TABLE OF CONTENTS Screw Theory permits us to represent in a precise mathematical way the interactions between two surfaces in contact. We can represent the ability of those surfaces to translate along or rotate around each other, and we can represent the fact that a surface can resist a contact force directed normally to it. We have now laid a theoretical foundation for representing assembly features using Screw Theory. We will now put this theory to work.
We will use this method to show how we can determine the degrees of freedom, amount of underconstraint, or amount of overconstraint. We will build our way up to models of assembly features in steps, starting with twist matrix models of basic surface contacts. We will see how we can build up familiar engineering features using basic surfaces in combination. In addition, we will see how to build engineering features directly, without starting from basic surface contacts.
We begin by showing how to use the methods given in Section 4.E.2.d.2 to perform motion and constraint analyses of features. The analysis may result in any of the following situations
The assembly is kinematically constrained, with no overconstrained degrees of freedom and no underconstrained degrees of freedom.
Some degrees of freedom can be underconstrained.
Some degrees of freedom can be overconstrained.
Some degrees of freedom can be overconstrained while others are underconstrained.
To find out which of these conditions applies to any...
