Start with something familiar
Imagine planning a meal for a group of friends. You need to know who is coming, what each dish uses, which food is already usable, and when the oven is free. A full pantry does not help if the missing ingredient arrives after dinner. Nor does a long recipe prove that you can cook it before guests arrive. Manufacturing planning applies that same care to parts, unfinished work, available time, and the promises made to customers.
Define the planning boundary
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.
Calculate with explicit rules
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.
Check before committing
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.
- Read case inputs
- Calculate the baseline
- Change one assumption
- Check and decide
Northstar worked case
All data below are fictional and complete for this calculation.
| Input group | Exact case data |
|---|---|
| 1 | Small demand weeks1–4:[20,30,25,25],opening10. Large demand:[10,15,15,20],opening5. No scheduled receipts. |
| 2 | Perfect yield; lot-for-lot; small runtime8min,large12min; ignore setup only in this lesson. Weekly usable capacity500min. |
- 1. Small MPS=[10,30,25,25]; large=[5,15,15,20].
- 2. Weekly loads=[140,420,380,440] minutes.
- 3. Total production145 good units; total load1380 minutes.
Base closing stock0 for both products and weekly capacity margins[360,80,120,60].
Assumptions
- Only the stated supply and demand exist; no hidden safety stock or open orders.
- Timing, yield, lot size, and setup follow the explicit case; do not import another lesson’s assumptions.
Where this can fail: This deliberately small model checks planning logic. It cannot establish supplier reliability, customer priority, or a statistical service guarantee.
Build, test and explain a plan
Northstar asks you to build a reusable planning model, not just report one answer. Use only the inputs below and the worked example. Small demand weeks1–4:[20,30,25,25],opening10. Large demand:[10,15,15,20],opening5. No scheduled receipts. Perfect yield; lot-for-lot; small runtime8min,large12min; ignore setup only in this lesson. Weekly usable capacity500min. Keep full precision in intermediate calculations and round only where the case requires whole units. Use separate tabs or clearly labeled paper grids for the baseline and each scenario. The eight hours are a self-paced practice estimate, not an experimentally validated duration.
Use paper or a spreadsheet. The estimates below include the study and worked example already on this page.
| Estimated hours | Activity |
|---|---|
| 0.5 | Study the terms and mark each input with its unit, date, and status. Write a half-page statement of the boundary of the model and list facts that are deliberately excluded. |
| 0.5 | Recalculate every worked-example step by hand. Compare the hand calculation with your model and explain any difference before moving on. |
| 3 | Build separate four-week stock tables and a combined resource table. Build formulas, a visible input table, and a reconciliation row. Add notes so another learner can reproduce the model without asking you for missing data. |
| 2 | Test weekly capacity400min; separately test small level production[23,23,22,22] and large[14,14,14,13]. Carry shortages as backlog rather than negative physical stock. Save each scenario separately. Compare quantities, dates, and any unresolved shortages. Trace the change from its input through every affected calculation. |
| 1 | Write a one-page decision memo naming the baseline result, the preferred action under each scenario, the remaining uncertainty, and the evidence required before execution. Do not invent costs or customer priorities. |
| 1 | Create a five-minute teach-back with one diagram and one checked number. Then use a second independent calculation to audit the model and revise unclear assumptions. |
Your deliverables
- An auditable input and calculation table with baseline and scenario tabs.
- A comparison table with numerical checks, dates, and unresolved gaps.
- A decision memo and a short teach-back using the supplied facts.
Check your practice work
- 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.
Keep these three ideas
- Choose dated finished-item output while separating target from feasibility.
- A numerical answer must retain its unit, timing, and assumptions.
- Use the scenario checks to test the model before using it to support a decision.
Common mistakes
- Combining values that refer to different dates or different physical units.
- Treating a modeled proposal or expected output as confirmed usable supply.
Optional video study
Choose dated finished-item output while separating target from feasibility.
- A master production schedule states which finished items the business intends to complete and when
- Small MPS=[10,30,25,25]; large=[5,15,15,20].
- Base closing stock0 for both products and weekly capacity margins[360,80,120,60].
First half: definitions and baseline.
Open the module media & quizPut this idea to use
Carry your assumptions into a practical tool, then compare your result with a short guide.
Open a related planning toolRead the related planning guidePractice with the planning gameThis saves a completion marker in this browser only. It does not verify time spent.