Overproduction: the waste that looks like a good day's output

Making early counts as much as making too much

Plants readily accept that building parts nobody ordered is wasteful, and resist the idea that building next month's order this week is the same problem. It is. The material is bought sooner, the capacity is spent on work that could have waited, the output occupies space, and if the order changes the plant is holding something it cannot sell. Building ahead also consumes the capacity that would otherwise have absorbed a genuine urgent requirement, which is why plants that build ahead so often find themselves expediting. The timing dimension is the one worth policing, because the quantity dimension is usually obvious.

The measures that pay supervisors to overproduce

Where an area is judged on machine utilisation, hours absorbed, or unit cost falling as run length rises, the reporting system is straightforwardly instructing people to build ahead. Under conventional absorption accounting, production that goes into stock rather than out of the door improves the reported result, so a month that ends with the plant full of unsold subassemblies can look better than one that ends clean. Nothing on the improvement side will hold against that until the measures change. This is a conversation for the plant manager and the finance function, not something a supervisor can resolve locally.

The setup argument and how to test it

The most common defence for a long run is that the machine is set and it would be wasteful to change over again. Sometimes that is true, particularly at a resource where capacity is genuinely tight. Test it by asking how long the extra output will sit before it is consumed, and what else the machine would have made instead. If the extra pieces will wait months and the machine had other work queued, the run was a transfer of cost rather than a saving. Where the argument keeps recurring, the underlying problem is changeover capability, and that is where the effort belongs.

How surplus conceals every other weakness

A pile of extra parts quietly compensates for scrap, for a machine that stops without warning, for absence, for a supplier who misses deliveries and for a process nobody has stabilised. That is why cutting overproduction feels like breaking the plant: the problems were always there, and the surplus was paying for them. Management has to expect this and treat the resulting stoppages as findings rather than as evidence the change was wrong. Reducing gradually, and fixing what each reduction exposes before going further, is the difference between a controlled experiment and a bad quarter.

Evidence that the plant is building ahead

Look for finished or part-finished items with no customer order attached, completions running ahead of the schedule sequence, an area where stock consistently ages, the despatch and packing area full of things not due to ship, and containers of a component whose parent product is on hold. Ask a planner how often they are asked to bring work forward to fill a machine. Check whether any part has been made more recently than it was last consumed. Each of these is countable and specific, which makes the conversation about a particular decision rather than about a principle.

Frequently asked questions

Is it always wrong to build ahead of demand?

No, but it should be a decision rather than a default. Deliberate building ahead makes sense before a known shutdown, ahead of a seasonal peak the plant cannot meet from current capacity, or to protect a customer during a planned equipment move. What separates that from waste is that somebody named the reason, agreed the quantity, and set a point at which the extra stock is expected to be consumed. Surplus that appears because a machine was free is a different thing entirely.

How do we stop overproduction without leaving machines idle?

Accept that some idleness at non-constraint equipment is the correct outcome, and give supervisors something legitimate to do with the time: changeover preparation, cleaning as inspection, training, maintenance tasks, improvement work. Agree that list in advance, otherwise people will fill the gap with production because it is the only visible option. At the resource that actually limits output, protect the time instead, since idleness there does cost the plant real capacity.

Our sales pattern is lumpy, so surely we have to build ahead?

Lumpy demand is a reason to hold some finished stock deliberately, decided with the commercial side and reviewed as the pattern changes. It is not a licence for the floor to decide independently what to make early. Separate the two: a planned finished-goods position agreed with sales, and a rule that production inside the plant is authorised by consumption or by the schedule. Confusing them means nobody can tell which stock was intended and which simply accumulated.