July 2013 6.1 Control loops 605
Algebraic signs of
the axes
When the programmer writes an NC program, he always assumes that the
tool (not the workpiece) is in motion. If the machine moves its workpiece-
holding element (table) in a particular axis instead of the tool, then the direction
of actual motion is opposite to the direction of axis motion. In this case the
direction of motion is designated with the same algebraic sign as the axis
direction, but with an apostrophe: +X´, +Y´ and +Z´:
Rotary axes A, B, C The directions of the rotary axes A, B and C follow the "right-fist rule." The
fingers of the closed right hand point in the proper rotational direction of an
axis when the thumb points in the direction of the associated linear axis:
+X
+X´
+Z
+Y
+X
+A
+B
+C
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