Coupling alignment is misleading. What you truly want is good shaft alignment. Dial indicators are used to measure the amount of physical misalignment in both the vertical and the horizontal planes. Using 2 dial indicators allows you to graph & calculate the amount of angular misalignment. All this measuring and calculating requires the services of a well-trained mechanic/alignment specialist. And time. And as we all know, labor costs money.
Enter the 'laser'. Improved technology that allows for easier training, much less time consuming, and unheard of accuracy. Light Amplification by the Stimulated Emission of Radiation. The Laser used to align shafts is a beam of light with a wavelength of 670 nanometers. The output power is less than 1 milli-watt, which, when compared with store registers, is 1/10th the output power! Federal regulations Code #21 specifies this a Class II laser. NY State considers this an approved, safe, laser product. Therefore, as approved Class II lasers, they are exempt from operator certification.
Shaft alignments with a laser begin with mounting directly to the shafts, same as the dial indicators. The major difference, however, is it doesn't matter so much how "crooked" the mount is, or how clean the shaft surface. The laser does not measure the physical difference from the shaft surface, but it measures the distortion from the imaginary centerline of rotation of the shaft. Precision Alignment has been defined as positioning of the shafts so the rotational centerlines are exactly collinear under operating conditions. The couplings simply keep the 2 shafts connected to enable the transfer of torque from the driver to the driven.
Absolute precision alignment cannot be achieved, so alignments are measured to a tolerance. With the improved measurement capabilities of lasers, the tolerances can be measured to an accuracy of 1 micron(.00004"). You can't read a dial indicator that close. Some laser equipment manufacturers use a single beam laser(with a reflector/mirror), while others use 2 laser beams. The accuracy is in the technology of the 'electrical' detector, so it really doesn't make a difference whether there are 2 projected beams or one projected and one reflected. The detector measures the difference between the 2 beams. The computer then calculates the alignment offset and angularity.
Alignment tolerances vary with the shaft speed. The faster the speed, the closer the alignment needs to be to protect the bearings. Coupling two misaligned shafts actually pushes, or pulls, the shaft against the bearings supporting them. The amount of this force that the motor(driver) has to overcome to turn the shaft can be calculated as wasted horsepower(energy). This in turn can be measured in amperage and shown in $$ expense. Several careful studies have shown that improving shaft alignment can save from 3% - 9% in energy costs.
Once again, investing in PM, will save you money!
