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Just what does it take to be successful at balancing?  Let’s start with some basics. First you need to have an understanding of the balancing process, next nomenclature: is it unbalance, imbalance, out of balance, or what? Use a consistent description and stick with it. Next, think about what the source of unbalance could be: is it uneven wear on parts? Voids within castings? Damage from impacting? Material buildup? Even though buildup is not usually a problem, when it begins to come off it rarely does so evenly thus creating an unbalance. In other words, unbalance is simply the uneven distribution of mass.
Simply review or collect data to ensure that the undesirable vibration is from unbalance and not some other issue such as a belt problem, misalignment, electrical issue, etc. Once you’ve determined that the vibration is indeed unbalance you need to inspect the object to be balanced. If it is not clean, clean it. Look for damaged or broken parts. On belt driven equipment inspect the belts as their frequency can be very close to running speed and can hinder the balance job. Make sure you have the proper tools for doing the balancing job, such as a balancing instrument capable of reading the vibration that is produced at running speed or what is commonly referred to as 1×or 1 times and capable of indicating the phase angle at 1×.  This could involve utilizing an optical tachometer, laser tachometer, magnetic pickup or even a stroboscope. Some tachometers will require a piece of reflective tape on the shaft for the tachometer to read from and this might require stopping the machine if still in service.

Tip: I try to place the tape horizontally, or along the axis of the shaft, with the leading edge of the tape on the trailing edge of the key way. This can be helpful if you ever have to return for another balancing job on the same machine.  You need to determine if you will be adding or removing material in order to balance the rotating component. If removing material, how will you determine how much you’ve removed;if adding weight, you need to make sure the weight you are adding is of a material that is compatible with the service the machine is exposed to. If adding material “weights”, how will they be attached? With set screws? Bolts? Clamps? Welded on? All this should be considered. One last tip: if after two runs you’re not there or almost there yet, you might need to stop and examine your process to ensure no mistakes have been made.
Download LUDECA’s 5-Step Balancing Procedure.

by Gary James CRL

Unbalance occurs when the rotor’s mass is no longer at the center of rotation.  Unbalance can be caused by many factors:

  • Assembly error
  • Machine tolerances
  • Eccentric components
  • Wear
  • Corrosion
  • Thermal distortion
  • Mechanical distortion
  • Material buildup
  • Bent components
  • Broken components

Many things can prevent the successful correction of unbalance.  Equipment resonance, bearing issues, product buildup and many more equipment problems can prevent a successful balancing  job from being completed.  All Equipment defects should be corrected before attempting to balance equipment.

by Trent Phillips