Siemens SINUMERIK 840C Installation Instructions Manual page 1089

12 Functional Descriptions
12.31.2 Description of function
It is possible to define for each individual channel whether or not its path speed must be
reduced by means of the PLC signal to channel "Do not reduce channel".
If a following axis is positioned within the reduction range, then the appropriate interface
signal: "Axis is in reduction range" is set. The PLC can transmit a message in response to
the output signals.
The display of the reduction factor and feed override * reduction factor can be configured
on the NC workstation WS800A. The reduced path feed of the channels is displayed in the
AUTOMATIC basic screen.
The minimum limit of the reduction factor corresponds to the value in MD 3936*. The SW
limit switch is approached with this minimum reduction factor. If the switch is reached, the
channels are braked at the max. acceleration rate and the reset alarm 148*/152* "SW limit
switch plus/minus" is output. The machining operation is halted. The axis is now positioned
behind the limit switch. The axis grouping remains intact.
MD 3936* "Minimum reduction factor" makes it possible to limit the distance traversed by
the axis passed the SW limit switch. 1 % corresponds to 100.
The following start-up procedure is recommended:
– Set "Min. reduction factor" to 1 %
– Traverse following axis at max. speed with monitoring of SW limit switch active
– If the distance by which the axis traverses past the SW limit switch is too large, then
the reduction factor must be decreased.
• Retraction
Retraction is possible only in the direction opposite to traversing. On the return path up to
the SW limit switch, the minimum reduction factor stored in MD 3936* is applied. From this
point onwards, the reduction factor is calculated in exactly the same way as for travel
towards to the SW limit switch, i.e. the reduction range is also effective when the axis is
moving away from the limit switch.
• Movements near the SW limit switch
The reduction factor always causes a reduction in the path speed when the following axis
is within the reduction range, even if it has not crossed the SW limit switch.
• G33 thread cutting
If the following axis enters the reduction range during thread cutting, then the spindle
speed is braked causing a dynamic lead error. The alarm "Stop during thread cutting" is
output.
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SINUMERIK 840C (IA)