Siemens sinumerik 840D sl Function Manual page 69

Examples:
1. Extreme example: A machine with rotatable tool has a C axis as its first rotary axis and an
2. Realistic example: A machine with nutator kinematics (universal head) with an axis
2.8.2 Orientation movements with axis limits
Calculate rotary axis position
If the final orientation in a 5-axis transformation is programmed indirectly in an NC block by
means of a Euler, RPY angle or direction vector, it is necessary to calculate the rotary axis
positions that produce the desired orientation. This calculation has no unique result.
There are always at least two essentially different solutions. In addition, any number of
solutions can result from a modification to the rotary axis positions by any multiple of 360
degrees.
The control system chooses the solution which represents the shortest distance from the
current starting point, allowing for the programmed interpolation type.
Determining permissible axis limits
The control system attempts to define another permissible solution if the axis limits are
violated, by approaching the desired axis position along the shortest path. The second
solution is then verified, and if this solution also violates the axis limits, the axis positions for
both solutions are modified by multiples of 360 until a valid position is found.
The following conditions must be met in order to monitor the axis limits of a rotary axis and
modify the calculated end positions:
• A generic 5-axis transformation of type 24, 40 or 56 must be active.
• The axis must be referenced.
• The axis must not be a modulo rotary axis.
• The following machine data may not be equal to zero:
Special functions: 3-Axis to 5-Axis Transformation (F2)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
A axis as its second. If the basic orientation is defined in parallel to the A axis, the
orientation can only be changed in the X-Y plane (when the C axis is rotating), i.e.
orientation with a Z component unequal to zero is not possible in this instance. The
orientation does not change when the A axis rotates.
inclined at less than 45
orientations within a semi-circle: The top semi-circle with basic orientation towards +Z
and the bottom with basic orientation towards -Z.
MD21180 $MC_ROT_AX_SWL_CHECK_MODE (check software limits for orientation
axes)
in a basic orientation parallel to the Z axis can only assume
o
Detailed description
2.8 Orientation
63