Siemens SINUMERIK 828D Function Manual page 1519

Two rotary axes
Two general solutions exist for two rotary axes. The control itself chooses these two solution pairs such that the
orientation angles resulting from the frame are as close as possible to the specified angles.
The two following options are available for specifying the angles:
1. If $TC_CARR21 or $TC_CARR22 contains a reference to a rotary axis, the position of this axis at the start of
the block in which the toolholder is activated is used to specify the angle.
2. If $TC_CARR21 or $TC_CARR22 does not contain a reference to a rotary axis, the values contained in
$TC_CARR13 or $TC_CARR14 are used.
Example
The control first calculates an angle of 10 degrees for one axis. The specified angle is 750 degrees. 720 degrees
(= 2 * 360 degrees) are then added to the initial angle, yielding a final angle of 730 degrees.
Rotary axis offset
Rotary axis offsets can be specified with system variables $TC_CARR24 and $TC_CARR25. A value not equal to
zero in one of these parameters means that the initial state of the associated rotary axis is the position specified
by the parameter (and not position zero). All angle specifications then refer to the coordinate system displaced by
this value.
When the machining plane is changed (G17 - G19), only the tool length components of the active tool are
interchanged. The components of the toolholder are not interchanged. The resulting tool length vector is then
rotated in accordance with the current toolholder and, if necessary, modified by the offsets belonging to the
toolholder.
The two toolholder angles α
selected (G17 - G19).
Limit values
Limit angles (software limits) can be specified for each rotary axis in the system variable set ($TC_CARR30 to
$TC_CARR33) used to describe the toolholder with orientation capability. These limits are not evaluated if both
the minimum and maximum value is zero.
If at least one of the two limits is not equal to zero, the system checks whether the previously calculated solution
is within the permissible limits. If this is not the case, an initial attempt is made to reach a valid setting by adding
or subtracting multiples of 360 degrees to or from the invalid axis position. If this is impossible and two different
solutions exist, the first solution is discarded and the second solution is used. The second solution is treated the
same as the first with reference to the axis limits.
If the first solution is discarded and the second used instead, the contents of $P_TCANG[1/2] and $P_TCANG[3/
4] are swapped, hence the solution actually used is also stored in $P_TCANG[1/2] in this case.
The axis limits are monitored even if the axis angle is specified instead of being calculated. This is the case if
TCOABS is active when a toolholder with orientation capability is activated.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
and α are determined using a frame, independent of the active plane currently
1 2
18.6 Toolholder with orientation capability
W1: Tool offset
1519