Overall flow matters – not the fullest station

A highly utilised instrument or a full bench may appear productive. For the laboratory process as a whole, however, the decisive question is whether samples, data and decisions move reliably through every connected step. If one stage starts or passes on more work than the next constrained stage can absorb, queues, additional handovers and less visible delays can develop.

The white paper “Lean Labor – Die Architektur guter Arbeit” puts it this way (editorial translation from German): “The fullest stage is not the best one. The best stage is the one that supports the overall flow most reliably, even under typical variability, friction and disruption.”

In analytical quality control, instrument schedules, qualified people, methods, reagents, sample preparation, data processing and review are interconnected. A free analytical instrument does not therefore automatically mean that laboratory capacity is available. Nor does the local utilisation of one station show how quickly the route to a reliable decision is actually completed.

One possible approach is to place visible limits on work in progress and position buffers deliberately. Work is then not released without limit towards a constrained stage. Demand, available capacity and downstream steps are considered together. Functional reserve remains available for typical variation, disruption, maintenance or urgent work.

5S can support flow when defined locations, unambiguous states and task-specific preparation make it visible what is waiting, what is being processed and what can be handed over in a complete state. The method does not, however, replace capacity decisions or technical prioritisation.

Whether a limit helps needs to be assessed locally: how much work is in progress at the same time? Where do queues form? How long do samples or data wait between steps? At the same time, are stability, storage, test deadlines, quality and urgent needs protected? There is no universally optimal utilisation level.

Observe one recurring process from intake to decision: which station looks full – and which stage actually determines the overall flow?