Stock on the shop floor as a symptom of something else

Every pile has a reason and the reason is the target

Walk the floor with the area supervisor and ask about each stack in turn: why is this here, who decided the quantity, and what would happen if it were half of what it is. The answers are informative and rarely flattering. A machine that stops without warning, a changeover long enough that nobody wants to repeat it, a supplying cell that occasionally sends bad parts, a planner protecting themselves against a schedule that changes weekly. Write the reason on a tag attached to the stack, so the conversation is about the underlying problem rather than about the stock figure.

Lowering the level deliberately to find out what breaks

The classic image is water covering rocks, and the practice that follows from it is deliberate and slow. Remove a container from a loop, watch what happens over several weeks, fix whatever stopped, then remove another. What makes this hard is not the technique but management's tolerance: the method works precisely because it causes a stoppage, and the stoppage arrives on a day that is already difficult. Agree in advance who can call a pause, how a genuine customer risk is protected, and that an exposed problem counts as a result rather than as a mistake by the team.

Storage turns a temporary buffer into a permanent asset

Once racking is installed, containers are bought and someone is employed to look after an area, the buffer has acquired defenders and a budget line. Space behaves the same way: any area created for overflow fills, then justifies itself by being full. This is the strongest practical argument against approving the extra mezzanine, the outside container or the additional stores headcount while an improvement effort is running. Where extra space is genuinely needed for a temporary reason, put an end point on it and name the person who will confirm it has been given up.

The obsolescence sitting in part-finished work

Part-built assemblies are the most fragile stock a plant holds, because they are committed to a specific design and cannot be sold or easily reworked. An engineering change, a superseded component or a lost programme strands them, and the loss is usually discovered long after the decision that caused it. Two habits help: check what part-finished quantities exist before approving a design change and specify how they will be dealt with, and review aged part-built stock regularly with someone senior enough to authorise writing it off without treating the decision as a personal failure.

What genuinely improves when stock comes down

Elapsed time through the plant shortens because there is less queue ahead of each operation. Quality feedback arrives sooner, so a process drift affects fewer pieces before someone notices. Less material is damaged, lost or found rusting. Space appears without a building project. Be sceptical of two false results: stock pushed onto a supplier who now holds it on your behalf, and stock moved into an external warehouse so it no longer appears on the floor. Neither reduces the exposure, and both remove the visibility that made the problem addressable.

Frequently asked questions

How is this different from setting stock levels and reorder rules?

Those are planning policies concerned with how much to hold and when to replenish, and they belong with the supply chain function. The improvement question is narrower and more awkward: what weakness inside the factory made that level necessary. A well-calculated buffer covering an unreliable machine is still evidence of an unreliable machine. Both activities are legitimate, but only one of them removes the underlying cause, and a plant that does only the calculation never gets to it.

Is it safe to reduce stock when our own suppliers are unreliable?

Not uniformly. Separate what protects you against external supply from what compensates for problems inside your own walls, because you control the second and only influence the first. Reduce internal buffers while leaving inbound protection alone, at least initially. Where an external supply risk is severe, holding cover is a rational decision that should be recorded as such, with a named owner and a periodic review rather than being left to grow quietly.

Our finance team likes stock because it supports the reported result. How do we respond?

Take the point seriously rather than dismissing it, because under conventional absorption accounting the effect is real in the short term. The counter-argument is about what happens next: written-off obsolete material, cash tied up, space consumed and delivery lead times that lose orders. Involve finance in the improvement work from the start, agree how the transition will be reported, and get the write-off exposure on the table early rather than discovering it at the year end.