Lookahead; Standard Functionality - Siemens SINUMERIK 828D Function Manual

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LookAhead

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.

LookAhead is only available for path axes, not for spindles and positioning axes.

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.

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.

Basic Functions

Function Manual, 09/2011, 6FC5397-0BP40-2BA0

B1: Continuouspath Mode, Exact Stop, LookAhead

3.3 Continuous-path mode

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