Siemens Sinumerik 840D sl Programming Manual page 192

Glossary
C axis
An axis which the tool uses to describe a controlled rotary or positioning movement.
C spline
The C spline is the most well-known and widely used spline. The spline runs along a tangent
and along the axis of curvature through all interpolation points. 3rd order polynomials are
used for this.
Channel structure
The -> programs of the individual channels can be processed simultaneously or
asynchronously with the channel structure.
Circular interpolation
In circular interpolation, the -> tool traverses between defined contour points at a definite
feedrate during the machining of the workpiece on a circular path.
Clearance control (3D), sensor-driven
The positional shift for a certain axis can be controlled as a function of a measured process
variable (e.g. analog input, spindle current...). This function can be used to maintain a fixed
distance automatically so as to fulfill certain technological requirements of the relevant
machining.
CNC programming language
The CNC programming language is based on DIN 66025 with high-level language
extensions. The CNC programming language and the high-level language extensions
support the definition of macros (sequenced statements).
COM
Part of numerical control system for the implementation and coordination of communication.
Command axis
Command axes are started from synchronized actions as a reaction to an event (command).
Command axes can be positioned, started and stopped fully asynchronous to the part
program.
Compensation axis
Axis with a setpoint or actual value modified by a compensation value.
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Programming Manual, 06/09, 6FC5398-7BP10-1BA0
ISO Milling