Digital Twin Series · Part 2
CAD Model vs Simulation Model vs Digital Twin
Three models of the same machine: which one answers which question?
A CAD model describes the shape: what the machine is. A simulation model adds physics: what the machine would do under a given load. A digital twin connects the model to the real machine through live data: what the machine is doing now and what it will do next. They are not rivals. Each one builds on the one before, and each is the right tool at a different time in the life of a machine. This page lets you compare them, see what real data adds in a beam example, follow them through the lifecycle and test yourself on which model to use.
One beam, three models. The CAD model gives the size and mass. The simulation predicts the deflection from the geometry and the material, assuming perfect joints. The real frame is a little softer. The twin starts as the simulation, then uses real measurements to correct itself. More measurements give a better correction, but noise in the measurements limits how far it can go.
| Aspect | CAD model | Simulation model | Digital twin |
|---|
| CAD model | Simulation model | Digital twin |
|---|
Tick what is true for your model. The result follows the usual definitions: a CAD model holds the geometry, a simulation model adds physics, a digital shadow follows the real asset with live data in one direction, and a digital twin is also validated, predicts what comes next and stays current over the life of the asset. Sending setpoints back to the machine is optional and marks a closed-loop twin.
The beam demo uses the textbook formula for a simply supported beam with a central load, with a made-up joint stiffness so you can see the idea. It is a teaching model, not a design tool. Check real structures with proper analysis and the applicable standards.