1 fundamentals of nc – HEIDENHAIN TNC 410 User Manual
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4 Programming: Fundamentals of NC, File Management, Programming Aids
Y
X
Z
Selecting the datum
A production drawing identifies a certain point on the workpiecee
— usually a cornerr — as the absolute datum. Before setting the
datum, you align the workpiece with the machine axes and move
the tool in each axis to a known position relative to the workpiece.
You then set the TNC display to either zero or a predetermined
position value. This establishes the reference system for the
workpiece, which will be used for the TNC display and your part
program.
If the production drawing is dimensioned in relative coordinates,
simply use the coordinate transformation cycles. For further
information, refer to section 8.8 “Coordinate Transformation
Cycles.”
If the production drawing is not dimensioned for NC, set the datum
at a position or corner on the workpiece, which is the most suitable
for deducing the dimensions of the remaining workpiece positions.
The fastest, easiest and most accurate way of setting the datum is
by using a 3-D touch probe from HEIDENHAIN. For further
information, refer to section 12.2 “Setting the Datum with a 3-D
Touch Probe.”
Example
The workpiece drawing at right illustrates the holes to , which
are dimensioned to an absolute datum with the coordinates X=0
Y=0. The holes to are referenced to a relative datum 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 to without any further
calculations.
4.1 Fundamentals of NC
X
Y
325
320
0
450
900
950
150
-150
750
0
300
±
0,
1