Selecting The Datum - HEIDENHAIN TNC 620 User Manual

3
Programming: Fundamentals, File Management
3.1 Fundamentals

Selecting the datum

A production drawing identifies a certain form element of the
workpiece, usually a corner, as the absolute datum. When setting
the datum, you first align the workpiece along the machine axes,
and then move the tool in each axis to a defined position relative
to the workpiece. Set the display of the TNC either to zero or to
a known position value for each position. This establishes the
reference system for the workpiece, which will be used for the
TNC display or your machining program.
If the production drawing is dimensioned in relative datums, simply
use the coordinate transformation cycles.
Further information:
If the production drawing is not dimensioned for NC, set the
datum at a position or corner on the workpiece from which
the dimensions of the remaining workpiece positions can be
measured.
The fastest, easiest and most accurate way of setting the datum is
by using a 3-D touch probe from HEIDENHAIN.
Further Information:
number 17), page 526
Example
The workpiece drawing shows holes
shown with respect to an absolute datum with the coordinates X=0
Y=0. The holes (5 to 7) refer to the relative datum with the absolute
coordinates X=450 Y=750. Using the Cycle DATUM SHIFT you can
shift the datum temporarily to X=450, Y=750 to program the holes
(5 to 7) without programing any further calculations.
104
Cycle Programming User's Manual
Datum setting with a 3-D touch probe (option
(1 to 4) whose dimensions are
HEIDENHAIN | TNC 620 | Conversational Programming User's Manual | 10/2015