Resource time and unit conversions

Understand the constraint

A capacity number has no meaning without a unit and a period. Twelve minutes per start means that thirty starts use three hundred sixty machine minutes. A half hour changeover contributes thirty more minutes once for the batch. The resulting load is three hundred ninety minutes. Compare that with four hundred eighty usable minutes for the same machine and shift. Headroom is ninety minutes. Do not compare a weekly total with a daily limit, or divide by a count of workers unless the route really permits parallel work.

Usable time must have a clear boundary. If a shift is described as four hundred eighty usable minutes, breaks have already been removed. Subtracting them again understates the capacity. If the calendar instead gives five hundred forty paid minutes and sixty minutes of breaks, the usable total becomes four hundred eighty. Planned maintenance and prior reservations belong in separate rows so another planner can see what changed. Setup may consume both the machine and a skilled person, while unattended run time may consume only the machine.

Interpret the result

A fast way to catch unit errors is to write the units next to every multiplication. Starts multiplied by minutes per start produces minutes. Hours multiplied by sixty produces minutes. A utilization percentage is load divided by usable capacity; it is not a count of good bottles. For the example the planned ratio is eighty one point two five percent. High use does not prove good service, because this machine could still wait for caps or finish after the carrier leaves.

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

Use three shifts with usable time 480, 420, and 480 minutes; starts 30, 25, and 35; run time 12 minutes per start; and one 30 minute setup in each shift. No work can move between shifts in the first run. Then test a 60 minute loss in shift three and moving five starts from shift three to shift two. 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

• Turn route times and calendars into a comparable load.
• 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.