HEIDENHAIN TNC 620 Programming Station, User Manual

Page: 125 / 695

Fundamentals 3.1
3
HEIDENHAIN | TNC 620 | ISO Programming User's Manual | 9/2016
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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: Cycle Programing User's Manual
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: "Datum setting with a 3-D touch probe
(option number 17)", page 533
Example
The workpiece drawing shows holes ( 1 to 4 ), whose dimensions
are shown with respect to an absolute datum with the coordinates
X=0 Y=0. The coordinates of holes
5 to 7 refer to the relative
datum with the absolute coordinates X=450 Y=750. By using the
ZERO POINT DISPL.
cycle you can shift the datum temporarily to
the position X=450, Y=750 and program the holes ( 5 to 7 ) without
further calculations.