Web cleaning

As industrial production became faster and more complex during the twentieth century, controlling contamination in web-fed processes gained importance. Surface contamination, originating from the material itself or the production environment, can affect downstream operations and contribute to equipment wear and safety concerns.^{[3][1][page needed]}

Particles on webs or sheets of materials can originate from several sources,^{[4]: 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 [2]: 133–134 [7][6]}
• particles generated by wear of machine components, including metals or plastics^{[1]: 112–115}
• ambient dust present in open production environments^[8][3]: 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 [3]: 170}
• inclusions or imperfections in laminated or coated products^{[2]: 141 [3]: 54}
• particles in electronics manufacturing may cause short circuits or impair the correct assembly of circuit boards^[4]: 7
• unacceptable dust in food and pharmaceuticals packaging^[2]: 134
• problems associated with feed preparation and conveying^{[3]: 63 [1]: 914}
• abrasive wear of machine parts^{[1]: 208 [9]}
• contamination related health problems^{[10][2]: 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 [3]: 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.^{[5][4]: 16–21}

Depending on the application and substrate, web cleaning is used to remove contamination,^[3]: 63 a procedure that can be performed using contact or non-contact extraction methods.^[6]