Calendars, starts, and expected good output

Understand the constraint

Northstar has next week demand of fifty one bottles plus six separate prior backlog bottles. Eighteen usable bottles are on hand and ten more arrive before demand. The net requirement is fifty one plus six minus eighteen minus ten, or twenty nine good bottles. If the forecast already contains an order, do not add that order again. Keep old backlog on its own row. A receipt after the due time cannot serve as opening stock merely because it appears in the same weekly report.

At an assumed yield of ninety seven percent, the planning start quantity is the ceiling of twenty nine divided by point nine seven. That equals thirty starts. Expected good output is twenty nine point one, which is an average calculation and not a batch guarantee. Real good output is an integer. If only twenty eight bottles pass inspection, the plan still has a one bottle gap. Do not convert expected output into a firm shipment without inspection or an explicit risk policy.

Interpret the result

Calendars tell us when usable work can occur. A resource with an expired qualification cannot be treated as qualified simply because it has spare hours. Likewise, a crew available after the truck departure cannot support that departure. Build separate rows for machine minutes, qualified crew minutes, inspection release, and dispatch cutoff. In this lesson every run starts and ends within its assigned day. More detailed job sequencing belongs in a subsequent scheduling review, but the date gates must already be visible.

Create one row for each resource or stock position and one column for each time bucket. Put the unit in the row label and keep inputs separate from calculated results. Begin with the smallest case you can verify by hand, then extend the same equations across periods. Give every receipt a usable date and every requirement a due date. Preserve the baseline before changing an assumption so the effect of an action is visible.

Validate and explain

Use a second check that follows the physical story. Count what enters, what is used, what waits, and what leaves. A plan that balances in total can still fail at an earlier cutoff. Mark any unavailable input as an assumption rather than filling it with a convenient zero. A zero means a known absence; an unknown value means the promise remains conditional. This difference belongs in both the model and the decision note.

A calculation becomes useful when it changes a choice. Compare the baseline with at least two scenarios, identify the first limiting condition in each, and explain what additional resource would actually change delivered output. Keep a service measure alongside any cost or value measure. State whether the choice maximizes value, protects a commitment, or reduces the worst shortfall. A different goal can produce a different sensible answer from the same facts. Finish by testing one deliberately wrong proposal, such as a receipt used before arrival or a quantity above a resource ceiling. Your table should make that error visible. Save the rejected proposal with a short explanation, because it teaches a reviewer how the checks work. The eight hours include rebuilding, scenario work, writing, and teach-back; they are self-paced estimates rather than measured completion times. Faster readers should deepen the checks instead of merely rereading the text.

Build, test and explain a plan

Build a three-day ledger with opening usable stock 18, receipts 10/0/0 before each day’s demand, demand 20/20/11, and the old backlog 6 due on day one. Planned starts are 0/20/10. Production is released before that day’s demand. First use expected yield 97%; then use observed good output 0/19/9; then delay the initial receipt to day two. Allow backlog, never negative physical inventory. The eight-hour estimate covers an original workbook or paper model, scenario calculations, checks, and communication; it is not experimentally validated.

Use paper or a spreadsheet. The estimates below include the study and worked example already on this page.

Your deliverables

• A reproducible planning table with inputs, formulas, units, and checks.
• A scenario comparison with service and resource consequences.
• A decision memo and short teach-back outline.

Keep these three ideas

• Separate expected output from guaranteed availability.
• Keep quantities, resource units, and due times explicit.
• Recheck all constraints after a change, and report remaining uncertainty.

Common mistakes

• Treating capacity in a later time bucket as available before the due gate.
• Calling an expected or conditional quantity a guaranteed shipment.