The mass center of gravity of a rotating object is not on its rotating axis, which generates eccentric force and force distance, thus causing vibration and support to bear unnecessary impact during rotation. How to solve this problem? Dynamic balance detection needs to be carried out with balancer to find out eccentric weight, eccentric distance and eccentric orientation. On this basis, eccentricity can be removed by weighting and reducing methods to ensure that the center of gravity of the rotating object is on its axis of rotation, and reduce vibration to ensure the balance of rotation.

Dynamic balance is also called double-sided balance. In any rotor with unbalance, its unbalance can be balanced by two correction planes. It can not be solved by static balance method, but can be corrected only on the dynamic balance machine. Before dynamic balance testing, we need to know the technical terms and calculation formula of dynamic balance testing.

If the balance accuracy of a motor rotor is required to be G6.3, the weight of the rotor is 0.2kg, the speed of the rotor is 1000rpm and the correction radius is 20mm, then the allowable unbalance of the rotor is 0.3g, because the motor rotor is usually double-sided corrected. Before selecting the balancing machine, the required balancing accuracy of the rotor should be considered.

I. Interpretation of Dynamic Balance Terms:

1. Rotor Balance Quality: Index to Measure Rotor Balance

In G=eper.Omega/1000:

G is the balancing quality of the rotor, with 11 grades per mm/s from G0.4-G4000;

Eper is the allowable unbalance rate per gmm/kg or rotor mass eccentricity um;

Omega is the angle of the highest working speed of the rotor, -2pi.m/60;

2. Permissible unbalance per unit mass of rotor (rate):

Eper=G.1000/omega=G.1000.60/(2pi.n)

_9549.G/n in g.mm/kg or um;

II. Simplified calculation formula of unbalance:

M=9549MG/r × In formula n:

M - Rotor mass unit (kg)

G - Selection of precision grade

R - Calibration Radius Unit (mm)

N - unit of working speed of workpiece (rpm)

M - Unbalanced Qualified Unit of Qualification (g)

3. The calculation formula of allowable unbalance is:

In mper=M*G* (60/2PI*r*n) X10^3 (g):

Mper - to allow unbalance;

M - represents the weight of the rotor itself;

Unit is - kg;

G - represents the balance accuracy level of the rotor;

Unit is - mm/s;

R - represents the calibration radius of the rotor;

Unit is - mm;

N - represents the speed of the rotor;

Unit is - rpm.

Before you select the balancer, you need to determine the rotor balance level approximately first. In 1940, the International Organization for Standardization (ISO) established the world-recognized ISO1940 balance level, which classifies the rotor balance level into 11 levels, with 2.5 times increment between each level, from G0.4 with the highest demand to G4000 with the lowest demand, in mm/s, representing the migration distance of imbalance to the rotor axis. As shown in the table below:

G4000

Crankshaft drive for low-speed marine diesel engines with rigid unit for singular cylinders

G1600

Crankshaft drive for large two-stroke engine with rigid mechanism

G630

Crankshaft drive of large four-stroke engine with rigid device; Crankshaft drive for marine diesel engine with elastic device

G250

Crankshaft drive for high-speed four-cylinder diesel engine with rigid unit

G100

Crankshaft drive parts for six-cylinder and multi-cylinder high-speed diesel engines; Complete engine for cars, trucks and locomotives

G40

Car wheels, hubs, wheels, propeller shafts, crankshaft drivers for six-cylinder and multi-cylinder high-speed four-stroke engines with elastic devices

G16

Drive shafts for special needs (propellers, Cardan drive shafts); Parts of the crusher; Parts of agricultural machinery; Individual parts of the car engine; Crankshaft Drives for Special Requirements Six-Cylinder and Multi-Cylinder Engines

G6.3

Gears of main turbines of merchant ships and seaships; Drum of high-speed separator; Electric fans; Rotor components of an aviation gas turbine; Pump impeller; Machine tools and general machine parts; General motor rotor; Individual parts of engine for special needs

G2.5

Gas and steam turbines; Machine tool drive; Medium and large motor rotors for special needs; Rotor of small motor; Turbine pump

G1

Drivers for tape recorders and recorders, CDs and DVDs; Grinder drive; Small armature for special needs

G0.4

Spindle of fine grinder; Motor rotor; Top