HEIDENHAIN iTNC 530 HSCI - Kinematicscomp

664 HEIDENHAIN Technical Manual iTNC 530 HSCI
6.4.9 KinematicsComp
Introduction Increasingly stringent requirements on workpiece tolerances constantly
increase demands placed on a machine tool. However, machine tools are
inevitably also subject to errors arising both from the production process and
the machine design. For example, according to ISO 230 each axis can have six
types of error. These include not only familiar errors, such as positioning and
angular errors, but also pitch, yaw and roll as well as the wobble of a rotary
axis.
This means in the end that the more axes a machine has, the larger the
number of error sources. The use of mechanical means to cope with these
problems requires considerable effort, particularly in the field of 5-axis
machining, or if large machines with parallel axes are involved. The axes are
also subject to drift, usually resulting from inhomogeneous temperature
distribution in the machine components. The drift becomes apparent in the
form of both linear movements (translations) and, quite often, rotational
movements (rotations).
The new KinematicsComp function (software option 52) of the iTNC 530
enables the machine manufacturer to save a comprehensive description of the
machine errors in the control. In the kinematics model, the manufacturer
describes the machine’s degrees of freedom and the positions of the rotary
axes. Until now it had only been possible to define the nominal geometry of
the machine. Now the actual behavior of all axes can be integrated in this
original kinematics model.
KinematicsComp can even be used to define position-dependent temperature
compensation. The required data is supplied by several sensors located at
relevant points on the machine.
KinematicsComp is capable of significantly improving the manufacturing and
contour accuracy, especially on large machines. The long distances traversed
and the large moving masses cause relatively large errors. Because the use of
mechanical means to reduce these errors requires a lot of effort, the economic
benefits achieved by KinematicsComp are especially significant for these
applications.
KinematicsComp requires a kinematics model of the machine, which
describes the real behavior of the machine as accurately as possible. The ideal
kinematics model of the machine must be described, as previously, in the KEY,
AXIS and COORD columns in the kinematics table. For KinematicsComp, the
kinematics table was extended by the column COMPTAB. In the lines of the
kinematics table with the 'Trans' KEY entry, constants or links to axis-error
compensation tables can be entered in the new column COMPTAB in order to
describe deviations from the ideal kinematics model.
Summary:
 The KinematicsComp software option 52 makes geometrical compensation
of comprehensive axis-dependent error sources possible.
 Only the position of the TCP Tool Center Point is corrected. This prevents
undesired movements of the rotary axis.
 Exact determination of the errors places high demands on metrology. Laser
interferometers, especially laser tracers, provide very exact measurement
of the errors of linear axes.