Siemens SINUMERIK 840Di Function Manual page 1741

Fig. 2-26
G450 transition circle
With the G function G450 active, on outside corners, the center point of the tool travels a
circular path along the tool radius. The circular path begins perpendicular to the path tangent
at the end point of the previous path section (program block) and ends in the perpendicular
position at the start point of the new path section (program block).
In cases where the outside corners are very flat, the response with G450 (transition circle)
and G451 (intersection) becomes increasingly similar → see Very flat outside corners.
If pointed outside corners are desired, the tool must be retracted from the contour → see
DISC.
DISC
The G450 transition circle does not produce sharp outside contour corners because the path
of the tool center point through the transition circle is controlled so that the cutting edge
stops at the outside corner (programmed position). When sharp outside corners are to be
machined with G450, the DISC instruction can be used to program an overshoot. Thus, the
transition circle becomes a conic and the tool cutting edge retracts from the outside corner.
The range of values of the DISC instruction is 0 to 100, in increments of 1.
DISC = 0
DISC = 100
Tool Compensation (W1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0
Example of a 90 degree outside corner with G450 and G451
... Overshoot disabled, transition circle active
... Overshoot large enough to theoretically produce a response similar to
intersection (G451).
2.4 Tool: Tool radius compensation 2D (TRC)
Detailed Description
2-61