Printed Packaging Defects: A Four-Point Framework for Identification and Classification

A Structured Troubleshooting Mindset for Print Defects

When a printing problem arises, start by seeing it clearly: what it looks like and how it stands apart from other defects. Next, trace its causes and the relationships among them—which cause is primary, which is secondary, and whether they operate independently or are linked.

The problems covered below share one trait: they can be seen either with the naked eye or with a microscope.

In broad terms, defects can be divided into two groups: image-edge errors and image-area errors. Image-edge errors occur when the image edges fail to match the original; image-area errors are abnormalities on the image surface. (Screen printing problems are not confined to these two groups. Image registration and alignment, ink-volume adjustment, and post-press finishing all affect print quality.) Four attributes can help identify, compare, and classify image defects: Position, which is where the defect appears in a continuous run relative to the entire image. If the position is recorded as 'same', the defect always shows up in the same spot.

Other possible position entries are 'various position', outside the printing area, or close to—but not exactly—the same spot. Direction refers to the defect's orientation relative to printing variables. For example, sawtooth edges are most visible when the angle between the image and the mesh line is 1°–10° or 80°–89°. Direction also covers squeegee scratches, squeegee length, and the orientation of the image edge. Size describes how the image containing the defect compares with a good printed product. For instance, scuffing makes the image larger, while edge loss makes it smaller. If image variation across prints is irregular, enter 'random' in the table.

Frequency means how often the defect appears on printed products. Some defects are always present, such as ghosting; some are occasional, such as ink lines; and some continue over several printed products before disappearing—in that case, enter 'both' in the table. These four attributes explain why fixing a fault during printing is better than fixing it afterward. Unfortunately, if printers do not understand how defects differ, identifying and resolving the problem becomes difficult. Beyond the four attributes above, every fault has one or more features that make it easy to recognize.

——This article is reprinted from China Packaging Network (pack.cn), original link: http://news.pack.cn/show-369990.html