The Unique Stealth Dual Beam Laser Technology Delivers Major Advantages in Real Shaft Alignment Situations
Many shaft alignment lasers on the market use the same opposed beam measuring technique, in which one beam shoots from the motor to a detector on the driven machine and another beam shoots back to a detector on the motor shaft. Only one beam is necessary to measure shaft offset, but the 2nd beam is necessary for the system to measure angular error by comparing the two readings at different angles. This arrangement is referred to as a “cross-fire” laser.
The main advantage of a cross-fire system is that only simple positional detectors are required to build a laser alignment. Nevertheless, the characteristics of this system also create some significant potential pitfalls. Firstly, in this design there are 2 of everything, potentially contributing to increased system errors. Secondly, backlash variation during the measurement cycle contributes to an angle error reading, causing inaccuracy, so backlash needs to be carefully controlled. Thirdly, angular measurement error varies with the head spacing, so to avoid detrimental measurement errors, either the heads cannot be brought too close together or very high resolution, high linearity detectors need to be used. Finally, as the head spacing gets longer, beam angle errors can greatly reduce the effective measurement range of the laser, so that pre-alignment may be necessary just to get laser readings.
Stealth dual beam laser systems use a very different measurement technique to get around the above problems. These lasers have dual beams shooting in the same direction. One beam measures position and the other beam is used to directly measure angle, with the same measuring cell in only one detector head. This system is far less affected by backlash; its angular accuracy is virtually the same at 100mm and at 2000mm head spacing, and the laser beams are far less inclined to run off the detector when initially setting up an alignment, greatly reducing the need for pre-alignment.
This video from Stealth Alignment pulls no punches in demonstrating some of the advantages of Stealth, and the pitfalls of cross-fire laser systems.
Video: Stealth Laser Technology v’s Cross Fire Lasers
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