Influence on the lookahead functionality (G115/G116/G117)
G115 General influence on the lookahead functionality (modal) G116 Influence on the calculation of block transition velocity (modal) G117 Reset the lookahead functionality (modal, initial state) 
Overview of the functionality of the lookahead function
Various single functions are implemented in the lookahead function. They limit motion velocities to maximum values in order to always maintain the permissible axis velocities and axis accelerations.
The following single functions influence the velocity profile:
(1) Calculation of maximum path velocities based on the maximum axis velocities of the axes participating in the motion as specified in the channel parameter list PCHAN00071.
(1) The velocity on the programmed path is limited so that each of the axes participating in the motion does not exceed its maximum axis velocity.
(2) Calculation of maximum path velocities on curved paths based on maximum chord error.
(2) In this case, a curve radius can be determined on each curve at the point of greatest curvature. A circular section can then be defined on this circle and its starting and end points correspond to a point generated on the path. Provided that the real mechanical system is moved along the associated chord, the height of the associated circular section can be included as an error criterion.
(3) Calculation of maximum path velocities on curved paths based on the maximum axis acceleration specified in the channel parameter list PCHAN00071.
(3) The maximum path velocity calculated based on the secant error can still be too high, particularly with a short tracing time and small circular movements. The resultant centripetal accelerations would then exceed the permissible axis accelerations.
(4) Calculation of path transition velocity based on the block transition geometry, taking into account the axes participating in the motion and the limit values specified in the channel parameter list PCHAN00071.
(4) As a rule, the relevant portions of the single axes alternate in the total motion with a block transition. However, this change in axis portions only occurs in the first tracing cycle on the new path (for linear motion). If it is assumed that the transition should take place without the generated acceleration (e.g. by the slope function), the resultant axis accelerations can be estimated. The maximum path velocity at block transition can then be calculated so that the maximum axis accelerations are not exceeded at the transition.
General case:
Normal mode with lookahead
After program start all functionalities of the lookahead function are switched on (G117). This ensures that the parameters specified in the channel parameter list PCHAN00071, e.g. maximum axis velocity and maximum axis acceleration, are always maintained.
Special case:
Switch off single functions of the lookahead function by G115
Programing Example
Influence the lookahead functionality (G115/G116/G117)
Nnn G115 = 0  (Switch off the single functions (2),(3) and (4)) (of the lookahead function) 
The table below explains the possible combinations of the single functions.
Notice
The corresponding selected or deselected functions always refer to all axes.
Overview of permissible identification numbers (ID) related to G115:
Single function 
(1) 
(2) 
(3) 
(4) 
0  * 



2  * 

 * 
4  *  * 


6  *  * 
 * 
8  * 
 * 

10  * 
 *  * 
12  *  *  * 

14  *  *  *  * 
*  Single function active 
 Single function not active 
Programing Example
Nnn G115 = 2 (Switch off single functions (2) and (3))
Nnn G115 = 12 (Switch off single functions and (4))
Nnn G115 = 14 (Switch off single functions after)
(program start, cf. G117)
Special case:
Influence the lookahead functionality with G116, G117
The G116 function disables the calculation of the block transition velocity (single function (4)) for single programmable axes. No reduction in block transition velocity (path velocity) takes place because of "corners" in the path.
Notice
In this case, the dynamic axis data (axis accelerations) are not normally maintained.
Programing Example
N10 G116 X1 Y2 (No reduction in block transition)
(rate of different axis)
(rates of the axes X or Y)
N20 G01 G91 X100 Y100 F1000
N30 X100
In this example, block transition N20/N30 is traversed without any drop in set velocity. The command values change at the block transition in jumps according to the axis portions on the path.
Attention
The coordinate value is only required for syntax reasons; otherwise it is irrelevant.
The G117 function reenables all single functions of the lookaheadfunction (default setting after program start).
Programing Example
Nnn G117  (Enable all single functions (1),(2),(3),(4)) (of the lookahead function) 