Problem Types
Paper Analysis
Wet End Survey
Wet End Audit
Press Section Analysis
Calender Barring
Soft Nip Calender Vibration
Winder Vibration
Calender Oxbow
Winding and Reeling
Vibration Audit





Paper Analysis - Uniformity is Key to Efficient Operation .

The uniformity of paper is of fundamental importance to the final product quality. Of the different types of uniformity, the basis weight and caliper uniformity are the most important. Without this uniformity a host of problems arise, including wrinkles, cockling, breaks, and misregister in the pressroom.

On-line scanners used to measure these properties have a number of limitations. Since the paper travels through the scanner in the machine direction while the scanner moves across the machine, the scanner is really measuring the paper in a triangular fashion. The algorithms in the scanner then determine the MD & CD components, to the best of their ability. Another limitation of the scanner is the low frequency response inherent in the radioactive (Beta) source. Different scanners filter the signal differently, and use different algorithms for separating the MD from CD components. This makes it difficult to compare the uniformity from one machine to the next.

To measure paper without the limitations of the on-line scanners, it is recommended that the basis weight and caliper of your paper be tested in both the MD & CD on an off-line profilograph, or TAPIO. The TAPIO unit is the closest instrument to a standard at the present time. Because of this, a benchmark of your paper uniformity compared to other machines can be obtained.

The CD strips, collected from the top of the reel, represent a true cross-direction profile. There is no possibility that MD components will confuse the analysis. A machine direction component is also obtained, due to the spacing between the strips. Finally a residual component that cannot be related to the MD and CD is determined. This component is used to determine headbox performance and is used by manufacturers to warranty the headbox.

To overcome the low frequency response of the Beta gauge in the mill sensor, MD butt rolls are slit from the parent reel on the winder. When these rolls are measured in the off-line scanner at low speed, the frequency response normalized to paper machine speed is very good. This gives a frequency response reading greater than 200 Hz, much higher than on-line scanners, immediately showing the frequencies at which basis weight barring is occurring.

A paper analysis including the MD and CD TAPIO testing is recommended on an annual basis. If, however, there is any suspicion of a problem, or after any major equipment change or machine speed-up, a paper analysis is also recommended.

If the variability is high a wet-end survey will be required to determine the source of the problem.


Contact the webmaster
©2014 Spectrum Technologies All Rights Reserved.