ABSTRACT
This chapter introduces the basics of force loops by considering conceptual structural components for the construction of machine tools and dimensional measuring machines. In particular, different design configurations are presented to illustrate the issues for each configuration and explain the concept of functional loop separation that provides a 494means of assessing different designs in terms of achievable precision and significant limiting components within the assembled mechanism. The following sections focus on positioning and machining tasks, describing structural loops in more detail and providing design guidelines for optimal behaviour. Having established tools for identification and characterisation, the definition and composition of a typical metrology loop is given, together with general design guidelines for optimising the metrological performance of the machines. Another important design consideration is the identification and analysis of thermal loops in the system. Following the definition of thermal loops, several design concepts are introduced for the reduction of thermal disturbances in instruments and machines. To illustrate application of the principles developed in this chapter, examples of state-of-the-art machines and instruments that apply these concepts are discussed.
