Sometimes the tech pack will be given, then you have to design taking into consideration this tech pack. In other projects, they will give you the dimensions of the internal components and you might have freedom to arrange them in the way that best fits the design. It all depends on what is fixed and what’s not before starting designing. When it comes to evaluation, many times you send the files over to the engineers so they can check your design (not only the concept, but also construction and internal arrangement of components) and give an answer about whether what you developed is possible or not. I’d say the best situation is when the kick off meeting includes engineers and marketing or sales people, so you have proper information from both sides. It also very convenient when you work in an company where the engineers are easily reachable, the feedback is flawless and the problems are solved efficiently at an early stage.
Creating solids out of surfaces could be a work for IDers, as well as determining the number of components for the housing, strength, if it could manufactured this or the other way, etc. You wouldn’t go into designing the components themselves, but how they are set within the product. Industrial designers don’t only take care of front end but also of the back end (including accurate prototyping, 3D printing, functional prototypes, etc) For sure there would be a point where engineers need to step in an evaluate the product from a technical point of view.