RollCal™ 2 - RollTest Measurements and Controls Oy : RollTest Measurements and Controls Oy

RollCal™ 2 is a fairly new system using the multipoint measurement principle enabling true measurement of roll roundness.

As paper machines´ production speeds have edged towards 2,000 m / min ( approx. 6,500 ft / min.) the roll geometry and overall condition deserve careful consideration.

RollCal™ 2 has been developed from RollCal™ but it provides additionally several new features.
The four-point measurement technique that RollCal™ 2 utilises True Out-of-Roundness™ measurement capability, which measuring the roll roundness always in the correct way. This is not the case with two-point roll measurement systems in spite of are they new, old or automated applications.

The optimised out-of-roundness of a workpiece and its impact on the paper making process have become critical factors especially in a certain roll positions. A good number of customers have been using RollCal™ 2 system for a few years and have proved that the improved measurement is needed ( See also RollControl™ i / 3D – Grinding ).

RollCal™ 2 can measure
shape
crown and compound crown
true out-of-roundness
concentricity
sag
roll alignment
grinder bed errors

True Out-of-Roundness™
There are hardly ever perfectly round objects.
Out-of-roundness is a serious fault in paper machine rolls, causing vibration and significant periodic variation in paper quality. However, out-of-roundness is difficult to eliminate in grinding and until RollCal™ 2 was developed it was impossible to measure correctly.
Out-of-roundness can be presented as a spectrum or a combination of various waveforms of different amplitudes. This spectrum starts at 2nd lobe, which corresponds to an oval shape. 3rd lobe corresponding to a triangular shape, 4th lobe corresponding to a rectangular shape, etc.
Even waveforms (oval form, rectangular form etc.) can be measured with a 2 – sensor measurement system, but odd waveforms will be missed. The multipoint measurement technique (Four-point-measurement) is needed to detect also the odd waveforms.

The RollCal™ 2 System employs multi-point contact measurement using simultaneous displacement measurements, at multiple angular positions around the roll circle. The multi-point principle is the only practical method of measuring true out-of-roundness of large cylindrical rolls that must be measured while positioned in a machine tool.

RollCal™ 2 features an asymmetric sensor arrangement coupled with advanced signal processing. These features separate true out-of-roundness from the error motion of the axis of rotation without filtering out even or odd waveforms.

RollCal™ 2 is capable of separating systematic and repeating error motions as well as non-repeating random motions.

The RollCal™ 2 System utilizes the floating 4-point measurement principle using two measurement probes with sensors and two support probes. The sensor arrangement at the measurement frame is optimized to give the best detecting capability of the common waveforms. The new design of the sensor arrangement, carbon fibre composite measurement frames, software and electronics improve the measurement accuracy, make the system more versatile and offer extensive reporting that can be used for studies on the roll irregularities and their impact on the paper quality.

Reports
The new software provides very comprehensive reporting capabilities, for example, an out-of-roundness measurement consisting of several cross-sections can be reported as:

• an ordinary graphic profile in a polar co-ordinate presentation
• a diagram presenting the recorded waveforms with their amplitudes huom!
• a colour-contoured sheet consisting of various cross sections, each colour tone representing certain amplitudes of deviation
• a 3D-surface chart
• as a 3D-cylinder, that can be rotated, with different colour tones indicate a certain amplitudes of deviation.

Similarly, measurement of diameter deviations can be reported as a graph.