During the classroom portion of a Fixturlaser GO Pro training class, at a sheet metal processing plant, one mechanic insisted the GO Pro alignment results were not repeatable in the field. The mechanic had the opportunity to use their GO Pro once before the training class and was convinced it would not repeat
For the “OJT” portion of the class we set out to align the machine in question. The mechanic offered a “good natured” bet against the GO Pro which of course I declined. The machine is a 25 HP electric motor and pump set, operating at 1800 RPM. As the pump is pumping etching acid to clean sheet metal prior to painting the pump was behind a wall, for safety, with only the coupling end of the shaft in view. Unfortunately photos were not allowed to be taken.
The first set of results indicated the vertical and horizontal alignment slightly out of tolerance. The class made a Verti-Zontal Compound MoveTM by adding shims to correct the vertical misalignment then adjusting the motor horizontally to bring it into tolerance.
After tightening the hold down bolts and re-measuring the results showed the alignment to be worse then when we started. Another set of measurements and different results, however still out of tolerance.
Non-repeating alignment results typically indicate something is loose. The sensor brackets, coupling backlash, hold down bolts, etc. We checked all we could see and everything was tight.
Several more set of alignment measurements revealed the same non-repeatable results. Something had to be moving on the pump end. As the acid had been drained from the pump we were allowed to open up the wall to view the pump. What we found hit us in the head like a 2 x 4! Literally, that was the problem a 2 x 4!
One of the pump’s 4 feet had broken off and a piece of 2 x 4 was wedged under it. Closer inspection revealed that acid had eaten away the wood and the foot was not supported by anything. As the pump was no longer securely mounted we had been attempting to align the electric motor to a moving target. All the mechanics had a good laugh at what we found.
Obviously, this pump had to be repaired or replaced before a precision shaft alignment could be performed, so we moved to another pump, and aligned it without incident.
Lesson(s) learned on the first pump?
1. Never assume anything when it comes to alignment, examine all machines being aligned.
2. You can’t align a moving target. Check that ALL hold down bolts are tight.
3. If your alignment results are not repeating more than likely something is loose, it’s not the tool.
4 Comments
Great blog post!
Good catch, yes a moving target would be difficult to align to. 🙂
Great article. It is amazing how basic practices seem to be forgotten until nothing else is working. Then it’s ‘I wonder if we have a bad foot.’
Makes for a long and frustrating alignment when you dont trust the tool, it is telling you something is wrong.