Siemens SINUMERIK 828D Function Manual page 157

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 continuous­path 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 continuous­path mode
If it is not possible to insert rounding blocks in continuous­path mode with rounding G641 due to the very short
block path lengths (e.g. zero­clocked blocks), the mode is switched over to continuous­path mode G64.
Basic Functions
Function Manual, 09/2011, 6FC5397-0BP40-2BA0
B1: Continuous­path Mode, Exact Stop, LookAhead
3.3 Continuous-path mode
157