Concurrent Engineering Overlap Simulator

Phase Overlap

Design/Test overlap 40%

Design maturity rate p 1.0

Downstream sensitivity q 1.0

Coordination overhead ×k 1.0

Project Outcome

Total lead time

0.0 wk

Rework hours

0.0 wk

Time saved vs sequential

0.0%

Rework iterations

Design phase (upstream) Test phase (downstream) Rework extension Overlap window

How it works

Based on the overlapping-development "evolution/sensitivity" model (Krishnan, Eppinger & Whitney). Design runs for T_up=10 weeks, Test for T_down=10 weeks. Letting Test start early (overlap) shortens the schedule, but Test then works from Design information that hasn't finished maturing — and some of that work has to be redone.

t_start   = (1-overlap) · T_up
τ         = t_start / T_up
E(τ)      = τ^p        (info maturity when Test starts)
S(τ)      = (1-τ)^q    (Test's sensitivity to later changes)
R         = S(τ) · (1-E(τ))     (rework fraction, 0..1)
rework    = R · min(T_down, T_up-t_start) · k
total     = t_start + T_down + rework

Overlap — how much of Design's remaining time Test starts working during. 0% = fully sequential (safe, slow); 90% = almost fully concurrent (fast, risky).
Maturity rate p — how quickly Design's output stabilizes. Low p = information stays volatile late into the phase.
Downstream sensitivity q — how strongly Test's work depends on the exact Design output it was given. High q = Test decays quickly, i.e. it only really suffers from changes made very early on.
Coordination overhead k — how expensive each hour of rework is in practice (meetings, re-tooling, requalification).

The sweet spot is the overlap level that minimizes total lead time — push overlap too far and rework eats the schedule gain; keep it at 0% and you pay the full sequential tax instead.

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