The RealCloth material requires the model to have proper and sensible UV coordinates.
Typically, NURBS models like those made in SOLIDWORKS don't have a UV layout that works well with RealCloth. For NURBS models, all surface patches will appear to have their own "UV islands". This makes the RealCloth material look disjointed at surface transitions, as you can see on the fillets/rounds of the cube. Furthermore, NURBS modelers tend to produce UV coordinates that are inconsistently sized and scaled, producing a stretched and scaled appearance on some surfaces. For example, notice how the texture on the corner surface is much denser than on the flat sides.
The only way to address this issue, is to unwrap the UV coordinates of the model. Luckily, since KeyShot 9, we provide the 'Unwrap UV' Geometry tool to do exactly that. Unwrapping is like the inverse process of cutting a flat piece of fabric to shape, in order to fully wrap around and cover your geometry.Here
is a Quick Tip on how to use the Unwrap UV tool.
Let me know if that helps.