B1: Continuouspath Mode, Exact Stop, LookAhead
3.3 Continuous-path mode
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
171
3.3.4
LookAhead
3.3.4.1
Standard functionality
Function
LookAhead is a function which is active in continuous-path mode (G64, G64x) and determines a foreseeable
velocity control for multiple NC part program blocks over and beyond the current block.
If a part program contains consecutive blocks with very small paths, only one velocity is reached per block
without LookAhead, enabling deceleration of the axes at the end of the block while maintaining acceleration
limits. This means that the programmed velocity is not reached at all. With LookAhead, however, it is possible to
implement the acceleration and deceleration phase over multiple blocks with approximately tangential block
transitions, thereby achieving a higher feedrate with shorter distances.
Figure 3-5
Velocity control with short distances and exact stop G60 or continuous-path mode G64 with LookAhead
Deceleration to velocity limits is possible with LookAhead such that violation of the acceleration and velocity limit
is prevented.
LookAhead takes plannable velocity limits into consideration such as:
• Exact stop at block end
• Velocity limit in the block
• Acceleration limit in the block
• Velocity limit on block transition
• Synchronization with block change at block transition.
Note
LookAhead is only available for path axes, not for spindles and positioning axes.
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