July 2013 6.12 Spindle 955
Monitoring the
spindle speed
With MP3350 and MP3351 you set the maximum permitted excessive spindle
speed. An NC stop with a subsequent emergency stop is triggered if actual
spindle speed > than the nominal spindle speed + the permitted excess
speed. With this function you can also have the spindle be monitored for
unexpected start-up.
In MP3350 you enter a relative value in percent, and in MP3351 an absolute
value, for the permissible excessive speed. The absolute value in MP3351 is
only used if the absolute value that results from MP3350 is less than the value
in MP3351.
If you want to use monitoring of the spindle speed for spindles with gear
stages, then you should be more generous with the tolerance that results
from MP3350 and MP3351, since the spindle speed can vary significantly
when switching between the gear stages.
A percentage value for the permissible shortfall of the nominal spindle speed
can be entered in MP3540. You can thus use this machine parameter for
monitoring whether the spindle speeds falls below a specific spindle speed
limit. (e.g. nominal spindle speed = 500 rpm, MP3540 = 20 % --> the
monitoring function will respond if the spindle speed falls below 400 rpm).
Monitoring is useful for power milling where the workpiece is to be machined
at a high feed rate and a low constant spindle speed. If the monitoring function
responds, an EMERGENCY STOP reaction is triggered in order to protect the
machine from possible damage, for example if the spindle comes to a
standstill while still engaged in the material. The error message "8BF0 Actual
speed value too small" is displayed. Monitoring does not become active until
the spindle speed exceeds the value defined in MP 3542.
Monitoring for falling below the lower spindle speed limit (defined in MP3540)
does not become active until the actual spindle speed exceeds the value
defined in MP3542. This threshold is required in order to avoid activating the
monitoring function before a reasonable shaft speed is reached (for example,
if the noise of encoders at the actual value of the spindle speed is of
subordinate importance, or in order to prevent monitoring from becoming
active when the tool plunges into the material).
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