B1: Continuous-Path Mode, Exact Stop, Look Ahead; Brief Description - Siemens SINUMERIK 840D sl Function Manual

B1: Continuous-path mode, Exact stop, Look Ahead

4.1

Brief Description

Exact stop or exact stop mode
In exact stop traversing mode, all axes involved in the traversing motion (except axes of modal
traversing modes) are decelerated at the end of each block until they come to a standstill. The
transition to the next block occurs only when all axes involved in the traversing motion have
reached their programmed target position with subject to the selected exact stop criterion.
Continuous-path mode
In continuous-path mode, the NC attempts to keep the programmed path velocity as constant
as possible. In particular, deceleration of the path axes at the block limits of the part program
is to be avoided.
LookAhead
LookAhead is a function for optimizing the continuous path mode.
Smooth machining of workpieces is necessary to ensure a high-quality surface finish. For this
reason, path velocity variations should be avoided during machining whenever possible.
Without LookAhead, the NC only takes the traversing block immediately following the current
traversing block into consideration when determining the possible path velocity. If the following
block contains only a short path, the NC must reduce the path velocity (decelerate in the current
block) to be able to stop in time at the end of the next block, if necessary.
When the NC "looks ahead" over a configurable number of traversing blocks following the
current traversing block, a much higher path velocity can be attained under certain
circumstances because the NC now has considerably more traversing blocks and more path
available for calculation.
This results in the following advantages:
● Machining with higher path velocities on average
● Improved surface quality by avoiding deceleration and acceleration processes
Smoothing the path velocity
"Smoothing the path velocity" is a function especially for applications (such as high speed
milling in mold and die production) that require an extremely steady path velocity. Deceleration
and acceleration processes that would cause high-frequency excitations of machine
resonances are avoided with the "Smoothing the path velocity" function.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
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