Cambridge Viscosity Blog

Optimize coating applications through tighter viscosity control

Dec 2, 2020 9:07:18 AM / by Patrick Riley

2020-12-02-Optimize-coating-applicationsWhen it comes to coatings, product quality can live or die by viscosity. A too-viscous mixture can result in bubbling and an inconsistent, bumpy, “orange-peel” texture. A solution that is not viscous enough can result in a coating that is too thin, drippy, or saggy. Plus, depending on the application, a coating that is too thin may not provide the necessary top-coat protection. In either case, a coating that has an off-spec viscosity in either direction can result in product rejection or product failure.

As such, it’s extremely important to monitor viscosity in coating applications. Doing so will result in higher product quality, less downtime, and improved product yields. Even better, viscosity management will deliver significant savings by optimizing the use of raw materials and reducing maintenance requirement.


Viscosity Measurement in a Wide Range of Coating Applications

By offering a permanent record of the viscosity, temperature, and temperature-controlled viscosity of the coating solution, in-process viscosity monitoring benefits all types of coating operations, from flow processes in optical coatings, dip processes in wire coatings, spray processes in automotive paints, and roll/printing processes in can coatings.

Wire enamel (dip coating). Magnet wire for the manufacture of electric motors, transformers and similar devices is coated with an electrically insulating enamel by a dip process (the coating process is repeated until the required thickness is obtained). In this application, the percent solids in the coating solution is the crucial parameter; if the coating solution contains a high percent-solids content, solvent costs can be reduced. Accurate management of the viscosity is crucial in controlling uniform film weight.

Optical Coatings (flow coating and dip coating). Traditionally, the cup method has been used to determine ideal viscosity for optical coatings, but the method lacks precision. To compensate, the operators typically add too much solvent to manage high-solid composition. In-line measurement with a viscometer ensures precise control of the viscosity so the product has the right amount of coating. This delivers tremendous savings by reducing raw material overuse and by reducing the amount of downtime required to measure the viscosity of the coating solution.

Beverage Can Coating (roll/printing process). Beverage, paint, and other types of commercial can packaging are commonly printed and then coated with a thin layer of overvarnish to protect the decoration. The varnish thickness is pretty important. If too much varnish is used, the can will appear bubbly, and if too little varnish is used the decoration will be easily scratched. The throughput of a can coating line is very high (>2,000 cans/mm. per machine). In this application the viscosity of the overvarnish should be managed on an in-line basis because of the rapid throughput and the significant potential loss. Cambridge viscometers are used to produce 28 billion cans in the United States alone on more than 50 can lines.

Automotive Paint (spray process). The paint job on a new car or truck is a vitally important part of the finishing process in automotive manufacturing. Mistakes in new vehicle paint jobs cost automakers millions of dollars each year. As many as 15-20% of vehicles are not painted correctly the first time, and the predominant reason for this is incorrect paint thickness. Viscosity management is the key to improving vehicle paint processes. By ensuring the correct viscosity, manufacturers can get a steady stream of painting through the system to the sprayer, to paint the vehicles right the first time. Cambridge Viscosity viscometers measure paint viscosity, temperature, and temperature compensated viscosity, sharing data with a central computer that monitors parameters and updates the viscosity every few seconds. This reduces viscosity-related paint defects.

Paper Coatings (roll process). Viscometers installed in coating lines monitor and help control the viscosity of coatings for specialty papers such as pressure-sensitive labels, folders and postcards. In-line viscometers provide more reliable viscosity measurements with a smaller degree of variability than rotational viscometers and require essentially no maintenance, thus minimizing the downtime of the process.

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Cambridge Viscosity’s ViscoPro reliably manages the viscosity of coatings used in a range of industrial processes. The system eliminates the difficulties inherent in the use of other systems, such as the problem of subjective data that is inherent in the cup method. Virtually all users of the viscometer report that the system provides more accurate, more precise and more reliable data than previously used cup methods. Since the system has only one moving part and no seals, it can be operated for long periods of time with minimum maintenance. The unit provides online real time measurements and is able to automatically control the composition of the coating to provide maximum product quality. Read more about the ViscoPro here

Download the ViscoPro 2100 Product Data Sheet

Tags: viscosity measuring solution, viscosity control, coating viscosity, viscosity management, Coating, ViscoPro 2100

Patrick Riley

Written by Patrick Riley

Vice President of Process Analytics

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