January 29, 2014
Converting Laser Alignment System Readings to Rim and Face Dial Readings
By Michael Keohane
VibrAlign released the free Laser-Dials App to aid laser system users who need/want to convert their laser shaft alignment system results to rim and face dial indicator readings. You can also use the App to convert dial indicator readings to laser readings. Most are interested in converting laser results to dials so that is what we will do here.
Proper laser and dial indicator shaft alignment methods lead to the same end result. Confusion typically occurs when dial indicator rim readings T.I.R. (total indicator reading) and Face (Gap) readings are compared to actual offset and angularity results as shown by the laser alignment system.
Setting the stage:
1 – All readings are in mils where 1.0 mil = .001” and 0.1 mil = .0001”. Example 10.5 mils = 0.0105”.
2 – The proper rim and face dial indicator mount (set up) is selected by pressing the “Mount” icon at the bottom of the Laser-Dial App. Also, select the correct face dial indicator orientation with the “Face“ icon.
3 – The face (gap) dial indicator reading represents the angularity as a slope (rise over run) when you divide the face or gap difference (top to bottom or side to side) by the swing of the face dial. For purposes of this discussion we will assume the face dial is indicating almost to the O.D. of the coupling so the swing would be the coupling diameter. This example will be for a 6 inch coupling diameter.
4 – The rim dial indicator reading is TIR. The true offset of the shafts is ½ of TIR.
5 – Rim and Face Alignment Tolerances are specified as 3 mils (thousandths) face and 3 mils (thousandths) rim. These are entered into the laser system’s built in tolerance table as .5 mils/1” Angular Tolerance (3 mils ÷ 6 inches) and 1.5 mils Offset Tolerance (3 mils TIR ÷ 2).
6 – The Validity Rule, for both the Rim and the Face dial readings, must be satisfied (top + bottom reading = side + side reading).
7 – Modern lasers typically display the angularity as mils/inch so there is no need to input a coupling diameter unless you are looking specifically for a gap value.
Initial results showing a machine misaligned
The top left photo shows the initial laser system results with a Vertical Angularity of -2.1 mils/1” and an Offset of -9.9 mils. The Horizontal Angularity is -7.8 mils/1” with an Offset of -7.9 mils.
The bottom left photo is the same initial results however the Vertical and Horizontal Angularity is shown as a Gap difference on the O.D. of the 6” diameter coupling. In this case -12.4 mil/6” and -46.9/6”
The top right photo is the Rim and Face Dial Indicator Mount (setup) from the Laser-Dials App. with the Vertical & Horizontal Angle and Offset laser results entered into their respective boxes.
The lower right photo are the dial results, as you can see the 12 to 6 o’clock face reading (in green) shows that there is a 12.6 mil gap difference top to bottom over 6 inches. Therefore 12.6 mils/6” = 2.1 mils/1”.
The 9 to 3 o’clock face reading (in green) indicates a 46.8 mil gap across 6 inches (-17.1 – 29.7) = -46.8 mils. Therefore -46.8 mils/6” = -7.8 mils/1”
The 12 to 6 o’clock rim reading (in red) of -19.8 mils is T.I.R. so -19.8 ÷ 2 = -9.9 mils offset as shown on the laser. From 9 to 3 there is a 15.8 mil T.I.R. difference (-17.8-(-2.0) = -15.8 therefore -15.8 mils ÷ 2 = -7.9 mils offset.
Final results showing a machine in alignment
The final laser system results show the Vertical and Horizontal Alignment to be in tolerance and once entered into the Laser-Dials App. the Rim and Face Dial Indicator values are better than the specific tolerances of 3 mil face and 3 mil rim.
VibrAlign Laser-Dials App available free on iTunes or Google Play
How to Convert Dial Indicator Specs from the VibrAlign Alignment blog:
Dial Indicator basics video (TIR, Validity Rule & TPS) on the VibrAlign you tube channel: