Siemens SINUMERIK 840D sl Function Manual page 170

Detailed description
2.3 Continuous -path mode
Overload factor
The overload factor restricts step changes in the machine axis velocity at block ends. So 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, which
is set in machine data, may be exceeded for an IPO cycle:
MD32300 $MN_MAX_AX_ACCEL (axis acceleration).
The velocity jump is the product of the axial acceleration * (overload factor -1) * interpolator
cycle.
The factor is stored in the machine data:
MD32210 $MN_MAX_ACCEL_OVL_FACTOR (overload factor for axial jumps in velocity).
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.
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.
The block transitions are always rounded irrespective of the set overload factor by setting the
machine data:
MD20490 $MC_IGNORE_OVL_FACTOR_FOR_ADIS (G641/G642 irrespective of the
overload factor).
Selection and deselection of velocity reduction
Continuouspath mode with velocity reduction according to overload factor can be selected
modally in every NC part program block by means of program code G64.
Continuouspath mode G64 can be
• Interrupted non-modally by selecting exact stop G09
• Deselected by selecting exact stop G60
• Deselected by selecting rounding G641
Implicit continuouspath mode
If it is not possible to insert approximate positioning blocks due to the very short block path
lengths (e.g., zeroclocked blocks) in continuouspath mode with rounding G641, the mode is
switched over to continuouspath mode G64.
The figure below shows how the function velocity drops according to an overload factor.
18
Basic logic functions: Continuouspath Mode, Exact Stop, LookAhead (B1)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0