A ramp that looks smooth on a chart can be brutal on a floor. The realistic curve is the one built from the pilot, not from the demand plan.
Ramp plans are usually drawn backwards from a launch date. That is understandable and it produces a curve that ignores the two things that actually limit early output: material lead times and process learning.
Material is the harder constraint because it is fixed by other people. The longest lead time in the bill of materials sets the earliest possible rate, and no amount of overtime moves it. Which is why the ramp discussion belongs in the same meeting as the material commitment discussion, not two weeks later.
Process learning is softer but real. First units take longer, first batches produce corrections, and operators get faster in a predictable way. A ramp that assumes target cycle time from unit one will miss, and the miss will be blamed on the supplier rather than on the plan.
The workable pattern is a stepped ramp with review points: a pilot, a first production batch at a modest rate, a review, then increases at agreed intervals with the forecast firm enough to buy material against. It reaches full rate slightly later than the optimistic curve, and considerably earlier than the optimistic curve actually would have.
— GANI Manufacturing engineering team