Meaning
Reduction in the uniformity of the signal as a scanner moves across the different elements of a printed barcode. The occurrence of a modulation drop indicates that some bars or spaces are not as distinct as others within the same symbol. Monitoring this metric is only required during the initial quality verification phase before the batch is released for shipment.
Signal Uniformity
Localized variations in ink density or substrate texture cause the scanner to perceive different levels of contrast. When a modulation drop is detected, it suggests that the printer is struggling to maintain a consistent output across the entire width of the label. This can be caused by a dirty print head or uneven pressure on the flexographic plate.
System Performance
High-speed scanners are more sensitive to these fluctuations than handheld devices. A large modulation drop can lead to a no-scan event, requiring the operator to manually enter the barcode number. This slows down the movement of goods through the fulfillment center and increases the risk of data entry errors.
Verification Standard
Quality engineers use specialized equipment to map the reflectance profile of the barcode. By analyzing the modulation drop, they can identify specific areas of the print that are below the required threshold for a passing grade. Correcting the ink flow or adjusting the tension on the label press usually resolves the issue.
Precise control over the printing environment is necessary to keep these signal fluctuations within acceptable limits.
