In the past (<1970) ’’Design Theory and Methodology’’ (DTM) was more an art or a profession. Nowadays, theories are taught in many engineering schools and reported being applied industrially. Below a not complete overview of some of these theories. The characteristic of all these design methods is that it is a sequence of iterative processes. At the start of the design process, the focus is more on fulfilling the function. While later in the design process, the emphasis is more on manufacturability. Various design methods and manufacturability characteristics are extensively explained in this platform. A good design stands or falls with its manufacturability.