W1: Tool offset
18.6 Toolholder with orientation capability
Basic Functions
1504
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
18.6.2
Kinematic interaction and machine design
Representation of the kinematic chain
The concept of the kinematic chain is used to describe the kinematic interaction between a reference point and
the tool tip.
The chain specifies all the data required for the toolholder data block in a schematic. To describe the concrete
case with a particular kinematic, the relevant components of the chain must be assigned real vectors, lengths
and angles. The chain represents the maximum constellation. In simpler applications, individual components can
be zero (e.g. kinematics with one or no rotary axis).
The machine does not have to have axes that rotate the tool and/or workpiece table. The function can be used
even if the orientations are set manually by handwheels or reconfiguration.
The machine design is described by the following parameters:
• Two rotary axes (v
1
and v
2
), each with one angle of rotation (α
1
or α
2
), which counts positively for clockwise
rotation facing the direction of the rotation vector.
• Up to four offset vectors (l
1
to l
4
) for relevant machine dimensions (axis distances, distances to machine or
tool reference points).
Zero vectors
Vectors v
1
and v
2
can be zero. The associated angle of rotation (explicitly programmed or calculated from the
active frame) must then also be zero, since the direction of the rotating axis is not defined. If this condition is not
satisfied, an alarm is produced when the toolholder is activated.
Less than two rotating axes
The option not to define a rotating axis makes sense when the toolholder to be described can only rotate the tool
in one plane. A sensible minimum data block may, therefore, contain only one single entry not equal to 0 in the
toolholder data; namely, a value in one of the components of v
1
or v
2
for describing a rotating axis parallel to the
axis where the angle of rotation α1 or α2 is determined from one frame.
Further special cases
Vectors v
1
and v
2
can be colinear. However, the degree of freedom for orientation is lost, i.e. this type of
kinematic is the same as one where only one rotary axis is defined. All possible orientations lie on one cone
sheath. The conical sheath deforms to a straight line if tool orientation t and v
1
or v
2
become colinear. Change of
orientation is, therefore, not possible in this special case. The cone sheath deforms to a circular surface (i.e. all
orientations are possible in one plane), if tool orientation t and v
1
or v
2
are perpendicular to each other.
It is permissible for the two vectors v
1
and v
2
to be zero. A change in orientation is then no longer possible. In this
special case, any lengths l
1
and l
2
, which are not equal to zero, act as additional tool length compensations, in
which the components in the individual axes are not affected by changing the plane (
G17
-
G19
).
