June 14, 2010
Proper Movement Sequence for Shaft Alignment
By Patrick Lawrence
One of the most important factors in successful shaft alignment is utilizing a proper sequence of moves. Understanding and utilizing this methodology will drastically decrease the time required to align shafts, and improve the effectiveness of your efforts.
First, be sure to perform the proper pre-alignment steps, such as minimizing soft foot and backlash. If you are unsure of these steps, please visit the Pre-alignment section of VibrAlign’s Alignment Resource Center.
Shaft misalignment occurs when the shaft rotational center of one machine (usually a fixed machine) does not align with the shaft rotational center of another (moveable) machine. The goal of shaft alignment is to correct this misalignment and make the shafts colinear. The two machines are almost always misaligned in a combination of angular and offset positions:
- Vertical/horizontal angular misalignment, where the shafts are not in the same vertical/horizontal plane.
- Vertical/horizontal offset misalignment, where the shafts are parallel vertically/horizontally, but not collinear, or in the same line.
After measuring the shaft positions to determine the angular and offset misalignment, the first step in correcting the machine is to correct the vertical plane. Whether you’re using indicators and have graphed the solution or using a laser system that did the math for you, correcting the vertical plane first allows for greater flexibility when making the horizontal move: once the vertical alignment is completed, you should theoretically be able to move the moveable machine as far as the hold down bolts will allow and still be aligned vertically. This is why it is so important to correct the vertical misalignment first.
The next step is to make the correction in the horizontal plane. Much like with adding or removing shims in the vertical plane, sliding the machine towards or away from you will correct both the angular and parallel offset misalignment together.
Once the correction moves are complete, tighten the hold down bolts at the feet and remeasure to confirm your work. Most alignments should be accomplished in one or two complete moves.