What is minimum detectable unbalance (Umin)?

Umin is the smallest unbalance that a balancing machine can reliably detect and display. It depends on the machine type, sensor sensitivity, display resolution, rotor mass, and balancing speed. A lower Umin means better sensitivity.

What is the difference between soft and hard bearing balancing machines?

Soft bearing machines operate below the first critical speed of the rotor-bearing system, measuring displacement. Hard bearing machines operate well below critical speed with stiff supports, measuring force. Hard bearing machines are generally faster to set up but may have slightly lower sensitivity for light rotors.

How does rotor mass affect achievable balance grade?

For a given Umin, a heavier rotor will have a better (lower) achievable residual specific unbalance (e = Umin/m). This means heavier rotors can potentially achieve better balance grades on the same machine.

What balance grades can typical machines achieve?

High-quality industrial balancing machines typically achieve G1.0 to G2.5. Laboratory-grade machines can achieve G0.4 or better. The achievable grade also depends on rotor speed — higher speeds make finer grades easier to achieve.

How is machine sensitivity verified per ISO 21940-21?

Machine sensitivity is verified by placing a known test unbalance on a proving (test) rotor and confirming the machine can detect and display it correctly. The test is repeated at different angular positions and the results must be within specified tolerances, following the Umar and URR test procedures of ISO 21940-21 (formerly ISO 2953).

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Calculadora de sensibilidad de máquina de balanceo

Calcule el desbalance mínimo detectable (Umin) y la clase de balanceo alcanzable para máquinas de balanceo con rodamientos blandos o duros según ISO 21940-21 (antes ISO 2953).

ISO 21940-21UminRodamiento blando / duro

Resultados

Desbalance mínimo detectable (Umin)

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Desbalance específico residual (eper)

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Clase de balanceo alcanzable

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Relación de reducción de desbalance (URR)

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Velocidad de servicio ω

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Desbalance mínimo detectable

El desbalance mínimo detectable (Umin) de una máquina de balanceo depende de la sensibilidad del sensor, el nivel de ruido electrónico y la resolución de la pantalla:

Clase de balanceo alcanzable

Donde ω es la velocidad angular a velocidad de servicio (no velocidad de balanceo).

Regla práctica: Umin debe estar muy por debajo del desbalance residual permisible (Uper) — típicamente no más de aproximadamente 10 % — para que la incertidumbre de medida no domine el resultado. Las propias máquinas de balanceo se describen y evalúan según ISO 21940-21 (antes ISO 2953), que define el desbalance residual mínimo alcanzable (Umar) y las pruebas de relación de reducción de desbalance (URR).