MYTH: “All Soft Foot can be corrected by proper shimming.”
TRUTH: Soft Foot is Machine Frame Distortion. This can sometimes be caused by problems not easily fixable by shimming, like pipe strain, which can only be properly corrected by adjusting the piping and interface with the machine. A good laser system with positional change monitoring capability (such as EASY-LASER XT770 with Easy-Trend) is the best way to detect and measure the effects of pipe strain.
Watch and learn more about Soft Foot!
by Yolanda Lopez
Soft foot can severely affect the operating condition of a machine, which will undoubtedly shorten its life expectancy. Here are a few simple tips to help avoid soft foot in your machines:
- Eliminate rust, dirt and any other contamination from the contact surfaces of the machine feet, shims and frame or foundation.
- Never insert more than four shims at a time beneath a single machine foot. More than three shims may cause a spring effect.
- Eliminate external forces on the machine such as those from connected piping, conduit, auxiliary supports, etc.
- Use high quality, clean and uniform shims when shimming is necessary.
Watch our Shaft Alignment Know-How video on Soft Foot
by Pedro Casanova CRL
Soft foot is every alignment technician’s worst nightmare and while correcting soft foot may not be easy, it is worth every minute you spend on it, because once done, the alignment of the machines becomes a much easier task. If you want to make aligning your machinery easier, quicker and more accurate, start by correcting soft foot.” —Alan Luedeking, Manager Tech Support – LUDECA. Inc.
The Soft Foot Checks and Corrections Crash Course Video provides insights and instructions on solving various types of soft foot, and demonstrates industry-leading techniques using laser alignment equipment.
by Ana Maria Delgado, CRL
When taking individual soft foot readings on a four-footed machine, one foot at a time, always with the other three feet tight, if the two highest values appear diagonally opposed to each other, you have “rocking” soft foot situation. There are three potentially correct shimming solutions to this problem, but only one best solution.
Here’s how to find it: Loosen both diagonally opposed soft feet, leaving the two not soft feet tight. Feel the shim packs. If one is loose and one is snug, mike the air gap that appears under the loose one and shim that one by the amount of the air gap. If both shim packs are loose, shim both feet, by roughly half the soft foot value you got for each of them individually, or mike the airgaps with both of them loose and shim those amounts individually at each soft foot respectively. There are subtleties involved with this procedure that are best learned in an in-depth training course, but this will already go a long way toward solving these problems. Note If your two largest soft foot values do not appear diagonally opposed, you do not have a rocking problem, and other causes and solutions must be explored, again best learned through specialized training.
Have you heard about our Soft Foot Wizard?
by Pedro Casanova CRL
Measuring machinery misalignment with today’s tools, particularly computerized laser alignment systems and well-designed bracketing, is no longer as difficult a task as it once was, when all you had were a straight edge, feeler gauges and maybe a set of dial indicators with some make-shift hardware.
Why then, is it that aligning the machinery to given target values is so often still so cumbersome and time-consuming? There may be several reasons, among them unnecessarily tight tolerances specified by the machinery vendor, or problems with worn-out bearings, or inadequate bases, lack of jackscrews, etc. But by far the greatest obstacle to expeditiously reaching your alignment goal is soft foot. ‘Soft foot’, or machine frame distortion can be measured by various means, and indeed it must be measured and corrected before proceeding with the alignment. Why? Simply because an uncorrected soft foot condition will make alignment a trial-and-error procedure where indicated corrective shimming and lateral moves no longer bring you to the expected results. Severe soft foot may also be quite harmful to the machinery itself.
Correcting soft foot may not be easy, but it is worth every minute you spend on it, because once done, the alignment of the machines becomes a much easier task. Many alignment systems available today have soft foot measuring programs, and the most advanced system even features a soft foot ‘wizard’ which analyzes the type of soft foot measured (there are a number of different soft foot conditions) and suggests how to correct it.
Conclusion: If you want to make aligning your machinery easier, quicker and more accurate, start by correcting soft foot.
by Ana Maria Delgado, CRL