Page 203 - Machinery Component Maintenance

Machinery Alignment 185

These light-weight, nonbulky devices are mounted on the equipmcnt
shafts, and only a cord-connected microcomputer module is external to
the beam emission and receiverldetector devices.
The prism redirects the beam and allows measurement of parallel off-
set in one plane and angularity in another, thus simultaneously control-
ling both. In one 360" rotation of the shafts all four directional alignment
corrections are determined.
The receiver is a biaxial analog photoelectric semiconductor position
detector, yielding mathematical results to within one micron. Data for
computation are entered automatically through a cable direct from the re-
ceiver/detector. The only information still to be entered manually is the
relative position, 4 times, at 0, 90, 180 and 270".
With the data automatically obtained from the receiver/detector, the
microcomputer instantaneously yields the horizontal and vertical adjust-
ment results for the alignment of the machine to be moved.
Physical contact between measuring points on both shafts is no longer
required, as this is now bridged by the laser beam, eliminating the possi-
bilities for error arising from gravitational hardware sag as well as from
sticky dial indicators, etc. The system's basic attachment is still carried
out with a standard quick-fit bracketing system, or with any other suit-
able attachment hardware.
If the reader owns an OPTALIGN@ system, he does not have to be con-
cerned with sag. Other readers must continue the checkout process.

Checking for Bracket Sag

Long spans between coupling halves may cause the dial indicator fix-
ture to sag measurably because of the weight of the fixture and the dial
indicators. Although sag may be minimized by proper bracing, sag ef-
fects should still be considered in vertical alignment, To determine sag,
install the dial indicators on the alignment fixture in the same orientation
and relative position as in the actual alignment procedure with the fixture
resting on a level surface as shown in Figure 5-1 I. With a small sling and
scale, lift the indicator end of the fixture so that the fixture is in the hori-
zontal position. Note the reading on the scale. Assume for example that
the scale reading was 7.5 Ibs. Next, mount the alignment fixture on the
coupling hub with the dial indicator plunger touching the top vertical rim
of the opposite coupling hub. Set the dial indicator to zero. Next, locate
the sling in the same relative position as before and, while observing the
scale, apply an upward force so as to repeat the previous scale reading
(assumed 7.5 Ibs in our example). Note the dial indicator reading while