TABLE OF CONTENTS This chapter is one of the most important in this book. It presents a way to design competent assemblies using the principles of kinematic constraint. We distinguish between kinematically constrained assemblies, deliberately overconstrained or underconstrained assemblies, and assemblies that contain constraint errors. Kinematic assemblies are capable of achieving rapid, accurate, and repeatable assembly at reasonable cost. Both Whitehead and Kamm make this point in their books. The car seat example shows this vividly.
The method of Screw Theory permits us to define assembly features as geometric entities capable of establishing constraint relations between the parts they join. Screw Theory also permits us to build up a joint between parts using arbitrary combinations of simpler features and then to examine the state of constraint that is established by that joint.
These concepts and tools permit us to use features and the connective assembly models defined in Chapter 3 to build kinematically constrained assemblies of rigid parts that lie at particular desired places and orientations in space so that they will achieve key characteristics as defined in Chapter 2. These concepts are mathematically precise and consistent, and they capture the most fundamental properties of assemblies. They can be used as the basis for computer models of assemblies, for motion and constraint analyses, and for other analyses, such as variation, that are discussed in later chapters.
