Find the root cause of MD and CD variation

Root causes of quality and process problems across the sheet: CD and MD profile variation, barring, vibration-related defects, streaks and periodic patterns. It is also used for printability and surface quality problems such as print mottle, gloss variation and formation, and for drying-related effects such as shrinkage or instability. With a millimetre-level sampling step, it reveals variation that is not visible in online measurements or standard laboratory tests.

Online scanners are essential for control, but high production speeds force them to use larger apertures, lower sampling rates and heavy averaging. Tapio Analysis is done at slow speed under controlled laboratory conditions, with millimetre-level apertures, millimetre sampling intervals and minimal filtering, and every sensor measures the same point. Small-scale profile details that are not visible in online data can be seen clearly.

Traditional laboratory tests typically give single-point or averaged values, often from separate samples or locations. The Tapio sensors are based on the same paper quality standards, but they measure continuous profiles non-destructively with a 1 mm sampling step and small measurement spots, several properties from the same physical point. That makes spectral analysis and direct correlation between properties possible.

Two samples can have similar averages and even similar CV%, while the structure of their variation is completely different. Tapio Analysis shows whether the variation is mainly at short or long wavelengths, whether it is broadband or periodic, and whether the same variation appears in several properties. This helps separate random material variation from repeating, process-related patterns.

The standard measurement covers basis weight, caliper, transmission, dual-sided gloss and ash, with density, bulk and relative ash calculated from them. A porosity sensor is available for suitable grades, and further physical properties can be measured at our partners after the Tapio measurement. Sample spacing is 1 mm in a standard CD measurement and 10 mm in a standard MD measurement.

Spectral and time-domain analysis find the repeating patterns, frequencies and wavelengths in the data. With the production line speed, roll diameters, rotating speeds or CD actuator spacings, the Tapio Analysis software connects periodic variation to these elements automatically. CD analysis links variation to actuator spacing, CD control or process non-uniformity; MD analysis links it to rotating components, vibration sources or drying effects. Comparing basis weight, caliper and ash from the same points shows whether the cause lies in forming, pressing or coating.

You do not need a hypothesis: we can first characterize the variation as measured. For root cause analysis, basic production line information helps: grade, machine speed, roll diameters, rotating components and CD actuator spacings. With this data, the variation can be linked to specific machine elements or process conditions.

It can often narrow the possible causes substantially and, in many cases, find a strong match with a machine element or process condition. A matching wavelength, correlation or repeating pattern is evidence of a likely source, but measurement data alone does not always prove causality. Our reports separate measured findings from their interpretation and recommend further verification where necessary.

Yes. We compare total variation, wavelength distribution, periodic components and correlations between properties, which is useful for comparing suppliers, grades, production trials or operating conditions. Earlier Tapio measurements, QCS profiles and other suitable data can be included, for example in before/after comparisons or to see whether a variation has changed over time.

Use the price calculator for an instant estimate based on standard project parameters. Final pricing depends on the exact scope and shipping. For larger projects or special requirements, email info@tapiotechnologies.com for a tailored quote. We respond within one working day, with no commitment required.

No. The Tapio team can handle the whole measurement and analysis process and deliver a complete report with conclusions. If you want to explore the data, the Tapio Analysis software is open source and free, and measurement data files are available on request. The software's loaders can also be extended to read QCS or other high-resolution profile data.