VMI VIBER X4, Manual, Page: 48 / 58

Vibration Measurement Instruments
4. Fine Balancing
Sometimes a small unbalance will remain when you have mounted the balancing
weights. You can then select to continue with fine balancing and the instrument
calculates new fine balancing weights in the same way as the instrument calculat -
ed the balancing weights. The number of Fine Balancing steps you can make is
limited to 64.
• Repeat step 3 to perform fine balancing but with new suggested weight and
place.
There are several reasons for having to add Fine Balancing weights:
• It is often difficult to place the balancing weight exactly at the angle that the
instrument has calculated.
• It is often difficult to place the balancing weight on exactly the radius that you
have written in the instrument.
• The stiffness of the bearing support is non-linear and depends on the vibration
level.
Once the balancing weights are in place, you should start the machine and mea-
sure at least one more time to check the result. You may have made a mistake
when you mounted the balancing weights or another fault may have arisen in the
machine.
Response matrix
VIBER X4™ calculates and stores the unbalance sensitivity called Response
Matrix while you are balancing. Next time you want to balance the same ma-
chine, you can use the Response Matrix and the instrument calculates the balanc-
ing weights directly after the first trial run, or if all the transducers are already
mounted, even while the machine is still in production. No trial weights need to
be mounted.
When you use the Response Matrix, all the transducers, including the RPM trans-
ducer, must be placed in the same directions and locations as when the Response
Matrix was first calculated.
You cannot use balancing with the Response Matrix if the bearing stiffness has
been changed. For example if:
• The machine has been moved from a stiff support to a support with springs or
rubber feet.
• The machine has been moved from a support with springs or rubber feet to a
stiff support.
• The weight of the machine has been changed by more than +/– 10%.
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