Question 4.7: Determine the absolute coordinates of working points shown i...
Determine the absolute coordinates of working points shown in Fig. 4.99a.
The absolute coordinates are measured from origin O; therefore, the coordinates of the working points (1, 2, …, 7) in Fig. 4.99a are determined as (1.0, 3.0), (-1.0, 2.0), (-3.5, -0.5), (-3.0, – 1.0), (-4.0, -2.0), (1.0, -2.5), and (3.0, -2.0) in Fig. 4.99b, respectively.
Absolute coordinates also apply to the default two-axis coordinate system for a CNC lathe. For a lathe, absolute coordinates take the reference from origin (X0, Z0) as shown in Fig. 4.100a. To find Z- and X-coordinates of a working point, project the working point on Z-axis and X-axis, respectively. The absolute coordinates of the working points P_{1} to P_{6} are determined in Fig. 4.100b. Note that the X-coordinates can be either radical (X_{R} ) or diametric (X_{D} ).
Incremental coordinates are measured from existing points. A new working point can be defined by specifying a relative distance of an existing point. Figure 4.101 shows an example of defining incremental coordinates for working points in a toolpath.
