Siemens SINUMERIK 840D sl Function Manual page 1863

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 starts with the normal position
(perpendicular to the path tangent) at the end point of the previous path section (program
block) and ends in normal position at the start point of the new path section (program block).
Where outside corners are very flat, the response with G450 (transition circle) and G451
(intersection) becomes increasingly similar → refer to 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.
Value
DISC = 0
DISC = 100
The programmable maximum value for DISC can be set via the machine data:
MD20220 $MC_CUTCOM_MAX_DISC (max. value for DISC).
Values greater than 50 are generally not advisable with DISC.
Figure 2-28
Basic logic functions: Tool Offset (W1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0
Significance
Overshoot disabled, transition circle active
Overshoot large enough to theoretically produce a response similar to
intersection (G451).
Example: Overshoot with DISC = 25
Detailed Description
2.4 Tool radius compensation 2D (TRC)
75