15.3.1 Introduction
Guideways are the elements or surfaces that carry and guide the moving elements such as workpiece holder/drives and wheel and dresser heads. Guideways can be divided into two categories— sliding and rolling element. Guideways of either type are often known simply as slideways. Their selection is dependent on many factors such as speed, acceleration, range of motion, accuracy and repeatability, stiffness, damping characteristics, thermal stability, weight, load capacity, slip-stick characteristics, ease of manufacturing, and cost including support equipment such as hydraulic pumps, chillers, filters, etc. In many cases, the choice is also dependent on which machine axis is involved and it is, therefore, opportune at this point to define the primary machine axes as defined by International Machine Tool Standards [Smith 1993], and some examples for the more common grinder types.
15.3.2 Definition of Axes
X-axis—The horizontal axis of motion parallel to the work-holding surface Y-axis—The axis of motion perpendicular to both the X — and Z-axes Z-axis—The axis of motion parallel to the principal spindle of the machine A-axis—The axis of rotary motion of a machine tool member about the X-axis B-axis—The axis of rotary motion of a machine tool about the Y-axis C-axis—The axis of rotary motion of a machine tool about the Z-axis
Additional linear axes follow sequentially backward through the alphabet; for example, dressing axes tend to be U and V, while rotary axes follow sequentially forward through the alphabet. Axes carrying in-line probes are also given letters generally out of sequence. After the three principal axes, labeling varies from one machine tool builder to another.
Misalignments in a system lead to the following types of error in slide motion (Figure 15.5).