Siemens Sinumerik 840D sl Programming Manual page 205

Programmable logic control
Programmable logic control systems (PLC) are electronic control systems whose functions
are stored in the control system as program. Hence, the structure and wiring do not depend
on the control functions. Programmable logic control systems are designed exactly like a
computer, i.e. they consist of a CPU with memory, I/O modules and an internal bus system.
The selection of the I/O modules and the programming language depends on the technology
used.
Programmable working area limitation
Limiting the traversing range of the tool to defined, programmable limits.
Programming key
Characters and character strings with an accurately defined meaning within the
programming language for -> part programs (refer to programming manual).
Protection zone
Three-dimensional zone inside a -> working area which the tool cannot reach (can be
programmed via MD).
Quadrant error compensation
Contour errors in quadrant transitions that are caused by frictional losses on the guide rails
can be corrected to a large extent with the quadrant error compensation. A circularity test is
used to define the parameters of the quadrant error compensation.
Rapid traverse
The maximum rapid traverse rate of an axis is, for instance, used to traverse a tool from the
idle position to the -> workpiece contour or to retract the tool from the workpiece contour.
Reference point
Point on the machine to which the measuring system of the -> machine axis refers.
Reference point approach
If the position measuring system used is not an absolute encoder, then reference point
approach must be started so that the actual values delivered by the measuring system
match the machine coordinate system values.
ISO Milling
Programming Manual, 06/09, 6FC5398-7BP10-1BA0
Glossary
205