HEIDENHAIN ITNC 530 - 6-2010 DIN-ISO PROGRAMMING User Manual page 518

Danger of collision!
The TNC cannot graphically simulate all traverse motions
actually performed by the machine. These include
traverse motions during tool change, if the machine
manufacturer defined them in a tool-change macro or via
the PLC,
positioning movements that the machine manufacturer
defined in an M-function macro,
positioning movements that the machine manufacturer
performs via the PLC.
positioning movements that lead to a pallet change.
HEIDENHAIN therefore recommends proceeding with
caution for every new program, even when the program
test did not output any error message, and no visible
damage to the workpiece occurred.
After a tool call, the TNC always starts a Test Run at the
following position:
In the machining plane at the position X=0, Y=0
In the tool axis, 1 mm above the MAX point defined in the
BLK FORM.
If you call the same tool, the TNC resumes program
simulation from the position last programmed before the
tool call.
In order to ensure unambiguous behavior during program
run, after a tool change you should always move to a
position from which the TNC can position the tool for
machining without causing a collision.
Your machine tool builder can also define a tool-change
macro for the Test Run operating mode. This macro will
simulate the exact behavior of the machine. Please refer
to your machine tool manual.
518 Test Run and Program Run