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.
Words to know: Setup, Capacity, Yield.
Define the planning boundary
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.
Calculate with explicit rules
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.
Check before committing
Aggregation is useful for a first capacity screen but cannot prove a detailed sequence is feasible. Two operations might compete for the same operator, or a curing delay might prevent same-day completion. Use the screen to identify overload and then check important timing relationships before releasing work.
Compare recovery actions in the same units. Ten extra starts add one hundred twenty minutes at this route, before any extra setup. Overtime creates usable minutes only if people, material, and support are available. A subcontract offer needs both a quantity and a confirmed due date to relieve a specific overload.
- 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 | 30 starts;12min/start;1 setup×30min;usable shift480min. |
| 2 | For four shifts,starts[30,36,40,24],setup counts[1,1,2,1],same runtime and capacity. |
- 1. Core load=30×12+30=390min;headroom90min.
- 2. Four loads=[390,462,540,318];margins=[90,18,−60,162].
- 3. With2 setups,max whole starts=floor((480−60)/12)=35.
At480min,max starts[37,37,35,37].
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. 30 starts;12min/start;1 setup×30min;usable shift480min. For four shifts,starts[30,36,40,24],setup counts[1,1,2,1],same runtime and capacity. 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 a four-shift load table and a formula-driven maximum-start column for each setup count. 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 | Reduce usable time to420min; separately improve runtime to10min without changing setup. 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
- 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].
Keep these three ideas
- Calculate load from starts and compare it with an honest time budget.
- 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
Calculate load from starts and compare it with an honest time budget.
- A shift on a calendar is not automatically the time available for production
- Core load=30×12+30=390min;headroom90min.
- At480min,max starts[37,37,35,37].
Second half: scenario comparison and decision.
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.