Machine tools are called machine making machines. Various machining and forming operations are executed by a variety of machine tools to produce mechanical parts. To maintain specified tolerances, the machine tools must have greater accuracy than the tolerances of the manufactured parts. The precision of a machine tool is affected by the positioning accuracy of the cutting tool with respect to the workpiece and the relative structural deformations between them. The engineering analysis and modeling of relative static and dynamic deformations between the cutting tool and workpiece are covered in this chapter.
MACHINE TOOL STRUCTURES
A machine tool system has three main groups of parts: mechanical structures, drives, and controls. The components can be observed from the horizontal computer numerically controlled (CNC) machining center shown in Figure 3.1.
The structure consists of stationary and moving bodies. The stationary bodies include beds, columns, bridges, and gear box housings. They usually carry moving bodies, such as tables, slides, spindles, gears, bearings, and carriages. The structural design of machine tool parts requires high rigidity, thermal stability, and damping. In general, the dimensions of machine tools are overestimated to minimize static and dynamic deformations during machining. The general design of machine tool structures will not be covered in this text. Instead, it is assumed that the relative static and dynamic compliance between the tool and the workpiece is measured experimentally or predicted with analytical methods.