Why balance a rotating part?
When a part’s mass isn’t evenly distributed around its axis of rotation, it generates a centrifugal force that rotates with the shaft. That force grows with the square of the speed, so a small amount of unbalance on a fast-turning part can do real damage. It shows up as vibration, noise, poor surface finish on machined parts, and shortened bearing, seal and coupling life. Balancing removes that force by adding or removing weight in the right places.
Static, couple and dynamic unbalance
Static unbalance means the center of mass is offset from the shaft axis. A statically unbalanced part will roll until its heavy side is at the bottom. It can be corrected in a single plane, which makes static (single-plane) balancing a good fit for narrow parts such as pulleys, fans, impellers and grinding wheels.
Couple unbalance happens when two equal heavy spots sit on opposite sides at opposite ends of the rotor. The part may sit perfectly still on knife edges, yet it wobbles end to end when it spins.
Dynamic unbalance is the combination of the two, and it’s what most real rotors have. Correcting it requires measuring the part while it spins and placing correction weights in two planes. Two-plane dynamic balancing is the right choice for longer parts like motor armatures, spindles, rolls, crankshafts and driveshafts.
Our balancing capacity
- Part weight from about 1 ounce to 5,000 lb
- Part length up to 30 feet
- Single pieces, prototypes and production runs
- Single-plane static and two-plane dynamic balancing
- Same-day and 24-hour emergency turnaround available
We balance fans, blower wheels, pulleys, electric motors, armatures, spindles, pumps, impellers, turbines, compressor rotors, crankshafts, driveshafts, boring bars, tool holders, cutting tools, agricultural equipment and aerospace components — and anything else that rotates.
Balance tolerances
We balance to your blueprint specification. If you don’t have one, we’ll recommend a tolerance based on the part’s type, weight and operating speed using the balance quality grades in ISO 21940-11 (formerly ISO 1940-1). For example, G6.3 is commonly used for fans, pumps and general machinery, while precision parts such as machine tool spindles typically need G2.5 or tighter.
Sending a part for balancing
- Tell us the operating speed and any required tolerance or drawing
- Note how keys should be handled (full key, half key or no key)
- Include mating parts that turn with it, such as a pulley or coupling half, if they should be balanced as an assembly
- Mark any areas where weight must not be removed or added
Not sure whether you need static or dynamic balancing? Call (586) 795-5550 and describe the part. We’ll tell you what it needs. If the part can’t come out of the machine, see field balancing.