关键要点
- Measure the full chain, including clearance, testing and release.
- Variability matters more than the average for stock planning.
- Testing and release time is a real and often ignored component.
The full chain
Contracting, production or allocation, loading window, ocean or land transit, discharge, customs clearance, inland transport, receiving, sampling, laboratory turnaround and release. Only the transit portion is normally quoted.
Average versus variability
Safety stock is driven by variability, not by the mean. A route averaging thirty days with a five-day spread needs far less cover than one averaging twenty-five days with a twenty-day spread.
Reducing lead time honestly
Pre-clearance preparation, advance document submission, pre-shipment testing and standing sampling arrangements shorten the chain. Shortening it by removing verification steps only relocates the risk.
需要核查的内容
- Each chain step measured from historical records
- Variability, not just average, used to size safety stock
- Laboratory turnaround included in the lead time model
需管理的风险
- Stock-out because clearance or testing time was excluded from planning
- Safety stock sized on average performance
- Unmeasured lead-time drift after a route change
常见错误
- Using the supplier's quoted transit time as the planning lead time
- Ignoring document preparation and legalisation time
- Cutting verification steps to recover schedule
常见问题
How much history is needed to model lead time?
Enough shipments on the same route to see seasonal and congestion variation. A handful of shipments gives an average but not a reliable variability estimate.
Is a longer lead time always worse?
No. A long but highly predictable lead time is easier to plan around than a shorter, erratic one.