The best alternative to using dial indicators for shaft alignment is to use a good laser alignment system such as the ROTALIGN® ULTRA or OPTALIGN® SMART. All the inherent problems and disadvantages of dial indicators are immediately eliminated. Here’s why:
- Training: Far less training and expertise is required of the millwright to use a laser system proficiently than to use indicators. No algebra or geometry skills are required for the technician to perform excellent alignments since the system performs all necessary calculations automatically. The entire setup, measurement, and correction process can be accomplished in less than half the time required with indicators. This saves downtime and saves money!
- No-Sag: The bracketing and components of the ROTALIGN and OPTALIGN laser systems are carefully designed to have their center of gravity directly between the support posts that hold them. The laser beam itself is weightless and thus no-sag exists with these laser systems. This saves setup time since sag does not have to be measured nor accounted for.
- No effect from End Float: The optical measurement principles used by the ROTALIGN systems render them entirely impervious to the effects of shaft end float, since the axial distance between sensor planes in the receiver is fixed. In the OPTALIGN system end float has no effect on angularity whatsoever due to the optical principles of a roof prism; the effect on the offset is negligible because even at the worst angles typically existent between misaligned machines the impact on the projected offset from the axial play is less than the measurement tolerance, whereas a face indicator is impacted directly by end float by the full magnitude of the axial displacement.
- Vibration mitigation: Even the most severe vibration from surrounding machines presents no problem for three reasons: First, the components are not overhung and therefore do not amplify the vibration. Thus the vibration of the components cannot exceed the amplitude of the vibration itself at the points on the machines where they are mounted. Secondly, the averaging of the readings can be adjusted so that the effect of any vibration on the laser beam is totally negated. Thirdly, the artificial intelligence that is programmed into the firmware of the system fires the laser beam at random intervals so that its pulse rate can never be in phase with any vibration. Thus all of the conditions that can render a dial indicator useless in these circumstances are eliminated.
- No Reading Errors or Parallax Effects: None of these potentially great human errors is possible with the ROTALIGN or OPTALIGN laser systems because all data collection is fully automated.
- No Tilting Error: As long as the laser system components can be securely mounted on the shafts or solid coupling hubs, no error can occur since the only movement registered is that of the beam across the sensor caused by misalignment of the shafts as they are turned. This is true even if the laser, prism, or receiver components are mounted cocked, or tilted with respect to each other!
- No Hysteresis Problem: No hysteresis errors can occur because there are no moving parts in the laser system components that can be affected by environmental conditions or rough handling. In fact, ROTALIGN and OPTALIGN systems are waterproof, shockproof, and dustproof. They can therefore withstand the rigors of use in an industrial environment far better than a delicate dial indicator.
- Measurement Resolution and Obstructions to Rotation: ROTALIGN and OPTALIGN have a measurement resolution of just 1 micron (0.00004″). This together with sophisticated artificial intelligence-based elliptical math models programmed in the firmware means highly accurate shaft alignment results can be obtained with only 70 degrees of shaft rotation, starting anywhere and stopping anywhere. ROTALIGN and OPTALIGN are totally independent of the clock positions that must be arrived at when measuring with indicators. Thus, obstructions to rotation are no longer a problem. The systems’ high resolution also means they are ideally suited to the task of measuring machine frame distortion at the coupling, sparing the millwright the problems and inaccuracies associated with mounting indicators at the machine feet for soft foot measurement. This too saves time and money.
Alignment, Articles and Case Studies by Alan Luedeking CRL CMRP