In our training classes, we really emphasize concentrating on three simple things. And taking care of those three simple things WILL make almost every alignment easier, regardless of the type of machine being aligned, or the tool being used. Do you want to have simple, easy alignments? Do you want to know the secret?
Do these three things:
1. Minimize soft foot.
You may get tired of hearing this, but I believe it is the most common reason for non-repeatability in shaft alignment. Not only can soft foot cause unwanted mechanical and electrical problems, it can greatly affect the repeatability of alignment values. Soft foot causes the moveable machine to change position, both vertically and horizontally, during the tightening process.
2. Control coupling looseness (often called backlash).
Any changes in the relative angular positions of the shafts will affect the readings – whether you are using lasers or indicators. Laser, reverse dial, rim and face – all can have errors if you don’t control angular position. Built-in inclinometers can greatly increase repeatability by allowing the aligner to minimize backlash as long as the angular position is monitored and controlled.
3. Tighten the machine feet down in a controlled, repeatable pattern.
Soft foot will almost never be zero. In addition, there are forces such as pipe and conduit strain, and unresolved problems such as dirt, burrs, etc. Any of these things can slightly change the position of the moveable machine during the tightening process. Of course, they should all be taken care of. But they never will be taken care of perfectly every time. So, the adverse effects of these variables can be minimized by tightening in a criss-cross pattern, just like tightening a pipe flange or head gasket. And if done in multiple passes of tightening, it can be further minimized.
No matter what you are using to measure alignment, controlling these three simple things can greatly increase your accuracy and repeatability, regardless of the alignment tool being used.