Siemens SINUMERIK 840D sl Function Manual page 187

Overload factor
The overload factor restricts step changes in the machine axis velocity at block ends. To ensure
that the velocity jump does not exceed the maximum load on the axis, the jump is derived from
the acceleration of the axis.
The overload factor indicates the extent by which the acceleration of the machine axis
(MD32300 $MA_MAX_AX_ACCEL) may be exceeded for an IPO-cycle.
The velocity jump results as follows:
Velocity jump = axis acceleration * (overload factor-1) * interpolator cycle.
The overload factor is saved in the machine data:
MD32310 $MA_MAX_ACCEL_OVL_FACTOR (overload factor for axial velocity jumps)
Factor 1.0 means that only tangential transitions with finite velocity can be traversed. For all
other transitions, the velocity is reduced to zero by changing the setpoint. This behavior is
equivalent to the function "Exact stop with interpolator end". This is undesirable for continuous-
path mode, so the factor must be set to greater than 1.0.
Note
For startup and installation, please note that the factor must be reduced if the machine is likely
to be subject to vibrations during angular block transitions and rounding is not to be used.
By setting the following machine data, the block transitions are rounded independent of the
set overload factor with G641/G642:
MD20490 $MC_IGNORE_OVL_FACTOR_FOR_ADIS
Activation/deactivation
Continuous-path mode with a reduction in speed according to the overload factor can be
activated in any NC part program block by the modal command G64.
Selecting the exact stop which works on a block-by-block basis enables rounding to be
interrupted (G9).
Continuous-path mode G64 can be deactivated by selecting:
● Modal exact stop G60
● Rounding G641, G642, G643, G644 or G645
Implicit continuous-path mode
If it is not possible to insert rounding blocks in continuous-path mode with rounding G641 due
to the very short block path lengths (e.g. zero-clocked blocks), the mode is switched over to
continuous-path mode G64.
Basic Functions
Function Manual, 01/2015, 6FC5397-0BP40-5BA2
B1: Continuous-path mode, Exact stop, Look Ahead
4.3 Continuous-path mode
187