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32 2 Machining Fundamentals
2.1 Fundamentals of Positioning
Setting the datum
Fixture Offsets
A production drawing identifies a certain form element of the work
piece, usually a corner, as the absolute zero datum. When setting the
datum, you first align the work piece along the machine axes, and then
move the tool in each axis to a defined position relative to the work
piece. Set the display of the CNC either to zero or to a known position
value for each position. This establishes the reference system for the
work piece, which will be used for the CNC display and your part
program.
If the production drawing is not dimensioned for that particular CNC,
set the datum at a position or corner on the work piece which is
suitable for deducing the dimensions of the remaining work piece
positions.
The fastest, easiest and most accurate way of setting the datum is by
using a 3-D touch probe from HEIDENHAIN Corp. Refer to chapter "7.3
Probing Cycles on page 197”.
Example 1: Offset
See "Fixture Offset (Work Coordinate System Select):" on page 136 for
more information on using the Offset cycle. Use the Offset command
to apply a Fixture Offset of the absolute zero datum to the corner of
WorkPiece #1.
Format: Offset Fixture #1 X10 Y10
Offset Fixture #1
Machining positions are now referenced from the lower left corner of
WorkPiece #1.
Use the Offset command to apply a Fixture Offset of the absolute
zero datum to the corner of WorkPiece #2.
Format: Offset Fixture #2 X60 Y10
Offset Fixture #2
Machining positions are now referenced from the lower left corner of
WorkPiece #2.