HEIDENHAIN TNC 407 (280 580) User Manual - Manual (Page 12)

TNC 425/TNC 415 B/TNC 407 1-11
1 Introduction
Fig. 1.9: The geographic coordinate system
is an absolute reference system
Fig. 1.10: Designations and directions of the
axes on a milling machine
1.2 Fundamentals of NC
Reference system
In order to define positions one needs a reference system. For example,
positions on the earth's surface can be defined absolutely by their geo-
graphic coordinates of longitude and latitude. The word
coordinate comes
from the Latin word for "that which is arranged." The network of longitude
and latitude lines around the globe constitutes an absolute reference
system—in contrast to the relative definition of a position that is refer-
enced to a known location.
Cartesian coordinate system
On a TNC-controlled milling machine, workpieces are normally machined
according to a workpiece-based Cartesian coordinate system (a rectangu-
lar coordinate system named after the French mathematician and
philosopher Renatus Cartesius, who lived from 1596 to 1650). The
Cartesian coordinate system is based on three coordinate axes X, Y and Z
which are parallel to the machine guideways.
The figure to the right illustrates the "right-hand rule" for remembering the
three axis directions: the middle finger is pointing in the positive direction
of the tool axis from the workpiece toward the tool (the Z axis), the thumb
is pointing in the positive X direction, and the index finger in the positive Y
direction.
0 ° 90 ° 90 °
0 °
30
°
30 °
60 °
60 °
Greenwich
+X
+Y
+Z
+X
+Z
+Y