HEIDENHAIN TNC 640, User Manual, Page: 160 / 948

Fundamentals, File Management | Fundamentals
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HEIDENHAIN | TNC 640 | Conversational Programming User's Manual | 10/2017
Selecting the preset
A production drawing identifies a certain form element of the
workpiece, usually a corner, as the absolute preset (datum). When
setting the preset, 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 control 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
control's display and your part program.
If the production drawing is dimensioned in relative presets, simply
use the coordinate transformation cycles.
Further information: Cycle Programming User's Manual
If the production drawing is not dimensioned for NC, set the
preset 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 presetting is by
using a 3-D touch probe from HEIDENHAIN.
Further information: "Presetting with a 3-D touch probe ",
page 772
Example
The workpiece drawing shows holes ( 1 to 4 ), whose dimensions
are shown with respect to an absolute preset with the coordinates
X=0 Y=0. The coordinates of holes
5 to 7 refer to the relative
preset with the absolute coordinates X=450 Y=750. By using
the
Datum shift
cycle you can shift the datum temporarily to the
position X=450, Y=750 and program the holes ( 5 to 7 ) without
further calculations.