Balancing high-speed rotors, such as those used in polygon optical scanners built by Waterloo Optics, is critical for several reasons. Polygon optical scanners are integral components in devices like laser printers and LIDAR systems, where they rotate mirrors at high speeds to direct laser beams for imaging or measuring purposes. The precision with which these mirrors are rotated directly impacts the device’s accuracy and efficiency.
Why is Balance Important?
Firstly, an unbalanced rotor can lead to significant mechanical vibrations. At high speeds, even a slight imbalance can generate centrifugal forces that magnify the rotor’s oscillatory motion. This not only leads to excessive noise but can also cause wear and tear on bearings and other structural components. Over time, this reduces the lifespan of the scanner and increases maintenance costs.
Secondly, vibrations from imbalance can directly affect the quality of the output. For instance, in a laser printer, vibrations can cause minute shifts in the positioning of the laser beam across the printing medium. This results in distortions or blurring of the printed text and images, thereby reducing the print quality. Similarly, in LIDAR systems, vibrations can lead to inaccuracies in the data collected, which could compromise the system’s reliability in applications such as autonomous driving and geographic mapping.
Furthermore, unbalanced rotors consume more power. The energy that could otherwise be used for productive work is wasted in overcoming the additional resistance caused by the imbalance. This inefficiency leads to higher operational costs and, in cases where battery life is a concern (like in portable devices), reduced performance and usability.
Lastly, balancing rotors contribute to safety. High-speed components, if failed, can disintegrate or cause the device to malfunction, posing hazards to operators and nearby equipment.
How to Quantify and Improve Balance
Two of the key parameters used in balancing a precision rotating optics are the imbalance and the balance grade. The imbalance is typically measured in grams-mm for our products, or miligrams-mm. This parameter is simply the amount of mass of imbalance held at what distance from the rotational axis. It is independent of speed. A polygon mirror with one gram of imbalance at one millimeter from the rotational axis has an imbalance of one gram-mm. This parameter is independent of speed, and does not reflect the level of vibration a device may have, or the level of noise one may hear from a device, since that is speed dependent.
The balance grade is a factor that takes into account the imbalance, the mass of the rotor, and the speed, and provides a measure of the negative effects of imbalance. The lower the balance grade, the lower the vibration, noise, etc. of the system.
Waterloo Optics Delivers High Quality Balanced Scanners
Typical results from the balancing process for a high speed polygon scanner are shown in the image here. In each successive step the level of imbalance (left axis) as well as the balance grade at 26,000 RPM (right axis) is reduced. The lowest standard grade for balance under ISO 21940-11 is 0.4. As seen in the table, Waterloo Optics is able to balance scanners well below this delivering smooth, low vibration performance.
Proper balancing of high-speed rotors is indispensable. It ensures operational efficiency, enhances the lifespan of the equipment, maintains the quality of output, reduces energy consumption, and upholds safety standards. In precision applications like polygon optical scanners, where even minor errors can have significant consequences, achieving optimal balance is paramount.