Siemens SINUMERIK 840Di Function Manual page 828

Detailed Description
2.4 Frames
Up to and including SW P6.1, the rotation activated by PAROT is calculated in the
programmable frame ($P_PFRAME), thus changing its rotation component.
With SW P6.2 and higher, the entire programmable frame remains unchanged, including its
rotation component.
The rotation component, which describes the rotation of the tool table, is then entered into
system frame $PARTFR, if bit 2 of machine data
MD28082 $MC_MM_SYSTEM_FRAME_MASK
is set.
Alternatively, the basic frame described in machine data
MD20184 $MC_TOCARR_BASE_FRAME_NUMBER
can also be used.
As with the note made in the description of the table offset, the second alternative here is not
recommended for use with new systems.
The rotation component of the part frame can be deleted with PAROTOF, independently of
whether this frame is found in a basic or a system frame.
The translation component is deleted when a toolholder, which does not produce an offset, is
activated or a possibly active orientational toolholder is deselected with TCARR=0.
PAROT or TOROT take into account the overall orientation change in cases where the table or
the tool are oriented with two rotary axes. With mixed kinematics only the corresponding
component caused by a rotary axis is considered. It is thus possible, for example, when
using TOROT, to rotate a workpiece such that an oblique plane lies parallel to the XY plane
fixed in space, whereby rotation of the tool must be taken into account in machining where
any holes to be drilled, for example, are not perpendicular to this plane.
Example:
On a machine, the rotary axis of the table points in the positive Y direction. The table is
rotated by +45 degrees. PAROT defines a frame, which similarly describes a rotation of 45
degrees about the Y axis. The coordinate system is not rotated relative to the actual
environment (marked in the figure with "Position of the coordinate system after TCARR"), but
is rotated by -45 degrees relative to the defined coordinate system (position after PAROT). If
this coordinate system is defined with ROT Y-45, for example, and if the toolholder is then
selected with active TCOFR, an angle of +45 degrees will be determined for the rotary axis of
the toolholder.
Language command PAROT is not rejected if no orientational toolholder is active. However,
such a call then produces no frame changes.
Machining in direction of tool orientation
Particularly on machines with orientational tools, traversing should take place in the tool
direction (typically, when drilling) without activating a frame (e.g., using TOFRAME or TOROT),
on which one of the axes points in the direction of the tool. This is also a problem if, when
carrying out oblique machining operations, a frame defining the oblique plane is active, but
the tool cannot be set exactly perpendicularly because an indexed toolholder (Hirth tooth
system) prevents free setting of the tool orientation. In these cases it is then necessary -
contrary to the actually requested motion perpendicular to the plane - to drill in tool direction,
as the drill would otherwise not be guided in the direction of its longitudinal axis, which
among other things would lead to breaking of the drill.
2-98
Axis Types, Coordinate Systems, Frames (K2)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0