Key takeaways
Short answer: Min-max replenishment orders enough to reach a maximum whenever stock falls to a minimum. Reorder point triggers a fixed-quantity order when stock hits a calculated threshold (demand during lead time plus safety stock). Min-max flexes with variable demand; reorder point is simplest for steady demand. On critical spares, the choice decides between stockouts and tied-up cash. See also why asset tags matter more than people think.
Min-max sets a floor and a ceiling for each part. When stock drops to the minimum, you order up to the maximum, so the order quantity varies with how far below max you are. It adapts naturally to lumpy demand because it always tops up to a known ceiling.
Reorder point sets one threshold — the demand expected during the replenishment lead time, plus a safety buffer. Hit the threshold and you order a fixed quantity, often an economic order quantity. It is predictable and simple, which suits steady consumption.
A plant stocks two critical spares. Bearing A is used steadily — two a week, lead time three weeks — so a reorder point of seven plus a safety buffer works cleanly with a fixed reorder quantity. Seal B is lumpy: nothing for a month, then five at once during a campaign. A reorder point keeps mis-firing, so min-max suits it better, topping up to a ceiling sized for a campaign. Same storeroom, two demand patterns, two methods — forcing one method on both would cause either stockouts or overstock.
Steady, predictable usage with a stable lead time: reorder point is clean and low-effort. Lumpy or seasonal demand: min-max adapts better. Either way, the part's criticality sets the safety-stock level on top of the method.
A cheap, fast-to-source part can run lean on either method. A critical, long-lead spare whose absence stops the line needs generous safety stock regardless of method — because the cost of a stockout (days of downtime) dwarfs the carrying cost of holding one more unit.
1. One method for every part. Lumpy and steady demand need different approaches.
2. Safety stock set by feel. It should reflect lead-time variability and criticality, not habit.
3. Ignoring lead-time variation. A reorder point built on average lead time stocks out when suppliers slip.
4. Treating MRO like production inventory. A spare's value is the downtime it prevents, not its shelf price.
Spare-parts availability is a reliability control: the right part on the shelf turns a multi-day wait into a same-shift repair, directly protecting Availability and OEE. The replenishment method is ultimately an uptime decision dressed as an inventory one.
Fabrico links spares to assets and work orders so you can see which parts actually drive downtime and stock them accordingly. Book a demo to connect spares, assets and uptime.
Neither universally — match to the demand pattern and lead time of each part.
It cushions both methods against demand and lead-time variability, sized by criticality.
It sets the safety stock and service level — critical, long-lead spares get more cushion regardless of method.
Yes — stockouts of critical spares extend downtime and cut Availability.
That ties up cash and storeroom space; the goal is the right stock for each part's pattern and criticality.
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