Lead times
A minimum order quantity is a schedule wearing a price tag
A minimum exists to cover fixed costs that do not scale down. Some of those costs are tooling, which the rest of this site is about. The others are time on a machine that is not making anything, and they are the reason a supplier can be entirely reasonable and still refuse your order.
What a changeover is
The bill a small order pays in full
Strip and mount
The previous tool comes out, yours goes in, and the machine is aligned and clamped. On a large press this is measured in hours, not minutes, and the press earns nothing for all of them.
First article
The first units are made to be measured, not to be sold. On a tight tolerance this can run to dozens of parts and a metrology bench before anything is signed off.
Purge and settle
A moulding tool runs cold at first and the material ahead of yours has to be purged out. Those units are scrap by definition, and they are charged to your run.
Strip again
At the end of your run the tool comes out and the next customer’s goes in. The same hours, at the other end, and they belong to your order too.
Every one of those is the same cost whether your order is 500 units or 50,000. Divided across 500, it is a real part of your unit price. Divided across 50,000, it disappears. That is the whole of what a minimum is pricing.
Scheduling
The part of a lead time nobody quotes
A quoted lead time is usually the RUN time plus a margin. It is not the wait for a slot. A small order goes in when it fits between two larger ones, and if it does not fit this month it waits for next month, which no line on the quotation describes.
Ask for the slot, not the lead time
The useful question is not how long production takes. It is what week your run is scheduled for, and what it is queued behind.
Ask what moves it
A run can usually be brought forward by paying for the changeover directly rather than amortising it. Some suppliers will quote that; most will not offer it unasked.
Ask about the split
Two shipments of 500 from one run of 1,000 costs one changeover and two freights. It is often cheaper than two runs of 500 and almost nobody proposes it.
Where this stops being arithmetic
Some minimums are cost. Some are a filter. The number looks identical.
A minimum set to recover a changeover is arithmetic, and you can negotiate it by changing the arithmetic: one run, two deliveries, or a paid changeover. A minimum set to keep small customers away is a business decision, and no amount of arithmetic moves it. Nothing on this page can tell you which one you are looking at. A supplier who will itemise the changeover is almost certainly in the first group.