Camera Applications in Pad Printing

The primary task of camera monitoring in pad printing is to ensure print quality. In the past, when printing on coins, cameras were used to rotate the coin so that the printed image aligned with the embossed design on the coin. Early cameras featured optics that required manual adjustments, limiting their use to single-product or single-task applications. Despite their high cost, these cameras offered only low-resolution megapixel capabilities.

Today, this technology has advanced significantly. Modern cameras feature electronic zoom and high-resolution optics. But what specific tasks can a camera perform in pad printing? Three key areas have emerged:

1. Measuring the substrate
2. Measuring the print
3. Quality control of the print

Measuring the Substrate

In the past, cameras merely ensured the coin was aligned with the print design. Today, they can provide correction values for X, Y, and angular positioning directly to the pad printing machine. Module or ML pad printing machines can use linear motors to compensate for these deviations automatically. This enables a level of printing precision that surpasses the tolerances of the substrate or transport system.

Measuring the Print

After printing, cameras can measure the printed image and generate correction values for subsequent prints. Module and ML pad printing machines adjust positions automatically to center the print within tolerances, achieving even greater accuracy.

Quality Control of the Print

Early camera systems counted pixels of the same color in the print image to identify issues such as unprinted areas. However, because the entire print image could slightly expand or shrink depending on the pad printing machine’s settings, this approach was unreliable. Improvements came with the ability to exclude edge areas from analysis, but the method remained limited.

Modern camera systems use AI-based quality control. These systems are trained with examples of “good” and “bad” prints to understand acceptable and unacceptable outcomes. Maintaining a well-organized library of reference images is critical for the success of this approach.