A plant delivering 68 percent OTIF is not a plant with a scheduling problem. It is a plant with a buffer problem. Every scheduler I have met tunes the schedule until it looks perfect — and then reality happens: a supplier is late, a machine trips, an operator is on leave. The schedule collapses. OTIF collapses with it.
The fix is a time buffer, not a stock buffer, placed ahead of the constraint. Sized correctly, it absorbs 90 percent of the shocks the schedule cannot anticipate. Buffer penetration is tracked daily — green, yellow, red — with a documented escalation for every red-zone entry within 24 hours.
In two Metals sites I ran this on, OTIF moved from 39 percent to 85 percent in 18 months, with zero capital spend. The trade-off, disclosed up front, is a 2–3 day extension of quoted lead time. Customers accept it once — because you actually hit the date every time after.