HEIDENHAIN TNC 370 User Manual page 153

5 Programming Tool Movements
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5.7 M Functions for Contouring Behavior and Coordinate Data
Setting the coordinates for the datum: MSl/M92
Standard behavior
Coordinates are referenced to the workpiece datum (see page I-21)
Scale reference point
The position feedback scales are provided with one or more reference
marks. Reference marks are used to indicate the position of the scale
reference point. If the scale has only one reference mark, its position is
the scale reference point. If the scale has several - distance-coded -
reference marks, then the scale reference point is indicated by the left-
most reference mark (at the beginning of the measuring range).
Machine datum - miscellaneous function M91
The machine datum is required for the following tasks:
l
Defining the limits of traverse (software limit switches)
l
Moving to machine-reference positions (e.g. tool-change position)
l
Setting the workpiece datum
Machine zero is identical with the scale reference point.
If you want the coordinates in a positioning block to be referenced to the
machine zero point, end the block with the miscellaneous function M91.
Coordinates that are referenced to the machine datum are indicated in the
display with REF.
Additional machine datum M92
In addition to the machine zero point, the machine
tool builder can define another machine-reference
position, the machine datum.
The machine tool builder defines the distance for
each axis from the machine zero to the machine
datum.
If you want the coordinates in a positioning block to
be referenced to the machine datum, end the block
with the miscellaneous function M92.
Workpiece datum
The user enters the coordinates of the datum for
workpiece machining in the MANUAL OPERATION
mode (see page 2-7).
Fig. 5.52: Machine datum @and workpiece datum @
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TNC 370