans thirty starts. Twelve minutes per start creates three hundred sixty minutes of running. One thirty-minute changeover makes total load three hundred ninety minutes. Against four hundred eighty usable minutes, the plan has ninety minutes of headroom. Headroom is a quantity of time, not a guarantee of output. A missing part or an unplanned inspection hold can block the job despite spare machine time. Similarly, enough bodies do not create more minutes. Material and capacity are separate feasibility tests that must both pass. Setup depends on the sequence and batch definition. If the shop changes from small to large and then back to small, it may pay two changeovers. In this lesson each additional batch beyond the initial prepared condition incurs the stated setup; the scenario table explicitly tells you the setup count. Do not infer a count from the number of product names alone. Now pause and test the plan with your own hands. Draw a row for each week. Name the unit at the top of each row. Put the input in one place and the result in a new place. Keep a copy of the first plan. Change just one fact, then run the sums once more. Ask what moved, why it moved, and who must act. If a date is too late, say so. If a part is not there, show the gap. If a count is based on an average, do not call it a sure thing. A plan is useful when the next person can check it and act on it. Write a short note that states the need, the choice, the risk, and the next check. Read it out loud to a peer. Ask that peer to find one weak claim. Use the feedback to make the plan clear. Each number should have a unit, a time, and a source in the case. Each change should have a reason. Each open gap should have an owner. These habits help a small team see the same facts and make a sound choice.

1. The planning question

   Original card with the two lesson goals.

   • Choose dated finished-item output while separating target from feasibility.
   • Calculate load from starts and compare it with an honest time budget.
   • Northstar fictional case
2. Inputs and units

   Original table highlighting input quantities and dates.

   • MPS
   • Capacity
   • State timing
3. First calculation

   Original equation card showing the first worked case.

   • Base closing stock0 for both products and weekly capacity margins[360,80,120,60].
   • At400min,base overloads occur in week2 at20min and week4 at40min.
   • Level plans small ending balances[13,6,3,0],large[9,8,7,0];loads[352,352,344,332],all within400.
4. Second calculation

   Original table showing the second worked case.

   • At480min,max starts[37,37,35,37].
   • At420min,loads unchanged;overloads[0,42,120,0] and headroom[30,0,0,102].
   • At10min,loads[330,390,460,270];all fit480 with margins[150,90,20,210].
5. Stress the plan

   Original side-by-side baseline and revised result cards.

   • Change one input
   • Recompute dependent rows
   • Expose the gap
6. Commit with evidence

   Original checklist with an owner and next review date.

   • Retain assumptions
   • Check the result
   • Name the next action