Whether for a brandnew design or a retrofit, simulation is often needed because :

•   The technology you are interested in is not available
•   Your budget doesn't allow you to acquire an expensive prototype
•   Real test is risky
•   There is not any time left for assembling a full system
•   Your customer wants it for yesterday
•   Your team wants to test several solutions and compare them
•   You would like to keep a way to reproduce its performances later
•   …

The more you wait, the more the system grows in age, the more a change in your design is expensive. What can you do ?

There are many parameters, many climatic conditions to test. The tolerances are too tight. The product is unmanufacturable. No risk can be taken. Fortunately you have the following possibilities :

•   Make a FMEA with a virtual prototype
•   Make quickly a variation study in parameters
•   Your supplier can supply you with a new model of its part
•   You can validate it through a stress, parametric analysis
•   Run a statistical analysis and allocate tolerances
•   …