Web cleaning

Web cleaning is a process used in industrial production to remove dust, fibres and other loose particles from moving webs or sheets. It is applied in the manufacturing and converting of paper, corrugated board, film, glass, nonwovens, tissue paper, and other substrates, in printing processes¹², as well as in electronics manufacturing, such as printed circuit boards³, semiconductor components and electronic assemblies, to prevent defects during assembly or downstream processing operations.⁴⁵⁶

As industrial production became faster and more complex during the twentieth century, controlling contamination in web-fed processes became increasingly important. Surface contamination, originating from the material itself or the production environment, can affect downstream operations and contribute to equipment wear and safety concerns.^{4: 170 1: 698, 917, 321}

Particles on webs or sheets of materials can originate from several sources,^5: 43–49 including:

• fibers or particles released from the material itself during production^2: 212
• contamination generated during converting processes such as cutting, creasing, folding, or stacking^{1: 374–377}
• electrostatic charge that attracts particles^{2: 133–134 76}
• particles generated by wear of machine components, including metals or plastics^{1: 112–115}
• ambient dust present in open production environments^84: 63

Contamination on webs or sheets can affect product quality and process stability in several ways, depending on the application and substrate. Reported effects include:

• defects during printing^{7: 4203 1: 320 1: 378 1: 730 2: 211 2: 233 4: 170}
• inclusions or imperfections in laminated or coated products^{2: 141 4: 54}
• particles in electronics manufacturing may cause short circuits or impair the correct assembly of circuit boards^5: 7
• unacceptable dust in food and pharmaceuticals packaging^2: 134
• problems associated with feed preparation and conveying^{4: 63 1: 914}
• abrasive wear of machine parts^1: 208 9
• contamination related health problems^102: 141

Substrates can be checked for surface contamination in various ways, often through a combination of in-line inspection during production and quality sampling. Specialised standards and inspection systems have been developed for print media such as paper and cardboard.^1: 128

In printing, in-line print inspection and measurement systems are used to detect defects that may indicate contamination. Keeping track of blanket or ink-cleaning intervals is another way to monitor the substrate's cleanliness: an increase in cleaning frequency often indicates higher levels of dust or contamination.^{1: 355 4: 29}

In the production of float glass, automated optical inspection (machine vision) is used for continuous detection of foreign particles, with tolerances set based on quality requirements and subsequent processing.¹¹

During the production of electronics, technical cleanliness inspection includes counting and analyzing particles on the substrate, as well as standardized tests for contamination on printed circuit boards and electronic assemblies.^{35: 16–21}

Depending on the application and substrate, web cleaning is used to remove contamination,^4: 63 a procedure that can be performed using contact or non-contact extraction methods.⁶

Contact cleaning systems rely on direct contact between the cleaning element and the substrate, for example, by using elastomer rollers, adhesive rollers, or brushes.^{1: 425 5: 62} These systems are typically applied where the material and surface characteristics allow mechanical contact without damaging the substrate. For instance, in the production of rigid substrates such as printed circuit boards, contact-based cleaning methods are commonly used to remove particulate contamination from panel or board surfaces before subsequent assembly steps.^5: 60

Non-contact cleaning systems remove particles without touching the substrate, typically using controlled airflow, ionisation, and vacuum extraction. These methods are often used in high-speed production environments or when sensitive surfaces require cleaning without mechanical contact.^{1: 266 1: 431}