Label stock quality control takes a giant leap forward

Managing the quality of self-adhesive label stock on laminating machines is now easier and more efficient than ever.

Producers of self-adhesive label stock are busy responding to the growing demand and supplying their products faster and in smaller series. This consequently means a significant increase in the number of grade changes on their laminating machines. To stay efficient, you have to be able to produce the needed grade according to its specifications as quickly as possible. Quality control plays an integral role in ensuring the desired quality, lowering costs and reducing waste.

Valmet has more than 50 years of experience from thousands of quality control system deliveries for pulp, paper, board and tissue production. The Valmet IQ Self-Adhesive Laminating Solution is based on this extensive know-how and represents the most comprehensive quality control system on the market for laminating machines.

We are now utilizing our automation, measurement and quality control know-how on laminating machines. The solution includes Valmet IQ measurements, scanners, profilers, quality controls, as well as process and quality vision solutions – all designed to boost the quality of the label stock.

Machine vision detect defects and identify root causes

An important element in this solution is Valmet IQ Process and Quality Vision. Consisting of the IQ Web Inspection System (WIS) and IQ Web Monitoring System (WMS), it detects quality defects and identifies their root causes.

WIS is a tool to inspect adhesive and silicone defects, laminate and unwinding. It provides new information to reduce the origins of web defects, thereby optimizing production quality and efficiency. With its cameras, WMS monitors unwinding and coating stations, and detects possible adhesive void and streak defects, as well as process issues.

New-generation Valmet IQ Web Inspection System for high measurement precision

The new Valmet IQ Web Inspection System, launched in May 2019, utilizes intelligent 8K camera technology, which combines the best features of an area scan (matrix) camera and line scan camera technologies.

More sensitive and reliable defect analysis can be achieved with multigeometry. It is also possible to replace several camera beams with one unit, resulting in cost-efficient, compact installation and lower service needs. Unique lighting technology enables the detection of print-critical defects that have not been visible before. This illumination provides excellent opportunities for 3D defect contrasting. Particularly longitudinal structures and oil stains, for example, which are often hard to detect with standard lights, are also highlighted. Precise detailed defect classifications can be made by means of the MIDA (Multiple Image Defect Analysis) and the latest software algorithms based on artificial intelligence principles.

Combining a camera-based system with a quality measurement system makes it possible to connect data from both these sources making it is easier to troubleshoot and find root causes.

Water level and curl control without steam

Compared with other solutions on the market, our moisturizing concept is unique. With today’s fast laminating machines that run over 1,000 m/min, you usually need several steamboxes and conventional moisturizers, since their capacities are not very high. Valmet has developed a solution with which all this equipment can be replaced by IQ Moisturizer. It enables you to control both the water level and curl without steam.

Whereas older-generation equipment can increase the moisture level by less than 1%, IQ Moisturizer can increase it by up to 3%. Additionally, it is possible to control both MD and CD moisture with Valmet IQ measurements and scanners. Another highlight is the closed loop control, which ensures unprecedented moisture and curl control accuracy – a totally new feature with moisturizers.

Online closed loop control and multipredictive (MPC) controls are a must on high-speed laminating machines to ensure runnability and quality.

More accurate measurement saves silicone costs

Valmet IQ Direct Silicone and IQ Adhesive Measurement together with IQ Converting Scanner play a major role in Valmet’s solution to ensure accurate sheet quality measurements on silicone coated release liners.

Another factor that makes this quality solution stand out is our patented technology that measures silicone by using middle infrared (MIR) spectroscopy. Measuring the –CH bonds, present in all silicone and adhesive types, makes it possible to accurately and independently measure silicone without any disturbance of the clay in the base paper unlike XRF (x-ray fluorescence) based instruments. Measurement accuracy is of utmost importance to stabilize the release force and lower silicone costs.

The direct adhesive measurement can measure all types of adhesives, such as solvent, emulsion and hot-melt. It is now possible to control the CD variation of adhesive, too.

According to our customers, the best feature in the quality control solution is its measurement accuracy. Earlier, you had to test paper samples in the laboratory to find out the amount of silicone or adhesive present. Now, you can now get accurate quality information online.