Equilibrado de rotores en tornos: Una solución rentable para mejorar la calidad del producto
En la fabricación moderna, donde la calidad del producto es de suma importancia, equilibrado del rotor se convierte en una parte esencial del proceso tecnológico. Sin embargo, la adquisición de equipos de equilibrado especializados puede resultar costosa para las pequeñas y medianas empresas. En este artículo, exploramos la posibilidad de utilizar tornos para rotor lo que puede reducir significativamente los costes de los equipos y mejorar la eficacia de la producción.
El torno como herramienta de equilibrado
The lathe, due to its design and functionality, can be successfully used for balancing rotors of various types and sizes. The main advantage of this approach is cost savings, as there is no need to purchase expensive specialized equipment. Additionally, using a lathe allows for balancing to be carried out directly during the rotor’s manufacturing process, which shortens production time and improves product quality.
Preparación para el equilibrado
Antes de iniciar el proceso de equilibrado, hay que dar varios pasos preparatorios:
- Elegir el torno adecuado: El torno debe tener suficiente rigidez y precisión para garantizar un montaje fiable del rotor y mediciones exactas de las vibraciones.
- Instalación del sistema de medición: Para medir el rotor vibración en el torno, un equilibrador portátil como el Balanset-1A puede utilizarse. Incluye sensores de vibración, un tacómetro, y programas informáticos para el análisis de datos y el cálculo de masas correctoras.
- Dealing with the spindle’s own unbalance: You do not have to balance the lathe spindle itself. Run the lathe with the chuck alone (rotor removed) and record the vibration vector: that is the baseline contributed by the spindle and chuck. If it is a significant fraction of the rotor reading, either subtract it, or — better — use the 180° index run (the “Mandrel eccentricity elimination” function, “F7 - Run Ecc”), which automatically separates everything that does not rotate with the rotor.
- Matching the rotor to the machine, not to the spindle: What matters is that the rotor’s unbalance force produces a measurable response on the bearing housings. A heavy, rigid lathe responds very little per gram of unbalance, so on a very light rotor the signal disappears in the noise, while a very heavy rotor may exceed the rated load of the chuck or the bearings. In practice, check that a properly sized trial weight gives a clean, repeatable amplitude and phase change before you trust any influence coefficient.
- Checking the runout of the rubber cover before balancing: On a rubberized shaft, mass unbalance and geometric runout of the covering are two different defects. Balancing cancels the 1× force; it cannot make an eccentric or oval cover round. Set a dial indicator against the covered surface and turn the shaft by hand: if the total indicated runout exceeds the product tolerance, grind or turn the cover concentric first — on the same lathe — and only then balance. A shaft that is balanced but still runs out will keep producing gauge bands, streaks and nip-pressure variation no matter how low the vibration reading gets.
En este artículo, detallaré nuestra experiencia y metodología en el equilibrado dinámico de rubberized shafts on a lathe machine – a solution that, admittedly, I was initially skeptical of due to the inherent rigidity and substantial weight of such machinery. Surprisingly, the operation was seamlessly executed, achieving the G 6.3 balance quality grade (ISO 21940-11, formerly ISO 1940-1).
Proceso de equilibrado del rotor en un torno en teoría
El proceso de equilibrado del rotor en un torno implica los siguientes pasos:
Fijación del rotor
El rotor se monta de forma segura en el mandril del torno o en los centros para garantizar la estabilidad durante el proceso de equilibrado.
Instalación de sensores
Fit one vibration sensor per correction plane — one on the headstock bearing housing and one on the tailstock or steady-rest housing — radially, as close to the bearing as possible, on a clean machined metal surface via a magnetic base. Do not mount sensors on the lathe bed, the apron or a guard: the 1× signal there is attenuated and dominated by the structure. Stick the cinta reflectante on a metal face (the shaft end or the chuck), not on the rubber covering, and aim the laser tachometer perpendicular to it.
Medición de la vibración inicial
The initial vibration level is measured at the speed you will use for the whole job. All runs — Run 0, the trial runs and the trim run — must be made at the same speed, because the influence coefficients are only valid for the speed at which they were measured.
Accounting for Eccentricity (immediately after Run 0)
Fixture and mandrel excentricidad adds a vector to the Run 0 reading that is not unbalance, and correcting for it would be wrong. Deal with it before the trial weight, not afterwards: tick the “Mandrel eccentricity elimination” checkbox in the Balanset-1A software, complete Run 0, then rotate the rotor 180° in the fixture and press “F7 - Run Ecc”. The software takes the vector half-sum as the eccentricity and the vector half-difference as the true unbalance, and only then unlocks the trial run. Doing this after the correction weights are already welded on means recalculating and redoing them.
How big should a trial weight be?
