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Flexo Feb2021

FTA Flexo Magazine features a Rheonics user case study – “Viscosity Standardization: One Printer’s Approach”

Overview

Flexographic printing focused magazine – Flexo (https://www.flexography.org/flexo-magazine/) publishes an in depth article showcasing the Rheonics SRV viscometers and the RPS InkSight Multi-Station Ink Control solution at a customer location in Netherlands.

Find the link to the the publication.
Flexographic Technical Association – Flexo Magazine Feature (flexography.org)

To download the pdf copy of the website, please use the link below.

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Introduction

Viscosity is a very important parameter in final quality of the printed matter

» If the viscosity is not correct, the flow behavior and ink layer thickness will vary, leading to deterioration of print quality
» Poorly adjusted ink viscosity may cause excessive ink consumption and unnecessarily high costs
» Viscosity automation and predictive tracking control results in waste reduction and efficiency improvements

Tight control with an accurate sensor, combined with a responsive control system, has enabled us to streamline our printing process while improving color quality and reducing waste.

Key value of inline ink monitoring and control solutions

Print Quality. The main purpose of viscosity control is to maintain print quality from start to finish of a job, no matter how long or complex.

Operating Efficiency. A second goal is improvement of operating efficiency. Efficiency starts with setting up a job. Being able to nail the proper viscosity for all stations without cut-and-dry tinkering means rapid job turnover, keeping the machines printing instead of idling.

Topics Covered in the article

  • Accuracy of the sensors
  • non-Newtonian behavior of inks and characterization with viscometers
  • Installation inside the press
  • Predictive Tracking Control
  • QA & Standardization
  • Real units of viscosity – Cup Seconds or mPa.sec?

Some figures from the article

Maasmond Paperindustrie bv Oostvoorne in The Netherlands houses a W&H Primaflex CS press, equipped with viscosity sensors and other automated print quality control systems.
Maasmond Paperindustrie bv Oostvoorne in The Netherlands houses a W&H Primaflex CS press, equipped with viscosity sensors and other automated print quality control systems.

Maasmond Paperindustrie bv Oostvoorne in The Netherlands houses a W&H Primaflex CS press, equipped with viscosity sensors and other automated print quality control systems.

Figure 1: Temperature dependence of ink viscosity

Figure 1: Temperature dependence of ink viscosity

Figure 2: Sensor installed in ink line

Figure 2: Sensor installed in ink line

Figure 3: The sensor after measurement in cyan ink

Figure 3: The sensor after measurement in cyan ink

Figure 4: Four symmetric resonator viscometers installed on press, using simple pipe tees as adapters

Figure 4: Four symmetric resonator viscometers installed on press, using simple pipe tees as adapters

Image 1: Real-time ink control is achieved through inline ink monitoring facilitated by placement of viscosity sensors at each print deck. They connect and transmit data to central, multi-station and single-station handheld consoles.

Image 1: Real-time ink control is achieved through inline ink monitoring facilitated by placement of viscosity sensors at each print deck. They connect and transmit data to central, multi-station and single-station handheld consoles.

Figure 5a: Temperature-compensated viscosity (black, 25cP) and temperature (green, ~18 degrees Celsius) vs. time, coarse vertical scale

Figure 5a: Temperature-compensated viscosity (black, 25cP) and temperature (green, ~18 degrees Celsius) vs. time, coarse vertical scale

Figure 5b: Same plot as 5a, with expanded vertical scale. Temperature compensated viscosity variation is less than 0.2 mPa.s.

Figure 5b: Same plot as 5a, with expanded vertical scale. Temperature compensated viscosity variation is less than 0.2 mPa.s.

Figure 6: Response of the system to adding a large volume of cool ink to a system running at 21 degrees Celsius. Note the rapid recovery time of the temperature-compensated viscosity.

Figure 6: Response of the system to adding a large volume of cool ink to a system running at 21 degrees Celsius. Note the rapid recovery time of the temperature-compensated viscosity.

Figure 7: Color density variation with ink dilution and viscosity

Figure 7: Color density variation with ink dilution and viscosity

Table 1: Numerical Values of Delta E 2000 and Color Strength vs. Dilution (Viscosity Difference is relative to sample 6)

Table 1: Numerical Values of Delta E 2000 and Color Strength vs. Dilution (Viscosity Difference is relative to sample 6)

Figure 8: Color density as a function of ink dilution and density. Delta E 2000 values are referred to sample 6.

