How to measure parallelism

Examples of parallelism measurement include mutual parallelism between rolls and other surfaces in papermaking machines, printing presses, rolling mills, etc. Other examples include overhead tracks, rails, press machine tables.



Parallelism measurement with angular prism

The laser beam is directed along the machine (the base line), but perpendicular to the measurement object. The principle is based on the beam being angled at 90° with the aid of an angular prism. In this way it is possible to measure a large number of objects on long machines by moving the angular prism along the machine in the direction of the laser beam. The detector (mounted on a magnet base, for example) is placed on the front and rear end of the measurement object. The results show the squareness in relation to the reference line graphically and digitally. A completed measurement shows the mutual parallelism of the measurement objects (e.g. rolls) in relation to the base line or one of the measurement objects. Machines of up to 80 meters in length and with 150 rolls/objects can be measured.

Parallelism measurement without angular prism

Mutual parallelism between rolls or surfaces can also be measured without an angular prism. The laser beam is directed parallel to and between two measurement objects. This method is most suitable when there are only a few objects to measure. The detector is positioned at the front end (A) of roll 1 and is zeroed at the display unit (see image). Then moved to the rear edge (B) of the roll and the measurement value read off. Move the detector to the front of roll 2 (C). Set to zero. Move the detector to the rear end (D) and read off the measurement value. The difference between the two measurement values in positions B and D is the parallel error.

Parallelism measurement with angle detector

Easy-Laser® E975 system for roll alignment has a special angle detector, and a digital precision level. The measurement principle is simple: position the laser transmitter so that the beam points straight across the rolls, towards the detector. The vertical angle is measured first, then the horizontal. This then constitutes the reference. Then move the detector to the roll to be adjusted, or back to the roll that is to replace the old one. Point the beam towards the detector again, and adjust the roll to the correct position. Done! This method means that even short stoppages can be used for measurement.