HEIDENHAIN TNC 407 (243 020) Technical Manual - Manual (Page 337)

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TNC 407/TNC 415/TNC 425 13 Hirth coupling 01.98
13 Hirth coupling
A frequent method of locking rotary axes and swivel heads is the so-called Hirth coupling in which
more or less finely splined plates engage to form a rigid connection.
The Hirth functions are implemented in the PLC program. The only operation in the NC is a rounding
off according to the grid spacing in MP430 when setting the datum point. Repositioning is initiated
as PLC positioning or an error message is displayed depending on whether the axis is automatically
or manually positioned with the Hirth coupling. MP420 defines the "Hirth coupling" functions and
MP430 the grid spacing. The positioning accuracy and other parameters are defined in free machine
parameters.
13.1 Positioning in Manual or Electronic Handwheel mode
The Axis in Position marker (M2011) is reset when selecting the 4th or 5th axis which is traversed
with the electronic handwheel. This can be used to initiate unlocking of the Hirth coupling. The same
applies to traversing with the axis direction key. Setting the Axis in Position marker starts a check of
the nominal position compared with grid. Repositioning is executed as PLC positioning by the
shortest route, i.e. to the nearest grid point.
13.2 Positioning in controlled mode
NC Start also resets the Axis in Position marker. This in turn initiates an internal check of the target
position. If the target position is not in the grid then an error message is displayed.