Siemens SINUMERIK 840D sl Function Manual

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B1: Continuous-path mode, Exact stop, Look Ahead 44.1 Brief DescriptionExact stop or exact stop modeIn exact stop traversing mode, all axes involved in the traversing motion (except axes of modaltraversing modes) are decelerated at the end of each block until they come to a standstill. Thetransition to the next block occurs only when all axes involved in the traversing motion havereached their programmed target position with subject to the selected exact stop criterion.Continuous-path modeIn continuous-path mode, the NC attempts to keep the programmed path velocity as constantas possible. In particular, deceleration of the path axes at the block limits of the part programis to be avoided.LookAheadLookAhead is a function for optimizing the continuous path mode.Smooth machining of workpieces is necessary to ensure a high-quality surface finish. For thisreason, path velocity variations should be avoided during machining whenever possible.Without LookAhead, the NC only takes the traversing block immediately following the currenttraversing block into consideration when determining the possible path velocity. If the followingblock contains only a short path, the NC must reduce the path velocity (decelerate in the currentblock) 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 thecurrent traversing block, a much higher path velocity can be attained under certaincircumstances because the NC now has considerably more traversing blocks and more pathavailable for calculation.This results in the following advantages:● Machining with higher path velocities on average● Improved surface quality by avoiding deceleration and acceleration processesSmoothing the path velocity"Smoothing the path velocity" is a function especially for applications (such as high speedmilling in mold and die production) that require an extremely steady path velocity. Decelerationand acceleration processes that would cause high-frequency excitations of machineresonances are avoided with the "Smoothing the path velocity" function.Basic FunctionsFunction Manual, 01/2015, 6FC5397-0BP40-5BA2 177