You already know the quoted lead time was wrong. What’s less clear is why, and whether it was predictable.
It usually was. Not because the supplier was dishonest, but because the number they quoted was a best-case estimate presented as a typical one. The conditions that make it accurate are rarely all true at the same time, and most suppliers don’t flag that when they quote.
Understanding what’s actually inside a lead time estimate is the difference between planning around a number and planning around a range with known risk factors.
The quoted number assumes everything goes right
A lead time quote is built on a stack of assumptions: the die or mold is already cut, the compound is in stock, the production queue has available capacity, first article passes on the first submission, and nothing changes on the drawing between order placement and shipment.
In a straightforward reorder of a qualified part, most of those assumptions hold. That’s when suppliers hit their quoted lead times, and it’s also the scenario the number was built around.
Custom parts, new profiles, new compounds, new programs, almost never hit all of those assumptions. Tooling takes time. Compounds that are theoretically in stock run out or get allocated to a larger customer’s order. Production queues shift. First article submissions fail on a dimension and the revision cycle adds weeks. The lead time that was quoted for a clean reorder gets applied to a program that has none of those conditions, and the result is predictable.
Tooling is the variable that surprises people most
When a supplier quotes lead time on a new custom part, the tooling time is either included in that number or it isn’t. If it isn’t stated explicitly, ask, because the difference matters by weeks, not days.
A new extrusion die runs two to three weeks in most cases. A compression or transfer mold runs three to four. Anything more complex than that can run longer. These aren’t delays, they’re the actual time the work requires. But they get absorbed into a total lead time number that the customer reads as time-to-shipment, when it’s really time-to-tooling-complete plus time-to-first-article plus time-to-approval.
Those stages don’t overlap. Each one completes before the next one starts, and each one has its own variables.
First article is where schedules go quietly wrong
A first article submission that passes moves the program forward. One that fails restarts a portion of the clock, tooling adjustment, another production run, another sample shipment, another review cycle.
Most program plans don’t account for one revision cycle, let alone two. The assumption is that first article passes because the drawing was clear and the supplier is competent. Both of those things can be true and first article still fails, because rubber behaves in production differently than it does in a CAD model. A tolerance that’s achievable in isolation doesn’t hold when the compound shrinks asymmetrically during cure. A cross-section that looked fine on paper creates die flow variation that shows up in dimensional measurement.
None of that is unusual. It’s normal rubber manufacturing, and experienced teams plan around it. The programs that get hurt are the ones that treated first article as a formality.
Capacity is invisible until it isn’t
A supplier’s production queue at the time of quoting is not the same as their production queue when your order is ready to run. Larger customers, expedited orders, equipment downtime, raw material delays, all of it affects where your job sits in the schedule, and none of it is visible from the outside.
This is especially true when a supplier is managing offshore production. Container cycles, customs holds, and port congestion add variability that doesn’t appear in a lead time quote because the supplier genuinely doesn’t know when it will affect them. The number they give is an average. What you get is whatever the actual conditions are on that particular shipment.
Domestic production doesn’t eliminate capacity variation, but it shortens the distance between a problem and a solution. A scheduling conflict that adds a week to an offshore program adds a day or two domestically, because the communication is direct and the options for recovery are closer.
The questions that produce a more honest number
Before accepting a lead time quote, ask the supplier to walk through the assumptions behind it.
Is tooling included, and what’s the tooling lead time specifically? What’s the current production queue for this type of part? What happens to the schedule if first article requires a revision? What’s the lead time on the raw material compound, and is it in stock today?
A supplier who can answer those questions with specifics, not ranges and hedges, has actually thought through the program. One who can’t is quoting a number they hope will hold and dealing with the exceptions later.
The honest lead time is the one built on stated assumptions. That number is almost always longer than the first one quoted. It’s also the one worth planning around.