# Flatness =straightness in two dimensions

Flatness measurement is carried out, for example, on machine tables, wire ends in papermaking machines, flanges and slewing bearings (circular planes), machine bases etc.

### Measurement of flatness/twist on rectangular planes

First, the beam is roughly aligned along and across the measurement object. The detector is then positioned on the selected measuring points and the values registered. According to the measurement, three of the measuring points are set to zero, and the other points are recalculated for the newly created reference line. The measurement values at the other measurement points will show the deviation from the laser plane. The measurement values can be recalculated so that any three of them become zero references, with the limitation that a maximum of two of them are in line horizontally, vertically or diagonally in the co-ordinate system. (If there are three in line, it is just a line, and not a plane!)

### Measurement of flatness/twist on circular planes

The measurement of flatness/twist on circular planes such as flanges is also based on the use of three reference points, situated at intervals of 120° around the circle. Decide the number of measurement points and which three will be the reference points on which the laser plane will rest. All measurement results displayed are now relative to the three selected reference points/laser plane.

### Flatness measurement with a reference plane parallel to the horizontal plane

The laser beam is adjusted according to the vials on the laser transmitter, and the measurement value at the first measurement point is set to zero. The measurement values at the other measurement points will show the deviation from the horizontal plane.

### Which points on the surface are to be measured?

When measuring flatness, it is important to decide which points on the surface are to be measured. These are marked in a co-ordinate system in the X and Y axes, or at each bolt hole, for example on a flange.

## Training

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