Question: Is there a CAD format, which allows to describe mechanical bonds between objects (axes, joints, springs, etc.) and/or motion of objects ?

Answer: 
Bear in mind that the KMeans function is stochastic (the results may vary even if you run the function with the same inputs' values). Hence, in order to make the results reproducible, you can specify a value for the `random_state` parameter.
Random state in Kmeans function of sklearn mainly helps to 

1. Start with same random data point as centroid if you use Kmeans++ for initializing centroids.
2. Start with same K random data points as centroid if you use random initialization.

This helps when one wants to reproduce results at some later point in time.