A safe starting point is a weight whose centrifugal force stays within 5–10% of the rotor weight. As a formula:
mde prueba = k · M · g / (R · ω²), k = 0.05–0.10
donde M is the rotor mass (kg), g = 9.81 m/s², R is the mounting radius of the weight (m), and ω = 2π·RPM/60 (rad/s). Example: a 50 kg rotor at 3,000 rpm with the weight at R = 0.2 m gives m ≈ 0.07·50·9.81/(0.2·314²) ≈ 1.7 g — grams, not hundreds of grams. That looks surprisingly small for a 50 kg rotor, but check the force: at 3,000 rpm those 1.7 g already pull F = m·R·ω² ≈ 34 N — about 7% of the rotor’s weight. Starting small is the point: stepping up is cheap, while an oversized weight is a real load on bearings and welds. The same force check works in reverse for any weight you are about to bolt on.
You don’t have to compute this by hand: the Balanset software includes a First Trial Weight Estimator that recommends both the mass and the starting angle from your rotor data, and a Prueba de impacto to check that you are not working near a natural frequency.
A good trial weight changes the reading by at least 20–30% in amplitude or 20–30° in phase. If the response is smaller, increase the weight stepwise — never jump straight to a heavy weight “to see something happen.”
Installing a Trial Weight
A peso de prueba of known mass is installed on the rotor, and the vibration is measured again. For two-plane balancing this is done in each plane in turn — a trial run with the weight in plane 1 (Run 1), then a trial run with the weight in plane 2 (Run 2) — so the software can measure the influence of each correction plane separately.
Cálculo de masas correctoras
El software Balanset-1A analiza los resultados de la medición y calcula las masas correctoras necesarias y sus ángulos de colocación.
Corrección de la masa del rotor
Dependiendo del diseño del rotor y de las capacidades del torno, la corrección de la masa puede realizarse mediante taladrado, fresado, soldadura u otros métodos.
Verificación del equilibrio
Tras efectuar las correcciones, se lleva a cabo una medición de vibraciones de control. El proceso se repite si es necesario hasta alcanzar el nivel de equilibrio requerido.
Dynamic Balancing in Practice
- Frecuencia de rotación: Typically, the working rotation speed of these shafts ranges between 300 to 500 revolutions per minute (rpm). In this particular case, we carried out the balancing at 550 rpm.
- Configuración: El eje engomado se montó en la máquina de torno y, a continuación, se colocaron estratégicamente los sensores, como se muestra en las fotografías adjuntas.
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
Equilibrado dinámico de ejes engomados
- Lecturas iniciales de vibración: Antes de equilibrar, el inicial vibration readings stood at 9 mm/s and 17 mm/s.
- Trial Runs: A two-plane job needs a trial run in each plane in turn — Run 1 with the weight in plane 1, then Run 2 with the weight in plane 2. A trial weight of 340 grams was welded on; it altered the vibration and fase readings by roughly 10%. Treat such a response as a bare minimum: for a clear, confident measurement we normally aim for a trial weight that shifts the vibration vector by 25–50%, but a heavy, rigid lathe responds very little per gram of trial mass.
- Ajustes de equilibrio: Post the trial runs with the trial weight, our Balanset-1A instrument indicated the need for the addition of 3100 grams on one side of the shaft and 4300 grams on the other, corresponding to corrections in dos planos. After these adjustments, vibration levels decreased to 2 mm/s and 4 mm/s.
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
- Puesta a punto: To further optimize results, we proceeded to add weights of 400 grams and 700 grams. Subsequently, another round of fine-tuning was executed by adding 200 grams and 400 grams. Due to spatial constraints, the weights were welded atop one another. Ultimately, these temporary weights were replaced with precision-cut, aesthetically pleasing counterweights crafted specifically for this shaft. The final vibration readings were an impressive 0.1 mm/s in both planes (a rounded figure — below 1 mm/s the instrument itself displays readings to three decimal places).
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
Equilibrado dinámico in situ de ejes engomados mediante una máquina de torno
Ventajas del equilibrado de rotores en tornos
Relación coste-eficacia
El uso de un torno para el equilibrado evita el gasto de adquirir equipos de equilibrado especializados.
Conveniencia
El equilibrado puede realizarse directamente durante el proceso de fabricación del rotor, lo que reduce el tiempo de producción.
Alta calidad
Las equilibradoras portátiles modernas, como la Balanset-1A, proporcionan una gran precisión de equilibrado, lo que permite reducir los niveles de vibración y mejorar la calidad del producto.
Conclusión
El equilibrado de rotores en tornos es una solución eficaz y económica para las empresas que buscan mejorar la calidad de sus productos y reducir los costes de producción. El uso de equilibradoras portátiles como la Balanset-1A hace que este proceso sea sencillo y accesible, incluso para talleres pequeños.
Recordatorios importantes
- Para obtener los mejores resultados, se recomienda utilizar instrumentos de medición de alta calidad y seguir estrictamente el procedimiento de equilibrado. Puede estimar el desequilibrio residual para su rotor con nuestro calculadora del desequilibrio residual (ISO 1940).
El equilibrado de rotores en tornos es un paso hacia el futuro de su producción, que se traduce en una mejora de la calidad del producto, una reducción de los costes y un aumento de la competitividad de su empresa.
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