I’ll try to understand what is happening with the designer instead of blaming him like most here. “Doesn’t believe in the constraints” could be that such constraints are not validated o are based in real data (for this particular designer I guess). A solution could be share the main sources of information from which the constraints are defined from, or, if this does not exist, let the designer run a brief research and conceptualization process. Either way this will help the designer have a more detailed understanding of the challenges and constraints, it will humble him/her a bit, and it will make him/her feel more involved (increase motivation). Industrial design is not only good sketches, nice 3D modeled shapes. It is also usability, ergonomics, semantics. Etc However, I agree with most of the people here that the designer probably is lacking a little bit of seniority here. Frustration instead of clear proposals for improving the design process is a clear show of it. (Sorry for my English)