HP Latex 1500 User guide - Page 400

Bands of light and dark zones These are periodic horizontal bands formed of a lighter band and a consecutive darker band. This pattern is mostly seen in solid color area fills (such as light purple or gray). There are three likely causes: ● Coalescence. This is due to an excessive amount of ink, and the ink being misplaced as it is deposited on the substrate, generating bands with more ink than other alternate bands. It can also be caused by firing too much ink in a short time. Coalescence is most likely to be seen in areas of high ink density. Here are some tips for solving this problem: - Use lower ink density. - Increase the number of passes. - Change the type of mask (large/uniformity). ● Printhead alignment. This is a clear contributor to banding. If printheads are not correctly aligned, the misplaced dots could correlate directly to the severity of the banding. To check printhead alignment, print the printhead alignment diagnostics plot (see Printhead alignment diagnostics plot on page 141). As a general rule, the biggest contributors to light-and-dark banding caused by printhead alignment are (in this order): - Bidirectional alignment - Inter-color alignment (alignment between different colors) Here are some tips for solving this problem: - Execute automatic alignment. - If the printhead alignment was done with a different substrate of different thickness, probably a new printhead alignment is needed. - Fine-tune the alignment by identifiying the offenders in the printhead alignment diagnostics plot. See Automatic alignment procedure on page 137. 392 Chapter 13 Troubleshoot print-quality issues ENWW