4-29
ROTALIGN 01.2000
Soft foot
SOFT FOOT is the condition whereby one or more machine feet are
not resting properly on the foundation but are being held down by
force with the foot bolts. Soft foot could be a result of:
• Non-coplanar machine mounting surfaces,
• Deformed machine frame or feet,
• External forces, e.g. from a connecting pipe or bracket, or
• Improper shimming or soiled machine feet.
The consequences of forcibly tightening down the feet are deformed
machine frames, bent shafts and distorted bearings, leading to high
vibration and premature failure.
Soft foot should be checked before aligning the shafts. This can be
done quickly and conveniently using the soft foot function. With the
laser and receiver mounted on the shaft in the usual way, the system
is able to sense any machine movement when the machine bolts are
loosened individually; if the computer is given the machine dimen-
sions, ROTALIGN can calculate from the shaft movement how much
each foot has raised as it is loosened.
Once you have established the foot movements, the results need to be
interpreted and translated into the thicknesses of the shim to be
placed under the feet. How straightforward this is depends on the
type of soft foot you have. The two main types are:
Parallel soft foot:
One or more feet are too short or too long.
This usually results in the machine rocking on the longer feet.
This is corrected by placing a shim under ONE of the short feet
(see illustration opposite).
Angular soft foot:
The base of one or more feet is at an angle
to the foundation and is only partly in contact. In this case it is
usually necessary to check suspect feet with a feeler gauge and
build up wedged shims.
Sometimes a combination of soft foot errors are present, making
correction somewhat more complicated. Please refer to the Soft Foot
appendix at the end of this manual for more examples.
If, approximately 10 seconds after entering "Soft Foot" mode, the
ROTALIGN fails to establish contact with the sensor, the "SENSOR
???" message will be displayed on the screen. The message is also
displayed if the receiver cable is disconnected while ROTALIGN is
in Measure, Move or Soft Foot modes. Check that both ends of the
cable are properly connected.
Horizontal machine alignment - measurement
F
Note
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