LINK Systems System 1100 Tonnage Monitor - Manual (Page 102)

USING SYSTEM 1100 TONNAGE MONITORS
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9-11
Figure 28. Clipping Due to Improper Tie Rod Tension.
the machine tooling stretches (strains) the tie rod by an amount
proportional to load and releases the compressive forces in the
uprights proportionally to load. If the tension on a tie rod
places a compressive force on the upright that is less than the
force released by the load, all compressive force will be removed
from the upright, and the signal from the strain link on the
upright will no longer be proportional to load.
This condition can be detected during calibration of a straight
side machine when strain links are mounted on uprights. If, at
rated tonnage, the calibration number associated with one or more
channels with input strain links mounted in approximately the same
place on each upright is required to be much higher to produce
equal tonnage readings on each channel of the System 1100 Tonnage
Monitor, improper tension of the tie rods is the most probable
cause of the higher calibration numbers. To determine if the tie
rod tension is the actual cause, reduce the load on the load cells
during calibration till the sum of the load cell tonnages is equal
to about 1/4 of rated machine tonnage, while making sure that
approximately equal loads are on the load cells. If the channels
with much higher calibration numbers now give tonnage readings on
the System 1100 that are much larger than the channels with lower
calibration numbers improper tie rod tension is indicated.
If a recorder, oscilloscope, or a personal computer with the Link
Systems Signature Analysis software is available during
calibration, incorrect tie rod tension can be seen on the waveform
for a channel as a clipped signal, as illustrated in Figure 27.
9.4.2 Snapthrough Forces