Siemens Sinumerik 840D sl Programming Manual page 194

Motion commands
10.6 Circular interpolation
Determination of the tangent direction
The tangent direction in the starting point of a CT block is determined from the end tangent of
the programmed contour of the last block with a traversing motion.
There can be any number of blocks without traversing information between this block and the
current block.
Syntax
CT X... Y... Z...
Meaning
CT:
X... Y... Z... :
Note
CT is modal.
As a rule, the circle is clearly defined by the tangent direction as well as the starting point and
end point.
194
Circle with tangential transition
End point in Cartesian coordinates
Programming Manual, 01/2015, 6FC5398-1BP40-5BA2
Fundamentals