Figure 8: Color density as a function of ink dilution and density. Delta E 2000 values are referred to sample 6.

Maasmond Paperindustrie bv Oostvoorne in The Netherlands houses a W&H Primaflex CS press, equipped with viscosity sensors and other automated print quality control systems.Figure 1: Temperature dependence of ink viscosityFigure 2: Sensor installed in ink lineFigure 3: The sensor after measurement in cyan inkFigure 4: Four symmetric resonator viscometers installed on press, using simple pipe tees as adaptersImage 1: Real-time ink control is achieved through inline ink monitoring facilitated by placement of viscosity sensors at each print deck. They connect and transmit data to central, multi-station and single-station handheld consoles.Figure 5a: Temperature-compensated viscosity (black, 25cP) and temperature (green, ~18 degrees Celsius) vs. time, coarse vertical scaleFigure 5b: Same plot as 5a, with expanded vertical scale. Temperature compensated viscosity variation is less than 0.2 mPa.s.Figure 6: Response of the system to adding a large volume of cool ink to a system running at 21 degrees Celsius. Note the rapid recovery time of the temperature-compensated viscosity.Figure 7: Color density variation with ink dilution and viscosityTable 1: Numerical Values of Delta E 2000 and Color Strength vs. Dilution (Viscosity Difference is relative to sample 6)Figure 8: Color density as a function of ink dilution and density. Delta E 2000 values are referred to sample 6.

Unique advantages with the Rheonics SRV sensors

Rheonics sensors have built-in temperature measurement, permitting the temperature of the ink to be monitored. This permits the viscosity readings to compensated for temperature, which is essential for ensuring consistent production through typical daily and seasonal temperature variations.

There are many benefits to using an inline viscosity sensor like the SRV for printing applications. and some include:

  • Works accurately in most coating systems with a broad range of ink compositions and viscosities – water-based, solvent-based, UV inks, metallic inks etc.
  • Maintains the set ink viscosity, extremely responsive to fresh ink additions
  • Rugged, hermetically sealed sensor head. The SRV can be cleaned inline with all standard CIP processes, or with a wetted rag, without the need for disassembly or recalibration
  • No moving parts to age or foul with sediment
  • Insensitive to particulate matter; no narrow gaps to foul with particulates
  • All wetted parts are 316L stainless steel—meets sanitary norms with no corrosion problems
  • Certified under ATEX and IECEx as intrinsically safe for use in hazardous environments
  • Wide operational range and simple integration—Sensor electronics and communication options make it extremely easy to integrate and run in industrial PLC and control systems.

Some images of the RPS InkSight system

  • Rheonics SmartView console integrated in printing machines
  • Some pictures showing the SRV viscometers inline installation inside the press
  • Standalone control cabinet
Photo 02 03 21, 20 48 50 (4)
Photo 02 03 21, 20 48 50 (4)
Photo 02 03 21, 20 48 50 (6)
Photo 12 01 21, 19 41 43
IMG 9748
Figure 2: Sensor Installed In Ink Line
Fig2. RPTC
Photo 02 03 21, 20 48 50 (4)Photo 02 03 21, 20 48 50 (6)Photo 12 01 21, 19 41 43IMG 9748Figure 2: Sensor Installed In Ink LineFig2. RPTC

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Conclusion

As printing speeds increase, and profit margins get tighter, “getting it right the first time” becomes much more important. An error in initial viscosity setting can result in producing several thousand meters of waste in no time at all. Tight control with an accurate sensor, combined with a responsive control system, has enabled us to streamline our printing process while improving color quality and reducing waste.

What is unique about Rheonics viscosity control?

  • Traditional viscosity measuring methods (like efflux cups) are inaccurate, tedious to use, and prone to errors. Continuous viscosity control with such methods is extremely inefficient and unproductive.
  • Many common viscosity measuring devices do not provide fine enough viscosity control and require high maintenance and frequent calibration.
  • Rheonics RPS InkSight Predictive Tracking Controller and SRV viscometers enable tight viscosity control throughout the print job, due to the the system’s ability to autonomously maintain viscosity within extremely narrow limits.
  • Printers can achieve unmatched color accuracy and quality with the RPS InkSight system and ColorLock software – which is designed in collaboration with printers, for printers.
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