Siemens SINUMERIK 840Di Function Manual page 158

Detailed Description
2.3 Continuous-path mode
Implicit continuous-path mode
If it is not possible to insert approximate positioning blocks due to the very short block path
lengths (e.g., zero-clocked blocks) in continuous-path mode with approximate positioning
G641, the mode is switched over to continuous-path mode G64.
The figure below shows how the function velocity drops according to an overload factor.
Fig. 2-3
2-10
Axial velocity change on block transition
Continuous-Path Mode, Exact Stop, LookAhead (B1)
Function Manual, 08/2005 Edition, 6FC5397-0BP10-0BA0