ViSmart™ Viscosity Sensor for Process Control in Printing Ink Applications Customer Application Challenges Making viscosity measurements outside the laboratory has challenged process engineers and quality control departments for years. Because viscosity can be directly affected by temperature, shear rate, and other variables that can be very different off-line from what they are in-line, existing laboratory viscometers are of little value in process environments. Measuring viscosity in-line with traditional instrumentation has been especially difficult within the inks and coatings arena due to the lack of a credible and cost effective means of measuring viscosity in-situ. With the advent of acoustic wave sensor technology it is now possible to monitor ink and coatings viscosity continuously, in-situ and in real-time.

Figure 1 – SenGenuity solid-state low shear bolt viscosity sensor

Controlling the quality of ink materials entering the pressroom ensures that print results are both reliable and repeatable. The viscosity of ink formulations need to be tightly controlled to ensure the precise and correct transfer of ink from the press to the paper. By monitoring and controlling the viscosity of the ink, press operators can significantly reduce product defects and the cost of poor quality. Changes in viscosity of inks and coatings are directly affected by temperature, shear rate and other variables that can be very different off-line from what they are in an in-line environment. It is therefore necessary to detect changes in viscosity within the process stream in real-time. In-line viscosity sensors eliminate the need for making process decisions based on intermittent “snapshot” data acquired from periodic sampling.

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Solution - The ViSmart™ Viscosity Sensor Most existing viscometers have been developed from off-line laboratory analysis technology. While these mechanical and electromechanical viscometers can be adapted for some in-line applications, they are generally not suitable for process environments where cost, size, robustness, and reliability in challenging conditions are critical considerations. With the SenGenuity ViSmart™ viscosity sensor, there is now a solid-state solution to the problem of measuring viscosity in real-time process applications. The sensor has a small form factor (Φ1.00” x L 3.40”) and has a standard ½“ NPT interface. The sensor is a solid-state device that has no moving parts and does not require on-site calibration. With an operating shear rate several orders of magnitude higher than fluid flow characteristics, acoustic wave sensors like the ViSmart™ viscosity sensor are unaffected by static, laminar, or turbulent flow. The ViSmart™ sensor calculates viscosity by measuring the power loss of an acoustic wave as it penetrates the liquid. The square of this loss is proportional to the product of frequency, density and viscosity. The ViSmart™ sensor also has an embedded temperature chip that is used to provide in-situ temperature measurements. The sensor can be connected to SenGenuity’s FluidTrackr™ hand-held datlogger (see Figure 2) or to a laptop computer via USB for use by quality control personnel making spot checks in the field. The sensor can also output data in standard 0-4V or 4-20mA output formats using the VisConnect (see Figure-4).

Figure 2 – SenGenuity FluidTrackr™ datalogger

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Customer Application Data A major printing house with expertise in flexographic and gravure printing deployed the ViSmartTM viscosity sensor on its printing machines as shown in Figure 3. The sensors measure the viscosity of the ink as it is delivered from the ink delivery tanks to the printing press. The sensors are integrated to the press control system using the VisConnect, which provides a standard 4-20 mA output (see Figure 4).

Figure 3 – Monitoring and controlling ink viscosity in real-time with the ViSmart™ sensor.

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Figure 4 – VisConnnect 4-20 mA output module Figure 5 shows ink viscosity data collected from 8 sensors (for 8 different colors) installed on the printing machine. The “dips” (at time interval 12:12:00 and 12:14:00) correspond to the sensor actually measuring an inconsistency that was related to a new batch of ink introduced into the ink delivery tank. Using this sensitive tracking capability, the customer is able to maintain a tight control over viscosity over long process runs, thereby ensuring high print quality.

Figure 5 –Continuous monitoring of ink viscosity on the printing press Page 4

Contact Information If you would like to learn more about our sensors and the applications we address please contact our applications engineering group at [email protected].

DISCLAIMER

Vectron International reserves the right to make changes to the product(s) and or information contained herein without notice. No liability is assumed as a result of their use or application. No rights under any patent accompany the sale of any such product(s) or information.

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© 2009 Vectron International All Rights Reserved SenGenuity • 267 Lowell Road, Hudson NH 03051, USA • Tel: 1.603.578.3025 • Fax: 1.603.578.4060 • www.sengenuity.com

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