Aggregate shared parts and control versions

Define the planning boundary

Northstar sells a small bottle and a large bottle. Both use one common cap, but each has its own body and label. Shared demand is added only after each parent has been exploded with its own recipe. The sum tells purchasing how many common parts are needed; the separate rows tell the planner who will be affected by a shortage.

A shared part does not imply that finished products are interchangeable. A large bottle cannot cover a small bottle order simply because their caps match. Keep product-specific stock separate. Use a common component pool only for truly identical and approved parts. The planning table should retain both the common total and the contributing parent quantities.

Calculate with explicit rules

Packaging provides a useful unit trap. In this lesson a carton contains six bottles and partial cartons are allowed only for planning consumption: each bottle consumes one sixth of a carton equivalent. Purchasing orders whole cartons. Multiply the total bottles by the fraction, then round at the purchasing boundary. Rounding each product first can increase the order without a physical need.

An engineering change has a date as well as a new part. Northstar changes the large bottle to a new cap in week three; small bottles keep the old cap. The old and new caps cannot substitute. The production start week determines the cap version in this exercise. Do not use the customer shipment date to choose the recipe unless that is the written rule.

Check before committing

When a change is proposed, preserve the earlier plan instead of overwriting its inputs. Compare old and new cap requirements, excess inventory, and missing new parts. A change that looks small at the product level can create a new supply gap if the new part has a long lead time.

For each shortage, record an allocation rule before distributing scarce stock. A proportional split, a due-date rule, and a protected customer rule answer different business questions. The arithmetic can show the consequences, but it cannot select a commercial priority without an explicit policy. State the rule in your memo.

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. Weekly starts small:[12,18,12,6]; large:[6,12,18,12]. One cap per bottle; old cap for all weeks1–2 and small only weeks3–4; new cap for large weeks3–4. Opening old caps40,new caps10. No receipts; lot-for-lot replenishment. Cartons hold6 bottles. 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.

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.

Keep these three ideas

• Combine multiple products while retaining a clear demand trail.
• 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.