When many engineers and other rotating equipment maintenance and operations professionals think of dynamic balancing, large machinery often comes to mind, such as compressors, pumps, and other big commercial and industrial systems. In fact, many of the components we balance at HI-TEK Balancing can be quite large. We balance rotating parts of all sizes – even rotors up to 22,000 lbs.
But not all rotating systems are big. Here at HI-TEK we generally consider “small rotors” under 1 pound in weight. Dynamic balancing small rotors requires precision interface to tooling and special concern for repeatability on and off tooling and balancing arbors. Many times small parts have shaft sizes under ¼ inch in diameter and they run at high speeds.
In fact, a lot of laboratory and medical systems are small, even tiny. We refer to the dynamic balancing of components this small as “micro balancing,” where unbalance is quantified using units such as gram inches, ounce inches, or micro ounce inches. Dynamic balancing small rotors to ISO 1940-1 specifications requires precision-machined tooling and balancing arbors. Small diameter shafts and bore fits can be expensive and difficult to machine — only a few tenths of a thousandth of an inch variable in the mounting bore of small cooling fans can make the arbor fit go from a loose fit to a very tight press fit.
Some of the micro balancing factors to consider include:
- Cost of machining super precision mounting diameters
- Perform vibration testing to find out what ISO balance grade is necessary
- Consider balancing at the next assembly level with shaft or drive installed
- Find out the amount of acceptable vibration
The term “micro balancing” is used in two different ways: it can refer to very tight tolerance balancing of rotating parts or it can refer to the component size. Micro balancing is a process in which rotating parts, such as small electric motor armatures, are mounted or rested on a force-measuring fixture in a dynamic balancing machine and spun to speeds high enough to measure the unbalance forces. Micro balancing requires the skills of a highly-experienced dynamic balancing technician and the ability to measure and understand tenths of thousandths of an inch and sometimes even millionths of an inch.
Often small parts are processed in their own support structure because the parts are so small it’s impossible to belt drive them. Small parts require machined tolerances so tight that assembling them after balancing causes repeatability and vibration problems. The solution is to fixture them as a unit in the balancer. At HI-TEK Balancing, we’ve successfully utilized micro balancing to process rotating parts as small as a pencil eraser weighing only a few grams.
Not every dynamic balancing shop can handle small systems, so if you’d like to learn more about micro balancing, contact us today.