Cycle Time Is Not A Capacity Promise

There are two numbers in a cleaning machine purchase. One is the cycle time, measured to the second and written into the contract. The other is the output, which appears in the business case and then in the monthly report. Between them sits about twenty percent, and nobody signed up for it.

I think the cycle time is the wrong thing to put in a contract, and I want to argue that properly rather than just complain about it.

The Number Everyone Signs

A cycle time is easy to define, easy to measure and easy to argue about, which are three good reasons it ends up in the acceptance document. The machine runs a hundred parts at the specified interval, a stopwatch confirms it, and the machine is signed off.

The difficulty is that the sign-off condition is a machine with nothing else happening. Parts arrive on time, nothing stops, the correct variant is loaded, and every part passes first time. None of those four conditions is true for a full shift, and all four are outside the definition of the cycle.

What It Leaves Out

Four things, and each of them is normal rather than exceptional.

The machine stops for filters, for a bath dump, for a nozzle set, for a jam. On a washer these are short and frequent, which is exactly why they get underestimated: no single event looks like a breakdown.

The machine changes over to another variant and waits for the first-part check. During that time it is available and producing nothing.

The machine rewashes parts that did not pass. Each of those consumes two cycles and returns one part.

The machine stops for a few seconds because a part was presented at the wrong angle or a sensor needed a wipe. Nobody records those, and collectively they take a real share of the shift.

Take a 450-minute shift and a 60-second cycle. That is 450 parts on paper. Deduct half an hour of stops, twenty minutes of changeover and a five percent rework rate, and the same machine delivers around 360. The cycle never changed. The capacity did.

Why A Washer Loses More Than Most Machines

Three properties make this worse on cleaning equipment than on a machining centre.

There is no buffer of finished parts. A machining centre that stops leaves a queue nobody needs yet. A washer that stops starves assembly immediately, because the parts it was going to make are the parts assembly is waiting for. Its downtime costs more than its own lost time.

Maintenance is frequent by design. Filters, nozzles, bath chemistry and pump seals are all consumables on intervals measured in shifts. Individually trivial, together the largest availability loss on the line.

Rework is invisible in reporting. A rewashed part does not appear as a defect; it appears as a part that was produced. A line running five percent rework has lost five percent of its capacity and has no record of it anywhere.

When Cycle Time Really Is Capacity

I am not arguing the cycle time is meaningless. It is the right measure in three situations.

When the machine is the constraint and everything else has slack, the cycle is the throughput. When the line runs one part for weeks, changeover disappears from the arithmetic. When the process is stable enough that rework is below one percent, the third loss is noise.

The problem is that most plants assume all three conditions hold before they have measured any of them, and then discover the gap in the first quarter of production rather than in the business case.

My Position

A cleaning machine contract should specify four things instead of one: the cycle with its handling boundary stated, the changeover time between two named variants, an expected interval between maintenance stops, and the filter arrangement that allows a change without stopping the line.

Those four describe what the machine contributes to output. The rest of the gap belongs to how the plant runs it, and a supplier should not be asked to guarantee that.

A buyer who specifies only the cycle is buying a number that will be met and a capacity that will not. That is not the supplier's fault, and it is not fixable after the order.

If You Only Change One Thing

Keep two lists from the first month of production, and keep them by hand if you have to.

The first is every stop, with its cause: filter, nozzle, bath, jam, door, sensor. The second is every part that went through twice, with the reason. Those two lists explain almost all of the gap between expected and actual output, and they cost nothing beyond the discipline of writing them down.

Once you have a month of those lists, the argument about cycle time stops being interesting, because you can see exactly where the twenty percent went.