NPI, DFM/DFA & Engineering Change worked example

Engineering Change Cost at 81% disposition share reworked: a worked example in npi, dfm/dfa & engineering change

Push disposition share reworked up to 81% and the picture changes. This example computes every intermediate figure at that operating point. A change-control board member weighing the cost of an engineering change against the risk of leaving the existing design in place.

The inputs for this scenario

  • Affected Parts in Field: 850 parts (unchanged)
  • Rework Cost Per Part: 12.5 $/part (unchanged)
  • Disposition Share Reworked: 81 % (raised for this scenario; the documented default is 70)
  • ECN Administration Cost: 3,500 $ (unchanged)

Working through the calculation

  • Applying the documented formula (ECN cost = affected parts x rework cost per part x disposition share% + administration cost) to the inputs above produces each figure below.
  • At this operating point the engine returns 12,106 $ for total engineering change cost, the number this scenario is built around.
  • At this operating point the engine returns 14.24 $ / piece for engineering change cost per unit.
  • At this operating point the engine returns 8,606 $ for variable engineering change cost.
  • At this operating point the engine returns 3,500 $ for fixed engineering change cost adder.

How this compares with the baseline

  • Against the tool's baseline example, where disposition share reworked sits at 70% and the headline result is 10,938 $, this scenario comes in 10.69% above the baseline at 12,106 $.
  • It computes the total cost of an engineering change by combining rework on the reworked share of affected parts with the fixed ECN administration cost, and breaks out cost per affected part. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Total engineering change cost: 12,106 $ (headline result)
  • Engineering change cost per unit: 14.24 $ / piece
  • Variable engineering change cost: 8,606 $
  • Fixed engineering change cost adder: 3,500 $

Run it with your numbers

  • Every input above is editable in the live Engineering Change Cost calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.