CAD defines geometry; simulation reveals flow. A 3D simulation (digital twin) captures time, variability and interactions—things a static plan misses.
It uncovers bottlenecks, queues, resource conflicts, changeover effects, operator/AGV routes, safety overlaps, buffer sizing, and cycle-time drift under different demand patterns. You can test what-if scenarios (staffing, routing, WIP caps, arrival windows) and quantify throughput, OEE, takt compliance, truck wait time, energy use before spending.
In short: CAD shows where assets go; simulation shows how the system really behaves.