With any shaft-to-shaft alignment, it is important to find the axis of rotation of one shaft relative to the other to eliminate the effects of mounting errors on the measurement. Traditional methods, like the rim and face method, attempt to do this but in reality still rely on machined faces and rims for accuracy. It is easy to see that an error in the flatness of a coupling face or the concentricity of the rim can affect the measurement.
The S-680 (and S-670) takes care of this problem by using software to perform a procedure that is similar to our NORMIN method. By rotating the laser and target together through 180º and taking multiple points along the way, the mounting errors can be calculated and programmed out of the alignment numbers. To do an alignment with our S-680 (S-670 is slightly different) a 5 step procedure must be followed:
STEP 1. In the MOTOR SETUP SCREEN the motor's foot dimensions, machine description and desired alignment tolerances are entered. Thermal growth offsets (the amount the motor grows from a cold start to operating temperature) are also entered at this stage.
STEP 2. The LASER SETUP SCREEN is then displayed and the laser and target are placed on the brackets and adjusted until the readings are within +/- .030" (0.8 mm) of zero. Adjustments to the vertical center are made by moving the laser up or down on the brackets. Adjustments to the horizontal center are made by an adjustment knob on top of the laser. For new motor installations, this screen is used to "rough in" the motor's large angular misalignment.
STEP 3. After laser and target setup and motor rough-in, the user turns to the SOFT FOOT SCREEN, which displays an easy-to-follow soft-foot routine that finds potential soft-foot problems and recommends corrective action. A note of caution: this soft-foot routine is best used with motor uncoupled to the driven unit. This is because a large pump and rigid coupling can prevent the laser from finding soft-foot problems. The laser measures shaft deflections caused by a soft foot and if the shaft is rigidly coupled to a driven unit it may not move much at all
STEP 4. Once the soft foot routine is completed the alignment can begin. The DATA TAKING SCREEN is displayed, which prompts the user to rotate the laser and target for data collection and analysis of mounting errors. The system (S-680 only) automatically senses when the laser and target are being rotated and when they stop. When rotation stops, the software automatically calculates the mounting errors and subtracts them from the misalignment readings. The user has choice of a coupled or an uncoupled routine.
STEP 5. Finally the user switches to the MISALIGNMENT SCREEN, which shows a graphical display of misalignment, including center and slope readings corrected for mounting errors, and shim values in all 4 axes. The readings and motor graphics automatically update when moves are made or shims added. The data-updating speed (averaging) can be adjusted to smooth out fluctuations in the readings due to air turbulence or vibration. Shim values displays are replaced by "IN TOLER." when the alignment comes into tolerance. The DATA TAKING and MISALIGNMENT screens also show a light meter that warns the user if bright light, such as the sun, is affecting the readings.
For motors with large misalignment, steps 4 and 5 may need to be repeated. In general, however, one set of shims and moves is all that is needed to perform the alignment